Presentation on theme: "Management Options for Soybean Rust; Resistance and Fungicides."— Presentation transcript:
1 Management Options for Soybean Rust; Resistance and Fungicides. Monte R. MilesUSDA-Agricultural Research ServiceDepartment of Crop SciencesNational Soybean Research CenterUniversity of Illinois, Urbana, IL
2 PHAKOSPORA PACHYRHIZI OBLIGATE PARASITEUREDINIOSPORESNO ALTERNATE HOST IS KNOWNDIRECT PENETRATIONINFECTION CYCLES IN 5 TO 7 DAYSIntroductionThe identification of Asian soybean rust in Paraguay in 2001(Morel and Yorinori, 2002) and its spread to over 90% of the soybean production in Brazil through the 2003 season has heightened the awareness that this disease will soon be a threat to production on the continental USA. With the yield losses this disease can cause it will have a big impact on profitability of soybean production.Asian soybean rust, caused by Phakopsora pachyrhizi, is an obligate parasite; it needs living tissue to survive. Urediniospores are the main spore stage. Teliospores and basidiospores have been produced but are not part of the disease cycle, since there is no known alternate host for basidiospores to infect. The pathogen penetrates directly, unlike the pathogens that cause rusts of wheat and corn. The infection process is not influenced by host surface features, stomata are not important in infection. Most parts of the soybean plant are infected, including the coleoptiles, leaves, petioles, stems and seedpods.C. STONE
3 São Desidério, Roda Velha, BA, March 8, 2003 J. T. Yorinori
4 Photo: M. Assunção (Embrapa Soja/CTPA)/José Nunes Jr (CTPA); Campo Alegre, GO
5 Management of Soybean Rust Short-term solutionsFungicidesLong-term solutionsHost resistanceSpecific resistancePartial resistanceYield stabilityCombination of fungicides and resistance
6 RESISTANCE TO SOYBEAN RUST SPECIFIC OR SINGLE GENE RESISTANCEPARTIAL OR RATE REDUCING RESISTANCEYIELD STABILITY OR TOLERANCE
7 Initial Screening of Germplasm Initial studies1961 ≈ 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
8 Specific Resistance Hartwig and Bromfield 1983 Showed that three soybean lines each carried a single dominant gene conferring specific resistanceEach gene was found to be at a different locusHartwig 1986Identified a fourth major gene for resistance
9 Host ResponseImmune reaction - hypersensitive reaction with rapid cell death near the infection site without sporulation - rarely seenResistant - red-brown (RB) reaction, lesions may or may not develop into sporulating pustulesSusceptible - Tan lesions that develop into sporulating pustulesC. STONE
10 GENE ACCESSION FOUND LOST Rpp1 PI200492 1960-62 1966 The resistance in Ankur, identified in the early 1970’s was lost in the late 1970’s , providing another example of the diversity in virulence seen in P. pachyrhizi populations overcoming single gene resistance. Only Bing Nang, the source of the Rpp4 gene, has not been reported to be defeated, although our observations both in the field in Paraguay and greenhouse inoculation tests indicate that it is susceptible to some isolates.
11 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.
12 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
13 VIRULENCE IS DIVERSE AND COMPLEX PHYSIOLOGICAL SPECIALIZATION HAS BEEN SEEN ON MANY LEGUMES, THE WILD GLYCINE RELATIVES OF SOYBEAN, AS WELL AS ON SOYBEAN ACCESSIONSPhysiological races of P. pachyrhizi were first described in 1966 when a set of nine single urediniospore isolates were inoculated onto six soybean and five legume accessions . The reactions of the nine isolates were similar on all six of the soybean genotypes, but six pathotypes were identified based upon their reactions on the legume accessions. The first example of virulence diversity on soybean cultivars was described in Queensland, Australia where one rust isolate was found to be virulent on the cultivar ‘Willis’ but avirulent on the accession PI , while a second isolate was virulent on both soybean genotypes. Several other studies have also shown considerable variation in virulence among isolates from the same field, as well as isolates collected from wide geographical areas . The summary on virulence is that it is diverse and complex. Not only is there physiological specialization in the interaction with soybean but it is also known to occur within the other legume species as well.
