Integration of partial resistance, plant density and use of fungicide for management of white mould in common bean

In‐row plant densities have not been studied for common beans with type II growth habit and contrasting reactions to white mould. Advanced breeding lines with partial resistance or susceptibility to white mould were combined with 4, 7, 10 or 13 plants m−1 and with or without fungicide at a constant between‐row spacing of 0.5 m in five sprinkler‐irrigated field trials conducted during the autumn–winter season in Brazil. White mould pressures in the trials covered the whole range from zero to moderate/high (46–60% of white mould severity index). In all trials, means of white mould incidence, severity and yield did not vary significantly between 7 and 13 plants m−1 for the partially resistant line, regardless of the fungicide levels. For the susceptible line, 13 plants m−1 increased white mould incidence and severity under moderate disease, regardless of the fungicide levels, and decreased yield compared with 10 plants m−1 when fungicide was applied twice under moderate/high disease pressure. For the susceptible line, 7 or 10 plants m−1 maximized yield in all trials, with or without fungicide applications. The results suggest that the current recommendation of 11–13 plants m−1 could be used for type II beans with partial resistance to white mould in either a conventional or organic system. For susceptible genotypes, 7–10 plants m−1 seems to be the most appropriate in‐row plant density. This study may improve the recommendation of in‐row plant density for type II beans cultivated under white mould pressure.