Analysis by detached leaf assay of components of partial resistance of faba bean (Vicia faba L.) to chocolate spot caused by Botrytis fabae Sard.

Abstract

Five faba bean (Vicia faba L.) genotypes with different levels of field susceptibility to chocolate spot caused by Botrytis fabae, were analysed for the components of partial resistance in a laboratory assay on living detached leaves. The incubation period (IP), the number of spots (NP), the lesion diameter (LD), the latency period (LP) and the number of spores/leaflet (NS), were determined and statistically analysed. Parameters LD, LP and NS were involved in characterising partial resistance, but IP did not appear to play a role. NS did not become a significant factor until 20 h after inoculation. Genotype FRY167 was most resistant with the lowest LD and NS values and the longest LP. In contrast, FRY30 had the highest level of susceptibility, with the highest LD and NS and the shortest LP. However, the resistant control BPL710 showed a slight deviation in that it expressed a long LP which was not significantly different from the values of the susceptible control Aguadulce. The absence of a correlation between LP and NS in BPL710 opens a discussion on the genetic control of its resistance.