Reaction of Global Collection of Rye (Secale cereale L.) to Tan Spot and Pyrenophora tritici-repentis Races in South Dakota

Abdullah, Sidrat,Sehgal, Sunish K.,Glover, Karl D.,Ali, Shaukat The Korean Society of Plant Pathology 2017 Plant Pathology Journal Vol.33 No.3

Rye (Secale cereale L.) serves as an alternative host of Pyrenophora tritici-repentis (PTR) the cause of tan spot on wheat. Rye is cultivated as a forage or cover crop and overlaps with a significant portion of wheat acreage in the U.S. northern Great Plains; however, it is not known whether the rye crop influences the evolution of PTR races. We evaluated a global collection of 211 rye accessions against tan spot and assessed the diversity in PTR population on rye in South Dakota. All the rye genotypes were inoculated with PTR races 1 and 5, and infiltrated with Ptr ToxA and Ptr ToxB, at seedling stage. We observed 21% of the genotypes exhibited susceptibility to race 1, whereas, 39% were susceptible to race 5. All 211 accessions were insensitive to both the Ptr toxins. It indicates that though rye exhibits diversity in reaction to tan spot, it lacks Ptr ToxA and ToxB sensitivity genes. This suggests that unknown toxins or other factors can lead to PTR establishment in rye. We characterized the race structure of 103 PTR isolates recovered from rye in South Dakota. Only 22% of the isolates amplified Ptr ToxA gene and were identified as race 1 based on their phenotypic reaction on the differential set. The remaining 80 isolates were noted to be race 4. Our results show that races 1 and 4 are prevalent on rye in South Dakota with a higher frequency of race 4, suggesting a minimal role of rye in the disease epidemiology.

Insights into Tan Spot and Stem Rust Resistance and Susceptibility by Studying the Pre-Green Revolution Global Collection of Wheat

Abdullah, Sidrat,Sehgal, Sunish Kumar,Jin, Yue,Turnipseed, Brent,Ali, Shaukat The Korean Society of Plant Pathology 2017 Plant Pathology Journal Vol.33 No.2

Tan spot (TS), caused by the fungus Pyrenophora tritici-repentis (Died) Drechs, is an important foliar disease of wheat and has become a threat to world wheat production since the 1970s. In this study a globally diverse pre-1940s collection of 247 wheat genotypes was evaluated against Ptr ToxA, P. tritici-repentis race 1, and stem rust to determine if; (i) acquisition of Ptr ToxA by the P. tritici-repentis from Stagonospora nodorum led to increased pathogen virulence or (ii) incorporation of TS susceptibility during development stem rust resistant cultivars led to an increase in TS epidemics globally. Most genotypes were susceptible to stem rust; however, a range of reactions to TS and Ptr ToxA were observed. Four combinations of diseasetoxin reactions were observed among the genotypes; TS susceptible-Ptr ToxA sensitive, TS susceptible-Ptr ToxA insensitive, TS resistant-Ptr ToxA insensitive, and TS resistant-Ptr ToxA toxin sensitive. A weak correlation (r = 0.14 for bread wheat and -0.082 for durum) was observed between stem rust susceptibility and TS resistance. Even though there were no reported epidemics in the pre-1940s, TS sensitive genotypes were widely grown in that period, suggesting that Ptr ToxA may not be an important factor responsible for enhanced prevalence of TS.

Characterization of Pyrenophora tritici-repentis (Tan Spot of Wheat) Races in Baltic States and Romania

Abdullah, Sidrat,Sehgal, Sunish Kumar,Ali, Shaukat,Liatukas, Zilvinas,Ittu, Mariana,Kaur, Navjot The Korean Society of Plant Pathology 2017 Plant Pathology Journal Vol.33 No.2

Tan spot, caused by the fungus Pyrenophora tritici-repentis, is economically important foliar disease in Latvia, Lithuania, and Romania; however, race structure from Baltic States and Romania is not known. In this study, we performed genotypic and phenotypic race characterization of a large collection of P. tritici-repentis isolates from these countries to determine race structure and utilize this information for better disease management and breeding wheat for tan spot resistance. We characterized 231 single spore isolates from Latvia (n = 15), Lithuania (n = 107), and Romania (n = 109) for Ptr ToxA and Ptr ToxB genes using two genes specific primers. A subset (139) of 231 isolates were further characterized for their race structure by inoculating them individually on tan spot wheat differentials set. Majority (83%) of the 231 isolates amplified Ptr ToxA gene suggesting prevalence of race 1 and 2. Further, phenotypic characterization of 139 isolates also showed wide prevalence of races 1 (68%), 2 (8%), 3 (11%), and 4 (5%) were also identified from Baltic States as well as Romania. Eighteen of the isolates (13%) did not seem to be of any of the eight known races as they lacked Ptr ToxA gene but they behaved like either race 1 or race 2, suggesting possibility of novel toxins in these isolates as their virulence tools.

