Maize Diseases in Asia

Daniel Jeffers CIMMYT/China, Yunnan Academy of

Agricultural Sciences, Institute of Food Crops

Kunming, Yunnan, d.jeffers@cgiar.org

Outline

• The major diseases affecting maize in Asia

• Climate change and the possible effects on pathogen profiles and disease

incidence, especially in the tropical regions, concomitant with high

temperatures

• Progress through conventional breeding

• Possibilities to implement marker-assisted breeding for improving disease

resistance

• Precision phenotyping for disease response

• Conclusions and prospects

Background

• Approximately 52 million ha of maize in the Asian region with roughly 30

million of temperate maize in China

• The remaining 22 million ha is subtropical and tropical maize.

• Maize area in the region has increased by 13.2 % between 2006 and 2011

with 86% of the increase in area occurring in China with the displacement of

other crops including wheat, rice, and soybean (FAO Stat, USDA/FAS,

2011)

• Diseases cause roughly a 12% yield loss across the region, and to meet the

demand for maize seen across Asia, breeding for host resistance is a key

component of the germplasm improvement activities to reduce losses,

provide yield stability, and maintain grain quality.

Major diseases affecting maize in Asia

Mai

ze M

ega

envi

ronm

ents

Ban

ded

leaf

and

she

ath

blig

ht

Com

mon

rus

t

Dow

ny m

ildew

s

Gra

y le

af s

pot

May

dis

leaf

blig

ht

Pha

eosp

haer

ia le

af s

pot

Pol

ysor

a ru

st

SC

MV

/MD

MV

Tur

cicu

m le

af b

light

Ear

rot

s

Asp

erig

illus

ear

ros

Fus

ariu

m v

ertic

illio

ides

ear

and

sta

lk r

ot

Ste

noca

rpel

la e

ar r

ot (

Dip

loid

a)

Temperate 4.0 3.0 5.0 2.5 3.5 5.0 2.5 2.5 1.5 2.5 4.0 2.5 3.5

Highlands 4.0 2.0 5.0 3.5 5.0 3.0 5.0 4.5 1.5 1.8 4.8 1.0 5.0

ST/Upper

wet MA 2.5 1.5 4.0 3.0 5.0 3.0 5.0 3.5 1.5 2.0 4.0 1.0 4.5

ST/Lower

wet MA 2.0 1.5 1.5 2.0 2.0 3.0 2.5 3.0 1.5 2.0 3.5 1.5 3.0

ST/Dry

mid-

altitudes

3.5 3.0 2.0 4.0 3.0 4.0 2.5 2.0 4.0 2.5 2.5 1.5 3.0

Wet

lowlands 1.5 4.5 1.0 3.8 1.3 4.0 1.5 2.0 3.5 1.5 2.0 1.0 2.5

Dry

lowlands 3.5 5.0 2.0 5.0 1.8 5.0 1.5 2.0 4.8 2.0 2.0 1.0 3.5

†Classification based on a 1-5 scale (1 = economically very important; 5 = not economically important); Source: Mahuku, 2011

Systemic Downy Mildew Pathogens of Asia

Peronosclerospora spp.

1. Thai variant, sorghum downy mildew (P.

sorghi, proposed P . zeae)

2. Java downy mildew (P. maydis)

3. Philippine downy mildew (P. philippinensis)

4. Rajasthan downy mildew (P. heteropogoni)

5. Sorghum downy mildew (P. sorghi)

2 3

5

1

4

Downy Mildew focus for Asian regional activities due to

severe disease losses associated with infection.

Breeding for resistance to this group of

pathogens has been a major priority in

tropical and subtropical environments

Primary tropical foliar

diseases favored by

warmer temperatures

Primary

subtropical and

temperate foliar

diseases favored

by cooler

temperatures

maydis leaf blight

(Bipolaris maydis)

Turcicum leaf blight

(Exserohilum turcicum)

polysora rust

(Puccinia polysora)

Common rust

(Puccinia sorghi)

Gray leaf spot

(Cercospora zea-maydis)

Banded leaf and sheath blight

(Rhizoctonia solani AG1-IA ) predominant

Primarily tropical and subtropical disease favored by warm humid conditions

Major ear rots in

the Asian region

Fusarium verticillioides ear rot

Fusarium graminearum ear rot

Aspergillus flavus ear rot

Stenocarpella maydis ear rot

Favored by cooler

temperatures

Favored by warmer

temperatures

Important not only for direct losses, but

as well for the mycotoxins they produce

including aflatoxins, fumonisins,

deoxynivalenol, zearalenone, and

diplosporin that make the grain unfit and

potentially lethal for human or animal

consumption

Post flowering stalk rots (PFSR) most prevalent in the

region

Fusarium graminearum stalk rot (Gibberella)

