CIP Annual Report 1981

8/9/2019 CIP Annual Report 1981

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Chile

Colombi

It started with experimentalpotato storage structures at Cl P sHuan cayo highlands station.

Objecti ves were simple on -farmst o res of low -cost local materials and updating the old d if fused light principle to preve ntunwanted sprouting in seedpotatoes .

he r objectives were met,the idea sp read rapidly .

By De cem ber 1981 some 350farmer -adopters were identifiedworl d wide . Fifty -two nationalscientists from 21 countries

Peru

Thmiland

w e re trained in post -harvesttechnology . Use of this tech nology in some countries is beingt es t ed , other countries areadapting it to local situations ,and still others are record ingwidespread farmer -acceptance .(See Thrust V and SocialScience Department sections).

Both farmer and experimentalstores are shown on these pages .

COVER PHOTO - E x perimentalpotato store under evaluationin Colombia, South America.

Npml

Nepal


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ontents

Cover Phot o . . . . . . . (In s id e front cove r)Di r ec tor Ge neral s Message . .Boar d of T rustees .C IP Research Sit es .C IP Donors 1981 . . . .Re g ional HeadquartersSurv ey of Researc h 1981Thrust I - Coll ect ion and Classi fica ti o n of Tu ber- Beari ng olanums

Thrust - Ma intenance Ut il ization and D istrib u tion of Tub er-

iii

v

vi

viivii i

ix

Bearing olanums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Thru st Ill - Control of Important Funga l Di seases . . . . . . . 15T hrust IV - Control of Im p ortant Bacter ial Di seases 2

Thrust V - Control o f Impo rt a nt Virus Di seases . . . . . . . . 27Thrust V I - Co n trol of Im p ortan t Ne matode and Insec t Pests 35Thru st V - Ph ys iolog ical and Agronomic Management of Potatoes 4 7Thr u st VI - Deve lop ment of Storag e and Proc essing T echno logyThrust IX - S eed Product ion Technolog y . .Regional Research and T rai ningSocia l Sc ience De pa rt m entTrain in g and Communications DepartmentPublication s by CIP Scie n tists .Research and Con sul ta n cy Contracts . .Staff .Financial Statements

57

6373

8597

105107109

3

This is th e tenth annual report pub l ished by the Int e rn a tion al PotatoCenter, Apartado 5969 Lima, Peru . Printed for worldwide di stribution ,t he re po rt cover s the p er iod of 1 Novemb e r 1980 - 3 1 October 1981 .

The In te rn atio n a l Potato Ce nt e r C IP ) is a no n- profit, a utonomoussc ienti fic in stitution establ ish ed by agree m e nt wi th the Gov e rn m ent o f Perufo r developin g and disse mi nating know led ge for greater u se of the potatoas a basic food. International fundi n g sources for techn ica l a ss istance inag r icu lture fina n ce th e Ce n te r.

Det a iled reporting o f C IP s ext e n sive act ivi ti es is b ey ond the scope ofthis publication. Ment ion of specif ic products by name do es not impl y

endo rs eme nt of o r discr imination agai n st such products by C IP .Cor r ec t citation for th is repo rt : In te rn a tional Pot ato Center. 1982.

C IP Annua l Report, 198 1. Lim a, Pe ru . 142 pp .Date of di s tribution: Jul y 1 1982


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Director General s Message

CI P celeb rated its 10th anni versary byho lding a Congress on Resea rch fo r thePotato in the yea r 2000 in February1982. Potato scie nti sts an d researchmanag ers fro m 56 coun tries attendedmaking thi s the broadest globa l repre

sen ta t ion of potato work ers ever to mee t.CIP u til ized the opportunity of theCon gress to up-dat e lo ng ter m plans for anumb er of high priori ty resea rch thru sts.

A large number of com pl imentaryletters have been received on the succe ssof the Congress. The principle ingredie nt sto th e success were, firs t, the exce en t mixof capab le sc ie ntis ts, and, seco nd, the e xce llen t tea m approach by a ll C IP worke rsto see that gues ts were wel l a t t ended.Prob ab ly due to the Cong ress and its concentr at ion on long term planning, andalso the rece nt public at ion of the t hirdedition of C IP's long term plan to t heyear 2000, C IP is receiving a n increasi ngnumb er of reques ts to help deve lopi ngcou nt ries produce their own advancedplanning fo r pota to improveme n t.

Du ring 198 1, CIP s a nnu al internalreview was used to implement C IP sstrategy fo r increasing the involvement ofThird World countries in the planning of.CIP' s program. Management has felt forsome time that Third W o rld co untri essho uld be involv ed actively i n th e periodicreviews but was concerned about theposs ib le effect on the excellent ope nfran k and c ri tica l discussions on programconten t which have been developed sincethe start of C IP. The participation ofleaders of potato prog rams in developi ngcountries in no way hindered the frankdisc ussions an d added a new d imension to

the rev iew ing a nd p lannin g of their program which C IP is conducti ng. Furthermore at the 1982 internal rev iew, CIP willbe t he firs t Center to have in attendancemembers of a TAC quinquennial reviewteam.

Due to C lP's deve lopment strategy t heeconomic pressures on t he CG IAR systemhave had lit t le if any effect on CIP'sprog ram. Th e quality of researc h bei ngprodu ced, the quantity of relevant tec hnolog y in CIP's tra nsfer system, andCIP 's ability to transfer technology withnational scient ists into growers' fie ldscon t in ue to incre ase even th ough CIP'sreal costs are slight ly decreas ing.

Donors co nt inue to show th eir in terestin Cl P's program and t he credib ility w h ichhas been deve lope d. We welcome themany favorable co mments Th ird Worldco un tries have given to donor s abo u tCIP' s prog ram. Th e rea l cri teria fo rfund ing C IP sho ul d be no t what we saywe have done but what Th ird Worldcount ries say we are doing for their foodprodu c tio n system s and the eco nomy oftheir farmers. Thr ee new dono rs jo in edCIP in 1981 and in the ea rly mont hsof 1982 four additional donors have in-dicated that they will invest in CIP'sprogram for the fi rst time.

Dr. Burton who h as bee n chairman ofthe program co mm ittee o fC IP's Board ofTru stees for t he past 6 years must receivespecia l recognit ion in this report. He has

not only been a ded ica ted board member,helping to guide ClP's program duringits rapi d grow th period, but he has alsopart icipated in man y Cl P tra ining programs an d the evaluatio n and planning


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of collaborat ion efforts w it h nationalp rogra ms. Also to be mentio ned is theexcelle nt parti c ipation of Dr. Fau stoC isneros, who has g iven continuit y ofre pr esentat ion from the host countr yinstitutions for the pas t 7 yea rs.

As we move in t o the sec ond 10- yea r

p er io d of CIP's existe nce , it is go od tolook back an d see how far we h av e come .Also we must loo k forwa rd and see howfar CIP has to go, what st ill needs to be

d o ne between n ow and the yea r 2000 forpot a to imp rovement in Thi rd World co untri es. Th ere can be no re laxing. I amconfide nt t hat the qu ant ity and qualityof CIP research will conti nu e to growwith th e sa me level of rea l funding. AndI am very sure that th e level of our co l-

laboration and peer re lat ionsh ip withscient ists i n T hi rd W orld co unt ries w illm ake a qu ant um jump du r ing these ne x t10 years.

RichardL

Saw yeri recto r GeneralIn te rn atio nal Potato Ce n ter

CIP s M ND TE

As one of the wor ldwide network of ce nter s funded by the Con sultativeGroup on In ternational Agricultural Res earch (CGIA R). CIP has t he following mand ate:

To develop , ad apt and expand the resea rch necessa ry for th e technology to solve priority prob lems that lim it pota t o production in developin g co un tr ies. Th is include s adapti ng the co llect ive know ledg e that ha scontributed to the ste pwise increa se in potato production in de vel opedcountries.

The Wor ld Po t ato Col lection which has been accumulated by CIP p rovides ampl e opportunity for researc h breakthroughs through t he ex p lo i-tation of th is large quantity of p revio usly una vailab le genet ic resources.

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IP Research Sites

lf ; =;:;:; J Desert ~ ~ ~ ~ mighlands Tropical, Humid Hills mm Lo w, Humid Tropicsr- - - - - - - -

Altitude a Molina Va ll e del Ma ntaro San Ramon L 2 ' ~ r ~ m ; ~ sJ{meters) :

5 000 t _ _ _ - :

Cross Section, Central Andes

At any one time research a t CIP sPeruvian facilities may be ongoingin desert alpine and high and lowjungle environments. These fourzones represented in CIP field locations are those in which nearly twobillion people live worldwide.

The range of physical environments is broad: from near sea levelto 3 000 meters altitude fromdesert to 2 000 mm rainfall, and- 5 C to 40C in temperature. Thedaylength range is limited.

The potato originated on th ehigh plains, altiplano in what isnow part s o f Peru and Bolivia. Thiscenter of diversity is not only forpotatoe s themselv es , but also for

most major potato diseases andpests.

CIP facilities are ideally locatedfor testing and identifying cloneswith resistance to a wide spectrumof biotic and abiotic pressures.These natural test environments areaugmented by extensiv e screenhouse and growth chamber facilities.The long-term comparative advantage of CIP is the exploitation/distribution /use of th e World PotatoColl ection maintain ed at Huancayo.Breeding and genetic manipulationsprovide new combination s of genesfrom this gene bank for screeningfor climatic adaptation re sistanceto specific pests and diseases , andgood y ield .

Temperature oc Daylength hr: minStation Latitude Altitude Rainfall

(S) m) Max Min Mean mm) 22 Jun 22 Dec Range(mean) (mean)

La Molina 12 05 240 22 16 19 15 11:25 12 : 50 01:25Huancayo 12007 3 ,280 21 5 13 720 11:25 12:50 01:25San Ramon 11 08 800 30 18 24 2 ,000 11:28 12 :46 01: 18Yurimaguas 5041 180 31 21 26 2 ,134 11:49 12 : 28 00:39

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CIP Donors 98

In 1972 only three donors w ere listed as contributing to th e financialsupport of th e Internationa l Pot at o Center. The donor list for 1981 isas follows :

SpecialCor e Project

Australian Dev e lo p ment A ist an ce Bureau .

Belg ian Go ve rnm en t . . .Canadian Intern atio na l e ve lopment Agen c y

(CIDA) . .Danish Intern ational Developm e nt Agency

(DAN ID A) . Europea n E co n omic Commun i ty . .

Federal German Government . .French Governm ent . .

In t er-American Deve lopmen t Bank IDB )In terna t ional D eve lopment Resea rc h Centre

(IDRC) . . .

x

x

x

Net herlands Gov ernm ent . . . . . . . . . . . . . . . . . . . X

Philippines Government . . . . . . . . . . . . . . . . . . . . X

Swe di sh Agency for R esea rch Cooperation wit hDeve lo p ing Countries SAR EC) . . . . . . . . . . . . X

Swiss De vel opm ent Cooperation an dHumanitari an Aid . . . . . .

