Adventures in Soybean Rust Research

Transcription

1 Adventures in Soybean Rust Research Glen L. Hartman Research Plant Pathologist and Professor USDA-ARS and Department of Crop Sciences University of Illinois

2 Outline Introduction Symptoms, signs, life cycle, and distribution Literature survey Pathogenic variation Host range Virulence diversity Host resistance Known genes Additional sources Summary

3 Symptoms and Signs

4 Soybean Rust Pathogens Phakopsora pachyrhizi the only species known to cause soybean rust up to 1992, although studies in the 1970s and 1980s indicated that Western and Eastern Hemisphere isolates differed P. meibomiae described in 1992 as a new species to represent isolates from the Western Hemisphere Pachyrhizus erosa (yam bean) Ticktrifoil Desmodium spp. (syn. Meibomia spp.)

5 Harmon, C.L., P.F. Harmon, T.A. Mueller, J.J. Marios, and G.L. Hartman First report of Phakopsora pachyrhizi telia on kudzu in the United States. Plant Disease 90:380.

6 Puerto Rico 1976 U.S. (9 States) 2004 Hawaii 1994 Columbia 2004 Paraguay Brazil Argentina Bolivia Uganda Zimbabwe S. Africa Australasia (first reported in Japan )

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9 Explosion of Refereed Publications

10 Categories of Refereed Publications Epidemiology Resistance Pathogen

11 2005 Sentinel Plots (from IPM PIPE) July 17 July 17 July 17 Dec 31 Dec 31 Dec 31

12 2008 Sentinel Plots July 17 July 17 July 17 Dec 31 Dec 31 Dec 31

13 Sentinel Plots 2011 July 17 What happened to soybean rust in the US? Subtropical rust Hosts die out Lacks capacity to overwinter Dec 10

14 Is rust still a threat? Are we prepared? Yes - monitoring and management through fungicides Do we have adequate information about the pathogen? Do we need to know more about host resistance?

15 Host Range Prior to 2004, the host range included 42 genera on 93 hosts Now, the host range includes 53 genera and 150 species About 120 of the 150 species occur in North America All hosts belong to the legume subfamily Papilionoideae (estimated 13,860 species) More capacity for expansion Slaminko et al Plant Health Progress, doi: /php rs. Slaminko et al Plant Disease 92: Kudzu, Pueraria lobata

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17 Pathogenic Variation of Isolates Perhaps the earliest report of pathogenic variation was from Taiwan in 1966 when isolates caused different reactions on five legume species including soybean This was confirmed in many other studies in Australasia, and also at the plant pathogen containment facility at Fort Detrick which has isolates dating back to 1972

18 An Isolate Collection Detached Leaf Cultures Resistant Provides controlled conditions for various types of research Twizeyimana & Hartman Plant Disease 94: Susceptible

19 Rust Reactions Entry TW 72-1 IN 73-1 Countries/USA states TW 80-2 ZM 01-1 BZ 01-1 PG 01-2 AL 04-1 AL 04-3 LA JP Iso 118 NIG ISO Japan/Brazil JP B BB I-1 BB I-2 72 USA ISO PI ( Rpp1) RB (4) T (12) RB (58) MX (58) PI ( Rpp2) RB (14) T (2) RB (1oo) MX (16) RB (9) T (63) RB (10) T (63) PI ( Rpp3) RB (11) T (6) PI459025B (Rpp4) RB (15) T (1) RB (66) MX (52) RB (5) T (67) 1. Pham et al Differential responses of resistant soybean genotypes to ten isolates of Phakopsora pachyrhizi. Plant Disease 93: Yamaoka et al Pathogenic races of Phakopsora pachyrhizi on soybean and wild host plants collected in Japan. Journal of General Plant Pathology 68: Twizeyimana et al Pathogenic variation of Phakopsora pachyrhizi infecting soybean in Nigeria. Phytopathology 99: Yamanaka et al Development of classification criteria for resistance to soybean rust and differences in virulence among Japanese and Brazilian rust populations. Tropical Plant Pathology 35: Twizeyimana & Hartman Pathogenic variation of Phakopsora pachyrhizi isolates on soybean in the United States from 2006 to Plant Disease 96:(in press). Tan Red-brown Immune MX = T/RB

20 Virulence Diversity No sexual cycle known Isolates known to be virulent even before genes for resistance deployed Diversity may exist in wild populations on other non-soybean hosts Somatic hybridization Germ tube anastomosis Vittal et al European Journal of Plant Pathology DOI /s Nuclear migration

21 Summary of Pathogenic Variation Virulence diversity isolates are known that overcome all genes for resistance Anastomosis and nuclear migration - shown to occur, but nuclear exchange not demonstrated Aggressiveness diversity comparisons indicate that isolates are not equal in disease severity, nor equal in their reproductive capacity Molecular diversity studies from Brazil, Nigeria, and USA show isolate differences in gene sequences (ITS 1 & 2) and markers (SSR), but molecular diversity does not relate to virulence

22 Resistance in soybean to Phakopsora pachyrhizi Non-host Immunity Complete resistance Incomplete resistance Partial resistance Susceptibility Tolerance

23 Sources of Resistance First reported in the 1970s and 1980s The entire collection (16,595) of the U.S. soybean germplasm was evaluated at Fort Detrick prior to the 2004 establishment of soybean rust in the continental U.S. (Miles et al. 2006) Many of these original sources have been evaluated and characterized in Brazil and the U.S.

