SPECIES COMPOSITION AND STRUCTURE ON MATING-TYPE LOCI AND VIRULENCE OF <i>PYRENOPHORA TERES </i>POPULATIONS IN THE NORTH-WEST REGION OF RUSSIA AND BELARUS
Due to climate change, ways of tillage, crop rotation disorders, changing of cultivars and uncontrolled introduction of seeds there is a change in species composition of crops pathogens. This is especially noticeable on the cereal leaf blights. The aim of the study was to determine the species composition of causal agents of barley leaf blights in North West region of Russia and Belarus. Surveys of barley were held in 2014 in 5 regions of Belarus and in the North West of Russia. It was found that the main pathogen of barley in all areas of research is <i>Pyrenophora teres</i>. In total 9 samples of populations of this pathogen were studied. By use of phytopathological test and PCR diagnostics with specific primers, it was shown that the majority of the population is represented by biological form <i>P. teres</i> f. <i>teres</i>, but in some cases blotch symptoms was caused by <i>P. teres</i> f. <i>maculata</i>. This form of the pathogen has been detected in the Ivanovo district of Brest Region, on the introduced from Western Europe spring and winter barley cultivars: Kangoo, Isocel, Salamandra and Nectaria. Apparently, the spread of new form of <i>P. teres</i> f. <i>maculata</i> in Belarus is due to the import of barley seeds from Western Europe. Using PCR, all pathogen populations were studied on the ratio of mating types idiomorphs. Most of the populations turned out to be panmictic. Nevertheless, in two populations of <i>P. teres</i> f. <i>teres</i> in Russia and in the one in Belarus one mating type was dominate. Among 2 populations of <i>Pyrenophora teres</i> f. <i>maculata</i> one was panmictic and another one consisted entirely from the isolates of one idiomorph. Populations of <i>Pyrenophora teres</i> f. <i>teres</i> were tested for virulence on the international set of barley differentials, consisting from 9 varieties. The populations from Russia and Belarus significantly differed on virulence to certain differentials. Average virulence of Belarus populations was lower than of the Russian populations. Positive correlation between frequencies of MAT1-1 isolates with average virulence of population was determined.