Un i te d Nations Deve lopment Progr amme

Unit ed Kingdom O ve rseas Deve lop men tAdministration (UKODA) .

Unit ed States Ag ency for In ternationa lDeve lopment (USAID) . . .

W. K. Ke llogg F ou nd at ion . .Spanish Go ve rnm ent . .

Mex ican Go vernment

J apan Economic Coo per ation Bur eau . . .In te rn at ional Fund for Agricul tura l Developmen t

( FAD) . . .World Bank

v

x

xx

xx

x

x


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Regional eadquarters

REGION I CIPAndean Latin America Apartado Aereo 92654

Bogot a B, D .E .. Colo m bia

REGION II C IPNon-An de an Latin America c/o EMBR APA

Caixa Postal 1 1 ) 131670 000 Brasilia, D.F .. Brasil

REGION l l C IPTrop ical Africa P.O. Box 25171

Nairobi, Kenya

REGION IV CIPNear and Middle East P.K. 9

Menemen, Izm ir, T urkey

REGION V CIPNorth and West Africa 11 Ru e des OrangersFrancophone) Ariana, Tunis, T u n isia

REGION VI CIPSouth Asia c/o NBPGR

IARI CampusNew Delhi, 110012, India

RE G ION VII CIPSoutheast Asia c/o PCARR

Los Ban os, Laguna , Philipp in es

T R USTS

The International Potato Center uses the term T hrust to refer tointegrat ion of research projects into units of common research activi t ies .

Each of the nine Thrusts has a Coo rdinato r responsibl e for th e unification of proj ect activities wit hin that Thrust. Th rust activities in developingcountries are coordinat ed by Cl P 's Regional Rese a rch and T raining organization. i ve research Departments serve as administrative units for groupingpersonnel ac cording to their prof essio nal discipline and for allocatingproj ect funding. Th e Departmen t of Training and Communicat ions, theDepartment of Social Science and the Department of Regional R esea rchand T r ining are support units.

Various rese arch di sc iplines coop era te through the Thrusts to developtechno log y for low in come farmers.

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The principal scientific resourceCIP has is the World Potato Collec-tion.

Within this collection of primitivecultivars and wild species are re-sistance factors and other beneficialcharacters required by developingcountries. The major portion ofCIP s research is directed to ex-ploitation of this resource and in-

volves cooperation between severaldisciplines.Collection of wild species con-

tinued with new accessions added,including rare species and twopreviously believed extinct. Fivenew species were named afterexhaustive study of herbarium col-lections in the Smithsonian Institute(Washington, D. C.). Classificationand identification of duplicates byelectrophoretic and morphologicalmethods continued. Removal ofduplicates has reduced the collec -tion by 14 percent. Duplicates wereretained as true seed. More than4,000 tuber samples and 200 seedlots were distributed to cooperatingscientists.

Tubers with combined PL RVand PVY virus resist ance were dis-tributed to several national programsand a controlled field evaluationwas conducted through RegionalResearch in Turkey and Argentina.A 15,000-clone set was evaluatedduring the year in Turkey and asmaller set in Argentina. To increasethe frequency of combined resist-ance of the two viruses in CIP mate-rial available to national potatoprograms, parental clones whichtransmit PLRV resistance to theirprogenies efficiently (good generalcombiners) have been identified.

Survey of Research 98

x

More than 50 percent of seedlingsfrom these parents resist PLR Vinfection in the seedling exposuretest. Recurrent selection has led toa dramatic increase in frequency ofPVY immunity, up to 82 percent.

Among fungal pathogens, lateblight continues to be first rankpriority both for breeding and indemand from national programs.

The selection process was accelerat-ed by seedling screening undergreenhouse cond itions at CIP s high-land research station in Huancayo.Field screening was reorganized anda new cooperative project developedin Medellin, Colombia with theInstituto Colombiano Agropecuario(ICA) . In 1982 this project will in-clude a previous test site at Toluca,

Mexico in collaboration with Insti-tuto N acional de Investigacion Agro-pecuaria (INIA) of Mexico. There isa much greater spectrum of pathogenic races of late blight in Colombiathan in Peru and i t is hoped thattesting both in Colombia and Mexicowill greatly improve screening ef-ficiency. Advanced clones evaluatedby national programs in Colombia,Kenya, Rwanda and Sri Lanka showuseful levels of resistance and yieldperformance and are being con-sidered for varietal status .

The second most important dis-ease worldwide in tropical countriess bacterial wilt. To identify sources

of resistance, two races of thepathogen are used. Sources of re-sistance presently identified includeSolanum sparsipilum S. chacoenseand S. phureja. Progenies derivedfrom crosses with S phureja haveperformed well in Brazil, Uruguay,Colombia, Kenya and Sri Lanka.


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Some advanced clon es hav e survivedsevere fi eld infection in Peru forthree seasons. In th e Philippines,where the disease is severe inmedium altitude ar eas, genetic resistance, combined with agrono micpractices, is being teste d to getadequate control.

The World Potato Collection is agood source of nematode resistance.Some diploid cultivars have highleve ls of resistance to four speciesand eight race s of root-knot nematodes. T h is is being in co rporatedinto tetraploid material. Resistanceto various cyst nematodes was id en

tified in some wild Solanum speciesand tetraploid crosses. Some advanced clones have been tested inColombia and Ecuador and are beingentered in national variety trials.

Root-knot nematode control bya parasitic fungus, aecilomyceslilacinus has proved of practicalvalue in th e coastal areas of Peru.After 3 years of field tests i t appearsto be comparable with control bythe most effec tive n ematicides.There is evidence that the fungu swill give some control of cys t nematodes as well . Cu l tures of the parasite are being distributed for testingunder the aegis of the internationalMeloidogyne project of North Carolina State Un ivers ity.

A major objective of CIP researchis development of technology toproduce potatoes from true potatoseed TPS). Genetic variability formos t necessary traits is availablein the germ plasm collection. R -sistance to late blight i s being introduced from S demi ssum using amult iline approach. Hybrid seed isbetter than open-pollinated seedtuber yield. Good progenitors ofhigh yielding uniform TPS progenieshave been identified, several familiesproduce more than a kilogram ofmarketable tubers per p lant.

x

Parallel with the TPS breeding,agronomic resea rch continues onimproved ways to establish seedlings in the field . Adequate supplyof phosphorus stimulates seedlinggrowth . Under heat stress, mu lching or transplanting in the sha de ofmaize improves seedling establ ishment. Pre-emergence damping-offof seedling s principally ca used byRhizoctonia can b e reduced byfungicidal treat ment of seed. Postemergenc e contro l of R solani andPythium spp. is more complex andinvolves soil temperature effects .

Combining use of TPS with production of commercial potatoesfrom tubers has led to researchon using TPS as a meth od to produce seed tubers. High densityplanting of TPS seedlin gs ca n produce a yi e ld of 500 to 600 useabl et ubers per square meter. Thus,approximately 100 square meters ofnursery, in the first mu l tiplicat ion,wou ld produce sufficient tubers toplant a hectare. Sub sequent multiplication s of these tubers wouldred uce the nursery area required.

Tuber moth is a major pest ofmany tropical potato growing areas.The probl em of control is being investigated in sever al parallel projects.R es istance has been identifie d inseve ral advanced clones and thistrait is inco rpora ted in the breedingprogram . Chemical contro l by

safe in secticides such as sy ntheti cpyrethrins has proved val uable inPeru and in Middle East and NorthAfrica. Recently field cont rol b ytrapping male moth s with synt he ticfe male pheromone traps has beeneffec tive in Per u . The tech niqu ecan also be used in potato stores .

Techn ology transfer has resultedin con siderab le use of low-costdiffused light storage by fa r m ers.In the Philippines, which was th efirst pilot pro ject for this t echnology, more than 150 stores have


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been built by farmers to preservetheir seed potatoes. Sri Lanka hasalso taken up this technology70 stores have b ee n constructedand Government credit for severalhundred more is r eporte d to becurrently available.

New research contracts have beenplaced with national institutions indeveloping countries to perform research of inter est to CIP. Includedare: a project in Chile to producea milk-like product from potatostarch by enzyme hydrolisis evaluation of the performance of heattolerant clones in Sri Lanka evalua

tion of lat e blight resistanc e inColombia and cyst nematode resistance in Ecuador. All these contractsand others are associated with theresearch of the CIP Thrust teams.

x

Social Science researc h continuesto be int egrate d with the biologicalresearch prioriti es. From a casestudy of the R egio nal storage technology tran sfer project a generaltransfer philo so phy has evolvedwhich include s problem iden t ifica

tion technology design testing andevaluation. This s being incorpo-rated into other Regional transferprojects. One new area of specificinterest is th e deve lopm ent of theTPS technology. The social scientists are collaborating in this projectat all stages both technological andfor eval uating social factors such aspotential cost savings. Research on

consumption and nutrition studiesand how they relate to agroecological zones rural versus urban popula-tion hav e continued. This aspectwill be concluded in 1982.


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hrust

Collection nd Classification o Tuber Bearing Solanums

Extensive collecting in southernPeru and short trips to northern -ru when weather permitted growthof wild potatoes. Approximately80 living wild accessions wer e collected including several scarce species. Among the group were twospecies formerly beli eved extinct.

Five new species were nam ed

Collection of n ew specimens ofwild potat oes continued. Explorations in E cuador and northern Peruwere can ce led du e to unavoidablecircumstances including unu suallydry conditions especially in northernPeru . In southern Peru several areas

of. the Departments of ArequipaTacna Puno Cusco and Apurimacwere explored. Short supplementaryco llecting trips were made to LaLibertad and Lambayeque. Duringthese trips 145 sites were identifiedwith wild potatoes in differentstage s of growth. Approximately80 living accessions were collected.Unfortunately i t is sometimes

impossible to collect specimens asseed balls or tuber s for examplemay not be present.

Valuable Collections

Some co llections obtained in1981 are ex tremely valuable. Forinstance the redisc ov ery of Sola-n u buesii a rar e spe cies whichwas considered extinct. After afrustrating search in 1980 it wasfinally found in March 1981 in aremote and isolated eco logical nicheof Urubamba in the Departm ent of

from the wild germ plasm collections of CIP following careful comparison with herbarium specimensof the Smithsonian Institute Washington D.C . Germ plasm distribution of 680 accessions were made astrue seed or tubers to CIP resear chdepartments Japan Peru NationalPrograms URSS and USA.

Cusco . t belongs to the seriesConicibaccata and is diploid 2n2x 24 chromosomes. Anotherattempt was made to recoll ectS pillahuatense a species also facingex tinction. The place where thisspecies might be found was locat ed.

