Management Options for Soybean Rust; Resistance and Fungicides. Monte R. Miles USDA-Agricultural Research Service Department of Crop Sciences National.

Management Options for Soybean Rust; Resistance and Fungicides.

Monte R. MilesUSDA-Agricultural Research Service

Department of Crop Sciences National Soybean Research Center

University of Illinois, Urbana, IL

www.soydiseases.uiuc.edu

OBLIGATE PARASITE

UREDINIOSPORES

NO ALTERNATE HOST IS KNOWN

DIRECT PENETRATION

INFECTION CYCLES IN 5 TO 7 DAYS

PHAKOSPORA PACHYRHIZI

C. STONE

São Desidério, Roda Velha, BA, March 8, 2003

J. T. Yorinori

Photo: M. Assunção (Embrapa Soja/CTPA)/José Nunes Jr (CTPA); Campo Alegre, GO

Management of Soybean Rust

• Short-term solutions

– Fungicides

• Long-term solutions

– Host resistance

• Specific resistance

• Partial resistance

– Yield stability

• Combination of fungicides and resistance

RESISTANCE TO SOYBEAN RUST

• SPECIFIC OR SINGLE GENE RESISTANCE

• PARTIAL OR RATE REDUCING RESISTANCE

• YIELD STABILITY OR TOLERANCE

Initial Screening of Germplasm

• Initial studies– 1961 ≈ 2,800 accessions screened in

Taiwan (U.S collection)– 1970 ≈ 4,000 accessions screened in

India (U.S. collection)– 1975 ≈ 1,675 accessions (MG V-X)

screened in Taiwan (AVRDC)• From these studies, sources of resistance

were found and the inheritance of resistance was characterized

Specific Resistance

• Hartwig and Bromfield 1983

– Showed that three soybean lines each carried a single dominant gene conferring specific resistance

– Each gene was found to be at a different locus

• Hartwig 1986

– Identified a fourth major gene for resistance

Host Response

• Immune reaction - hypersensitive reaction with rapid cell death near the infection site without sporulation - rarely seen

• Resistant - red-brown (RB) reaction, lesions may or may not develop into sporulating pustules

• Susceptible - Tan lesions that develop into sporulating pustules

C. STONE

GENE ACCESSION FOUND LOST

Rpp1 PI200492 1960-62 1966

Rpp2 PI230970 1972-74 1978

Rpp3 PI462312 1973-75 1977

Rpp4 PI459025 1980-83 2004

Virulence diversity of P. pachyrhizi

• In Australia, 8 isolates were separated into 6 races using wild Glycine species as the differentials.

• Native populations of wild Glycine spp show differential responses.

• In China, nine isolates that had a susceptible reaction on soybean were separated into 6 phenotypes using asparagus bean, kidney bean and short podded yam bean.

Virulence diversity of P. pachyrhizi

• In a screen of 42 single spore isolates from Taiwan, 9 races were identified using 11 G. max resistant sources.

• No resistant source was effective against

all isolates

VIRULENCE IS DIVERSE AND COMPLEX

PHYSIOLOGICAL SPECIALIZATION HAS BEEN SEEN ON MANY

LEGUMES, THE WILD GLYCINE RELATIVES OF SOYBEAN, AS

WELL AS ON SOYBEAN ACCESSIONS

PARTIAL RESISTANCE• REDUCES THE RATE OF AN

EPIDEMIC BY SLOWING DOWN PATHOGEN

• USUALLY NOT A SINGLE GENE

• USUALLY NOT RACE SPECIFIC

• NOT A +/- TYPE OF EVALUATION

• EVALUATED OVER TIME

• GROWTH STAGE IMPORTANT

HOW DOES PARTIAL RESISTANCE OR

“SLOW RUSTING” WORK?• REDUCES INFECTION FREQUENCY-

FEWER LESIONS• INCREASES LATENT PERIOD -

PATHOGEN NEEDS A LONGER TIME TO PRODUCE UREDINIA AND SPORES

• REDUCES SPORE PRODUCTION- FEWER UREDINIA AND FEWER SPORES / UREDINIA

DIFFICULT TRAITS TO WORK WITH

EXAMPLE OF PARTIAL RESISTANCE - PUSTULE COUNTS

Entry

Pustules per plant

Pustules per leaf

Pustules at node 7

AGS 129 1,776 41 104

AGS 181 3,849 130 87

GC 82345-20-2 5,934 168 176

GC 82349-6-1 2,108 49 150

KS 8 2,715 76 107

SRE C-56A 803 23 25

SRE C-56E 709 19 29

SRE D-14C 2,159 58 17SRE D-14D 2,100 54 51

G. L HARTMAN

HOW WILL PARTIAL OR “SLOW RUSTING” RESISTANCE BE

EVALUATED ?• DISEASE SEVERITY OVER TIME

– ESTIMATED PER PLOT– AREA AFFECTED, DEFOLIATION,

GREEN LEAF AREA• PATHOGEN REPRODUCTION OVER TIME

– PUSTULE COUNTS, SPORE PRODUCTION, LATENT PERIOD

• GROWTH STAGE IS IMPORTANT– RELATIVE LIFE TIME (0-100%)

Yield Stability• Relative yielding

ability of soybeans under stress from rust

• Compare yields between fungicide-protected plots and non-protected plots

• Yield stability assessment - Needs to be done with

adapted germplasm

Yield Loss Differences

1 2 3 4 5 6 7 8 9 10 11 120

20

40

60

80

100Y

ield

lo

ss

(%)

Soybean entry

LOW YIELDSTABILITY

MOSTYIELDSTABILITY

GOIAS

Photo: Mauricio Assunção – Embrapa Soja/CTPA; Campo Alegre, GO

MATO GROSSO

Primavera do Leste, MT: 21.02.03

Fungicides will be the primary tool to control Asian soybean

rust in the near future.