Fusarium stalk rot (F. verticillioides syn F. moniliforme)

Stenocarpella maydis stalk rot (syn. Diplodia)

Macrophomina stalk rot (M. phaseolina)

Late wilt or Cephalosporium stalk rot (C. maydis)

Both Marcrophomina stalk rot and Fusarium stalk rot can be favored by high temperatures

SCMV/MDMV is found in tropical to temperate areas, while RBSDV is primarily

a problem of the temperate China and a related virus, MRDV in Iran

Rice Black-Streaked Dwarf Virus (RBSDV) Sugarcane Mosaic Virus. Maize Dwarf Mosaic Virus

(SCMV/MDMV)

Climate Change and Potential Change in Pathogen Profiles

•Based on climate change models we can expect more extreme weather events

in the future, and some areas including South Asia elevated temperatures.

•Maize production will be effected and as well the pathogens of predominance

can change based on the environmental conditions that favor their development.

•It is difficult to predict where the changes will occur for foliar diseases, but stress

related diseases including many of the ear rots and stalk rots can be expected to

have a significant impact on maize production under these conditions. Most

notable could be the severity of Fusarium ear rot and Aspergillus ear rot,

Fusarium stalk rot, and Macrophomina stalk rot.

•Linking improved agronomic practices including conservation agriculture,

together with breeding activities for heat and drought stress, and selection for

resistance to the stress related ear and stalk rots, would combine a more

favorable environment with important yield stability and grain quality traits.

Progress for Improved Disease Resistance Through Conventional Breeding

• Most disease resistance found in maize is quantitative resistance, and is

oligogenic to polygenic. Few sources of qualitative resistance have been

effectively used for maize.

• Losses to many of the key diseases in the Asian region have been reduced

significantly due the effective use of conventional breeding activities, though

a good understanding of the basis of resistance often is lacking.

• Population improvement activities over several cycles of selection, has

significantly improved performance of the germplasm both for agronomic

traits as well as quantitative resistance to maize diseases.

• Resistance to the foliar diseases including maydis and turcicum leaf blights,

gray leaf spot, polysora and common rust, and downy mildew are all

diseases effectively controlled through conventional breeding, where under

disease pressure the susceptible genotypes could be eliminated before

recombining the germplasm.

• The diseases where less progress has been achieved are banded leaf and

sheath blight, post flowering stalk rots, ear rots, RBSDV in Central China

and MRDV in Iran.

Example of selection for turcicum leaf blight resistance under artificial

inoculations for four subtropical populations, CIMMYT, Mexico.

Evaluation on a disease scale of 1-5, 1= 0% infection, 5= 100% infection.

P501C4 P42C9, P44C10 P45C10 QPM line recycling

S2 S7 S2 S7

TLB # Families Accum # Families Accum # Families Accum # Families Accum

(1-5) % % % %

1 4 0.8 1 2.9 1 0.2 0.0 0.0

1.5 194 37.9 11 35.3 15 3.0 16.0 16.7

2 210 78.0 12 70.6 124 26.0 40.0 58.3

2.5 92 95.6 5 85.3 198 62.7 32.0 91.7

3 16 98.7 5 100.0 124 85.7 6.0 97.9

3.5 7 100.0 0 . 55 95.9 2.0 100.0

4 0 . 0 . 21 99.8 0.0 .

4.5 0 . 0 . 0 99.8 0.0 .

5 0 . 0 1 100 0.0 .

total 523 34 539 96

mean 1.9 2.0 2.6 2.2

Example of selection for resistance to sorghum downy mildew under artificial

inoculations. CIMMYT, Farm Suwan Thailand.

Source: Vasal, 1999

% Downy mildew Material

0-10 11-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 91-100

Population 103 115 44 12 8 2 1 0 0 0 0

Population 147 97 33 15 4 1 1 0 0 0 0

Population 100 EVs 77 12 0 1 0 0 0 0 0 0

Population 145 EVs 237 23 3 1 0 0 0 0 0 0

Population 300 EVs 94 8 0 0 0 0 0 0 0 0

Population 345 EVs 155 6 0 0 0 0 0 0 0 0

MDR-DMR TLY 2007 324 11 4 0 0 0 0 0 0 0

Susceptible check 0 0 0 0 0 0 0 0 0 1

Progress in Understanding Disease Resistance Through the Use of

Molecular Breeding Techniques in the Asian Region

• The use of molecular markers to study the inheritance of resistance

to disease has been used for many of the major maize diseases

found in Asia, and has provided insight for the basis of quantitative

resistance (Prasanna et al. 2010).

• There has been successful tagging, validation and the transfer of

resistance QTLs to susceptible genotypes in several studies, but

even more studies have not been able to reach this goal of putting

molecular assisted selection into an effective breeding program.

