Stability of the association of molecular markers with common bacterial blight resistance in common bean (Phaseolus vulgaris L.)

Common bacterial blight (CBB) caused by Xanthomonas campestris pv. phaseoli is an important disease of common bean (Phaseolus vulgaris L.) throughout the world. Two random amplified polymorphic DNA (RAPD) markers (R7313 and R 4865) linked to genes For CBB resistance, that were transferred to P. vulga ris by an interspecific cross with Phaseolus acutifolius, were identified i n a previous study. The current study was conducted to examine the use of t hese markers for selecting CBB resistant material from 85 F-5:6 lines deriv ed from crosses between two of the resistant lines used previously in the l inkage study and susceptible breeding lines. The results showed that these two markers were located on the same linkage group and explained 22% (P = 0 .0002) of the variation in response to CBB in the current population. Seven ty per cent of the lines that had both markers were classified as resistant in a disease test of the F-5:6 lines, whereas 73% of the lines that had ne ither of the RAPD markers were susceptible. The results indicated that the marker-disease resistance associations remained stable in a plant breeding programme and that they can be used for marker-assisted selection of CBB-re sistant beans.