A comparison of susceptibility to feeding by the black bean aphid (Aphis fabae) between two varieties of beans (Phaseolus vulgaris) (Gloria and Nua 45) commonly grown in Zimbabwe

Abstract

Gloria and Nua 45 are two of the most commonly grown sugar bean varieties in Zimbabwe. Beans are a cheap alternative source of protein and have been on high demand due to the ever-rising meat prices. Gloria and Nua 45 are being affected by the black bean aphid (Aphis fabae) feeding which is the most problematic insect pest of beans. The aphid feeds on foliage of plants resulting in stunted growth and reduced yields. A comparison of susceptibility to feeding by A. fabae was done to determine which one of the two varieties is least affected by the aphid. Two glasshouses containing both varieties of beans were used and one of the glasshouses was not inoculated with the aphid and this served as the control. The plant heights, leaf areas and 100-seed weights of the two varieties were compared after a 90-day period. The experimental design was Randomised Block Design (RBD) with each block having three replicates in each glasshouse. It was difficult to create homogeneity due to confounding factors (temperature and exposure to sunlight) in the glasshouses hence this choice of experimental design. Data collected on plant height, leaf area and 100-seed weight were subjected to one-way analysis of variance (ANOVA) for RBD using SPSS version 21. Dunnett test was done to compare each variety to the control. Multiple comparisons for the effect of aphid feeding on plant height, leaf area and 100-seed weight was done using Tukey post hoc tests. Both varieties in the glasshouse that was inoculated with the aphid were susceptible to feeding. However, the plant heights, leaf areas and 100-seed weights varied significantly (p<0.05) between the two varieties with the least values of these parameters being recorded for Gloria. The one-way analysis of variance showed that the plant heights, leaf areas and 100-seed weights of plants in the control glasshouse did not vary significantly (p>0.05). Therefore, this study indicated that Nua 45 is the least affected variety between the two (Gloria and Nua 45). Therefore, this study recommends that in areas infested by the black bean aphid (Aphis fabae) Nua 45 should be cultivated as it is the more resistant variety.