It was impossible however to collect living material because themain access road was blocked andlack of horses frustrated furtherat tempts.

Another little -known species alsoin the process of ext inction isS amabile. Fortunately aftersever al futile attemps during thepast 10 yea rs several ripe berri es of

this species were collected during1981.As a co mplementary work co l-

lect ions wer e made of several accessions of other species rathe r difficultto obtain including S. limbanienseS. rhomboid e ilanceolatum S. coeles-tispetalum S. santolalla e S lyco-persicoides and S. abancay ense.Other fairly common and widelydistributed wild species such asS. bukasovii S. megis tacrolobumS. acaule S. raphanifolium andS marinas ense were also collectedduring these trips.


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ew Species

New species identified duringtaxonomic studies of wild tuberbearing species includ ed S. cala-calinum and S. correllii both fromEcuador and S. antacoch enseS irosinum and S sawyeri. Directconsultations during a short visit tothe National Herbarium , Smithsonian Institution, Washington,D.C., helped to clarify some taxonomic problems.

An atte mpt is being made toreduce t he complex work of taxonomic interpretation in the tuberbearing Solanum and its biosystematics. An active program ofintercrossings has been started. Thispermits , among other things, theund ersta nding of some s pecieswhich are not more than pan mi ct icpopulations or, accessions which inthe past have been modifi ed throughintrogre ssion from sympatric species .

In addition to collecting samples,a donation of more than 200 accessions of wild potato species fromBolivia was made by the GermanDutch-British-CIP Expedition to

2

that country. All these samples aretrue seed and are being kept und erstorage a t CIP .

During 1981 distribution ofwild germ plasm was extensive(Table I-1).

Table 1 -1. Distribution of wild potatospecies in 1981

Institution

International Potato Center , PeruBreeding and Genetics Dept.Nematology Dept.Pathology Dept.Physiology Dept .

University of Kobe, JapanNa t ional Potato Program, PeruVavilov Institute , USSRU.S.D .A. IR-1 Project, USAInternational Plant Research

Institute , USA

TOTAL

No .Accessions

3996

20038

5273

168

10

680

Drawings of new potato species, So/anum bur-tonii and So/anum sawveri are viewed by their

namesakes , Dr . Glynn Burton (center), longtime member of CIP s Board of Trustees , andDr. Richard L. Sawyer (right) CIP s directorgeneral. Pointing out details is Carlos Ochoa ,who discovered the new species and who headsCIP s Department of Taxonomy.


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Thrust

Maintenance Distribution and Utilization oTuber - earing Solanums

Andean cultivars in the WorldPotato Co llection of 7,050 cloneswere reduced by 14 percent afterplacing morphologically and electrophoretically similar duplicates intrue seed storage . More than 4,000tuber samples and 200 seed lotswere distributed.

A population breeding approachfor the highland tropics combinesselection of earlines s and resistanceto frost, late blight, and potatoviru s Y (PVY).

Tuber production from hybridizedtrue potato seed (TPS) s generallysuperio r to that produced by op enpollination or selfing. Genetic variability exists for most of traitsimportant to TPS . Late blight resistance is being introduced usingmajor genes of Solanum d e missumin a multiline approach . Goodprogenitors of high yielding, uniform TPS prog eni es have beenidentified. Sev eral TPS familie s produ ce more than 1 kg of market abletub ers per plant.

Major progre ss was made in se-lec ting paren t al materials with highgeneral combining ability for tuber

And ean cultivar s planted in th efie ld in 1981 tot aled 7 049 acce ssion s of which 2 ,639 were id en t ified as duplicat es in 719 group s At o tal of 1,003 access ions , both morpho logically and elec trophoreti cally id e ntical, w ere eliminat ed fromclonal propagation to be preservedonly as true seed.

A breeding pro gram began tocr ea te bulk hybrid popul ations com -

3

yield, earliness , and adaptationto hot and humid environments.Disease resistance was incorporatedin these populations.

Field evaluation of potato leafrollvirus (PLRV) and/or PVY resistancein 22,000 seedlings a t mid- elevationtropics yielded approximate ly 2,500selections for further evaluation .Yields compared favorably withtropi cally-adapted clones.

Three parental clones were identified with high general combiningability for potato leafroll virus(PLRV) resistance . Pollen from thet hird cycle of selection for PVYresistance in which 82 percent ofthe segreg ates are immune will beused on PLRV resistant parents forcombined re sistance in TPS population s. The se populations shouldhave up to 70 perc ent PVY resistantseedlings and will be distributed toregional and national programs .

Average yield of bacter ial wiltresistant selection s from S phurejaS sp rs p lum and S. chaco ensecro ss es has s ignifi cantly impro vedand

re sistance t o fivepathotypes

exists .

bining special a t t ribu tes identifiedin Andean po ta to cultivar s . Emph asis wa s on th e production of seedstocks using singl e and bu lk crosse sof a ccession s with resistanc e to thesam e patho gen s. Of 213 see d families obtain ed , 17 5 were re sis tant toon e of eight pathog ens; 28 to twodiff erent patho ge ns, and 10 to threediffer ent pa thog ens (Tabl e II -1 .


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A total of 4, 162 tuber samplesand 198 seed lots of Andean cultivars were distributed for screeningand us e.

Combining Resistances

Population breeding was initiatedto combine frost resistance (F),late blight (LB), PVY and ea rlinessin current material developed forthe highland tropics . Preliminaryseedling screening of crosses between LB F resistant clonesand PVY immune clones are inTable II-2 .

Two-factor seedling screening for

LB PVY and F PVY independently is expected to average 16 percentand 9 percent of survivors, respectively. Selected progenitors derivedfrom clonal testing for three factorsand selection for desirable agronomic characters will be used ina phenotypic recurrent se lectionbreeding sch eme.

EarlinessIn regard to earliness, a prelimi

nary experiment on tuberizationresponse to long photoperiod underartificial conditions was co nductedon five families that co mbin e late xearly, medium x early and earlyx early material. Tuberizationresponse under 16- and 24-hourdaylength indicates that when latematuring material is crossed to

Tabl e 1. World Po tato Collection.Hybrid seed combining resistances topathogens within Andean potato cultivars.

Numberfemaleparents

Bulk pollen fromAndean cultivars resistantto :

13 Late Blight (LB)6 Powdery Scab (PSI

14 Black wart (BW)30 Soft rot (SR)35 Potato virus X (PVX)

6 Potato virus Y (PVY)53 Root knot18 G obodera pa Iida (GP)

(Sub-total 1751

1 LB + PS2 LB + RK2 LB + PVX1 LB + PVY1 BW + PVX2 BW RK8 PS + GP1 P S + RK1 S R + PVY3 PVX + PVY4 A K + PVX2 GP + G rostochiensis (FR)

(Sub-total 28)

1 LB+ BW + GP1 LB+ PS + PVY2 LB+PVX + PVY3 LB + R K + G P

(Sub -t otal 10)

TO T L 213

BW + PVX + A KBW + PVX + GRRK + GP + GR

Table 112 Frequency of resistance to LB , F, and PV Y independently in (L B F) xPVY crosses in seed ling screening.

Families Seedlings O/oscreened screened for: Seedlings Survivors Survivors

19 Frost 2055 347 17

19 Late blight 1778 533 3019 PVY / 878 469 5319 PVY Y 878 850 97

PVY J common strain PVY Y necrot ic s train

4


18/144

Tuberization percent

--------:;;16h light0 24h light / ,, ' .

8 1 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ; < ~ ~ : . _ _~ ~ ~ ~

1st. cuttings ,

2nd cuttings ,60

0 L x E374068.4

xLTXYBK

LxE374080.2

xLTXYBK

M x EAtzimba

xDT0-33

,

ExEAtlantic

xDT0-33

ExELT-2

xM. Tropical

L = late; E = ear ly; M = medium maturities.

Figure 11 1. Percent tuberization of single leaf node cuttings from seedlings.

early material there is a range from4.5 percent to 30.8 percent of genotypes that tuberize early. Responseto tuberization increases as materialapproaches early maturity in remaining crosses.

This technique may help accomplish two purposes:

1) To improve earliness as acomplement to other screenings on material so far developed for the highlandsprovided earliness is introduced from other sources,and

2) To screen out late maturinggenotypes in segregatingfamilies that will be distributed to regions or coun

try programs.

A total of 22,057 virus resistantseedlings were field evaluated in SanRamon for agronomic performance.Of these, 10,231 were from the

5

PVX + PVY group, 11,207 fromthe PLRV group and 619 from thePVY + Late Blight group. Retained2,783 clones were for further evaluation and selection in 5-hill plots.Distribution of seedling yieldscompared favorably with tropicallyadapted control clones, LT -1 , LT-2,and DT0-2 Figures 11-2 and 11-3).

Seedling screening of the new

generation of seedlings continuedfor PVY + PVX, PVY alone andPLRV alone. Frequency of phenotypes resistant to PVY during threecycles of recurrent selection increased from 43.4 percent in cycle Ito 82.1 percent in cycle III. Apollen bulk from the third cycle ifcrossed with susceptible femaleparents would yield 70.2 percent

resistant progenies.

P RV Resistance

In the PLR V resistance work thegeneral combining abilities of a


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Percent ofpopulation

18

Check clones

LT-2 LT -1 D T 0 -2

2 3 4 5 6 7 8 9 1 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 2 1 2 2 2 3 2 4 2 5 2 6

Total tuber yield x 1 grams)

Figure 11 2. Tuber yield di str ibution of PVY and PVY PV X resistant clones of firstyear seedlings, San Ramon, January-Ap r il 1981 .

Figure -3. Tuber yield distribution of PLRV resistant clones of first year seedlings,San Ramon, January-Apr il 1981.

Percent ofpopulation

22

18

14

10

6

2

0

Check clones

L T -2 , L T -1 , OT0-2

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18Total tuber yield x 1 gramsl

6


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numb er of femal e parents wastested. Eac h clone identifiedpreviously as resistant to PLR V infield exposures, was crossed tothree distinct pollen bulks. Thepollen bulks serv ed as wide geneticbas ed teste rs. The high pe rforman ce

of progenies resulting from crosseswith highly heterozygous testersindicat es that these clones hav e asuperior general combining ability.As expecte d, clon es resistant toPLRV LR bulk) co ntribu ted thehigh est pollen bulk effect whenseedling progenies were exposed toPLR V-beari ng aphids.

The pollen from th e third cycle

of selection for PVY res is tancewill now be crossed w ith the bestcombiners for PLR V res istan ce

to produce a hi gh frequency ofcombined PVY PLR V resist ance.For instance, leafr oll resistant cloneLR 5 .3 produced an average of56. 7 perc ent symptomless progenywhen ino culated with PLRV. Anexpected 70.2 perce nt of the proge

ny resulting from th e cro ss wi th thethird cycl e PVY p op ulation will b eresistant to PVY. Nearly 40 p erce ntof the progeny from the crossLR 5.3 x PVY-R-III bulk will possessco mbined resistan ce to PLR V andPVY. This type of progeny, wh enprovided as tuber families to a-tional Programs, will be ideal material from which to select local ly

adapted clones resi sta nt to th e majoraphid-transmitted viruses, PVY andPLRV .

