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

Abstract

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.

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

“…(2020). In each trial, WM pressure was considered low when the mean of the susceptible group (G5) exhibited WMI ≤25% or WMSI ≤15%; low/moderate, 26%–45% of WMI or 16%–30% of WMSI; moderate, 46%–65% of WMI or 31%–45% of WMSI; moderate/high, 66%–85% of WMI or 46%–60% of WMSI; and high, >85% of WMI or >60% of WMSI (adapted from Lima et al., 2019).…”

“…These 12 genotypes were selected in VCU trials conducted between 2008 and 2011 and subsequently evaluated in six advanced trials and two straw tests by Lima et al (2020). In each trial, WM pressure was considered low when the mean of the susceptible group (G5) exhibited WMI ≤25% or WMSI ≤15%; low/moderate, 26%-45% of WMI or 16%-30% of WMSI; moderate, 46%-65% of WMI or 31%-45% of WMSI; moderate/high, 66%-85% of WMI or 46%-60% of WMSI; and high, >85% of WMI or >60% of WMSI (adapted from Lima et al, 2019).…”

“…Similarly, in Nebraska, USA, WM severity (percentage of the aboveground portion of bean plants infected by S. sclerotiorum) lower than 40% did not affect bean yield (Kerr et al, 1978). Due to the considerable year-to-year variation in WM intensity (Lima et al, 2019(Lima et al, , 2020Reich & Chatterton, 2022;Teixeira et al, 2019;Vieira et al, 2022), trials for this type of study must be repeated for two or more years. In trials with WM pressures between zero and moderate levels, selection for partial resistance to WM may be ineffective.…”

“…To improve the WM management, the combination of fungicide applications with the use by growers of a WM-resistant bean cultivar is a promising approach (Lima et al, 2019;Miklas et al, 2013;Vieira et al, 2022).…”

Stem, leaf and cotyledon resistance responses to a prevalent Sclerotinia sclerotiorum pathotype in Australia highlight new opportunities to improve white mould resistance in common bean

“…However, regional variation in agronomic and market factors further complicates such efforts, as a successful commercial cultivar must be both adapted to the local climate in terms of high yield and meet the preference of local consumers in terms of grain attributes such as seed size and colour. Meeting consumer preferences for improved common bean cultivars can be an additional ongoing and large undertaking for breeding programs (Lehner et al 2015;Lima et al 2017). In addition, S. sclerotiorum has wide diversity, with isolates varying in their aggressiveness and interaction with host resistance in common bean.…”