Publication details

Identification of new powdery mildew resistance genes in Hordeum vulgare

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Year of publication 2007
Type Article in Proceedings
Conference Plant biotechnology: impact on high quality plant production
MU Faculty or unit

Faculty of Science

Field Genetics and molecular biology
Keywords barley; genetic mapping; DNA markers; powdery mildew
Description Blumeria graminis DC. f. sp. hordei Ém. Marchal is the obligate biotrophic fungus which causes powdery mildew in barley (Hordeum vulgare L.). Powdery mildew is one of the common foliar diseases in temperate climates. The control of powdery mildew disease can be achieved through the use of resistant varieties of barley. Considering the limited number or complete lack of resistance genes in cultivated barley, other Hordeum species have been screened for effective resistance genes to powdery mildew. A very promising new source of resistance genes to important barley diseases including powdery mildew is the progenitor of cultivated barley H. vulgare ssp. spontaneum. Mapping of powdery mildew resistance genes by means of genetic markers utilizes the identification of markers linked to the resistance genes and the location of known genes on the barley genetic map. DNA markers are the primary tools useful for genetic mapping. The objective of our work was to map resistance genes against powdery mildew in two F2 populations derived from crosses between the winter barley variety Tiffany and the wild barley accessions PI466461 and PI466197 using simple sequence repeat (SSR) markers. Sequence tagged-site markers from target chromosomal regions were used for the development of cleaved amplified polymorphic sequence (CAPS) markers linked to the resistance genes of interest. Linkage detection was carried out with 149 plants of each F2 population and with 120 SSRs and 18 CAPSs. Map Manager QTXb17 package software was used to construct linkage groups and establish orders and map distances for each group of markers. A two-locus model of resistance was shown by genetic mapping of both F2 populations. In PI466461, one gene coincided with the Mla locus with an expected position 8 cM proximal to the RGH1aI1a marker designed for the known RGH1a gene sequences. The other and new resistance locus derived from the wild accession was found on the short arm of chromosome 7H. It was mapped close to the sub-telomeric region of this chromosome and is flanked by the markers Bmag0021 and EBmag0794 at the distances of 4 and 9 cM, respectively. Until now, neither a dominant/semi-dominant major gene nor a quantitative trait locus conferring powdery mildew resistance has been located on the upper arm of chromosome 7H of barley. In PI466197, molecular analysis revealed a highly significant linkage with the markers Bmac0213 and MGB402 on the short arm of chromosome 1H, which is the position consistent with the Mla locus. The other gene was located between the markers Bmac0134 and MWG878 on the short arm of chromosome 2H, which could be a newly identified locus of powdery mildew resistance. The prospect of our work is to find markers tightly linked to resistance genes so that breeders could use them for marker-assisted selection.
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