Identification of wheat samples for resistance to toxins of Pyrenophora tritici-repentis (Ptr)
Pyrenophora tritici-repentis (Ptr) is a causal agent of tan spot in wheat in Kazakhstan, as it has been around the world. The pathogen produces host-specific toxins which interact with the wheat host sensitivity loci. The aim of this study was 1) to identify whether selected Kazakhstani isolates of P. tritici- repentis possessed the Ptr toxin genes ToxA and/or ToxB and 2) to identify the wheat varieties resistant to HST ToxA and ToxB. As a result of the analysis of the frequency of occurrence of PTR races, it was found that races 7 (25%) and 8 (41.6%) dominate in isolates from southern Kazakhstan, and race 4 (62.5%) prevails in northern Kazakhstan. Twenty single spore isolates collected from wheat-growing areas of the South and North of Kazakhstan representing the P. tritici-repentis population were characterized for the presence of the Ptr ToxA and Ptr ToxB genes, using two gene specific primers. Eight (40%) Kazakhstani P. tritici-repentis isolates were positive for the ToxA gene, and two isolates (10%) were positive for the ToxB gene. ToxB gene was not previously found in our country, but the results of this study show the appearance of this toxin in south Kazakhstan. Eleven (64.7%) wheat varieties resistant to HST ToxA were identified using molecular markers linked to the tsn1 gene, insensitive to Ptr ToxA. The identified genotypes are recommended for use in breeding for wheat resistance to tan spot.