Diversity of Rhopalosiphum padi L. Collected in Different Geographic Zones of Russia in Relation to the Type of Development

The bird cherry-oat aphid (Rhopalosiphum padi L.) is a major pest of cereal crops, characterized by significant variability in reproductive strategies and population-genetic structure. However, the nuclear-genetic and clonal structure of R. padi populations in Russia remain insufficiently studied. We investigated the genetic diversity and clonal structure of 71 R. padi clones collected in the northwestern and southern regions of European Russia and analyzed their association with life-cycle types. Reproductive strategies were determined experimentally based on traits such as autumn remigration, production of sexual morphs, and overwintering ability. Genetic variation was assessed using seven microsatellite loci; genetic relationships were analyzed via multilocus genotypes, analysis of molecular variance, Neighbor-Joining and UPGMA clustering methods, and principal coordinate analysis. A total of 116 alleles were identified. Northwestern populations exhibited complete multilocus diversity (each clone represented a unique multilocus genotype), whereas repeated genotypes were found in southern populations (G/N = 0.83). Genetic differentiation between regions was significant based on allele frequencies (FST = 0.092; p = 0.001) but not based on allele size variation (RST = 0.019; p = 0.085). Northwestern populations were holocyclic, while southern populations were predominantly anholocyclic, although in-between life-cycle types were found in both geographic regions. Three microsatellite alleles (R5.29b_170, R2.73_286, and S17b_161) showed an association with the life cycle type; based on these, a “life cycle index” (LCI) was developed, enabling the classification of analyzed clones in accordance with experimental phenotyping results. The data indicate significant genetic diversity and incomplete geographic differentiation among Russian R. padi populations and also suggest candidate molecular markers for further study of the genetic basis of reproductive strategies.