Comprehensive approach to replenishing the English walnut gene pool through the study of local seed populations in Krasnodar Region

Abstract

promising genotypes in the areas where this species grows. The identification of the valuable breeding forms of English walnut among local seed populations facilitates the solution of breeding problems and replenishes the collections of genetic resources with valuable specimens. In this work, we aim to assess the prospects of using new forms to solve breeding problems by means of phenotypic evaluation and molecular genetic analysis. The search for promising forms was carried out in 2022–2023 on the territory of settlements in the different districts of Krasnodar Krai. Economically valuable traits were recorded according to the “Program and Procedure for the Studying the Varieties of Fruit, Berry, and Nut Crops.” In order to assess the level of genetic diversity in the sample of new, promising forms of English walnut, SSR genotyping was carried out using seven microsatellite DNA markers: WGA001, WGA376, WGA069, WGA276, WGA009, WGA202, WGA089. The heterogeneous group of varieties and elite breeding forms of the North Caucasus Federal Scientific Center of Horticulture, Viticulture, and Winemaking, representing the overall diversity of the collection, was also included in the studied sample. The comparison of the polymorphism level in the studied specimens for both individual markers and the entire sample of markers suggests a relatively high heterogeneity of the new, promising forms included in the study. The use of UPGMA, PCoA, and analysis in STRUCTURE software allowed genetic relationships to be established between the new, promising forms and specimens from the genetic collection of the North Caucasus Federal Scientific Center of Horticulture, Viticulture, and Winemaking. The new forms were found not to form a separate cluster and to generally have an intermediate position between the three genotype groups in the gene pool collection. For the new forms, the effect of the Central Asian geneplasm was established, which determines the presence of several valuable breeding traits. Given the data on the genetic diversity of new, promising forms of English walnut relative to the genetically contrasting sample of breeding forms from the collection of the North Caucasus Federal Scientific Center of Horticulture, Viticulture, and Winemaking, it is reasonable to involve new forms in breeding in order to enrich the local English walnut gene pool.