Abstract

George Muhamba Tryphone, Luseko Amos Chilagane, Deogracious Protas, Paul Mbogo Kusolwa and Susan Nchimbi-Msolla

Common bacterial blight (CBB) caused by Xanthomonas axonopodis pv phaseoli (Xap) is an important disease of common bean in Tanzania causing severe damage. This study was carried out to introgress resistance to CBB to the adapted common bean in Tanzania with the facilitation of molecular markers along with determining the inheritance and heritability of the disease. Crosses were made between the adapted parent Kablanketi and the resistant parent Vax 4 and their F1, F2 and the backcrosses to both parents generated. The phenotypic evaluation was carried out after inoculation with Xap and the molecular marker was applied on the F2 generations using the SCAR marker SAP 6 linked to a QTL for CBB resistance. The result shows no significant deviation from the expected 3:1 (χ2 = 0.47; P>0.05) in the F2 population and 1:1 for the backcross to the susceptible parent. These results that resistance in Vax 4 to Xap is conditioned by the presence of dominant genes. The moderate heritability of 0.32 was estimated implying that resistance is conditioned by one major gene which has effects of partial resistance. There were significant correlation between the phenotypic reaction and molecular marker screening (resistant QTL) (r = 0.502; p<0.05). This indicates there are greater chances of selecting resistant individuals using molecular markers which also exhibited resistance under field conditions.