Pavel Lízal

Identification of resistance genes against powdery mildew in four accessions of Hordeum vulgare ssp. spontaneum

SummaryFour newly detected accessions of wild barley (Hordeumvulgare ssp. spontaneum) resistant to powdery mildew caused by Blumeriagraminis f. sp. hordei were studied with the aim of finding the number of genes/loci conferring the resistance of individual accessions, the type of inheritance of the genes and their relationships to the Mla locus. F2 populations after crosses between the winter variety ‘Tiffany’ and four wild barley accessions and use of microsatellite DNA markers were focused on the identification of individual resistance genes/loci by means of their chromosomal locations. In PI466495, one locus conferring powdery mildew resistance was identified in highly significant linkage with the marker Bmac0213. This location is consistent with the known locus Mla on chromosome 1HS. In the other three accessions the resistance was determined by two independent loci. In PI466197, PI466297 and PI466461, one locus was identified on chromosome 1HS and three new loci were revealed on chromosomes 2HS (highly significant linkage with Bmac0134), 7HS (highly significant linkage with Bmag0021) and 7HL (significant linkage with EBmac0755). Our prospective aim is identification of further linked DNA markers and the exact location of the resistance genes on the barley chromosomes.

New CAPS Marker for Selection of a Barley Powdery Mildew Resistance Gene in the Mla Locus

In PI466495, a powdery mildew resistance source of wild barley (Hordeum vulgare ssp. spontaneum), one gene conferring powdery mildew resistance was identified in the Mla locus. In this paper, the RGH1a gene sequence was used as source for the development of a cleaved amplified polymorphic sequence (CAPS) marker. Co-segregation between this marker and powdery mildew resistance was analysed by specific DNA fragments associated with each allele of the gene using 286 F2 plants derived from a cross between winter barley (H. vulgare L.) variety ‘Tiffany’ and PI466495. For the co-dominant marker RGH1aI1a, three fragments, 370 bp, 82 bp and 59 bp in size, were amplified from F2 plants exhibiting resistance reaction types 0 and 0–1 to powdery mildew; whereas two fragments, 429 bp and 82 bp in size, were amplified in susceptible plants. Simple procedures based on polymerase chain reaction and restriction enzyme digestion allowed for identifying the plants susceptible to powdery mildew (Blumeria graminis f. sp. hordei) and plants homozygous or heterozygous for the resistance allele. The RGH1aI1a marker was positioned 0.85 cM to the resistance gene and the efficiency of marker-assisted selection (MAS), evaluated as the probability of crossing-over between the marker and the targeted gene, was 99%. The CAPS marker RGH1aI1a is a valuable candidate for MAS and gene transfer into barley varieties susceptible to powdery mildew.

Genetic analysis of thirteen accessions of Hordeum vulgare ssp. spontaneum resistant to powdery mildew

Thirteen accessions of wild barley (Hordeum vulgare ssp. spontaneum) resistant to powdery mildew caused by the fungus Blumeria graminis f. sp. hordei were studied with the aim of determining the number of resistance genes and their allelic relationships to the Mla locus on the short arm of chromosome 1H. In five accessions (PI391130, PI466193, PI466200, PI466495 and PI466510), the resistance was caused by one gene, in seven accessions (PI354949, PI391081, PI466158, PI466197, PI466211, PI466297 and PI466461) by two independent genes and in PI301004 by three independent genes. The type of inheritance of all analysed genes except two was dominant or semi-dominant; only one of two genes in PI391081 and PI466297 was recessive. Allelism tests confirmed that in 10 accessions one gene was allelic with the Mla locus, and in three accessions (PI391081, PI466193 and PI466297) the resistance genes were different from the Mla locus.