14 PARTIAL RESISTANCEREDUCES THE RATE OF AN EPIDEMIC BY SLOWING DOWN PATHOGENUSUALLY NOT A SINGLE GENEUSUALLY NOT RACE SPECIFICNOT A +/- TYPE OF EVALUATIONEVALUATED OVER TIMEGROWTH STAGE IMPORTANT
15 HOW DOES PARTIAL RESISTANCE OR “SLOW RUSTING” WORK? REDUCES INFECTION FREQUENCY- FEWER LESIONSINCREASES LATENT PERIOD - PATHOGEN NEEDS A LONGER TIME TO PRODUCE UREDINIA AND SPORESREDUCES SPORE PRODUCTION- FEWER UREDINIA AND FEWER SPORES / UREDINIADIFFICULT TRAITS TO WORK WITH
16 EXAMPLE OF PARTIAL RESISTANCE - PUSTULE COUNTS EntryPustules per plantPustules per leafPustules at node 7AGS 1291,77641104AGS 1813,84913087GC5,934168176GC2,10849150KS 82,71576107SRE C-56A8032325SRE C-56E7091929SRE D-14C2,1595817SRE D-14D2,1005451G. L HARTMAN
17 HOW WILL PARTIAL OR “SLOW RUSTING” RESISTANCE BE EVALUATED ? DISEASE SEVERITY OVER TIMEESTIMATED PER PLOTAREA AFFECTED, DEFOLIATION, GREEN LEAF AREAPATHOGEN REPRODUCTION OVER TIMEPUSTULE COUNTS, SPORE PRODUCTION, LATENT PERIODGROWTH STAGE IS IMPORTANTRELATIVE LIFE TIME (0-100%)Partial resistance, or rate reducing resistance, is also known in soybean . Lines with partial resistance in field evaluations were rated as moderately resistant since fewer lesions developed on plants throughout the season. In greenhouse studies, host-pathogen combinations that resulted in RB reaction types tended to have longer latent periods, lower rates of increase in pustule number over time, and smaller lesions compared with susceptible interactions that resulted in a TAN reaction type .
18 Yield Stability Needs to be done with adapted germplasm Relative yielding ability of soybeans under stress from rustCompare yields between fungicide-protected plots and non-protected plotsYield stability assessment -Needs to be done with adapted germplasm
19 Yield Loss Differences 20406080100LOW YIELDSTABILITYYield loss (%)MOSTYIELDSTABILITY123456789101112Soybean entry
20 GOIASPhoto: Mauricio Assunção – Embrapa Soja/CTPA; Campo Alegre, GO
22 Fungicides will be the primary tool to control Asian soybean rust in the near future. The primary tool in the control of the disease will be the use of fungicides. Single gene resistance has not been durable, partial resistance has been difficult to work with, leaving tolerance or yield stability as the selection method used in breeding programs. Tolerance is defined as yield stability in the presence of the disease compared to plots protected by fungicides (Hartman, 1995). Cultural practices have not been shown to be effective in control of the pathogen; recommendations were inconsistent and varied by location. The most effective practices were avoidance or were practices that maximized yields in the absence of the disease.
23 FUNGICIDES REGISTERED FOR USE ON SOYBEAN AND LABLED FOR CONTROL OF SOYBEAN RUST CHLOROTHALONILBRAVO (SYNGENTA)ECHO ( SIPCAM AGRO)AZOXYSTROBINQUADRIS (SYNGENTA)
24 FUNGICIDES ON THE SECTION 18 EMERGENCY EXEMPTION REQUEST MYCOBUTANIL *PROPICONAZOLE *PYRACLOSTROBINPYRACLOSTROBIN + BOSCALID **TEBUCONAZOLETETRACONAZOLETRIFLOXYSTROBIN + PROPOCONIZOLE* APPROVED BY EPA, ** BOSCALID IS REGISTERED
25 ALL FUNGICIDES ARE NOT THE SAME CURATIVEABSORBEDTRANSLOCATESKILLS FUNGAL TISSUEUSE AFTER INFECTIONTRIAZOLESPROTECTANT+/-ABSORBED+/-TRANSLOCATEPREVENTS INFECTION OR SPORULATIONUSE BEFORE INFECTIONSTROBALURINS AND CHLOROTHALONILS
26 FUNGICIDE EFFICACY TRIALS IN SOUTHERN AFRICA AND SOUTH AMERICA EVALUATE FUNGICIDES THAT ARE LABLED OR ON THE SECTION 18 REQUESTCOMPARISON OF 2 AND 3 APPLICATIONS WITH FIRST APPLICATION SOON AFTER FLOWERINGFungicide Efficacy. Many fungicides have been evaluated to control soybean rust. Early research from Asia indicated that mancozeb was effective (Hartman et al., 1992). Other compounds available at the time were compared to mancozeb and were effective, but results varied by test (Table 1). More recently, fungicide trials in India (Patil and Anahosur, 1998) and Southern Africa (Levy et al., 2002) have identified several triazole compounds and triazole mixes. Among the more effective were flusilazole + carbendazim, difenoconazole, and triadimenol.M. Miles
28 RECCOMENDATIONS FOR CHEMICAL CONTROL BRAZIL AND SOUTHERN AFRICA ARE THE SOURCES OF INFORMATIONFORMULATIONS WE WILL HAVE WILL DIFFER FROM BRAZIL AND AFRICANOT ALL FUNGICIDES WILL BE AVALIABLE IN THE U.S.
