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 [U romyces appendiculatus (Pers,) Unger var. appendiculatus], An effectiv e control strategy for this disease is to breed cultivars with durable resistance. Information on the inheritance, genetic relationships, an d mapping of genes with molecular markers for specific resistance (SR) , adult plant resistance (APR), and abaxial leaf pubescence (ALP) is n eeded to pyramid the desired genes for durable resistance, ALP was fou nd to be associated previously with APR in Andean germplasm, The objec tive here was to identify and map RAPD markers for the genes controlli ng SR, APR, and ALP and to examine their relationships. Five rust path otypes were inoculated on the unifoliate leaves of 68 recombinant inbr ed (RI) lines derived from 'PC-50' (presence of SR, APR, and ALP) x XA N-159 (absence of SR, APR, and ALP). SR was determined by a single maj or gene (Ur-9) to the five rust pathotypes with no detection of recomb inants, The fourth trifoliolate leaves were inoculated with one pathot ype (A88T-4b), A single major gene Ur-12 controlled APR to that pathot ype, 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 populatio n resulting from the elimination of RI lines with SR, an Fz population was developed from a cross of two homozygous RI lines selected for un ifoliate susceptibility to pathotype A88T1-4b and for resistance and s usceptibility of the fourth trifoliolate leaves to tag RAPD markers li nked 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 a ny linkage group or other markers. The gene Pu-a (ALP) was mapped at 2 0.2 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 li nkage group 4b, This is the first report of mapping a gene for APR in common bean.