Data evaluation and storage for CIP s World Potato Collection.

WORLDPOT TOCOLLECTIOND T B NK

7


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Bacteria l Wilt

Breeding for resistance to bacte-rial wilt, Pseud omona s solanac ea-rum concentrated on three groupsof genetic material. The first groupconsisted of 24 highly selected re-

sistant clones d er ived fromS

phu-reja. These clones were inter-crossed and also crossed with severalsources of resistance different fromS phureja. Eight p erce nt of 30 ,000seedlings survived following screen-ing with pathotype 013, race 3 ofP sola nacearum. Eighteen clonesfrom earlier cycles of selection hada survival rate of 90-100 per ce n t

when grown in an infested field.Average yield per plant was 1.1 kg.The second group was derived

from tetraploid x diploid crosses.The diploid resistant parents wereselected from a population consisting of the two wild sp eciesS chacoense and S. sparsi pi lum andthe cultivated species S phureja.The tetraploid parents came from apopulation adapted to the lowlandtropi cs and selected for earliness.From 343 clones grown under ho tconditions and after a second fieldevaluat ion only 19 clones wereretained. Despite cases where twogenomes wer e cont r ibuted from awild pa rent, excellent tuber shapeand yields of up to 1.45 kg perplant were record ed. The averageyield of the population selected forfurther breeding was 1.34 kg perplant.

The third group use d in 1981was a population consisting ofS chacoense S sparsi pi lum andS phureja. Wild species wer e usedto incorporate new sources ofr esistance to bacterial wilt into t hebr eed in g popul a tion s. Selected re-sistant diploid clone s from recurrentselec tion were us ed in tetraploid xdiploid mating s as indicated in th eprevious paragraph. The diploid

8

population underwent a furthercycle of selection. From 11,500seedlings test ed against four andsometimes five pathotypes ofP solanacearum 40 clones wereintercrossed in 203 different com-binations and about 100 ,000 se edswere obtained. Ten thousand seedswere sown and 7,468 seedlings raisedand tested against the v irulentstrain 013 of race 3 of the bacterialwilt pathogen. More than 2,000seedlings 33 percent) of the population survived this test. When t heoriginal wild diploid population wastested against the same pathotype,i t showed a similar survival rate

about 30 percent). The increasein individual families was up t o67 percent.

True Potato Seed TPS)

As part of a study of the geneticsof tru e potato seed TPS), a NorthCarolina Mating Design II and TypeFamily Comparisons were used.

A set consisted of the progeniesof eight parental clones, four plantsdesignated females and each matedto four plants used as males. Tensets were included. The sixteenfamilies of a set were grown in tworeplications per set in a randomizedcomplete block d es ign at Lima andSan R amon.

Parental clones used in the DesignII were al so se lfed, allow ed to openpollin ate, or bulk pollinated toderive addit ional family typ es.Multilin es were created by mixingequal numb ers of seeds of four ofthe crosses made in each set . Thesefamilies we re included n the setswhich co n t ained the controlledcrosses from the same parents. Thenumber of entries included in eachof the family types was: singlecrosses 160); open-pollinated 20);selfed 20); bulk cross 20); and,multiline 10).


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Ta b le -3. Genotypic and pheno t ypic correlation s design .

Ph enotyp ic C or r ela t ions Genoty p ic Co rr e la t io n s

No . Tub x Yie ldNo . T ub x Gn. Un .No . T u b x Gn . App lNo . Tub x T ub SizeNo . Tub x No . BerriesYie ld x Gn. U n .

.7442

. 10 59

. 234 7

.8 058

.0 67 3

.10401 277

.40 27

. 1324

2 40 1.7 3712 4 55

Yie ld x Depth EyeYie ld x Gn . Ap p.Yie ld x Tub SizeYie ld x No. Berries

1663.625 1.7 331.3816

3 12 3.7570.4471.5 09 4

Gen e ti c variance compone nts andh er itability es timates indicate th e

presence of additive genetic variancefrom most of the trials studied.Her it ab ili ty est im ates show thatco n siderab le progress can be madewhen se lect in g to improve thesepopulations for the ex ploitation ofTPS as me ans of p rod ucing a commercial potato crop.

In Tab le II -3 a number of ph en otypic and genotypic correlations for

pairs of traits are presented . Ofgreat est int erest is the rather highgenotypic corre lat ion betw ee n totalyie ld an d number of berri es suggesting th a t fami li es wit h h igh y ieldand prolific berry production willbe an easy combination to achieve.

Comparisons of proge nies comprised by multilin es, sing le crosses,

open-pollinated fa mi lies (O P) , sel f s,and females c ross ed wit h po ll en

bu lks bulk crosses) ar e pr e sentedfor a se ri es of traits in Tab le II -4.Bu lk crosses, mu l tilines, and sing lec rosse s h ave a higher tota l y ie ldtha n OP s an d se lfs. This, com b inedwit h th e greate r uniformity of si ng lecrosses compared with mu lti linesand bulk crosses, has led t o thepol icy of em phasizing single crossesfor future te st ing in CIP s regional

tr ia ls.

In developm ent and identificat ion of good progenitors whichwill generate high yie ld in g, u n i formTPS pr oge ni es , severa l clones wereid entifi ed h av ing good general andsp ecific co mbinin g ability fo r yie ldand uni for m ity of tubers. Several

Table 11-4 . Mean t ra it values measured in diff eren t fami ly ty pes propaga te d from truepotato seed *.

Famil y typ esT raits

Si ngle OpenMulti line cros s pollinat ed

Germinat io n (O/o) 92.2 a 88.5 b 87 .7 bTr a nsp lan t surviv a l 4 0.7 a 40 .4 a 39.5 bNo. t ubers (log) 2.39 a 2.37 a 2 .24 bY ield (log) .77 a .75 a .54 bUnifo r mity** 5 .46 b 5 .89 a 5. 8 4 aT ub er size .0 2 a .02 a .02 a

* Mean sepa ra t ion by Du n can s .0 5 , horizontal compariso n s o n ly .R ated 1-9, w h ere 1 = east and 9 = h ighly d es ir le.

9

BulkSe lf cross

85.2 c 81.4 d39.6 b 39.8 b2.13 c 2. 4 3 a

.4 5 c .79 a6. 0 6 a 5 .42 b

.0 2 a .02 a


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TPS families have a yield of morethan 1 .0 kg of marketable tubers perplant and about 0.2 kg of smallertubers which may be used as seedtubers Table II-5). t should benoted that, in spite of the arbitrarychoice of the pollen source to

produ c e the bulk cross hybrids,marketable tuber yields in theseTPS families were co mparable withthat of the single cross TPS families.In general, however, the uniformityof tubers size, shape, color) in thesingle cross TPS families was supe-rior to the bulk cross hybrids.

Another group of 48 TPS familiesproduced from the North CarolinaDesign I Mating System was alsoevaluated in La Molina for its poten-tial adaptab ilit y to produce potatofrom true seed. Table II-6 gives thetuber yield and uniformity characteristics of the 12 most promisingTPS families. Th e yield and uni-

formity of these families are as goodas the commercial varieties producedfrom seed tubers which were usedas testers.

CONTRACT RESEARCHDuring the year CIP continued

contract support of the neotu-berosum breeding program a t Cornell University, Ithaca, New Yark,U.S.A. Research is directed towarddevelopment of populations andselected clones within these popula-tions which will be suitable forbroad adaptation.

Clones of andigena representing371 original accessions were backcrossed for the second time to themore advanced neotuberosum popu-lation. These population s shouldsegregat e for a high frequency ofresistance to potato viruses Y and

Tabl e 115 Tub er yield kg/plant) and uniformit y ratings of 10 sing le and 10 bulk

cross TPS families

Tube r yieldHybrid TPS families Uniformity

Marketable Unmarketable

377935.27 x Bulk ESR 1.059 0.16 42 x 378017 .2 1.225 0 .11 43 377922.30 x Bulk ESR 1.100 0.16 34 x 378017.2 1.234 0 .09 55 377892.7 x Bulk ESR 1.100 0.14 3

6 x 378017.2 1 .406 0.15 37 377891 .19 x Bulk ESR 1.108 0.18 28 x 378017 .2 1.049 0.15 59 377888.17 x Bulk ESR 1.077 0 .11 2

10 x 378017 .2 1 .042 0 .11 411 377887.17 x Bulk ESR 1 .013 0.13 312 x 378017.2 1.084 0.13 413 377885.15 x Bulk ESR 1.222 0 .08 214 x 378017.2 1.223 0 .12 315 377877.9 x Bulk ESR 0.930 0.18 216 x 378017 .2 1 .281 0.10 417 377871.28 x Bulk ESR 0 .961 0.15 2

18 x 378017.2 1.221 0.15 419 65 -ZA-5 x Bulk ESR 1.352 0.12 320 x 378017 .2 1 .163 0.21 3

ESR = Early clones adapted to San Ramon conditions1 = east uniform 5 = very uniform.

10


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Tabl e 11 6 . Tuber yield kg / plant) and uniformity tr it s of th e 12 promising TPSfamilies.

Hybrid TPS familiesTuber yie ld

UniformityMark etab le Unmarketable

1 377250.7 x 377904 .10 1.331 0.1 7 32 377877 15 x 377904 .10 1.174 0. 19 33 377887 .74 x 377877.9 1.192 0 .06 44 377922.15 x 377964 .5 1 .115 0 .11 45 377935.27 x 377964.5 1.161 0 .07 56 377964.3 x 378017 .2 1 .172 0 .01 47 377891.19 x 37 8017 .2 1 .3 10 0 .08 58 377887 59 x 377904 .1 1.314 0. 15 49 377933.13 x 377904 .1 1.332 0.20 3

10 378015.7 x 377904.1 1.520 0.10 311 377887.29 x 377896.12 1.104 0 . 512 377887 .74 x 377920 .37 1 .050 0 .20 4

. 1 = least uni fo r m 5 =very uniform .

Wild potato collection in gree nhouse, Huancayo, Peru.

11


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X, lat e blight and wart as well asear ly maturity and good tuber type.The advanced neo t uberosum 7thcycle se lections were grown in twoobservation plots and retested forresistance to late blight, scab PVXand PVY. On the basis of thesetests, 27 clones have been selectedfrom an initial population of 36,000.

t is believed that ll clones areresistant to PVY ; PVX resistance isbeing verified. The mean blightscore on a 1 to 10 scale was 5.4 in1980 and 1.6 in 1981.

