Bruchid Infestation Was Associated With Agronomic Traits in Field-grown Faba Bean Genotypes

Abstract

Bruchus rufimanus, a univoltine seed weevil (bruchid), can cause severe seed yield and quality losses in faba beans restricting crop profitability and expansion. Chemical insecticide applications have been reported of low effectiveness and thus, growing genotypes tolerant to bruchid has been suggested as an alternative. Ten faba bean (Viciafaba L.) accessions belonging to three varieties (var. major (seven accessions), var. minor (two accessions), var. equina (one accession)) were tested under field conditions for two growing seasons. Agronomic and seed traits were determined in an attempt to associate any tolerance to bruchid with easily-assessible, highly-heritable characters in order to be used as indirect selection criteria. The genotypes varied in bruchid tolerance (percentage of bruchid emergence holes (BD), percentage of endoparasitoid (Triaspis thoracica) emergence holes and bruchid infestation level (BI = BD + PD)), agronomic traits and seed properties. The dark-colored, small- and medium-seeded accessions (var. minor and var. equina), commonly used for feed, had the lowest BI (4.21–8.17%) ranging below the limit of 10% set as the highest acceptable for using faba beans as feed. Large-seeded accessions (var. major), which had light-colored seed coat (testa) with yellow hue, showed BI from 11.80% up to 24.54%, far-above the limit of 3% for seeds used as food. Apart from the seed size and color, susceptible genotypes had more seeds per pod, less pods and less branches per plant, possibly offering an easy access to females for laying more eggs on the limited number of pods, albeit the more space and food (higher protein content per seed) they offer to the developing larvae. Phenols and tannins in seeds, a putative chemical defense mechanism against bruchid, did not associate with the percentage of bruchid- or endoparasitoid-damaged seeds. Concluding, certain plant architectural traits and seed properties related to bruchid infestation in faba beans can be used as useful tools to select tolerant genotypes.