Reaction of Global Collection of Rye (Secale cereale L.) to Tan Spot and Pyrenophora tritici-repentis Races in South Dakota

Sidrat Abdullah,Sunish K. Sehgal,Karl D. Glover,Shaukat Ali 한국식물병리학회 2017 Plant Pathology Journal Vol.33 No.3

Rye (Secale cereale L.) serves as an alternative host of Pyrenophora tritici-repentis (PTR) the cause of tan spot on wheat. Rye is cultivated as a forage or cover crop and overlaps with a significant portion of wheat acreage in the U.S. northern Great Plains; however, it is not known whether the rye crop influences the evolution of PTR races. We evaluated a global collection of 211 rye accessions against tan spot and assessed the diversity in PTR population on rye in South Dakota. All the rye genotypes were inoculated with PTR races 1 and 5, and infiltrated with Ptr ToxA and Ptr ToxB, at seedling stage. We observed 21% of the genotypes exhibited susceptibility to race 1, whereas, 39% were susceptible to race 5. All 211 accessions were insensitive to both the Ptr toxins. It indicates that though rye exhibits diversity in reaction to tan spot, it lacks Ptr ToxA and ToxB sensitivity genes. This suggests that unknown toxins or other factors can lead to PTR establishment in rye. We characterized the race structure of 103 PTR isolates recovered from rye in South Dakota. Only 22% of the isolates amplified Ptr ToxA gene and were identified as race 1 based on their phenotypic reaction on the differential set. The remaining 80 isolates were noted to be race 4. Our results show that races 1 and 4 are prevalent on rye in South Dakota with a higher frequency of race 4, suggesting a minimal role of rye in the disease epidemiology.

Insights into Tan Spot and Stem Rust Resistance and Susceptibility by Studying the Pre-Green Revolution Global Collection of Wheat

Sidrat Abdullah,Sunish Kumar Sehgal,Yue Jin,Brent Turnipseed,Shaukat Ali 한국식물병리학회 2017 Plant Pathology Journal Vol.33 No.2

Tan spot (TS), caused by the fungus Pyrenophoratritici-repentis (Died) Drechs, is an important foliardisease of wheat and has become a threat to worldwheat production since the 1970s. In this study a globallydiverse pre-1940s collection of 247 wheat genotypeswas evaluated against Ptr ToxA, P. tritici-repentisrace 1, and stem rust to determine if; (i) acquisition ofPtr ToxA by the P. tritici-repentis from Stagonosporanodorum led to increased pathogen virulence or (ii)incorporation of TS susceptibility during developmentstem rust resistant cultivars led to an increase in TSepidemics globally. Most genotypes were susceptible tostem rust; however, a range of reactions to TS and PtrToxA were observed. Four combinations of diseasetoxinreactions were observed among the genotypes;TS susceptible-Ptr ToxA sensitive, TS susceptible-PtrToxA insensitive, TS resistant-Ptr ToxA insensitive,and TS resistant-Ptr ToxA toxin sensitive. A weakcorrelation (r = 0.14 for bread wheat and –0.082 fordurum) was observed between stem rust susceptibilityand TS resistance. Even though there were no reportedepidemics in the pre-1940s, TS sensitive genotypeswere widely grown in that period, suggesting that PtrToxA may not be an important factor responsible forenhanced prevalence of TS.

Characterization of Pyrenophora tritici-repentis (Tan Spot of Wheat) Races in Baltic States and Romania

Sidrat Abdullah,Sunish Kumar Sehgal,Shaukat Ali,Zilvinas Liatukas,Mariana Ittu,Navjot Kaur 한국식물병리학회 2017 Plant Pathology Journal Vol.33 No.2

Tan spot, caused by the fungus Pyrenophora triticirepentis,is economically important foliar disease inLatvia, Lithuania, and Romania; however, race structurefrom Baltic States and Romania is not known. Inthis study, we performed genotypic and phenotypicrace characterization of a large collection of P. triticirepentisisolates from these countries to determinerace structure and utilize this information for betterdisease management and breeding wheat for tanspot resistance. We characterized 231 single sporeisolates from Latvia (n = 15), Lithuania (n = 107), andRomania (n = 109) for Ptr ToxA and Ptr ToxB genesusing two genes specific primers. A subset (139) of231 isolates were further characterized for their racestructure by inoculating them individually on tan spotwheat differentials set. Majority (83%) of the 231 isolatesamplified Ptr ToxA gene suggesting prevalenceof race 1 and 2. Further, phenotypic characterizationof 139 isolates also showed wide prevalence of races 1(68%), 2 (8%), 3 (11%), and 4 (5%) were also identifiedfrom Baltic States as well as Romania. Eighteenof the isolates (13%) did not seem to be of any of theeight known races as they lacked Ptr ToxA gene butthey behaved like either race 1 or race 2, suggestingpossibility of novel toxins in these isolates as theirvirulence tools.