Eighty-nine new select ions weremad e from 5,702 hill s which usedthe same clones which producedthe 7th cycle neotuberosum population. These had prior screeningfor late blight and PVX and PVY.Sev e ral hundred select ions hav ebeen made which are tuberosum xneotuberosum hybrids. The mostadvanced of the se ha s been releasedas the variety Ro sa. Three otheradvanced hybrid selectio ns are inregional yield trials.

The evaluation of large numbersof clones under different environmenta l co nditions is a formidabletask for a breed ing progra m servinga b road geographic area . To assistCIP a predictive system for yieldperformance s be ing developed byAgriculture Canada Research Station. During 2 y ears eight cultivars

weretest ed at nin

e sites using Kennebec and Spun ta as co ntrol cultivars to estimate environ mentaleffects at each site. Data from foursites were used as contro l sitesfor developing r egress ion equationsfor eac h of eight cultivars.

Using these regres sion equat io n sand the values of the contro l cu l-tiv ars for the other five sites, it ispo ss ible to predi ct the yie ld of eachof the test cultivars in each of thefive test sites. In reality, datafrom eac h of the five test sites provided both actual and predicted

12

yield for each test cultivar. Thispermitted the measurement of thecorrelation between observed andpredicted yield values. In four ofthe five locations the model predicted the actual yield . t is anticipated that the efficiency of themodel will be improved with anexpanded array of controls.

Agricultural University, Wagening en, The Netherlands, has produced colchicine-doubled Solanum

uberosum x S. pinnatisectumcoded 4x -EP, in which CIP has detected leafroll virus immunity. Further successful crosses with 4 x - EPmat erial open the possib ility oftransmitting PLR V-immunity intomo re advanced material. Etuberosaspec ies also appear to have goodPVY resistance.

S. jamesii accession PI 275265,with resistance to brown rot androot-knot nematod e, ha s been successfu lly crossed with S. bulbo-castanum and with the bridgingTV 5 genotype S. uerrucosum withS. tub erosum cytoplasm).

In breeding new la te bl ight resista nt ma terial special attention isdirected to a new ly created te t raploid gene pool of three Mexicanspecies, S. uerrucosum S. bulbo-castanum and S. stoloniferum .Crosses of this tetraploid materialwith a diploid S. tuberosum producing 2n gametes, resulted insterile triploid hybrids whic h arebeing doubled through explantculture. The diploid S. tuberosumclone contributed only n-gametesto the progeny.

The potato breeding program a tBal carce, Argentina continue d onthe utilization of genetic varia bili tyin tuberosum, andigena, hybridtetraploids and diploids to improvevirus resistance and adaptation t otuberizat ion under lon g days. Morethan 360 parental comb ination swere crossed successfully resulting


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in more than 100 000 seeds forsubsequent planting.

In field selections occupyingapproximately 8 hectares 10 458clones were harvested including1 249 clones from five previousyear s . In cytogenetic studies of 2ngamete production involving 157diploid clones the percentage of2n microspores: 89 0 percent; 18 1 percent; 17 2 percent to 5 percent; 2 6 percent to 10 percent;1 21 percent to 25 percent;3 81 percent to 90 percent ; and7 91 percent to 100 percent.

Materials with virus resistanceand the capacity to tuberize underintermediate photoperiod and relatively high temperatures sent to CIP:two Argentin e tbr cultivars; sixintroduced tetraploid clones; 11diploid hybrids and four tetraploid

hybrids obtained by species crossesat Balcarce.At the Instituto de Producci6n

y Sanidad Vegetal of the Facultyof Agrarian Sciences UniversidadAustral Valdivia Chile researchhas been coordinated on the collection maintenance identification

Wild potato species growing on rocky hillside near Lima Peru .

3


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recovery and clonal evaluations ofwild old species cultivated from Etu-berosa Solanum brevidens, S etu-berosum, S fernandezianum andtuberosa potato series S. magliaand S tuberosum . The collectioncontains 496 entries collected

between 3248 and 4440 southlatitude and 71 20 to 78 50longitude. Maintenance is by tu-

14

hers, plants, cuttings, meristem andtrue seed. Collection identificationby electrophoretic tuber proteinspectra has shown 246 percent coin-cidence with some of the primitivecultivated varieties. A range of use-ful agronomic and nutritional char-

acteristics has been identified in thecollection.


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hrust

Control of Important Fungal Diseases

More than 70 000 seedl ings werescreened for late blight resistan cein growth chambers and in a newgreenhouse inoculation facility a tHuancayo.

Twenty super ior resistant cloneswere se lected from 2 ,000 in cooperative field screening with the Institu

to Colombiano Agropecuario ICA)and transferred to th e national program for multiplication and bre eding . Advanced selected clones ofMexican origin performed well in

Late Blight

Field screening at Rionegro Co

lombi a in cooperation with Instituto Colombiano AgropecuarioICA), during two further evalua

tions resulted in selection of 20superior clones for varietal testingby the national program. Theseclones and some other selectionswere used in t he ICA breeding program . Following an initial evaluation, an additional 1 79 clones w ere

selected for further testing.Duplicates of all selected clon eswer e multiplied in the low aphidpopulation area of San Jorge, Colombia to assure low virus incidence.In all evaluations of late bligh tresistance, in fection rat e was low.However, in co mp aring yield ofclones not protected by fungicideswith protected clones low infection rate in the unprotected pl otscorrelated well with a difference inyield between treatments .

In Rionegro trials CIP -pat ho gentested clones, ASN-69 .1 , CGN-69.1,

15

Colombia, Kenya, Rwanda, and SriLa nka.

Pre-emergence damping -off ofTPS is mainly caused by Rhi zoc to-nia and can be reduced by fungicideseed treatm e nt. Post emergencedamping-off, particularly at hightemperatur es, is a comp lex involving soil temperature R solani and

y thium spp. a nd seems more difficult to control.Chemical co ntrol is effective for

smut and pink rot but not forclerotium ro l f si i

CEX-69.1, Atzimba and Murca hadconsistently low infection rates.

These clones are of Mexican origin.Atzimba and CGN-69.1 pro ducedmore than 1 kg per hill. In Keny a,Rwanda and Sri Lanka, among co nsistent blight resisters and hi ghe styield ers wer e Atzimba and otherMexican clones.

Out of 212 clone s and vari etiestested for blight resistanc e a tHuanuco , Pe ru 50 wer e resistantwhile 27 were no t inf ec ted suggesting apparent immunity due toR-genes). Most isolat es of thefungus from Huan uco w ere of th e1 , 3, 7 race, pos sibly the re sul t oft he rather wide disp ersal of t he newvariety Molin era with the R l R3R7 genes.

Growth chamb er tests with some30 000 see dlings r esulted in anav erage selectio n of 15 per ce nt.Greenhou se tests in Hu a ncayo on a10 percent se lection level from50 000 seedlings ar e being evaluated.


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Table 111 1 . Eff ect of fungicidal seed treat ment on Rh izoc tonia damping-off inartificially-infested soil*.

TPS fungicidal Av erage 0 /o Average wet wt.Treatment tolerance germination at 28 days

g/kg seed) at 28 days** gm)

Dithane M-45 3.7 77 a 10Cupravit 3.7 73 a 12Vitavax 2.5 8 5 a 12Vitavax + Dithane 3.7 76 a 12PCNB 1 .2 72 a 6Control 0 44 b 5

Tuckey s test .05 = 24. 1

Seed treatment by acetone infusion for 10 minu te s. Se eds generally tole rate higher fun gicida lamounts up to about 5 g/kg seed. The seed tolerance ran ge for PCNB was extremely narrow .

Average of two experiments eac h w it h four repl icat ions .

True Potato Seed TPS)

Studies on contro l of pre-emergence damping-off of TPS causedby R hizoctonia solani ind icate aso lu tio n through fungicidal seedtreatment Table II I -1) or so il t reatment (Table III-2). Pos t em e rgenc e

damp ing- off co mpl ex in the fieldin volves so il temperature s of 30 Cand above, an d in fection by Rhizoc-tonia and Phy thium spp. Integratedco ntrol is th e m ost approp riate inreduci ng fie ld losse s. Included areuse of vigoro us seedlings at t ran s-

p lanting , us e of shade com andtimed appli cat ions of soil fungicidesduring the critical infection phas e.

Soil-Borne Pathogens

Repe ating expe rim ents on co ntro lof pink rot Phytophthora eryt hr o- ptica) gave sim il ar results. Themethod consists of a pre-plant in gfumigati on, fo ll owed by ap pli catio n of Ridomil a systemic fu n gici d e with spec ifi city to Phyco-myce tes at plant in g. The methodwas employed on a large sca le using

Table -2. Effect of fungic idal treatments of ar t ific ia lly-infes ted soil o n incidence ofpr e -emerg enc e damping-off caused by Rh izoctonia so/ani

Do sage ca usingTreatment Optimum dosage phytotoxicity

g / kg soil) g/kg so ill

Dithane M-4 5 0 . 1 0.5Cup ravit 0 . 15 1Vitavax 0 .1 0 .4Vi t a vax + Dithan e 0 .3 0 .5PCN B** 0. 15 0 .5

Control 0 0

Tuckey s test .05

Average of two experiments each o f four replications.Causes de layed ge rmination and leaf burn of primary lea v es.

16

Average 0 /ogerminationat 28 days *

83 a5 1 b8 2 a78 a43 b

47 b

13 .1

Av erage we t wtat 28 da y s

g m) *

14 . 5 a5.5 cd

12 .5 ab10 .9 b

3.8 d

7 .3 c

3.5


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methyl bromid e fumi gat ion belowa plastic tar p Figur e II I -1) orDazomet a methylisothiocyanatereleasing compound) fo ll owed byirrigation and se a lin g of t h e upperso il-l ayer. Th e res ul t was lowin ciden ce of p ink rot in the ger m

plasm co ll ect ion. Exper im ents tooptimize the do se of th e fumigant sDazomet and Ridomil Tab le IIl-3 ,show ed that rate s of 200 to 300 kgDazomet and 20 kg Ridomil per hagave b est control.

In addition to chemical controlmethods, a gradual improvement ofsoil structure by incorporation oforganic material from rotatio n cro psc orn , wheat an d p eas helped

reduce diseas e in c id ence .In control of smu t, Angiosorus

lan i one fumi gant application of

Figure 1. P a rt of the field at Huancayobeing fumigated with methyl bromidefor cont rol of pink rot Phytophthoraerythroseptica). Pla stic sheets whitestrips in photo) alternately cove r soilinjected with the f umig a nt . A week laterthe plastic is r em ov ed a nd t h e alternate

17

Dazom e t or methyl bromide sign ificantly reducted this disease andincreas ed y ield during two cropp ingseaso ns. PCNB, Alli san and Tecto-60applied to the crop we re as effectivein incr ea s in g yield as fumi ga nts.PCNB r edu ce d disease incid e nce aswell as the fum igants teste d.

