Inheritance and RAPD tagging of multiple genes for resistance to net blotch in barley.

A doubled haploid barley (Hordeum vulgare L.) population that was created from a cross between cultivars 'Léger' and 'CI 9831' was characterized by RAPD (random amplified polymorphic DNA) markers for resistance to isolate WRS857 of Pyrenophora teres Drechs. f. sp. maculata Smedeg., the causal agent of the spot form of net blotch. Resistance, which initially appeared to be conferred by a single gene from the approximate 1:1 (resistant : susceptible) segregation ratio of the doubled-haploid (DH) progeny, was found to be associated with three different genomic regions by RAPD analysis. Of 500 RAPD random primers that were screened against the parents, 195 revealed polymorphic bands, seven showed an association to the resistance in bulks, and these seven markers were mapped to three unlinked genomic regions. Two of these regions, one of which was mapped to chromosome 2, have major resistance genes. The third region has some homology to the chromosome 2 region. This study demonstrates the simultaneous location of markers for more than one gene governing a trait by using RAPD and bulked segregant analysis (BSA).