Incorporation of combined resistance to common bacterial blight and common bean viruses into bean bruchid resistant genotype

Dissertation

The study was undertaken to incorporate resistance to Common Bacterial Blight (CBB), Bean Common Mosaic Virus (BCMV) and Bean Common Mosaic Necrosis Virus (BCMNV) into a bean bruchid resistant genotype which have farmer preferred traits (Kablanketi type) to improve common beans yield and increase the storage time of the common beans in Tanzania. First, Arcelin- Phytohaemmagltinin-Alfa (APA) bruchid resistant bean genotypes were phenotypic screened against Xanthomona axonopodis pv. Phaseoli (Xap) (the causal agent of CBB disease) and BCMV diseases. Results showed 3 genotypes with resistance to disease pathogens i.e AO 29-3-3A, KT020, and 13A/59-98-3x3-3A while BR 59- 63-10 had intermediate resistance to CBB but complete resistant to BCMV, while ‘Kablanketi’ was susceptible to both diseases. Selection based on phenotypic screening was done, at which BR 59-63-10 line having bruchid resistance and BCMV was selected and KT020 resistant line to CBB and BCMNV was used as non-recurrent parent to incorporate CBB and BCMNV resistance into BR 59-63-10 (recurrent parent). A single way cross was used between recurrent parent BR 59- 63-10 and non-recurrent parent KT020. The F 1 s were self-pollinated to produce the F 2 generation; F 2 s were screened using Sequence Characterized Amplified Region (SCAR) markers for presence of resistance genes using SAP6, SW13 and ROC11 markers. Nine F 2 individuals had combination genes for CBB, BCMV and BCMNV, while 17 had combination of two genes for resistance and 10 had only one gene for resistance to either of the diseases. Forty plants were phenotypically validated with Xap in the screen house and 31 plants were resistant to Xap. Moderate high narrow sense heritability of 61.1% and 66.8% for CBB, on leaf and pod respectively were obtained, which indicating selection can be done in early generation for CBB. Results showed that CBB resistance was conditioned by one major gene. Result also demonstrated a positive correlation between phenotype and marker score (r=0.41for SAP6) which implied that there high chance of obtaining resistance individual using marker assisted selection to cut down time spent on phenotypic selection. These lines carrying disease resistance need to be fixed for resistance and evaluated in bruchid feeding trials to validate presence of APA protein after which, they will need field evaluation prior to release.

The McKnight Foundation through Bean Bruchid Project