Influence of Growth Stage and Leaf Age on Expression of the Components of Partial Resistance of Faba Bean to Botrytis fabae Sard.

In detached leaf tests on faba bean (Vicia faba L.), genotypes partially resistant and susceptible to Botrytis fabae were examined. Expression of four components of partial resistance to a virulent isolate of B. fabae differed depending on the plant age and the leaf age of the genotypes. The incubation period of resistant genotypes at the podding stage was longer than that of susceptible genotypes at the same stage. The area under disease progress curve (AUDPC) of the lesion size increased from the seedling to the flowering stage but declined at the podding stage in all genotypes. Differences between resistant and susceptible genotypes for lesion size were significant except on old leaves from plants at the podding stage. The latent period decreased, and spore production increased with increasing growth and leaf age but there was significant interaction with the genotype. These last two components of partial resistance were more clearly expressed at all growth stages on FRY167 (highly resistant) but were expressed only at the seedling and podding stages on FRY7 (resistant). The resistant line BPL710 was not significantly different from the susceptible genotypes for the latent period at any growth stage, and for spore production at the seedling and flowering stages. Leaf age affected all genotypes, but with a significant interaction between leaf age and growth stage. Components of partial resistance were more strongly expressed on young leaves from plants at the seedling or flowering stage

Effets de la température et de la dose de l'inoculum sur les composantes de la résistance partielle de la fève au Botrytis fabae Sard

National audienceFive faba bean genotypes partially resistant and susceptible to Botrytis fabae were used at the laboratory to follow the effect of the temperature and the concentration of the inoculum on the expression of four components of partial resistance. The incubation period was longer at 5 degrees C and appeared significantly shorter from 10 degrees C to 25 degrees C but did not allow a good discrimination between the genotypes. The area under disease progress curve (AUDPC) of the lesion size increased from 5 to 25 degrees C with significant differences between the genotypes especially starting from 15 degrees C. The latent period decreased and spore production increased from 10 degrees C to 20 degrees C but were expressed only at 20 degrees C and 25 degrees C. The size of the lesions and the number of spores increased and the latent period decreased with increasing the inoculum concentration. The inoculation by 2.10(5) and 2.10(6) spores/ml gave a better expression of resistance. With 2.10(4) spores/ml, the two components latent period and spore production were not expressed on the resistant genotype BPL710

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

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