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 f rom a cross between cultivars 'Leger' and 'CI 9831' was characterized by RA PD (random amplified polymorphic DNA) markers for resistance to isolate WRS 857 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 : susceptibl e) segregation ratio of the doubled-haploid (DH) progeny, was found to be a ssociated with three different genomic regions by RAPD analysis. Of 500 RAP D random primers that were screened against the parents, 195 revealed polym orphic bands, seven showed an association to the resistance in bulks, and t hese seven markers were mapped to three unlinked genomic regions. Two of th ese 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).