Identification of sources of resistance to the black bean aphid, Aphis fabae Scopoli, in Faba bean, Vicia faba L., accessions

In several parts of the world, important yield losses are caused to Faba bean due to attack by the black bean aphid Aphis fabae Scopoli. Although resistance could be a good alternative to chemical control, its genetic basis is still largely unknown; and its phenotypic expression is still poorly described, making crucial the permanent evaluation of genetic resources available in different countries; together with using adequate agronomic parameters and statistical inference. In this study, two Faba bean collections provided by Faba bean breeding programs of Tunisia and Spain were evaluated for resistance to A. fabae during two consecutive years in the field, based on infestation rates and three yield parameters: number of grains (NG), weight of grains (WG) and weight of pods (WP). Principal components analysis (PCA) showed that the most effective parameters contributing to response variation were the weight of pods (WP) and the number of grains (NG). Genotypes were grouped based on clustering patterns inferred from PCA and UPGMA, both showing the existence of two distinct groups: a resistant group characterized by high WP; and in most cases high NG values; and a susceptible group characterized by a low WP; and in most cases a low NG + WG. Furthermore, tolerance to infestation was identified in one genotype from the Spanish collection. Our results demonstrate that WP is the most reliable parameter for resistance selection; and that the genotypes V1, V9 and V16 from the Tunisian collection and V2e and V7e from the Spanish one should be exploited for their resistance potential.