Fungicide s did not significantlycontrol so u thern blight Sclerotiumrolfsii) in th e fie ld in San R amon.Supporting evid e nc e was ob tainedin greenhous e t es t s. Preliminaryres ult s o n effects of crop rotationon in c id e n ce of so uthern bl ight indicat e th at the number of sclero t ia

in so il is hi gh wh en potato es followpotato es but is reduced w h en beansfollow potatoe s and is virtually zerowhen ri ce or corn follow pota toes .

strips ar e fumi gated. As a result of thistreatm e nt , followed by use of a systemicf un gicid e at planting, the germ plasmcollection and most of the breedi ng stockwer e fo r th e f ir st t ime virtually fre. e ofpink rot.


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Durin g th e curr en t pl an t in g seaso n in Sa n R am on , h izoc tonia so -la ni w a s im po r ta n t in th e soil -bo rn eco mpl ex . Of vario us f umi gan ts andfungi cid es tes t ed under la b orato rycondi t io ns Benl ate and Vit avax were

t he most p ote nt in h ib itors of t h isfun gus Tab le III- 4). Res ul ts alsosu ggest th at und er t he war m co ndit ion s of Sa n Ram o n , PCN B ma ybe less e ff ect ive than Be nl ate an dV it avax .

T abl e 3 Ef fect of D a zom et a n d Rid o mil o n pink rot Phytoph thora erythrosep tica)in ci d e n ce .

Chemical applied (kg/ha) Yield (kg / plot) a t ha r ves t

Dazomet Ridomil 5g Infe cted tu be rs Healthy tu b e rs of over 60 g

0 0 3.9 e 17 .0 e0 20 2.2abede 26 .2 d0 30 0.9 abed 31 .5 b de0 40 0 .5ab 32.8 b de

200 0 2.4 bede 28 .8 de200 20 0 . a 37.3 ab200 30 0.7 abe 36.3 ab200 40 0 .5ab 35 .6 abe300 0 2 .7 cde 26 .2 d300 20 0 .3 a 42.1 a300 30 0 .2 a 36 .5 ab300 40 0 .2a 39 .8 a400 0 2.8 a cde 3 2 .9 b de400 20 0 .8 abed 3 8 .5 ab400 30 0 .2a 37 .9 ab400 40 0 .2a 36 .2 abc

Pota to var iety Ticahuasi w as p la nt ed in a facto ri al 4 x 4 design in ra nd o m iz ed c om plete b locks.Tu be rs we re d isinfecte d wi th so d ium hypoc h lo rite p r io r to planting. Plo t s of 3 r ows of 3 m at1 m sp ac ing a nd 10 hills per row. Dazo met (Basami d, 98 o gran u late, BAS F ) ap p lied 1 m on t hpr ior t o p lanting, disked in to so , irrigated, ke pt u nd er plast ic tarp durin g 2 weeks a nd lef tto ae r a te for anot her 2 weeks p r ior to plan t ing . Ridomi l 5g, ap p lied t o furro ws at p lan t ing .Con trol s were t reate d th e same as other in a ll respects excep t fo r p ro du ct t o be tes t ed . A lltreat ments re c eived F u r adan an d Te mi k a t t ime of pl an ti ng at a ra t e of 60 and 25 kg/ ha, res pecti ve ly .

CONTRACT RESEARCH

D urin g the past 10 yea r s considerab le progress h as been made atCo rn ell University in in corporati n gresist ance to Ph y to p hthora inf s t nsfro m So l anum tuberosum spp. andi -gena into Corne ll b ree d in g populatio n s In plant pat h ology contractresea rch 277 adva n ced br eeding linesand h eat to lerant clon es were testedfo r ge ner al resistance to P infestans.Clon es N 503- 1 58, and NY 59 hadhig h l eve ls of fo liar r esista nce tolate blight. In coopera ti ve fie ld tests

18

of Corne ll mate rial in Co lo rado,clo nes NY 59, NY 6 1 Rosa) andNY 63 showed hi gh lev e ls of ear lybligh t Altern ia solani) resis t ance .NY 59 and NY 63 also ha d h ighleve ls of res istan ce to Verticilliumspp .

In other potato disease researc hat Cornell, enzy m e -linked im mun osor ben t EL ISA ) assays are use droutinely to de tect potato lea fr ollvirus and viruses Y, S and M Pota t oleaf tissue has been u sed fro m bot hfie ld and gree n ho use grow n p lantsan d from p lan ts grown in vitro.


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Table 111 4. Laboratory screening of selected fungicides against soil borne fungi

0 /o Control of Fungus {after 10 days)

Fungus 18c 28 CR so ani Fungicide and concentration Mycelium Sclerotia Mycelium Sclerotia

Beniat e 100 g/ml 100 100 100 100100 g/ml 100 100 100 100

Vitavax 100 g/ml 100 100 100 100200 100 100 100 100

Cupravit 100 28 NA 6 6200 43 NA 11 53

Basamid 100 38 NA 28 62200 52 NA 44 N A

PCNB 100 83 NA 7 NA

200 50 NA 47 NADithane 100 27 NA 80 70

200 88 NA 82 40

Poly ram 100 80 NA 74 65200 78 NA 73 9

Ant Racol 100 82 NA 80 56200 85 NA 88 57

Tecto 100 NA NA NA NA200 NA NA N A NA

* A sclerotial species of Rhizoctonia so aniBased on sclerotial counts in treated plates and control after 15 days.

0 No. of Sclerotia in control test - No. o f Sclerotia in treatmentfo Control for Sclerotia = x 100No. of Sclerotia in control

19


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hrust V

Control of Important Bacterial Diseases

Selection for bacterial wilt resistance is now made with two racesof Pseudomonas solanacearum before late blight testing. Resistance sources include Solanumsparsipilum and S. chacoense as wellas S. phureja. Progenies from thelatter are now performing well inBrazil, Uruguay, Colombia, K enya,

and Sri Lanka . Resistant survivorsfrom over 54,000 seedlings wereidentified with some of the advanceselections yielding 1 kg or moreper plant . Wilt resistance in highlyselected clones has survived overthree seasons under severe field

Seedling screening and field evaluation of tuber families developed forresistance to bacterial wilt receivedmajor emphasis. Screening includedtuber families for export and forfield testing in Peru. In both casesseedlings were separately inoculatedwith strains of races 1 and 3 ofPseudomonas solanacearum.

From a total of 19,840 seedlings73 resistant clones were selected

infection at two locations in Peru .Survival of P solanacearum in

soil is largely dependent upon presence of susceptible plant roots asroots of non-hosts do not supportbacterial multiplication. Infectionof potato (CIP-Lima) was mos tsevere in infested soil with rootsof susceptible Heliconia spp. andS nigrum.Of the tuber soft rot ba cte ria,Erwinia chrysan the m is generallymore invasive than E. carotovorasubsp. carotovora which is onlyslightly more invasive than E csubsp. atroseptica in potato tubers .

(Table IV-1). Half were distributed to CIP Regions and half wereevaluated for agronomic performance at CIP -Lima. Most clones arealso being field tested for bacterialwilt resistance in Peru and in othercountries. The source of resistanceto bacterial wilt in all these clonescontinues to be S. phureja althoughthe final incorporation of resistancegenes from some diploid clone s such

Table IV 1. Seedling screening for development of potato clones with bacte rial wiltresistance for export (19801981).

NO families NO seedlings L BT. survivors NO cuttings NO resistant clones

40 ( 80/ 81) 5,840 607 47330 ( 81) 10,000 1,614 1,23412 ('811 4,000 458 70

9 ('81 / 82) 1,785

Total 91 21,625

As of mid '81 seedlings were not screened in itially for resistance to late blight.Data unavailab le.

2

382312

73


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as S. sparsipilum and S. chacoenseis underway. The resistant clone spresently available were derivedfrom crosses among advanced resistant clones as well as crosse s withclones adapted to tropical conditions. Information on resistance andagronomic behavior indicates thatsome of these clon es are promisingin Brazil, Uruguay, Colombia, Kenyaand Sri Lanka.

In other research institutionsev aluated a total of 23 ,948 seedlingsto select outstanding clones for distribution to CIP Regions. Of 11,000evaluated during two field tests 153remained resistant. Clones are nowno longer screened initially for resistance to late blight , because largenumbers of potentially bacterial wiltresistant seedlings were previouslyeliminated.

Yield potential trials were plantednear San Ramon, one in the infestedplot at 1,050 m elevation duringthe rainy season, and the other ina wilt-free plot at 850 m duringthe drier season supplementaryirrigation). Of 126 clones plantedin infested plots 13 were withoutfoliar wilt symptoms or tuber infection. After three seasons of consecutive evaluation 26 clones hadup to 10 percent wilted plants; nineclones were without tuber infectionTable IV-2). Of 68 clones in the

wilt-free plots 21 yielded more than500 g/plant.

At Umari 2,400 m) out of 70clones planted in t he wilt-infestedplot 15 clones did not show foiiarwilt or tuber infecti on . After threeseasons of consecutive planting atUmari 11 clones have shown up to10 percent wilted plants with notuber infection Table IV-2).

A 57-clone trial in an infectedfield in Yurimaguas at 180 m inthe Amazon basin had four cloneswithout wilt symptoms or tuber in-

Tab le IV -2 . Clones show ing from up to10 percent wilted plants and no tuber infect ion by P so anacearum after 3 yearsof consecutive field evaluation at Umari2 ,400 m and San Ramon 1,050 m).

22

San Ramon

BR 62 5Cruza 148

BR 63 15

MB 5 39

MB6 1

MB 14 :8MB 34 22

MS36 19

MS82 60

Umari

BR 62 5

Cruza 148BR 63 76

MB 6 42

MB 14 1MB 42 MB 56 1MB56 11

MB 60 32

MS 35 4PSP 30 10

fection. Yields were low because ofheat stress.

At La Molina at 240 m in coastaldesert 110 clones were plantedfor multiplication and agronomicevaluation, including the first fieldevaluation of 27 clone s developedfor export in 1980. Twenty-twoclones yielded above 1 kg/plant andsix over 1.5 kg / plant.

Some common jungl e floor weedsat Yurimaguas were tested for theirinfluence on survival of P solanacea-rum in soil, using susceptible potatoas the indicator of survival. Theplants tested were two Heliconiaspp. var. Amarilla and var. Cresta de

Gallo, and two Solanaceae, Solanumtopiro cocona) and Suikawito unidentified). S. nigrum a commonfield weed in Yurimaguas, was alsotested. Plants were inoculated bysoil infestation with Yurimaguas potato isolates 077, 141, 108and142,Tea Gardens 015 and a Huancayo042 isolate. To each pot wereadded 40 ml of 2 x 1 0 8 bacteria/ml.

