Generation mean analysis for resistance to bacterial brown spot disease in dry bean

Dry bean (<i>Phaseolus vulgaris</i> 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 <i>Pseudomonas syringae pv. syringae,</i> 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 (<i>P </i>&lt; 0.001), and scaling test parameters A and C were significant (<i>P</i> &lt; 0.001) revealing that variation in data was not sufficiently explained by additive [d] and dominance [h] components. Five parameters <i>viz</i>. mean [m], [d], [h], additive × additive epistasis [i], and dominance × dominance epistasis [l] were significant (<i>P</i> &lt; 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.