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New Virulent Races of Barley Leaf Rust and Stem Rust Pathogens in the the United States

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New Virulent Races of Barley Leaf Rust and Stem Rust Pathogens in the the United States New virulent races of barley leaf rust and stem rust pathogens in the the United States J. Nirmala, M. Rouse, X. Chen, Y. Jin, USDA‐ARS Cereal Disease Laboratory, USDA‐ARS, St. Paul, MN Annual rust surveys *Wheat stem rust *Rye stem rust *Oat stem rust *Wheat leaf rust *Barley leaf rust *Oat crown rust Goals of the annual race surveys * To determine the pathogenic variation present in the rust population * To detect new races of rust that pose a threat to the commonly grown cultivars * Rust isolates obtained from surveys are used in testing cereal germplasm for rust resistance * Facilitate breeders to identify and introgess new sources of resistance into relevant germplasms 1) Physiologic specialization of Puccinia graminis in a single field in Washington, USA on barley 2) Scenario of barley leaf rust surveys in the United States from 2010‐2013 in terms of virulence Physiologic specialization of Puccinia graminis in a single field in Washington, USA on barley Stem rust P. graminis f. sp. tritici P. graminis f. sp. secalis Life cycle of wheat stem rust Illustrated by Jackie Morrison, CDL, USDA‐ARS Early maturing wheat Barberry Eradication cultivars combined program with multiple sources (1918‐1990) of resistance Limited sexual reproduction Emergence of new races/stem rust epidemics Stabilized the Pgt population Barberry was not completely eradicated!!! 1989: QCCJ minor epidemic 1996: QFCS 2008: QFCN, RFCS QFCS is the most prevalent race in the US today! (Kolmer et al., 2007) QFCS is believed to have originated from the Pacific North West Stem rust races identified in the US from 2008‐2014 Year Races identified 2008 QFCS, RFCS, QFCN, QCCD, QCCJ, QCCN 2009 QFCS, JCCD, QCMN, QFCJ, QFMN, SCCS 2010 QFCSC 2011 QFCSC, QCCDC, QCCJB 2012 QFCSC, MCCDC, QFMSC, GCCDC, GFCNC, GFCSB, GFCSC, GFHNC, LFCSC, RFCSC, QCCSC, LDCNC, QFCNC, QFCDC, QCCNC, QCCDC 2013 QFCSC 2014 QFCSC, RCRSC Barley field in Arden, WA (2007) Races identified from the barley field in Arden, WA Race Isolates Race Isolates QCBBB 2 BBBBB 19 BCBGB 4 BCBBB 8 GHBBB 1 GCBBB 5 BMBBB 2 QCBGB 4 QHMJC 6 QCMBB 5 QCBQB 2 QCCNC 1 SFBDB 1 QHBGB 1 GCBGB 4 BBBGB 2 BCBQB 1 LCBNB 1 JCBBB 9 BCGGB 1 BCBGC 2 SCBBB 1 GCCBB 1 83 isolates were derived from the bulk inoculum 23 different races identified from a single barley field in Arden, WA Virulence frequency across 83 isolates of P. graminis on the 20 North American differential lines 80 70 60 50 40 30 20 10 Percent Virulence Percent 0 5 21 9e 7b 11 6 8a 9g 36 9b 30 17 9a 9d 10 Tmp 24 31 38McNair Resistance Gene Sources of barley stem rust resistant genes Source of resistance Cultivar/line used Rpg1 Chevron, Morex , Peatland, Q21861 Rpg2 Hietpas5 Rpg3 PI382313 Rpg5/rpg4 Q21861, QSM16 and QSM20 Rpg6 212Y1 RpgBH Black Hulless RpgU Peatland Steptoe, Hiproly Experimental methods Experiments were conducted in duplicates at two different temperatures (21o C and 24o C) Races MCCF and QCCJ were run as controls in all the experiments Unusual results were re‐evaluated in duplicates Rust infection types in barley 0; 0;1 10; 12 3‐2 3 3+ Courtesy: Dr. Brian Steffenson Number of isolates virulent on stem rust resistance genes Sources of No of isolates vir. No of isolates vir. resistance at both 21/24°C only at 24°C Rpg1 2* 2 Rpg2 55 Rpg3 35 rpg4/Rpg5 None None Rpg6 3 RpgU 1 RpgBH 1 Overall avirulent, mesothetic Isolates within race group displayed different reactions Races virulent on stem rust resistance genes Sources of No of isolates vir. at both No of isolates vir. only at 24°C resistance 21/24°C