title: Insights into Tan Spot and Stem Rust Resistance and Susceptibility by Studying the Pre-Green Revolution Global Collection of Wheat.
abstract: Tan spot (TS), caused by the fungusPyrenophora 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-repentisrace 1, and stem rust to determine if; (i) acquisition of Ptr ToxA by theP. tritici-repentisfromStagonospora nodorumled 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 disease-toxin 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.
authors.affiliation: Department of Agronomy, Horticulture and Plant Science, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: Sidrat
authors.initials: S
authors.lastname: Abdullah
authors.affiliation: Department of Agronomy, Horticulture and Plant Science, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: Sunish Kumar
authors.initials: SK
authors.lastname: Sehgal
authors.affiliation: United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Cereal Disease Laboratory, University of Minnesota, St. Paul, MN 55108, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Department of Agronomy, Horticulture and Plant Science, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: Brent
authors.initials: B
authors.lastname: Turnipseed
authors.affiliation: Department of Agronomy, Horticulture and Plant Science, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: Shaukat
authors.initials: S
authors.lastname: Ali
keywords: Puccinia graminis f. sp. tritici; foliar disease; host-selective toxin; wheat; yellow spot