Results are shown in Table IV-3 andillustrated in Fig. IV-1. S. nigrumwas infected by all Yurimaguasisolates, and two of the isolates infected 10 percent of Heliconia sp.


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Figure IV-1. Determination of persistenceof P solanacearum in soil by planting apotato P) next to the test plant the topof which has been cut CT) at pot-brimlevel, 52 days after soil infestation. Left,whole plant; center CT+ P), uninoculated

var. Amarilla. Persistance of isolatesdetermined by infection of susceptible potatoes grown n the samepots for a further 60 days, occurredn varying degrees as influenced by

the initial weed host. Heliconias and

23

cut check and right, soil infested with isolate 042. n this example the emergedpotato is wilting after 20 days, demonstrating greater persistance with Cocona,than with Suikawito.

solanaceous pl ants appear to play arole in maintaining P solanacearumin jungle soil.

A study began to determine capabilities of strains of P solanacea-ru of tropical origin to produce


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Table IV-3. Perc entage of plants infected Inf.) with isolates of Pseudomonas so ana-ce rum 52 days after soi l inf estation and persista nce of the bac terium Per.) in the soild etermined b y infectio n of su sceptible potatoes grown in the sa m e pots for an ad d itional 6 0 da ys.

T est Plants*Isolates

and t heir S nigrum Cocona Suikawito Cresta Am a ri Ila Checkbiov ar lInf . Per . Inf . Pe r. Inf. Per . In f . Per . Inf . Per . Per .

0 15 I) 0 0 80 0 0 0 50 0 20 0042 I) 100 0 60 0 40 0 0 0 20 0077 I) 30 0 10 0 0 20 0 50 10 50 0141 I) 30 0 10 0 0 20 0 100 10 40 0108 Ill 30 0 60 0 0 0 5 0 0 40 0142 II) 20 0 80 0 0 0 67 0 60 0A ver age 35 0 80 0 13 0 52 3 38 0

Based on 10 plants each , except for Cresta in which there we re three .

bacte rio ci n. Bacteriocins are nonreplicating, prot ei n-contain in g bacter ic id a l su bstances, produced bycerta in st rain s of bacter ia and activeagainst ot her strains of t he samespecies. In a preliminary test of22 stra in s o nl y four prod u ced asignifica n t amo un t of bacter iocinthat inh ib ited t h e growth of theother strai ns. A no n-virulent mutantof one of these stra ins will be usedin a contro l study of bactelial wil tin Ymimaguas.

Erwinia Diseases

Screening tubers of se lect edclones for resistance to Erwinia chr y-santhemi a soft rot organism, contin ued usin g t he Infec t ivity Titration In oc u lat ion m et h od . A totalof 403 clones were eva luated: twoof 120 tropically a dapted clones,two of 1 59 clones with frost and lateblight resista n ce, and seve n of 124diploid clones were mod erate ly wi ltresistant Tab le IV-4). Clone s ratedas resistant in 1980 /1981 will beplanted for mul t ip lication, retestedfor tub er resis ta n ce to E chry -santhemi Ecy) and for th e fi rst tim ealso to E carotouora su bsp. caroto

24

uora Ecc) and subsp. atrosepticaEca).

The pat h oge n ic ity of the t hr eeErwinias was tested on tubers ofcu ltivars Revo lu cion and Yungaywith two stra ins of each Erwinia att hr ee inoculum co n centratio ns. AsFigure IV-2 shows, Ecy strains weresign ificantly more pat h ogenic thanEcc or Eca strains.

CO NT RAC T RESEAR CH

Research a t the Univ e rsity ofWisco nsin confirms the red u ctionin de ca y by Erwinia caratouora following vac uum infiltration wit h di fferent co nc en t rations of calci umso lu tions into potato t u bers. Analyses of perider m a n d cortex tiss u e byatomic e mis sion spectropho tome-try indi ca ted that bacterial decayde creased from 48.9 percent to2.6 p e rcent when the concentrat ionof calciu m in creased from 0.1 percent to 0.5 1 percent in the peridermand from 0.02 per ce nt to 0.08 percent in the cortex . Sim ilar an a lyseswer e m ade of periderm samp les fr omtu hers h arvested fr o m a fie ld st ud yinvo lving differ en t leve ls of calc ium


38/144

and ni t rogen sources. Calci um concentrations and soft rot potentialin dices were also inversely corre latedin this study. Calcium nitrate wasthe preferred source of calcium.The specific role of calcium withrespect to the inverse correlation

between leve ls in periderm tissuean d the ability of soft rot bacteriato decay potato tubers has not beendetermined.

Conflicting reports exist regardingth e capacity of Pseudomonas sola-nacearum to su rvive in the soil . CIPco n tract researchers at the University of Wisconsin have conc ludedthat the bacterium is not capableof long-term survival in the soil asobserved under growth room andgreenho u se conditions. Using ahi ghl y selective medium wh ich theydeveloped, quantitative determinations of P solanacearum in soil,rh izosphere and roots were possible.

The fi n ding t h at the bacte r ium ca nin fect and multiply in the roots ofno n-host, symptomless p lan ts mayexplain the controversial su rvival ofthe bacterium in so il and the failureof many rotation programs.

In studies of the binding of

P solanacearum to host cell walls,labelled strains of the bacteriumwere interacted with suspe nsion ofcultured cells from tobacco andpotato. Avirulent strains of P so la-nacearum were found to bind morerapidly and strongly to plant ce llwa lls than viru lent strai n s . T hi sat tachment has been considered asan initial recognition step leadingto the hypersensitive response intobacco.

In itial attempts to induce resistance in potato to P solanacearumby prior inoculation with avirulent,bacteriocin-producing strains havegiven promising results.

T b le IV-4. Moderate ly resistant c lones to rwinia chrvsanthemi out of 159 d eve loped

for resistance to frost and late b light F-L), 120se

lected for lowland t rop ics

LT ) and124 diploid clones DC).

Clon e

373 0 59.9379483.3377 823 .3

3 77 89 1 .11 xNeo tb r. Bulk lcus 1 22OC H 858770 2 1 99OCH 1084 0OCH 560470 283270201 4H-32 C heckl

Di ameter of rot ted area mm l *a t di ffere nt inocu lum con ce n trat io ns

4.4 x 106 8.8 x 10s 1.76 x 10 s

6 .2 3.4 0.06.8 4.75 0.06.3 3.6 2.0

6.6 5.3 2.34.5 3. 0 0. 06.4 5.6 1 .06.4 5.0 0 .05.6 3.5 o o6.2 5.75 0.06.0 2.6 0.06.2 4. 0 0.0

11 . 1 13.3 14.0

Prog ra m

F-LF-LLT

LTDCDCDCDCDCDCDC

Diam e ter of rotted are a mml 72 h after inj ecting 0.01 ml of inoculum 5 mm d ee p in the tuber .lnoculum concentration expressed in bacteria / ml.

25


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Agronomists explain results of bacterial wilt infection to wom n farming in Rwanda

26


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hrust

Control of Important Virus Diseases

Resistance to potato leafroll virusPLRV) was identified by exposing

more than 10,000 TPS as seedlingsto PLRV-carrying aphids, transplanting resistant survivors to thefield, growing them to large plantsin PLRV expos ure and evaluatingfor vine and tuber type, and yieldwithin 8 months. Resistance isnow present in good quality, highyielding clone survivors of heavyand successive PLRV exposures.Extreme resistance exists in selections of Solanum etuberosum xS pinnatisectum which will not

Potato Leafroll Virus PLRV)

Extreme resistance, not acceptingPLR V by either graft or aphidMyzus persicae) inoculation, exists

in 14 colc hicine-doubled seedlingsegregates from c ro sses of Solanumetuberosum x S. pinnatisectum4X-EP) produced in the Nether

lands. Moderate resistance, becoming inf ected by graft inoculationbut not by aphid inoculation, andsusceptible, becoming infected byboth methods, was a lso dete cted.Freedom from PLR V followingexposure was estab lish ed by ELISAsero lo gy and by grafting to Daturastramoni . The mode of inheritance of this resistance is beingst udi ed . Extremely resistan t 4X-EPseedlings can be crossed with the

TV5

hybrid, S. uerrucosum withS tuberosum cytoplasm).

Seedling Resistance Evaluation

During winter, 10,920 see dling sexposed for one week to PLRV-

27

accept PLR V by graft inoculation.PVY immunity is now positive

ly id entifi ed in parents by graftingand in more than 10,000 seedlingsby spray inoculation. Populationbreeding for PVY immunity inthree generations increased resistantsegregates from 43 percent to82 percent. Resistance to the potato spindle tuber viroid s in oneaccession of S. acaule. Sensitizedlatex or antiserum for virus detection in almost do ubl e the quantitiespreviously suppli ed was sent to 14developing co untrie s.

carryi ng M persicae were later trans

planted a nd moved outdoors forsymptom development and hardening. Visibly healthy survivors weretransplanted to the field during coolweather, May to September. Thisseason is best for obtaining goodpopulations of aphids, strong sy m ptoms of leafroll, and good tuberizati on. Scheduling one large annualevaluation test of 10,000 seedlingsFigure V -1) saves 9 to 10 month s

of screenhouse bench s pa ce and 8 to9 m o n ths in time required to reac hthe 5- to 10 -hill field evaluationfreeing screen h ouse space for cloneresistance evaluation in increasinglylarge numbers. PLRV see dling resistance in families is best evaluatedin the second generatio n.

PLRV Resi s tance in Clones

CIP-703266, one of three outsta ndin g 1980 clones, did not showvirus infection in 1981 e ld trialsFigure V-2). t was the second


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OLD SCHEDULE MONTHS NEW SCHEDULE

Seedlings TPS)

PLRV. lnoc.......'I

; t ty 7

u b e r s l

Dormancy--:::::l,....

1-Hill Plots

1elect Clonesro r m a n c y ~(5-10 Hill Plots)

Figure V-1. Modifications in methods forselecting PL RV resistant segregates .

highest yielding clone among 118producing more than 5 kg froma 5-hill plot in 97 days . ClonesCIP -701752 and CIP-703232 weresimilar in performance.

Relative PLRV Resistance

Relative resistance of 4 selectedclones to PLRV was determined withvarious densities of aphid populations Table V-1). Although allclones had been resistant to naturalfield infection, differences in le ve lsof resistance became apparent withincreased inoculum pressure.

Thirty-two isolates from differentsource s maintained in Physalis flori-dana were compared by ELISA se-rology using two antiserum sources,a Swiss isolate from cv. Claustarand a Scottish isolate PLRV-G. AllPLRV isolates reacted similarly with

0

234567

8

9

Seedlings TPSJ

PLRV - lnoc .......Transf. Jiffy 7*

Outside.,_Symptomless

1-Hill PlotsJ

Select Clones

or" ancy

5-10 Hills

10111213 Total Time

Saved8 months)415

16

17

28

both antis era suggesting a serologicalrelationship. Two isolates originallyfrom wild spec ies in the Andeanregion caused mild symptoms inP floridana They had the lowest

Table V - 1. PLRV resistance in advancedCIP clones exposed to population den sitiesof PLRV carrying aphids .

