Localization of rust resistance genes in old local Russian flaxes by methods of classical genetics

Abstract

Flax rust, a disease that destroyed a significant portion of the yield before the creation of resistant varieties, is currently defeated, but it can cause new outbreaks as identical resistance genes are used in breeding. Since only one of the allelic genes can be introduced into a variety, the aim of this work is to identify genes for resistance to the disease in lines selected during the evaluation of old Russian flaxes from the VIR collection. The original accessions were added to the collection in 1922, that is, before the release of breeding varieties, so their genes are of natural origin. The analysis was performed on an artificial infectious background by methods of classical genetics, including the test for allelism. Nine monogenic lines with the original R genes were crossed to tester varieties for six loci: K, L, M, N, P, and Q. F2 hybrids in the phase of cotyledon leaves were inoculated with monopustule clones of the fungus, not virulent to any of evaluated genes. Gene allelism was checked by the absence of the segregation. It was exactly proven that R genes of the k-716 line from the Pskov kryazh (gc-32) and the k-780 accession from the Minsk oblast (gc-33) were located in the P locus, the gene of the k-846 line from the Ivanovo-Voznesensk oblast (gc-39) was in the M locus, and the gene of the k-834 line from the Vladimir oblast (gc-38) probably belonged to the K locus. The segregation in the crosses of all testers to the k-630 line from the Simbirsk oblast (gc-25) showed that its gene was not allelic to any of the known loci. Probably, there was a formerly unknown locus. The location of the other genes failed to be identified due to the linkage between loci N and P and the presence of several resistance genes in some lines. The gene in gc-9 was in either M or K locus; and the genes of gc-34, gc-40, and gc-46 were located in P or K. Since all the evaluated genes were original, the genes of these lines were different alleles of the identified loci.