31 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 NEEDEDDAYS BETWEEN APPLICATIONSTHE FUNGICIDE NEEDS TO PENETRATE THE CANOPY
32 ADDITIONAL RECCOMENDATIONS- STROBALURIN FUNGICIDES NEED TO BE USED AS A PROTECTANT, ONCE RUST IS AT 5-10% THEY DO NOT ALWAYS PROTECT YIELDSTROBALURINS ARE SINGLE SITE MODE OF ACTION - USED ONLY ONCE PER SEASONMANY TRIAZOLES MAY NOT HAVE THE RESIDUAL NEEDED FOR 20+ DAY INTERVALSENVIRONMENT WILL HAVE AN EFFECTMIXES OF TRIAZOLES AND STROBALURINSROTATE THE FUNGICIDES
33 OK, SO WHAT DO I USE? THERE ARE MANY QUESTIONS THAT NEED TO BE AWNSERED FIRST THE SECTION 18 EMERGENCY EXEMPTION REQUESTS HAVE 3 OR 4 SENARIOS WITH RECCOMENDATIONS THAT DEPEND ON PRESENCE OR PREDICTION OF RUSTIS 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?
34 HOWCAN WE PENETRATE THE CANOPY? AERIAL AND GROUNDNORMAL AND HIGH VOLUMETYPE OF NOZZLE FOR GROUND APPLICATIONApplication methods. One of the more critical application challenges for protecting the soybean crop from yield losses due to soybean rust is to penetrate the canopy and deliver the fungicide into the middle third of the canopy. Fungicides are not used in most soybean production areas, so little work has been done to develop fungicide application programs for the crop. Both aerial and ground applications are used in South America. Multiple application methods are being used in Southern Africa, with the most effective methods being those where penetration and canopy coverage are the greatest. Examples of effective methods include air assist and high pressure lateral discharge equipment, increased pressure delivery and increased water volume per hectare.Currently, there is a multi-state project to evaluate high and low volume application in aerial and ground systems using predominantly 30-inch row spacing. Within the ground application program are different nozzle types that would be available on a commercial basis today. Included are the flat fan nozzle that would be used for Round up application, as well as air induction and twin jet nozzles. Preliminary data from both aerial and ground application show the need for high volume (10 gal. aerial and 20 gal. ground applied) to penetrate the canopy into the middle third. There is need for additional experimentation before a fungicide application method can be developed to economically protect the soybean crop.M. MILES, 2003
35 FUNGICIDES ARE USED IN SOYBEAN PRODUCTION IN THE MID AND DEEP SOUTH RESULTS ARE MIXED.QUADRISQUADRIS + WARRIORNOT ALWAYS ASSOCIATED WITH PEST CONTROL.D. HERSHMAN, U OF KY.
36 WHAT WILL WE HAVE FOR THE FUTURE? FUNGICIDESYIELD STABILITYPARTIAL RESISTANCECOMBINED SINGLE GENESGENES FROM RELATED SPECIESTHE MOST SUCCESFULL APPROCH WILL HAVE ALL IN COMBINATIONM MILES, 2003
37 RESEARCH SUPPORTED BY: USDA-ARSUSDA CSREESUNITED SOYBEAN BOARDREPRESENTATIVES FROM THE CHEMICAL INDUSTRY