Inheritance of Resistance to Common Bacterial Blight in Tepary Beans

Abstract

Common bacterial blight, incited by the bacterium Xanthomonas campestris pv. phaseoli (Xcp), is a serious disease of common beans [Phaseolus vulgaris (P. v.)]. Some tepary beans (P. acutifolius) are resistant (R) to Xcp and used to breed P. v. with R to Xcp. The objective was to determine the inheritance of the reaction to different strains of Xcp in crosses between susceptible (S) and R tepary lines. The parents, F2, and F3 populations from six tepary crosses involving 3 R × S, 1 R × moderately (M) R, and 2 R × R were inoculated with Xcp strains EK-11, LB-2, and SC-4A. Different single dominant genes controlled the reaction to different Xcp isolates in R × S crosses. Coupling linkage was detected between the genes controlling the reactions to each of the Xcp strains in the crosses NE #4B(s) × NE #19(R) and NE #4B(S) × CIAT-640005(R), except for NE #8A(MR) × NE #4B(S) with strains EK-11 and LB-2 and EK-11 and SC-4A. Transgressive segregation for S was observed in the F2 and F3 NE #8A × NE #8B(R), indicating that the parents possessed different genes for R. No segregation for reactions occurred n the F2 NE #8B × NE #19 and NE #19 × CIAT-640005, indicating that these parents possessed the same genes for R to the three strains.