Peculiarities of interaction of Tsn1 and ToxA genes in Triticum aestivum – Pyrenophora tritici-repentis pathosystem

Abstract

The tan spot caused by the Pyrenophora tritici-repentis is a harmful and widespread disease in the Russian Federation. Last years, it has been proposed to carry out marker assisted selection (MAS) against the dominant allele of the gene Tsn1 determining the susceptibility to tan spot to speed up the breeding process. However, in these studies, the factor of the population diversity of the pathogen on the effector genes is underestimated, especially on the ToxA gene controlling the synthesis of necrosis inducing toxin Ptr ToxA in susceptible cultivars with the complementary gene Tsn1. In this paper, the results are analysed of inoculation of 24 soft winter wheat cultivars with dominant and recessive Tsn1 alleles by P. tritici-repentis isolates, characterized by the presence or absence of the ToxA (ToxA+ and ToxA–) effector gene. Using the example of the interaction between Tsn1 alleles and P. tritici-repentis ToxA effector gene in specific pairs of genetically characterized wheat samples and pathogen isolates, it was shown that the same sign of “formation of necrosis on leaves” in combinations of different genotypes of variety–isolate (Tsn1Tsn1– ToxA+/ToxA– and tsn1tsn1 – ToxA+/ToxA–) had a different genetic nature. 41.7 % of the cases of gene interactions did not correspond to the gene-to-gene scheme. This result is explained by either the presence of necrosis inducing toxins in isolates other than Ptr ToxA, or decrease in the level of ToxA gene expression in different wheat genotypes.