Effect of rhizobia inoculation on response of adopted bean cultivars to common bacterial blight infection

Abstract

Common bacterial blight (CBB) [Xanthomonas axonopodis pv. phaseoli (Xap) and Xanthomonas fuscans subsp. fuscans (Xff)]. is the second most devastating disease of common beans in mid altitude bean growing areas of Uganda. The disease affects seed quality and can reduce yield by up to 45% and may be more in susceptible cultivars. CBB is very difficult to control due to the seed-borne nature of the pathogen. Although an integrated disease management approach has been recommended for its management, the disease still causes significant losses. Therefore, there is a need for more effective options. This research investigated the potential of the bacteria rhizobia to induce resistance against CBB in common beans. The study revealed that moderate resistance exists in adopted bean cultivars in Uganda. Inoculation of common beans (Phaseolus vulgaris) with Rhizobia induced resistance to CBB but not all tested genotypes showed the same response as some showed higher induced resistance than others. This indicates that there is potential for use of rhizobia in biological management of CBB disease when combined with the variety resistance and other agronomic practices like crop rotation and residue management. More Rhizobia strains should be isolated and tested on a number of genotypes to establish the right Rhizobia genotype combination. Further research should be carried out to establish the relationship between induced resistance and nodulating ability of different bean varieties.