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Genetic dissection of common bacterial blight resistance in the Andean gene pool of common bean

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Mr Mwiinga Mulube

KT PhD Scholar

PhD in Plant Breeding and Seed Systems, University of Zambia, 2022-2025

Supervisors: Dr Kelvin Kamfwa and Professor Paul Gepts (University of California, Davis).

Project objectives

  1. To determine the incidence and severity of Common Bacterial Blight (CBB) in major bean growing areas of Zambia.

  2. To identify genomic regions and candidate genes associated with CBB resistance in the Andean Diversity Panel of common bean.

  3. To Map Quantitative Trait Loci (QTLs) for CBB resistance in an Andean population derived from a cross of the bean varieties Inferno (ADP 631) and Kabulangeti.

  4. To determine the effectiveness of the CBB major-effect QTLs SU91 and SAP6 against CBB strains in Zambia.

  5. To evaluate the yield stability and genotype × environment interaction (G×E) of CBB resistant elite lines.

Progress to date

  1. A diagnostic survey of CBB incidence and severity was carried out on the main bean growing areas in Zambia (ten districts which account for over 70% of production were targeted). Preliminary results showed a wide distribution of CBB ( 90.6 %) in the production area compared to anthracnose (60%). The level of damage caused by CBB (60.3 %) was also higher than for ANT (38. 8%). Farmers were asked about their source of seed (CBB is mainly transmitted through seed): 73.3 of the farmers interviewed obtained their seed from agro-dealers, and the remainder reused saved seed.

  2. A study was undertaken to identify genomic regions and candidate genes associated with CBB resistance in the Andean Diversity Panel (ADP, a potential source of resistance). 400 ADP lines were screened for CBB resistance in greenhouse conditions and scored using the CIAT severity scale (1-9).GWAS was conducted on 6 strains (Xa3353, Xa484, ZM4, Chito, UNZA and LSK). QTLs on pv3, pv7, pv9 & pv 11 were identified as very important in conditioning resistance against the Zambian strains.

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Mr Mwiinga Mulube

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Mr Mulube collecting diseased samples during a CBB diagnostic survey (i); CBB symptoms on leaves (ii); and in a severely affected field (iii); at the University of California, Davis, during a five-month training visit in 2023 (iv); with Travis Parker (v).

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