SSR Variability of Stem Rust Pathogen on Spring Bread Wheat in Russia

Abstract

Wheat stem rust caused by Puccinia graminis f. sp. tritici Erikss. & E. Henning (Pgt), which used to be a harmful disease of winter wheats in the southern part of Russia, has been largely affecting the yield of spring bread wheat in the territories of temperate climate zone since 2009. A total of 222 Pgt isolates were obtained from samples of susceptible cultivars of spring bread wheat in Central and Volga regions, and Omsk and Novosibirsk provinces in 2019. Genotyping of the isolates was carried out at 16 SSR loci. Number of alleles, proportion of heterozygotes and deviation from Hardy-Weinberg equilibrium were determined at each SSR locus. Based on genetic variability of SSR genotypes, it was shown that the Pgt population is subdivided into two large clusters in the territory of Russian temperate climate zone: “European” population (the Central region) and “Asian” one (the Volga region and two main wheat provinces of Western Siberia). Both the Pgt populations are characterized by a mixed mode of reproduction (sexual and clonal), but different sources of inoculum seem to shape a genotype structure within them. A group of Pgt genotypes with high variability, the inbreeding coefficient closed to zero and low observed heterozygosity was revealed among samples from Omsk. Moreover, two singular SSR genotypes identified among the Asian samples of Pgt isolates should attract a special attention in monitoring of stem rust in order to disclose unexpected rapid changes of the pathogen in the corresponding regions and to prevent the disease outbreak.

Comparative analysis of Argentinian and European populations of Ramularia collo‐cygni on barley

“…Genetic diversity was assessed and the relationships between isolates were compared by Bayesian, multivariate and genetic distance‐based approaches based on previous similar studies (Hassett et al., 2023; Linde & Smith, 2019; Poudel et al., 2019; Skolotneva et al., 2023). Allelic frequencies, effective allelic richness per locus and per population (Ar), rarefied to the population with the lowest sample size, the number of observed multilocus genotypes (MLGs) and the number of MLGs after rarefaction at the smallest sample size (eMLG), and distribution of genotype abundances (evenness, E ) were calculated (Grünwald et al., 2003; Ludwig & Reynolds, 1988; Pielou, 1975).…”

“…Allelic frequencies, effective allelic richness per locus and per population (Ar), rarefied to the population with the lowest sample size, the number of observed multilocus genotypes (MLGs) and the number of MLGs after rarefaction at the smallest sample size (eMLG), and distribution of genotype abundances (evenness, E) were calculated (Grünwald et al, 2003;Ludwig & Reynolds, 1988;Pielou, 1975). Nei's unbiased gene diversity index (H exp ;Nei, 1978) and Simpson's index (λ;Simpson, 1949) were estimated for each population using the R package POPPR (Kamvar et al, 2014) in Rstudio. To assess the reproduction strategy of Rcc from our populations, linkage disequilibrium (LD) analysis was performed to determine deviations from random association (no linkage hypothesis) between the SSR loci.…”