Antonín Dreiseitl

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.

Characterization and chromosomal location of powdery mildew resistance genes from wild barley PI282605

The objective of this work was to find the identity of three resistance genes against powdery mildew by mapping in an F2 population derived from a cross between winter barley (Hordeum vulgare L.) variety ‘Tiffan’ and the wild barley (H. vulgare ssp. spontaneum) accession PI282605, an effective powdery mildew resistance source.ZusammenfassungDas Ziel dieser Untersuchung bestand in der genetischen Kartierung und Charakterisierung von drei Mehltau-Resistenzgenen in einer F2-Population der Kreuzung der Wintergerstensorte ‘Tiffany’ (Hordeum vulgare L.) und der Akzession PI282605 der Wildgerste (H. vulgare ssp. spontaneum), einer effektiven Mehltau-Resistenzquelle.

Postulation of genes for resistance to powdery mildew in spring barley cultivars registered in the Czech Republic from 1996 to 2010

Powdery mildew caused by the airborne biotrophic fungus Blumeria graminis f. sp. hordei is a common disease of barley. Although it can be controlled by fungicide applications, genetic resistance is an efficient and more environmentally acceptable way of limiting its effect on yield and quality. Spring barley is the second largest cereal crop in the Czech Republic and seventy spring barley cultivars (cvs.) were registered from 1996 to 2010. Seedlings of 43 cvs. were tested for reaction to selected isolates of the pathogen and resistance genes were identified using the postulation method. The following 12 known resistance genes were postulated namely, mlo, Mla6, Mla8, Mla12, Mla13, MlaRu4, MlaN81, Mlg, MlLa, Ml(Ab), Ml(Ro) and Ml(St) and two unknown resistances were found in Paulis and Prosa. Four cvs. (Azit, Paulis, Respekt and Tocada) were heterogeneous for mildew response. The most frequently found gene was mlo, which was present in 29 cvs. In nine of 15 cvs. without mlo, Mlg occurred and in seven cvs. genes located in the Mla locus were postulated. A newly identified resistance in Prosa will be further characterised. This report demonstrates that resistance gene postulation from multi-race tests remains an essential research tool for postulating genes for resistance to plant pathogens.

Resistance of barley variety ‘Venezia’ and its reflection in the Blumeria graminis f. sp. hordei population

Genetic resistance is an efficient and environmentally acceptable way of limiting the damaging effects of plant pathogens on yield and quality of crops. Tests of winter barley variety Venezia revealed an unknown resistance to all tested Blumeria graminis f. sp. hordei isolates. Response type arrays (RTAs) obtained here were created using common avirulent (RT 0) isolates and virulent (RT 4) isolates that first appeared in 2011. RTA of Venezia was identical to RTAs of six other varieties, but differed from RTAs of all other previously tested varieties. Venezia was the first variety to be registered with this resistance, and it is recommended that the resistance be designated Ve. Among 905 isolates randomly collected from the Czech aerial pathogen populations from 2009 to 2015, 13 contained Ve virulence. Each of the isolates differed from the others and thus belonged to different pathotypes. Seven of these 13 pathotypes were collected in the western region of the Czech Republic in an area close to Germany, where Venezia was grown. This finding could support the hypothesis that pathotypes virulent to Venezia have migrated from Germany into the Czech Republic.