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SOYBEAN BREEDING IN BRAZILRust Resistance
José Francisco Ferraz de ToledoEmbrapa Soybean
MAIN CHALENGES
Large country - long distances Ever decreasing governmental fundsIncreased competition - private companies Private sector partnershipsKeep market shareNematode resistanceRust resistance / tolerance
EMBRAPA’s Institutional Arrangements for Soybean Breeding
SOUTHERN BRAZIL - 1Partnership – Embrapa and
Meridional Foundation
North
Northeast
Central
Southeast
South
CENTRAL BRAZILPartnership – Embrapa,
Agenciarural and CTPA
NORTHEASTERNBRAZIL
Partnership – Embrapaand FAPCEN
SOUTHEASTERNBRAZIL
Partnership – Embrapa, Epamig and Triangle Foundation
BrazilianRegions
SOUTHERN BRAZIL - 2Partnership – Embrapa and Pro-Seeds
Foundation
PERIODArea
103 haAreaIndex
Production103 Ton
Prodctvkg/ha
21,528.5 2,033
2,324
2,600
28,679.3
49,141.6
100.0
116.5
178.5
ProdIndex
ProdctvIndex
100.0 100.0
114.3
127.9
133.2
228.3
1991- 1995 10,589.5
1996 - 2000 12,340.5
2001 - 2006 18,900.6
•Early and Medium maturity groups are sowed in over 90% of the Parana State soybeanarea
Soybean yield genetic gain in Brazil
Genetic gain (%) Parana* State Mato Grosso State Mean
Maturity group E M E M L All
1981- 85 1.8 1.3 - - - 1.55
1985 - 90 0.89 0.38 - - - 0.64
1995 - 2000 - - 1.4 1.7 1.5 1.55
Annual mean 1.35 0.84 1.4 1.8 1.5 1.38
Important aspects in a breeding program for disease resistance
Economic impact (present and future)Incidence in time and space (or probability of occurrence)Pathogen variability: races and reproduction, dispersal and survival capacitySources of resistanceInheritance of resistanceEvaluation and selection methods
Soybean breeding for rust resistance
Rust is economic important and aggressive disease
Availability of resistance sources:o Identification of new resistant genotypes
o Major genes - identification of new majorresistance genes
o Minor genes
Major genes: inheritance, allele testing, molecular markers, backcrosses, winter season, etc. The idea is to incorporate ASAP these genes into the adapted Brazilian germplasm
Minor genes: quantitative trait with a relatively high genetic complexity. In this case, the program develops hundreds of segregating populations every year and grow the populations under disease pressure using natural selection
Major and minor genes together, trying to obtain desirable genotypes
Strategies to develop soybean cultivarsresistant / tolerant to rust
There are major genes already identified different from Rpp1 to Rpp4Those genes are being transferred into the Brazilian genetic germplasm through single crosses and backcrossesMolecular markers are being developed and may help stacking resistance genes
Soybean rust – major genes
Asian rust resistance – Major genes
Rpp1 - PI 200492, Tainung 3, Tainung 4, L85-2378Rpp2 - PI 230970, L86-1752, PI 197182, PI 230971,
PI 417125Rpp3 - PI 462312Rpp4 - PI 459025, L87-0482, Rpp5,6,… - Abura, PI 200487, Shiranui, PI 416819,
PI 417503, PI 416810, PI 417115, PI 417421,PI 423966, GC84058-21- 4
Major gene resistance
TAN RB
There are several different possibilities to consider:
Minor genes per se conferring resistance / tolerance Genes delaying disease developmentMinor genes with complementary effects to major genes, sometimes called background effect
Soybean rust – minor genes
Narrow sense heritabilities of rust severity investigated on F3 family means from crosses between genotypes carrying minor genes
hr2 = 0.42 to 0.74, therefore, moderate to high
These heritability values suggest selection is likely to result in genetic progress
First results from breeding forquantitative resistance
Early soybean genotypes evaluation and selection for Asian rust resistance does not ensure resistant adult plantsQuantitative genes expressing additive gene action for resistance to Asian rust are dispersed among soybean cultivarsSelection for Asian rust resistance based on F3 or later family means is likely to result in satisfactory genetic progress
First results from breeding forquantitative resistance
ns and ** indicate non-significance and significance at the 1% level of probability, respectively.
