Gene Action of Cassava Resistance Metabolites to Whitefly (Bemisia tabaci)

Abstract

Several metabolites are linked to cassava resistance to whitefly. There is limited information however, on the mode of gene action of the metabolites associated with cassava resistance to whitefly (Bemisia tabaci). The objective of the study was to determine the combining abilities and mode of gene action of salicylic acid, antioxidative capacity, total phenolic content, flavonoid, tannin, peroxidase and protein of selected cassava genotypes. Ten genotypes were crossed in half diallel and the parental and 45 S1 progenies evaluated for nymph count, whitefly count, leaf damage and sooty mold at Namulonge in season two of 2016. In season one and two of 2017, the parental genotypes and their corresponding forty-five S1 progenies were evaluated in randomized complete blocks with two replications for Bemisia tabaci population and leaf damage and leaf metabolite content assayed. The results indicated highly significant (P<.001) differences among genotypes for general combining ability (GCA) to antioxidative capacity; (P<.05) for total phenolic content, peroxidase and protein and (P<.01) for salicylic acid, tannin and flavonoid. The specific combining ability (SCA)showed significant (P<.001) differences for salicylic acid; (P<.01) for antioxidative capacity and total phenolic content. The additive variance was significant (P< .05) for flavonoid, protein; (P<.01) for antioxidative capacity, total phenolic content, tannin and peroxidase. The dominance variance had high significance (P<.001) for salicylic acid; (P<.05) for flavonoid and (P<.01) for antioxidative capacity and total phenolic content. Although additive gene action was higher than non-additive, both were influencing most metabolites indicating complexity of inheritance. A critical evaluation is necessary when exploiting metabolite related traits in breeding for resistance to Bemisia tabaci.