Genetic and molecular analysis of new sources of resistance topowdery mildew in barley (Hordeum vulgare ssp. spontaneum)

Thirteen newly identified resistance sources of wild barley Hordeum vulgare ssp. spontaneum to powdery mildew (fungal organism Blumeria graminis f. sp. hordei) were studied with the aim to identify the number of genes conferring resistance to powdery mildew, their allelic relationships, their allelism with Mla gene and the other aim was to localise individual genes on barley genetic map. The genetic as well as the molecular analyses were performed in the segregating F2 populations of crosses between winter barley cultivar Tiffany and individual resistance sources. In five resistance sources the resistance was found to be determined by one gene, in seven sources by two independent genes and in one source by three independent genes. The mode of inheritance of all analysed genes except one was determined to be dominant or semi-dominant, only one was recessive. Allelism tests confirmed that one resistance gene in all sources was Mla. Apparently, various alleles of Mla often participate in the genetic determination of this trait and the gene belongs to those with the highest efficiency. Our next interest was focused on the identification of new resistance genes. Therefore, two resistance accessions, PI466197 and PI466461, with two powdery mildew resistance genes were included in linkage recombination analysis in F2 generations by means of microsatellite DNA markers. Microsatellite markers were generated from barley genome maps and databases. So far amplification method has been optimized for 115 SSR markers. Polymorphism between the parents (H. spontaneum accessions vs. Tiffany) has been investigated with 90 SSR markers and analysed by agarose and polyacrylamide gel electrophoresis. The polymorphism of investigated sources ranged from 48 to 64%. Bulk segregant analysis was used for identification of markers linked with resistance genes. In PI466197, linkage was confirmed with Bmac0213 marker on the short arm of chromosome 1H (Mla locus) and Bmac0134 marker on the short arm of chromosome 2H. In PI466461, the resistance gene was linked with Bmag0021 marker on the short arm of chromosome 7H. The prospect of our work is the selection of progeny with fully effective resistance genes, single or in combinations, which is impossible with classical methods. Therefore, individual resistance genes have been mapped by means of DNA markers and tightly linked markers developed. The results can offer new possibilities in barley breeding.