Screening for resistance of the common bean genotypes to common bacterial blight, and bean common mosaic virus

Abstract

Common bacterial blight (CBB), and bean common mosaic (BCMV) limit common beans (Phaseolus vulgaris L.) production worldwide. This study was carried out to perform phenotypic screening and asses the leaf reaction of a resistant line to CBB and BCMV. The experiment was conducted using a Completely Randomized design with three replications under screen-house conditions. Four improved bean genotypes for bruchid resistance were collected from bean improvement projects at the Sokoine University of Agriculture and one commonly cultivated susceptible cultivar was collected from a local market. Bean seeds were sown in a pot with sterilized soil and Xap inoculated by spraying with a bacterial suspension at 18 days after planting, while mechanical inoculation was performed for BCMV on 10 days old leaves. Disease severity of CBB was assessed three times at 14, 21, and 35 days after inoculation using a 1-9 CIAT scale, while for BCMV, symptoms were assessed at 15 days after inoculation. Results show significant differences (p≤0.001) on resistance to both diseases among the common beans genotypes tested. 13A/59-98-3x3-3A (scored 1.3 for CBB; no infected plant with BCMV), AO 29-3-3A (scored 2.0 for CBB; no infected plant with BCMV) and KT020 (scored 1.3 for CBB; only 1 plant was infected with BCMV) had resistance to both diseases while BR59-63-10 was resistant to BCMV and intermediate resistance (scored 3.5) to CBB. Kablanketi was susceptible to both diseases (scored 8 for CBB; 2 plants infected with BCMV). This study verified the resistance against CBB and BCMV in three lines obtained from SUA used for breeding multiple disease resistant cultivars.