These researchers are analyzing worldwide populations of the wheat leaf rust fungus Puccinia triticina for genetic variation using simple sequence repeat markers (SSR) and sequence data. Populations from central Asia, South America, North America, Europe, Russia, China, and the Middle East are tested for allelic diversity, Hardy-Weinberg equilibria, observed and expected heterozygosity, and differentiation of groups of molecular genotypes within regional populations. Continental populations are also compared for population genetic parameters and for genetic distance. Isolates with identical genotypes from different continents indicate recent genotype migration between continental regions. SSR data and sequence data is also used in coalescence analysis using a Bayesian approach to determine evolutionary relationships between the different genotype groups.
Populations of P. triticina have been genotyped at the University of Minnesota Genomics Center, using sequence based genotyping. A collection of 565 international isolates from 11 wheat growing regions worldwide and 188 isolates from the U.S. collected in 2016-2018 have been genotyped. Analyses with bioinformatics specialists at MSI are currently underway to determine the genetic relationships between the regional groups using the SBG data. These data will be used to supplement the SSR data set previously worked on. Analysis of the SBG data done by MSI indicated the presence of nine distinct groups of P. triticina in the current U.S. population. Two of these groups had not been described in previous genotyping work. These new groups of isolates had distinct virulence to leaf rust resistance genes in wheat.
Wheat cultivars with long lasting resistance to the wheat leaf rust fungus are characterized genetically to determine their chromosome location and leaf rust resistance gene identity. The resistant cultivars are crossed with a susceptible genotype and recombinant homozygous F6 lines are derived. The F6 lines and parents are genotyped with the 90K single nucleotide polymorphism array. The polymorphic SNPs are mapped to chromosome location using various software programs.
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