Mapping genes for specific and adult plant resistance to rust and abaxial leaf pubescence and their genetic relationships using randomly amplified polymorphic DNA (RAPD) markers in common bean

Dry bean (Phaseolus vulgaris L.) production is limited by bean rust [Uromyces appendiculatus (Pers,) Unger var. appendiculatus], An effective control strategy for this disease is to breed cultivars with durable resistance. Information on the inheritance, genetic relationships, and mapping of genes with molecular markers for specific resistance (SR), adult plant resistance (APR), and abaxial leaf pubescence (ALP) is needed to pyramid the desired genes for durable resistance, ALP was found to be associated previously with APR in Andean germplasm, The objective here was to identify and map RAPD markers for the genes controlling SR, APR, and ALP and to examine their relationships. Five rust pathotypes were inoculated on the unifoliate leaves of 68 recombinant inbred (RI) lines derived from 'PC-50' (presence of SR, APR, and ALP) x XAN-159 (absence of SR, APR, and ALP). SR was determined by a single major gene (Ur-9) to the five rust pathotypes with no detection of recombinants, The fourth trifoliolate leaves were inoculated with one pathotype (A88T-4b), A single major gene Ur-12 controlled APR to that pathotype, The Ur-9 gene (SR) was independent of and epistatic to the Ur-12 gene (APR), Because of the low number of APR lines in the RI population resulting from the elimination of RI lines with SR, an Fz population was developed from a cross of two homozygous RI lines selected for unifoliate susceptibility to pathotype A88T1-4b and for resistance and susceptibility of the fourth trifoliolate leaves to tag RAPD markers linked to the Ur-12 gene (APR), The single major gene Pu-a determinated ALP and was not linked to Ur-9 (SR) and Ur-12 (ALP). The gene Ur-9 (SR) was linked to RAPD marker J13-1100 at 5 cM and was not assigned to any linkage group or other markers. The gene Pu-a (ALP) was mapped at 20.2 cM from 116,500 and 3.9 cM from marker G3,1150 in linkage group 3, The Ur-12 gene (APR) was mapped at 34.6 cM from marker 013.1350 in linkage group 4b, This is the first report of mapping a gene for APR in common bean.