Rpg1 BCBGB, GCBBB GCBBB,BCBBB Rpg2 GCBGB, QCMBB, BMBBB, BBBBB, BBBBB, BCBGB,BMBBB, JCBBB, BCBGB GCBBB Rpg3 BCBGB, JCBBB, QCBBB GHBBB, QHMJC, BMBBB, GCBBB, BMBBB rpg4/Rpg5 None None Rpg6 LCBNB, BCBGB, QCMBB RpgU BCBBB RpgBH QCBGB Isolates within race group displayed different reactions Conclusions so far!!! * This population exhibited high level of diversity 23 races were identified from 83 isolates. * Virulence to barley stem rust Rpg1, Rpg2 and Rpg3 detected * Virulence to Rpg6, RpgU and RpgBh detected only at higher temperature Scenario of barley leaf rust survey in the United States from 2010‐2013 in terms of virulence Barley leaf rust Puccinia hordei Most commonly found rust on barley Macrocyclic and heterocious Reproduces asexually in the US Sporadic epidemics in the past No significant yield loss of barley 2013‐2014 Barley yield losses due to rust pathogens Barley leaf rust survey in the United States Low number of samples received! Year No of samples No of isolates 2010 1 3 2011 12 ‐ 2012 43 122 2013 16 48 2014 18 54 Barley leaf rust resistance genes Seedling resistance genes : Rph1‐19 Adult plant Resistance : Rph20‐24 Rph3, 7 and 9 employed world wide Rph7 in the USA Virulence to Rph7 was detected in the 1990s Barley leaf rust resistant cultivar, Doyce released Differential set for barley leaf rust Gene Line Rph1 Sudan Notable Supplement Lines Rph2 Peruvian Rph3 Estate Gene Line Rph4 Gold Rph14 PI 584760 Rph5 Magnificient Rph15 Bowman NIL Rph 6+2 Bolivia ( old) Tunisia 17 Rph7 Cebda capa Tunisia 34 Rph8 Egypt 4 Rph9 Hor 2596 Rph10 Clipper BCB Rph11 Clipper BC 67 Rph12 Triumph 2010 P. hordei isolates from Virginia on cultivar Doyce ISOLATE Gene Line 10VA01‐1 10VA01‐2 10VA01‐3 Rph1 Sudan 33‐ LIF 3 3 LIF Rph2 Peruvian 3 3 33+ Rph3 Estate 33+ 33+ 3+ Rph4 Gold 33+ 3 3 Rph5 Magnif ;1 ;1 ;1 Rph6 Bolivia(new) ;1‐ ;1/3 ;1 LIF Rph6+2 Bolivia(old) 33‐;3 3+ Rph7 Cebda Capa 33+ 3‐; 33+ Rph8 Egypt 43‐ 3‐ 3 Rph9 Hor 2596 23‐ 333‐ Rph10 Clipper BCB 23‐ 3 ‐ Rph11 Clipper BC 67 3‐ 3‐ 23‐ Rph12 Triumph ; 1; ;1‐ Rph13 PI 531849 3‐ 33+ 3 Rph14 PI 584760 ;1 3‐N1+3‐N Rph15 I 95‐282‐2;N;N;N Rouse et al., 2013, Plant Disease Disease reaction of P. hordei isolate 10VA01‐3 on selected barley lines bearing leaf rust resistance genes Rph15 Rph7 Rph5 Rph4 NIL 17 Rph3 584760 Bowman Doyce Cebda capa Magnificient Tunisia PI Estate 2012 Barley leaf rust survey Region States Collections Isolates Received Derived East DE, NC, NY, 22 63 VA South TX, MO 8 24 North NE, MN, WI 9 26 West CA, OR 3 9 Total 11 43 122 Summary of 2012 barley leaf rust survey 2013 Barley leaf rust survey Region States No. of samples No. of isolates East VA, NY 8 24 North MN, WI 2 6 West WA 6 18 Total 5 16 48 Summary of 2013 barley leaf rust survey in the USA 120 100 80 Virulent 60 North East Percent 40 West 20 0 Rph3 Rph4 Rph5 Rph6+2 Rph7 Rph14 Tunisia Tunisia Doyce 17 34 Gene/ Variety Conclusions * Virulence to barley stem rust resistance genes Rpg1, Rpg2 and Rpg3 identified * Isolates with and without temperature‐sensitive response to barley stem rust resistance genes Rpg6, RpgU and RpgBh detected * These isolates are also virulent to Sr9g, Sr9d, Sr21 and Sr35 in different combinations * Virulence to barley leaf rust resistance gene Rph3, 5, 14, 17, and Tunisia 17 identified Please send samples for rust survey!!! Breeding barley to both stem rust and leaf rust is essential and should be integrated with alternate /novel rust control strategies to mitigate yield losses from emerging new races Acknowledgements Cereal Disease Lab University of Minnesota Dr. Matthew Rouse Dr. Brian Steffenson Dr. Yue Jin Dr. Shahryar Kianian Dr. Les Szabo Sam Stoxen Washington State University Jerry Ochocki Mark Hughes Dr. Xianming Chen, USDA‐ARS Dr. Andris Kleinhofs.
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