18.7015.111.45CV%
3.4213.888.01Mean
0.41ns4.40ns0.013ns108Exp. Error
0.47ns8.24**0.012ns34G x S
0.58ns5.76ns0.005ns2Plant stage (S)
2.32**14.03**0.012ns17Genotype (G)
SevLPIPdfSource ofVariation
Table 1. Mean squares from an analysis of variance for infectionincubation period (IP), latent period (LP) and severity (Sev) in genotypes inoculated with Phakopsora pachyrhizi in three sowing dates.
a52.67ab4.44a8.00BRS 133
c31.67abc3.56a8.00PI 562312
b42.67abc3.50a8.00BRS 231
b43.00bcd3.11a8.00PI 200492
--cd3.00a8.00BRS 232
d23.67cd2.94a8.00BRS 258
d18.67cd2.94a8.00PI 459025
d18.67d2.39a8.00PI 230970
Spore germinationSeverityIPGenotype
Means of infection period, severity and spore germination (%)of Phakopsora pachyrhizi.
c12,33ab12,67c10,33a14,00BRS 255RR
bc12,89ab12,33bc12,33a14,00BRS 231
bc12,89ab14,00bc12,00a12,67PI 200492
bc13,11ab14,33bc11,00a14,00BRS 154
bc13,17ab14,50bc14,00a11,00BRS 258
bc13,33ab12,00bc14,00a14,00BRS 133
bc13,44ab14,00bc14,00a12,33BRS 184
abc14,00ab14,00bc14,00a14,00BRS 214
abc14,11ab14,33bc14,00a14,00BRS 245RR
abc14,67ab12,67bc14,00a17,33EMBRAPA 48
abc14,78ab14,00abc16,33a14,00BRS 137
abc14,89ab14,33abc16,33a14,00BRS 232ab16,61a18,00ab17,50a14,33PI 459025a16,67ab14,00a22,00a14,00PI 230970
MeanInocul at V3Inocul at V5Inocul at R1 Genotype
TABLE – Latent period means of Phakopsora pachyrhiziinfection for inoculation at three plant stages.
Cross: Embrapa 48 x BRS 154
2
12
9
5 5
6
2
1
0
2
4
6
8
10
12
14
0-5 5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45 45-50 50-55 55-60
Severity score interval (%)2004/05
Num
ber
of F
3fa
mili
es
BRS 231
BRS154
Embrapa 48
Rust severity progress 2005/06
1015202530354045505560657075
2nd Assessm 3rd Assessm 4th Assessm
BR01-18437
BRS 184
BRS 231
BRS 232
RB
TAN
Rust severity progress 2005/06
10
1622
2834
40
4652
5864
70
2nd Assessm 3rd Assessm 4th Assessm
BR01-18437PI 200487PI 230970PI 459025-AShiranui
RB
All new resistant sources are being studied in allele testing to identify new major loci (RB reaction)
Identification of new sources (both RB and TAN reaction) based on experimental and commercial field information from Embrapa´sPartners
Genetic inheritance studies
Soybean rust – ongoing activities
Resistant / tolerant population development
Keep large population (> 3,000 individuals)Late sowings (later than Nov 15)Inoculation and irrigationSusceptible borders of several maturity groupsAdapted populations: plant selection for progeny rows in breeding programNon-adapted populations: plant selection for further crossing
Strategies for cropping RB cultivars withone or more major genes for rust resistance
Strategy 1: no fungicide application = high risko IF resistance doesn’t break – OK with good yield potentialo IF disease establishes and resistance breaks – significant
losses
Strategy 2: one fungicide application = average risko IF resistance doesn’t break – OK with good yield potentialo IF resistance breaks – some loss
Strategy 3: two fungicide applications = low risko IF resistance doesn’t break – OK with good yield potentialo IF resistance breaks – small losso Gain? Stability in areas with inefficient control
PI 200487(Kinoshita)
Border rows
MTBR 95 08675 BRS Gralha
BRS Pirarara BRS Tiana
Rust resistance experiment – hill plots
Rust resistance experiment – hill plots
Thanks !
Equator
Tropic of Capricorn