Identification of coupling and repulsion phase RAPD markers for powdery mildew resistance gene er-1 in pea

Powdery mildew is a serious disease of pea caused by the obligate parasite Erysiphe pisi Syd. Random amplified polymorphic DNA (RAPD) analysis has emerged as a cost-effective and efficient marker system. The objective of this study was to identify RAPD markers for powdery mildew resistance gene er-1. The resistant cultivar Highlight (carrying er-1) and the susceptible cultivar Radley were crossed, and F3 plants were screened with Operon (OP) and University of British Columbia (UBC) primers, using bulked segregant analysis. A total of 416 primers were screened, of which amplicons of three Operon primers, OPO-18, OPE-16, and OPL-6, were found to be linked to er-1. OPO-181200 was linked in coupling (trans to er-1) and no recombinants were found. OPE-161600 (4 ± 2 cM) and OPL-61900 (2 ± 2 cM) were linked in repulsion (cis to er-1). The fragments OPO-181200 and OPE-161600 were sequenced and specific primers designed. The specific primer pair Sc-OPO-181200 will be useful in identifying homozygous resistant individuals in F2 and subsequent segregating generations. Sc-OPE-161600 will have greatest utility in selecting heterozygous BC\dn6 nF1 individuals in backcross breeding programs.Key words: bulked segregant analysis,Erysiphe pisi, pea, RAPD.