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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. |
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