Management of white mold in common bean using partial resistance and fungicide applications

Abstract

White mold (WM) is a damaging disease of common bean in Brazil and fungicide applications can effectively control it. However, in the absence of fungicide, some type III bean genotypes have exhibited less WM disease and higher yields under field conditions than the current Brazilian cultivars. Here we assessed the possibility of reducing the number of foliar fungicide applications to control WM using genotypes partially resistant to WM. The production of sclerotia was also assessed. We conducted sprinkler-irrigated trials combining genotypes (susceptible, moderately resistant or partially resistant to WM) with a number of fluazinam applications (0, 1, 2 or 3) under low, low/moderate, moderate or high WM pressure. Under low and low/moderate pressure, one fungicide application reduced WM disease for the susceptible genotype, but did not affect WM disease for the partially resistant genotype. In these conditions, fungicide did not affect yield for either of the genotypes. Under moderate and high pressure and in the cross-site analysis, genotype-by-fungicide interactions were nonsignificant for WM incidence, WM severity index, yield and sclerotia weight. Averaged across site and fungicide, the partially resistant genotype presented a 30% lower WM severity index and produced 2.3-fold fewer sclerotia than the susceptible genotype. We conclude that partially field-resistant beans may contribute to the integrated management of WM, with a potential, at least under light pressure, to reduce the use of fungicide.