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).