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Szabo, L.J.

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Szabo
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L.J.
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Szabo, L.J.
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2015 - 20162
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Author: Gale, S. × AGROVOC: PUCCINIA GRAMINIS ×

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    Kenyan Isolates of Puccinia graminis f. sp. tritici from 2008 to 2014: virulence to SrTmp in the Ug99 race group and implications for breeding programs
    (American Phytopathological Society (APS), 2016) Newcomb, M.; Olivera Firpo, P.D.; Rouse, M.N.; Szabo, L.J.; Johnson, J.W.; Gale, S.; Luster, D.G.; Wanyera, R.; Macharia, G.; Bhavani, S.; Hodson, D.P.; Patpour, M.; Hovmoller, M.S.; Fetch, T.; Yue Jin
    Frequent emergence of new variants in the Puccinia graminis f. sp. tritici Ug99 race group in Kenya has made pathogen survey a priority. We analyzed 140 isolates from 78 P. graminis f. sp. tritici samples collected in Kenya between 2008 and 2014 and identified six races, including three not detected prior to 2013. Genotypic analysis of 20 isolates from 2013 and 2014 collections showed that the new races TTHST, TTKTK, and TTKTT belong to the Ug99 race group. International advanced breeding lines were evaluated against an isolate of TTKTT (Sr31, Sr24, and SrTmp virulence) at the seedling stage. From 169 advanced lines from Kenya, 23% of lines with resistance to races TTKSK and TTKST were susceptible to TTKTT and, from two North American regional nurseries, 44 and 91% of resistant lines were susceptible. Three lines with combined resistance genes were developed to facilitate pathogen monitoring and race identification. These results indicate the increasing virulence and variability in the Kenyan P. graminis f. sp. tritici population and reveal vulnerabilities of elite germplasm to new races.
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    Phenotypic and genotypic characterization of Race TKTTF of Puccinia graminis f. sp. tritici that caused a Wheat Stem Rust Epidemic in Southern Ethiopia in 2013–14
    (American Phytopathological Society (APS), 2015) Olivera Firpo, P.D.; Newcomb, M.; Szabo, L.J.; Rouse, M.N.; Johnson, J.W.; Gale, S.; Luster, D.G.; Hodson, D.P.; Cox, J.A.; Burgin, L.; Hort, M.C.; Gilligan, C.A.; Patpour, M.; Justesen, A.F.; Hovmoller, M.S.; Woldeab, G.; Hailu, E.; Kotu, B.H.; Tadesse, K.; Pumphrey, M.; Singh, R.P.; Yue Jin
    A severe stem rust epidemic occurred in southern Ethiopia during November 2013 to January 2014, with yield losses close to 100% on the most widely grown wheat cultivar, ‘Digalu’. Sixty-four stem rust samples collected from the regions were analyzed. A meteorological model for airborne spore dispersal was used to identify which regions were most likely to have been infected from postulated sites of initial infection. Based on the analyses of 106 single-pustule isolates derived from these samples, four races of Puccinia graminis f. sp. tritici were identified: TKTTF, TTKSK, RRTTF, and JRCQC. Race TKTTF was found to be the primary cause of the epidemic in the southeastern zones of Bale and Arsi. Isolates of race TKTTF were first identified in samples collected in early October 2013 from West Arsi. It was the sole or predominant race in 31 samples collected from Bale and Arsi zones after the stem rust epidemic was established. Race TTKSK was recovered from 15 samples from Bale and Arsi zones at low frequencies. Genotyping indicated that isolates of race TKTTF belongs to a genetic lineage that is different from the Ug99 race group and is composed of two distinct genetic types. Results from evaluation of selected germplasm indicated that some cultivars and breeding lines resistant to the Ug99 race group are susceptible to race TKTTF. Appearance of race TKTTF and the ensuing epidemic underlines the continuing threats and challenges posed by stem rust not only in East Africa but also to wider-scale wheat production.
    Publication