Strategy to identify common beans with resistance to white mould for dry-irrigated areas: Additional evidence

Abstract

In a previous study, common bean (Phaseolus vulgaris L.) genotypes were selected in the field for reactions to white mould (WM), caused by Sclerotinia sclerotiorum. These genotypes, along with the resistant control A195, were then evaluated in both field and greenhouse (straw test) conditions. The results showed that field trials effectively identified high-yielding WM-resistant genotypes for dry-irrigated conditions. Here we challenge the results of this study with new data and methodology by conducting six sprinkler-irrigated trials from 2015 to 2017 with five genotype groups (G). Three groups comprised genotypes previously studied: G1, seven partially resistant; G4, two intermediately resistant; and G5, three susceptible. G2 consisted of four lines selected for partial resistance in the current study. The resistant control group, G3, comprised the genotypes A195, G122, Cornell605, and Ouro Branco. WM was absent (one trial), or pressure was either low/moderate (two trials) or moderate/high (three trials). The average seed yield ranged from 2207 (G3) to 3178 kg/ha (G1). The contrast G1, G2 versus G3 was nonsignificant for incidence and severity index, indicating that genotypes selected for resistance in the field were as resistant as the resistant control genotypes. Additionally, the groups selected for resistance yielded 43% more and produced 33% less sclerotia weight compared with the control group. Our results reinforce the effectiveness of selecting WM-resistant genotypes using beans originally bred for purposes other than WM-resistance, specifically targeting dry-irrigated areas. Furthermore, our results suggest that the use of genotypes selected for partial resistance reduces inoculum levels in the soil.