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Title: Common bacterial blight resistance QTL BC420 and SU91 effect on seed yield, seed weight and canning quality in Dry Bean

item Miklas, Phillip - Phil
item FOURIE, DEIDRE - Agricultural Research Council Of South Africa
item CHAVES, BERNARDO - Washington State University
item CHIREMBE, CONSTANCE - Agricultural Research Council Of South Africa

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2016
Publication Date: 3/3/2017
Citation: Miklas, P.N., Fourie, D., Chaves, B., Chirembe, C. 2017. Common bacterial blight resistance QTL BC420 and SU91 effect on seed yield, seed weight and canning quality in Dry Bean. Crop Science. 57:802-811.

Interpretive Summary: Common bacterial blight is a seed borne disease that seriously limits dry bean production and quality worldwide. The effects of two common bacterial blight resistance genes SU91 and BC420 on seed yield, disease severity, seed weight and canning quality were examined across five field environments and two disease treatments (inoculated and non-inoculated). There were no seed yield-drag effects observed indicating the QTL can be deployed without harming yield potential in environments which lack the disease. The SU91 gene contributed a significant yield advantage under severe disease pressure. Both genes helped to maintain seed size under moderate to high disease pressure. Canning quality was adversely affected by BC420 gene. Overall our results indicate that BC420 and SU91 genes are recommended in combination for effective control of common blight epidemics. However, it is warranted that breeders continue to closely monitor BC420 gene for negative effect on canning quality in dry beans.

Technical Abstract: Genetic resistance is useful for integrated control of common bacterial blight (CBB) disease which limits dry bean (Phaseolus vulgaris L.) production worldwide. Resistance QTL from tepary bean (Phaseolus acutifolius A. Gray) and other sources have been used to develop common bean lines with high levels of CBB resistance. This study examines the effect two QTL from tepary bean, BC420 (B) on chromosome Pv06 and SU91 (S) on Pv08, have on agronomic (seed yield, seed weight) and canning quality traits (water uptake, percentage washed drained weight -PWDWT, texture, and visual appearance). Sixteen small white dry bean near-isogenic lines (NILs), representing four homozygous genotypes for the BC420 and SU91 QTL: BBSS, bbSS, BBss, and bbss, the donor resistant parent Teebus-BC5 (BBSS) and recurrent susceptible parent ‘Teebus’ (bbss), were tested in replicated, inoculated and non-inoculated field plots, across five environments in South Africa. Plots were inoculated with a mixture of Xap (Xanthomonas axonopodis pv. phaseoli) and Xff (X. fuscans sbsp. fuscans) isolates (X326, Xf260, Xf410). It was determined that BC420 and SU91 QTL did not cause a yield penalty in non-inoculated plots in environments with low to no disease. SU91 provided yield protection under severe disease pressure, and both QTL in combination reduced disease severity score under moderate to high disease pressure. Seed weight was maintained in lines with the QTL under severe to moderate pressure, and was unaffected by the QTL in low to no disease environments. Water uptake was significantly reduced in genotypes with BC420 (BBSS, BBss) and likely influenced traits measured subsequently: lower PWDWT, firmer texture, and less attractive visual appearance, causing slightly reduced canning quality overall. Deployment of BC420 and SU91 QTL can be safely recommended for control of CBB, as no agronomic penalty was observed in CBB-free conditions, but canning quality should be closely monitored in lines with BC420.