FUNGICIDES REGISTERED FOR USE ON SOYBEAN AND LABLED

FOR CONTROL OF SOYBEAN RUST

CHLOROTHALONIL• BRAVO (SYNGENTA)• ECHO ( SIPCAM AGRO)

AZOXYSTROBIN• QUADRIS (SYNGENTA)

FUNGICIDES ON THE SECTION 18 EMERGENCY

EXEMPTION REQUEST

• MYCOBUTANIL * • PROPICONAZOLE *• PYRACLOSTROBIN• PYRACLOSTROBIN + BOSCALID **• TEBUCONAZOLE• TETRACONAZOLE• TRIFLOXYSTROBIN + PROPOCONIZOLE * APPROVED BY EPA, ** BOSCALID IS REGISTERED

ALL FUNGICIDES ARE NOT THE SAME

CURATIVE• ABSORBED• TRANSLOCATES• KILLS FUNGAL

TISSUE • USE AFTER

INFECTION• TRIAZOLES

PROTECTANT• +/-ABSORBED• +/-TRANSLOCATE• PREVENTS INFECTION

OR SPORULATION• USE BEFORE

INFECTION• STROBALURINS AND

CHLOROTHALONILS

FUNGICIDE EFFICACY TRIALS IN SOUTHERN AFRICA AND SOUTH AMERICA

EVALUATE FUNGICIDES THAT ARE LABLED OR ON THE SECTION 18 REQUEST

COMPARISON OF 2 AND 3 APPLICATIONS WITH FIRST APPLICATION SOON AFTER FLOWERING

M. Miles

RECCOMENDATIONS FOR CHEMICAL CONTROL

• BRAZIL AND SOUTHERN AFRICA ARE THE SOURCES OF INFORMATION

• FORMULATIONS WE WILL HAVE WILL DIFFER FROM BRAZIL AND AFRICA

• NOT ALL FUNGICIDES WILL BE AVALIABLE IN THE U.S.

RECOMMENDATIONS FOR CHEMICAL CONTROL

• FIRST APPLICATION NEEDS TO BE AT OR SOON AFTER FIRST FLOWER - IN ZIMBABWE THIS WAS 50 DAYS AFTER PLANTING.

• 2 OR 3 APPLICATIONS ARE NEEDED• 14 - 20 DAYS BETWEEN APPLICATIONS• THE FUNGICIDE NEEDS TO PENETRATE

THE CANOPY

ADDITIONAL RECCOMENDATIONS-

• STROBALURIN FUNGICIDES NEED TO BE USED AS A PROTECTANT, ONCE RUST IS AT 5-10% THEY DO NOT ALWAYS PROTECT YIELD

• STROBALURINS ARE SINGLE SITE MODE OF ACTION - USED ONLY ONCE PER SEASON

• MANY TRIAZOLES MAY NOT HAVE THE RESIDUAL NEEDED FOR 20+ DAY INTERVALS

• ENVIRONMENT WILL HAVE AN EFFECT• MIXES OF TRIAZOLES AND STROBALURINS• ROTATE THE FUNGICIDES

OK, SO WHAT DO I USE?THERE ARE MANY QUESTIONS THAT

NEED TO BE AWNSERED FIRSTTHE SECTION 18 EMERGENCY EXEMPTION

REQUESTS HAVE 3 OR 4 SENARIOS WITH RECCOMENDATIONS THAT DEPEND ON PRESENCE OR PREDICTION OF RUST

• IS THE RUST PRESENT? HOW SEVERE?• DO YOU NEED CURATIVE FUNGICIDE OR

WILL A PROTECTANT FUNGICIDE WORK? • ECONOMICS AND TIME OF SEASON?• WHAT IS THE PRE HARVEST INTERVAL

OF THE FUNGICIDE YOU WANT TO USE?

HOWCAN WE PENETRATE THE CANOPY?

• AERIAL AND GROUND

• NORMAL AND HIGH VOLUME

• TYPE OF NOZZLE FOR GROUND APPLICATION

M. MILES, 2003

FUNGICIDES ARE USED IN SOYBEAN PRODUCTION IN THE MID AND DEEP SOUTH

• RESULTS ARE MIXED.• QUADRIS• QUADRIS + WARRIOR • NOT ALWAYS

ASSOCIATED WITH PEST CONTROL.

Yield Data From 51 Grower Fields,Yield Data From 51 Grower Fields,2003.2003.  Trt. Yield (bu/A) Q+W 53.84 NT 49.21 Q+W Difference +4.63*

*ANOVA P = 0.03 NET GAIN = $15.34

D. HERSHMAN, U OF KY.

WHAT WILL WE HAVE FOR THE FUTURE?

• FUNGICIDES• YIELD STABILITY• PARTIAL RESISTANCE• COMBINED SINGLE

GENES• GENES FROM RELATED

SPECIES

THE MOST SUCCESFULL APPROCH WILL HAVE ALL IN COMBINATION

M MILES, 2003

RESEARCH SUPPORTED BY:

• USDA-ARS• USDA CSREES• UNITED SOYBEAN

BOARD• REPRESENTATIVES

FROM THE CHEMICAL INDUSTRY