24 Plant Pathogen Containment BSL-3 Facility, Bldg. 374, Fort Detrick, MD

25 Resistance of Soybean Germplasm Rust Locations Paraguay Vietnam Florida Detached leaves and greenhouse - Univ. of Illinois

26 Genes for Resistance Rpp1 (PI ) - resistant against the monospore isolate Q-1 from Australia (McLean and Byth 1980) Rpp2 (PI ), Rpp3 (PI ) and Rpp4 (PI B) - characterized by their responses against specific P. pachyrhizi isolates purified at Fort Detrick (Bromfield and Hartwig 1980; Hartwig 1986; Hartwig and Bromfield 1983)

27 Additional Genes for Resistance Rpp5 - identified in Brazil in 2008 (Garcia et. al., 2008) Rpp1, Rpp2, Rpp3, and Rpp5 - genetic evidence indicates all have multiple alleles For example, Rpp1b (PI A) distinguished from Rpp1 by a differential reaction to isolate ZM 01-1 (Chakraborty et al. 2009) In addition, some sources of resistance have stacked genes PI and possibly PI and PI may have resistance genes Rpp3 and Rpp5 (Kendrick et al. 2011) UG5 (a cultivar from Uganda) may have Rpp1 and Rpp3 Many other sources not yet genetically characterized, so new genes (Rpp6 to Rpp?) may be added

28 Resistance gene Rpp1 Source PI PI B Soybean linkage group Rpp1-b PI A G G Flanking markers 1 Sct_187, Sat_064 Sat_117, Sct_187 2 BARC , BARC Reference Hyten et al Garcia et al Chakraborty et al Rpp1-? PI A G 1 Satt 191, Sat_372 Ray et al Rpp1-? PI G 1 Satt 191, Sat_064 Ray et al Rpp2 PI J 1 Sat_255, Satt620 Silva et al rpp2 PI J 1 Satt215, Sat_361 Garcia, et al., 2008 Rpp3 PI C2 1 Satt460, Sat_263 Hyten et al Rpp3-? PI C2 1 Satt134, Satt460 Monteros et al Rpp4 PI G 1 Satt288, AF Silva et al Rpp5 PI , PI , PI N 1 Sat_275, Sat280 Garcia et al rpp5 PI N 1 Sat_275, Sat280 Garcia et al [Rpp5] PI N Hartman et al CAB Reviews. 1 Sat_275 & SSR03-866, SSR & SSR Kendrick et al. 2011

29 Non-Soybean Sources of Resistance Glycine species G. canescens single and two dominant genes (Burdon 1988) G. argyrea single dominant gene (Jarosz & Burdon 1990) G. tomentella single, two, and three dominant genes depending on the ploidy level (Schoen et al. 1992) Pueraria species 10 accessions tested; three immune, one resistant, the rest susceptible (Jordon et al. 2010) More than 10 legume species showed a differential reaction (Slaminko et al. 2008), e.g.: Crotalaria incana, C. lanceolata, Lupinus perennis Neonotonia wightii Vigna adenantha

30 Quantifying Resistance - Sporulation Entry Incomplete Lesion type AUSUPC Williams TAN 223 a PI RB 199 a PI RB 163 b PI B (Rpp4) RB 110 c PI (Rpp2) RB 78 d PI A (Rpp1b) RB 38 e Partial Entry Lesion type AUSUPC Williams TAN 223 a PI (Rpp1) TAN 235 a G 7955 (Rpp3) TAN 157 b PI TAN 153 b PI TAN 139 b PI TAN 127 b Means from separate inoculations with isolates BZ01-1, PG01-2, TH01-1, and ZM01-1. Area-under-sporulating-uredinia-progress-curve (AUSUPC) values were calculated from the number of sporulating uredinia combined from two 1-cm diameter circles based on five assessment dates. Miles et al Plant Disease 95:

31 Quantifying Resistance QPCR Soybean genotype Reaction type No. of uredinia Fungal DNA (pg) Williams 82 TAN 8.4 a d 581 a TGx E TAN 6.5 a 624 a PI TAN 6.6 a 389 ab PI A TAN 4.1 b 219 b PI RB 3.2 b 324 ab PI TAN 1.9 c 72 c PI (Rpp3) RB 0.5 d 43 cd PI RB 0.1 de 8 e UG5 IM 0.0 e 0 f Quantified from 1.7 cm diameter circle around the inoculation point Paul et al Plant Disease 95:

32 Tolerance to Soybean Rust Relative yielding ability of soybean genotypes under stress from rust Compare yields between inoculated non-protected plots to inoculated-fungicide protected plots Rust tolerance publications Hartman et al Plant Disease 75: de Oliveira et al Fitopatologia Brasileira 30: Jarvie & Shanahan Field Crops Research 114:

33 Summary of Resistance All the named soybean genes for rust resistance are also mapped (some now stacked in elite breeding lines) There are no genes characterized with resistance to all isolates Major gene resistance in the other species has not fully characterized Genes related to partial resistance and tolerance have not been designated or mapped Rust resistance from G. tomentella has now been introgressed into soybean

34 Acknowledgements Soybean Associations Illinois Soybean Association and other state associations, North Central Soybean Research Program, and the United Soybean Board USDA-ARS, APHIS, and NIFA US-AID and FAS Personnel at Fort Detrick, the Soybean Germplasm, and the Laboratory for Soybean Disease Research International collaborators