Occurrence of tan spot (Pyrenophora tritici-repentis) in 2021/2022 growing season

Pyrenophora tritici-repentis (Died.) Drechs, the agent of tan spot, is an economically important pathogen of wheat. It causes grain quality distortion and yield losses up to 53%. Ptr is a necrotrophic pathogen and produces three types of necrotrophic effectors (NEs) (Ptr ToxA, Ptr ToxB and Ptr ToxC) that induce necrosis and chlorosis. The genetic basis of the Ptr-host interaction also includes genes that provide race-nonspecific resistance. In 2022, the percentage of genotypes infected with Ptr in the collections of "disease nurseries" ranged from 11.4% to 94.3%. The lowest number of infected genotypes (11.4%) was recorded in breeding pro-grams for resistance to prevalent pathogens. A low number of genotypes infected with Ptr was also found in the collection of wild relatives (18.4%), while the highest percentage of genotypes susceptible to Ptr was found in varieties originating from Kazakhstan (94.4%). Disease index of Ptr ranged from a trace level up to 50% or more. The length of the Ptr conidia ranged from 73.4 mm to 107.2 mm. Conidia width ranged from 15.5 to 22.8 mm. The results of this study indicated on genotypes that could be used as sources of resistance to Ptr, and also could be introduce in further studies of the mechanisms that provide resistance for Ptr.