Many reasons can account for this including a limited capacity to

identify small effect QTLs, large genotype x environment

interactions, and not being able to fine map the resistance QTLs.

Opportunities for improving the capacity to use molecular

tools to develop molecular marker assisted breeding

• The development of association mapping through linkage disequilibrium

analysis and the use of SNP markers, has greatly improved the power to

dissect the inheritance of quantitative traits (Yan et al. 2011). This has the

capacity to arrive at the gene level due to the coverage of the genome.

• Nested association mapping, with multiple parents included in crosses, and

a common parent in all crosses, has also improved the capacity to

understand the inheritance of complex disease traits (Kump et al. 2011).

• High throughput genotyping platforms are currently available and when

linked with precision phenotyping in the field, can provide the information

needed to effectively use MAS in a breeding program for complex traits.

Current genotyping costs are dropping and will make this a method more

adapted for use in breeding programs. CIMMYT activities will push for the

use of high throughput genotyping in rapid cycle genomic selection, to

develop robust germplasm with added stability for biotic and abiotic stress

traits, in high yielding germplasm.

• The use of doubled haploids to speed up the breeding process will be an

integral part of these changes.

Precision phenotyping

• Precision phenotyping is essential to take full advantage of the new

molecular tools for the identification of complex quantitative traits,

and will facilitate the effective use of genome wide selection in our

breeding activities.

• This includes the use of an appropriate field design and statistical

analysis, providing optimal environmental conditions for disease

development, having virulent pathogens, and the capacity to record

the most appropriate phenotypic traits associated with resistance at

the optimum time.

• CIMMYT recognizes precision phenotyping is a limitation frequently

for working with complex biotic and abiotic stress traits, and globally

there will be activities to improve phenotyping within CIMMYT and

by our research partners, through regional training courses.

Production of fungal cultures in

the lab for use in performing

artificial inoculations in the field.

Pathogen isolates should be

prescreened to use the most

virulent isolates in field

evaluations.

Fusarium graminearum ear rot

Aspergillus flavus ear rot F. verticillioides ear rot

Turcicum leaf blight

Maydis leaf blight

Sugarcane Mosaic Virus

Maize Dwarf Mosaic Virus Downy Mildew

Artificial inoculations to characterize resistance attributes of maize genotypes

Precision phenotyping

• New techniques including metabalomics, and proteonomcis may be

needed to work with some complex traits like ear rot resistance.

Seed based defense mechanisms implicated in resistance

to ear rots

Fusarium ear rot

Pericarp thickness

Cuticular waxes

Amylase inhibitor

Pathogenesis-related

proteins (PR)

Gibberella ear rot

4-ABOA

Diferuloylputrescine

E-ferulic acid

Dehydrodimers of ferulic acid

Guanylyl cyclase like protein

(ZmGC1)

Aspergillus ear rot

Cuticular Waxes

Β-1,3 gluconase

14kDa trypsin inhibitor

Pathogenesis-related proteins

(PR10)

Ribosome inactivating protein (RIP)

Zeamatin

Aldose Reductase (ALD)

Glyoxalase I (GLXI)

Anionic peroxidase

Peroxiredoxin 1 (PER 1)

Water stress inducible protein

(WSI)

16.9/17.2 kDa Small heat shock

protein

Globulin I and II

Late embryogenesis abundant

protein (LEAIII)

Cupin domain containing protein

(Zmcup)

Some of the Key Research Collaborative Activities for Improving our

Capacity to Develop Disease Resistant Germplasm for Use in Asia

CSISA I, CSISA II

IMIC-Asia

CCAFS

NSFC Project, “Genetic dissection and molecular

improvement of resistance to three major maize foliar

diseases in China based on joint linkage-association

mapping” led by Dr. Jianbing Yan, Huazhong Agricultural

University (HZAU), Yunnan Academy of Agricultural

Sciences (YAAS), Sichuan Agricultural University (SCAU)

and CIMMYT

DTMA Project, Africa

IMAS Project, Africa

MasAgro Project, Mexico

Conclusions

• Disease resistance breeding activities in the Asian region have provided

many useful products for adding yield stability and quality to Asian maize

production.

• Several diseases including banded leaf and sheath blight, ear rots, post

flowering stalk rots, RBDSV and MRDV still have not identified diverse

resistant sources as seen with many of the foliar blights, and downy mildew.

• To meet the great demands for the future, including a production

environment often less favorable due to climate change, new tools including

rapid cycle genomic selection will be needed to develop robust abiotic

stress tolerant, disease resistant high yielding germplasm.

• Networking will improve the capacity of all research groups in the region to

benefit from the new molecular tools, and deliver the best products to the

farmers.