Reproductive potential of the black bean aphid (Aphis fabae Scop.) on a range of faba bean (Vicia faba L.) accessions

The black bean aphid is one of the main insect pests of faba bean, leading to yieldlosses in many countries. The aphid inflicts damage to faba bean through directphloem feeding and indirectly by transmission of several viruses. Sources of geneticresistance or tolerance to the aphid have been hard to identify and to use in breedingbecause of the high environmental variability of the attack, the weak and partialnature of the resistance when found, and the low repeatability of experiments. Arange of molecular genotyping tools is now available for identifying the genes under-lying key traits in faba bean. Hence, we screened the responses of eight inbred lines(Columbo, Albus, Closed-flower, Diana, Hedin/2, Icarus, ILB938/2, and Mélodie/2) offaba bean, derived from commercial cultivars and experimental germplasm, to aphidinfestation in controlled (no-choice-test) and field (preference test) conditions. In thecontrolled environment, aphid performance was assessed by measuring fecundityand determining the intrinsic rate of natural increase (rm). In the field experiment,population growth was examined on Columbo, Closed-flower, Hedin/2, andILB938/2 during June and July. Each week, 10 plants in each plot, randomly chosenat the start, were screened for aphid colonization and number of plants attacked. Foreach plant, an index number was given reflecting the severity of aphid presence. Ourresults demonstrate a clear conformity between the results obtained from the indoorpot experiments and the field experiments. In both experiments, ILB938/2 showedpartial resistance with significantly lower fecundity,rm, and field infestation whencompared with the known susceptible line Columbo. The consistently strong perfor-mance of ILB938/2 against the black bean aphid suggests that it carries a factor orfactors rendering it unconducive to aphid landing, feeding, and/or reproduction. Fur-ther investigation into the resistance mechanisms of ILB938/2 is planned

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