Abstract
ABSTRACT Dry bean (Phaseolus vulgaris L.) is a key protein and income source grown worldwide. This study determined gene effects influencing resistance to the bacterial brown spot (BBS) disease caused by Pseudomonas syringae pv. syringae, and estimated heritability in a dry bean cross between A55 (resistant) and cultivar RS7 (susceptible). Generations derived from the parents, namely F1, F2, two backcross generations, and the parents themselves were analysed. The six generations were cultivated in a randomised block design with two replications and inoculated with BBS isolates at two weeks after planting. Disease scoring was done at two weeks after inoculation using standard scale (1–9), where 1 represented highly resistant, and 9 represented highly susceptible. Generation means differed (P < 0.001), and scaling test parameters A and C were significant (P < 0.001) revealing that variation in data was not sufficiently explained by additive [d] and dominance [h] components. Five parameters viz. mean [m], [d], [h], additive × additive epistasis [i], and dominance × dominance epistasis [l] were significant (P < 0.001). The [h] and [l] effects had contrasting signs, indicating duplicate epistasis. Significant non-additive gene effects, together with moderate heritability, suggested that phenotypic selection for resistance, especially in early segregating generations, would be ineffective in conventional breeding.
Published Version
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