VIRULENCE OF APPLE SCAB PATHOGEN POPULATION IN BELARUS

One of the most important directions for protection of apple tree against scab in the world fruitgrowing is breeding and further cultivation of resistant varieties. However, there are a number of drawbacks in this area, and the main are duration of creation of commercially relevant and at the same time sustainable variety, and the problem of variety resistance loss due to appearance of new more aggressive races of pathogen. This article presents the results of studying the virulence of isolates from host plants – apple varieties with Rvi6 gene of resistance to scab gene. In the apple scab population 14 virulence genes were identified of 19 known. There is an increase of the genetic diversity of populations of pathogen of apple scab – Venturia inaequalis in the last forty years due to quality and quantity of genotypes. The genetic structure of populations of the pathogen showed new virulence genes – p-10⁺ , p-11⁺ and p-14⁺ , increase in the number of virulence genes was determined. The strains of the pathogen of apple scab, obtained from the host plants with Rvi6 gene, have different virulence properties, and also have common virulence genes in relation to some differentiator varieties. In the scab population genes of virulence р-1⁺ and р-14⁺ dominated. A group of scab pathogen strains was determined combining high virulence and aggressiveness: BM-3, BM-9, Bsl-1, Dr-3 and Zr-4, which must be included in the inoculum to create an artificial background when selecting resistant to scab apple hybrids. Monitoring of the genetic diversity of virulence and aggressiveness allows to systematically adjust the selection strategy for apple trees. Using of the defined strains of apple tree scab pathogens for creation of artificial infectious backgrounds with the maximum variety of virulence and aggressiveness genes will allow to objectively assess the stability level of both the apple tree original forms and the hybrids

Venturia inaequalis, apple tree hybrids, resistant varieties, breeding, scab, strains, population, diversity, virulence genes, aggressiveness, selection

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