CloneAphids per plant

5 25 50

4.2 0 5 0 /5 1/515 .12 0/5 3/5 3/523.2 0/5 3/5 3/511.4 2/5 2/5 4/5Renacimiento{susceptible control) 5/5 5/5 5/5

Spro ut s at the 2-3 leaf stage exposed toPLRV carrying yzus persicae in sc reenhouses, La Molina , 1981. PLRV was detect ed by visual symptoms confirmed byELISA se ro logy.Numerator = plants infected . Denominat o r = plants exp6sed to in f ect ion.


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Figure V-2. After 2 years of PLRVfield expos ure, clone CIP-703266 right)showed no PLRV and good vigor. A susceptible clone l eft) with PLRV sy mptom sand poor growth.

ELISA values suggesting a serological difference to European strains or

a peculiar characteristic to developonly low concentrations of virus ininfected plants.

PVY Immunity in Seedlings

Before clones are used as parentsthey are thoroughly tested for immunity to PVY . Immunity toPVY was present in five clones ofS tuberosum ssp. andigena and in

Table V-2 . Recurre nt se lectio n for increasing frequency of PVY immun e t e tr aploid genotypes.

Cross*

S x S

x S

R 1 x R 1R

2 x R 2

Generationof selection

Numberplants

118617524700

R = resist a nt ; S = suscept ibl e .Tu key s w 0. 05 ) : 9.32 .

0/o resistantgenotypes

0436082

29

S stoloniferum PVY immunity inclones PG 295 and BL 61.74.167was constant with seven other distinct Peruvian PVY isolates.

incr easing frequency of resistant genotyp es in three generationsof crossing was demonstrated ina populat ion bree d ing approachTable V-2) by inoculating seedling

populations twice in selecting forPVY immunity . Resistant genotypes incre ased in each generationat statistically significant levels.

Resistance to Potato Virus Y PVY)

Seedlings were spray inoculatedwith p y y o alone or simultaneously

with PVX and later symptomlessplants wecfe again inoculated byhand. From a total of 9,457 inoculated see dlings, 19 p erce n t werepotentially immune to PVY and25 percent to both PVY + PVX. Ofthese, 47 and 28 plants, respectively,are haploid (2n = 2x = 24).

Progeni es first scree ned for frostor lat e blight re sistanc e we re mechanically ino culated with PVY 0 .From 347 frost resistant seedlings ,59 percent survived PVY selectionand from 53 3 lat e blight resista n tseed lings 7 3 percent were selected.


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PVY Strains in South America

Potato virus Y (PVY) strains infarmers fields of the Andean regio nexist as: Ecuador - PVY 0 andp y y c ; Peru (coast) - PVY 0 ; Pe ru(sierra) - pyyN; Central (Chile) -p y y o and PVYN ; South (Chil e) -PVY 0 ; and Argentina - pyyN. InEcuador PVYN and in ArgentinaPVY 0 were no t detected in commer cia l potato fie ld s .

All isolates from Ecuador (PVY 0or p y y c ) and all from Chile exceptone (PVY 0 or pyyN) inducednecrot ic local le sio n s (NLL) ondetac hed leave s of clone A6. On

A6 plants they indu ced first N LLand later sy ste mi c n ec rosis andmos aic. One isolate from Chile didnot induce NLL on detached leavesbut caused mo sa ic on inoculat e dplants. These deviant strains havebeen detected previously in Peruand Europe.

Selected PVY is o lates from theAndean region were mechanicallyinoculated to commonly grownAnd ea n cultivars. More virulen tPVY isolates were obtained inhigher frequency from Argentinaand Chile than from Peru. PVY 0and p y y c from Ecuador were theleast virulent.

Plants or detac hed le ave s of twoclones of S. c hacoens e TEI andTE 2 used for PVY detection inPoland and in the Soviet Union,were mechanically inoculated with39 isolates from Ecuador, Pe ru,Chile, and Argentina. PinpointNLL were induc e d by most PVY 0and pyyN isol ates. No PVY isolatebeca me systemic on TE. GenerallyTEI and TE 2 were not as useful asA6 except that TE diff e rentiat esEcuadorian isolat es of PVY 0 andp y y c and certain other deviantpotyvirus strains. Some isolates induced N LL 1 to 1.5 mm in diam ete rth at killed non-d etac h e d le aves.

30

A potyvirus, code named UF,do es not produc e lo cal lesions oninoculated leaves of clone A6 bu tbecomes systemic producing veinnecros is. t produces local lesionsin S d emis sum Y and S. chacoense

s do other PVY strains. I t was aphid

transmitted from i co tiana occiden -talis. Cultivars Kenn e bec, Radosa,and Wauseon develop partial veinnec rosi s and lower leaf chlorosiswith green areas. Clavela, MariaTropical and Arran Pilot react withsystemic chlorotic spots, mosaic,and deformation of leaf margins.The virus did not rea ct serologically against anti sera to PVY 0 andPVYN. Howe ver, i t did give a positive react ion against an antiserumto an atypical stra in of c(Gl aa dblaaje) from th e Netherlands.UF and p y y c Glaadblaaje behavesimilarly when grafted to potatoesand on certain indicator hosts. UFis appare ntly an unusual strain of

c . Because UF cannot be detected by antisera to the commons trains of PVY, an antiserum specificfor UF has been prepared for distribution.

Potato Spind le T uber V iroi d

Polya c rylamide gel electrophoresis(PAGE) as now modified allows 50sa mple s per day with high se nsitivitywhen test plants are grown at 25C

or higher. The PAGE and thetomato test under continuous lightare equally sensitive; but the latteris not suited for large scale testing.Germ plasm clones maintained inour in vitro collect ion, free of PSTVby P-t\GE tests, were also tested bya nuclei c acid hybridization (cDNA)technic. All CIP samples were freefrom PSTV confirming the high

sensitivity of PAGE test and thatCIP materials for export are indeedfree of PSTV.

Diffi culties exist in producingan antiserum to a protein induced


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or enhanced by PSTV in infectedplants. Isolation and characterization of the antigen in pure formhave not bee n successful.

Resistance to PSTV

Several resistant clones fromS acaule accession, OCH 11603,were tested. They resisted infectionunder co nditions permitting infection of susceptible plants. Other accessions of S acaule and wi ld speciesdid not carry simi lar resista nc e .

Antiserum for Virus De t ectio n

L atex sensitized to PVY, PVX,and PVS was distributed in largerlots in 1981 , total amounts moreth an doubled Table V-3). Approximately the same nu mber of countries received shipments. Brazil,Japan and Banglad es h recei ved undiluted antisera, eno ugh for 8,000,6,000, and 7 ,000 tests for PVX,PVY and PVS, respectiv ely.

Equally suitable for the latextests are glass ring slides, Baerman

slid es, perspex plates and p la sticpetri plates. However, with plasticpetr i plates as currently used atCIP ) reactions are clearer and easie rto read, p lates are more suitab le forlarge scale testing , and can be reusedseveral times.

Potato Yellow Vein Disease PYVV)

PYVV diseased plants free ofPLR V indic a te that the two virusesare in dependan of each other. Grafttransmission was successful o nlyto potato; mechanical tran smission failed. A filamentous virus,c. 650 nm long, was isolat ed frominfected plants of

cv. Sacoby

enzy matic Driselase) tissu e d igestion befor e differential centrifugation Figure V -3 . Unusual crys tallike structures seem to be int ernal lyassociated with the cloropl asts ofinfe cte d plants.

Potato Deforming Mosaic

This disease was present in cv.Serrana. Potato was the on ly sus -

Table V-3. Sensitized lat ex distributed to different countries or used at CIP n 1981.

Sensitized La te x forCountry

PVX PVY PVS APLV . \PMV

Argentina 5 5 5Bangl ades h 62 62 62

Bolivi a 6 6Chile 40 40 40Ecua dor 6 6 6 6 6India 21 21 21 6Korea 8 8 8Kenya 6 6 6Mexico 7 7 7Netherlands 3 3 3 3 3Pakista n 8 8 8Peru 10 10 10Philippines 62 62 62 10 10Turkey 10 3 3

254 247 241 25 19CIP 476 335 154 257 257

Total 730 582 395 282 276

. Amounts in ml (1 ml = 80 tes ts .31


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Figure V-3. Particles purified from potato with yel low vein symptoms. Crossbanding s visible in all virus part icles.Stained in 1 percent uranyl acetatep 4 0

ceptible host by graft inoculationfrom an extensive host range attempted. The virus could not bepurified following Dris elase tissuedigestion. Pectinase-cellulase beforedifferential centrifugation yieldedrelatively low numbers of isometricparticles approximate ly 28 nmdiameter with hexagonal outlines.Further work will involve purification and production of an antiserum. The virus was not transmitted by aphids in either a persistentor non-persistent manner.

32

P78 Disease

Defined spread ing chloroticspots develop on inoculated leavesof Samsum tobacco. Virus isolationdirectly from potato leaves andvirus purification by conventiona lmethods failed. No bacteria norfungi were detected in diseasedplants. In infected sap of cloneMaria Tropical adjusted to pH 4.5elongated rod-shaped particles ofundetermined length fo rm ed extensive masses . These are being studiedfurther.

New Tobacco Streak Virus

A virus iso late from potato codedSBlO causing a mild mosaic withhost range and properties resembling


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tobacco streak virus (TSV) is considered a new strain because ofserological and comparative hostrange differences. t is serologicallymore closely related to TSV-B fromsoybeans in Brazil than to the typestrain TSV-HF. When inoculated

onto potatoes SBlO generally causesa mild mosaic or symptomless infection. Progeny tubers from infectedmother plants were, except in twoclones, virus-free. The virus seemsnot to be a threat to potato production. The virus is readily transmitted through seeds of Nican-dra physalodes and Chenopodiumquinoa Enzyme-linked immunosorbent assay (ELISA) can be usedto detect the virus at a concentration of 1 ng/ml or in infectedC quinoa sap diluted 10 - 0

air Sprout

Hair sprout has been of relativelyhigh frequency in tuber sproutsgrown from either tubers of fromTPS in La Molina over the past3 years. Sprouts from germinating

tubers are thin and usually produceweak plants late in emergence.Plants seldom reach normal size,resemble those with mycoplasmadisease, purple top wilt, and yieldsare markedly reduced. Stem apicesare frequently but not alwaysseverely rolled somewhat chloroticor pink and aerial tubers in leafaxils are frequent. Plants wilt anddie prematurely. Repeated attemptsto observe

Documents

CIP Annual Report 1981