Abstract. The purpose of the study. Isolation of Alternaria sp. and their PBS differentiation. The article presents the results of isolation of phytopathogenic fungi of the genus Alternaria spp. from wheat plants and their genetic differentiation using iPBS (Inter Primer Binding Site Polymorphism) analysis. As a result of monitoring studies, it was shown that the fungi Alternaria spp. are the dominant component of the pathocomplex of fungi affecting the embryonic zone of seeds and ears of wheat in the northern regions of Kazakhstan. The pathocomplex of Alternaria is formed by isolates of A. alternata, A. infectoria, and A. tenuissima. Methods. Genetic differentiation of the isolates was performed using iPBS analysis. This method is based on the use of conserved sequences of tRNA binding sites (Primer Binding Sites) as PCR primers. This method is versatile and effective for the direct detection of polymorphism between individuals; therefore, PBS primers can be used in almost any organism, including fungi. Results. Analysis of the PBS primers showed that they all have high resolution in the differentiation of Alternaria spp. The obtained amplification products showed high variability among isolates, both within one species and at the interspecies level. The level of detectable polymorphism varied from 47.43 % to 80.81 %, with an average of 61 %. The size of the amplified PCR fragments ranged from 200 to 3000 bp; on average, amplification was observed from 5 to 15 bands per isolate. Practical significance. This work made it possible to obtain new data on the genetic diversity of Alternaria phytopathogenic fungi for the subsequent development of a strategy for plant protection against Alternaria.

Species of the genus Alternaria are widely distributed as saprophytes on plant residues, as well as pathogens of various plant species. On wheat seeds, Alternaria fungi are localized in the endosperm and fruit shells, causing symptoms of "black germ" disease, and are a dominant component of the wheat seed microbiome. Recently, due to the high potential danger of these fungi, much attention has been paid to the study of the genetic variability of populations that exist in certain climatic conditions. Using retrotransposon sequences as markers increase knowledge about phylogenetic relationships within populations of phytopathogenic fungi, as well as their biodiversity. The iPBS (inter-priming binding sites) method used in this work was applied to detect genetic polymorphism of isolates of the genus Alternaria, as the most frequently encountered genus (the frequency of isolation was more than 50%). The isolates were isolated from wheat seeds that were cultivated in various ecological regions. The 4 iPBS primers used in this study amplified 387 fragments, 352 of which were polymorphic. The level of detected polymorphism varied from 66% when using primer 2224 to 100% when using primer 2242. The information content index of the PIC (polymorphism information content) primers varied in the range of 0.894-0.987. Analysis of genetic polymorphism revealed significant genetic variability among fungal isolates. Genetic analysis of amplification profiles of isolates of fungi of the genus Alternaria conducted using the GenAlex 6.5 software differentiated all isolates into 2 large groups. Isolates of A. infectoria were isolated in a separate cluster. Isolates of A. alternata and A. tennuissima were grouped in a different cluster depending on the species. Research results show that the iPBS method is highly effective for the genetic differentiation of phytopathogenic fungi at both intraspecific and interspecific levels.