A CODOMINANT RANDOMLY AMPLIFIED POLYMORPHIC DNA (RAPD) MARKER USEFUL FOR INDIRECT SELECTION OF BEAN GOLDEN MOSAIC-VIRUS RESISTANCE IN COMMON BEAN

Bean golden mosaic virus (BGMV) is a devastating disease of common bea n (Phaseolus vulgaris L.) in tropical America. The disease is effectiv ely controlled by combinations of genetic resistances, The most widely deployed source of resistance to BGMV is a recessive gene (bgm-1) der ived from the dry bean landrace cultivar Garrapato (Mexico) that condi tions a nonmosaic partial resistance response to the pathogen, To expe dite introgression of partial resistance into snap bean for southern F lorida and other susceptible dry bean market classes for the Caribbean and Central American regions, a RAPD marker tightly linked to bgm-1 h as been identified, Two contrasting DNA bulks, one consisting of five BGMV-resistant and the other five susceptible F-6 recombinant inbred l ines, were used to screen for polymorphic fragments amplified by 300 d ecamer primers in the polymerase chain reaction, RAPDs generated betwe en the bulks were analyzed across F-2 populations segregating for the marker and the gene, One codominant RAPD marker (R2(570/530)) tightly linked to the recessive resistance gene bgm-1 was found, The 530-base pair (bp) fragment was linked in repulsion with bgm-1 and the other 57 0-bp fragment was linked in coupling, No recombinants between R2(570/5 30) and bgm-1 were observed among 91 F-2 progeny from one dry bean pop ulation, and there were two recombinants (4.2 cM) observed among 48 F- 2 progeny combined across four snap bean populations, Assays of R2(570 /530) across susceptible germplasm and lines likely to have the 'Garra pato'-derived partial resistance to BGMV have revealed that the codomi nant marker is gene-pool nonspecific and maintains its original linkag e orientation with the recessive bgm-1 gene through numerous meioses, The codominant marker is useful for rapidly introgressing partial resi stance to BGMV into susceptible germplasm.