Phytochemical Characterization of Six Sesame (Sesamum indicum L.) Genotypes and Their Relationships with Resistance against the Sweetpotato Whitefly Bemisia tabaci Gennadius

Abstract

To determine the phytochemical relationship of six sesame (Sesamum indicum L.) genotypes and their resistance against whiteflies (Bemisia tabaci Gennadius), a randomized complete block field trial with six treatments (genotypes) and four replications was conducted in the Microsur growing area of the Municipio Santa Rosalìa, Portuguesa State, Venezuela. Whitefly eggs and nymphs were counted weekly during 6 wk in each experimental plot. At the end of the crop cycle, the presence or absence of eight secondary metabolites from each plant organ in experimental plots was determined. The relationship among the genotypes was observed by means of a phenogram and the respective analyses of principal coordinates. Significantly different characterizations were found on the 19x10 and 43x32 genotypes. An analysis of principal components was conducted with metabolites in the leaves and the values of foliar acidity. This analysis separated the genotypes 19x10 and 43x32 from the other genotypes with the lowest foliar acidity values. These two genotypes harbored the lowest incidence of eggs and nymphs of whiteflies (nearly 10 and 50% of the total incidence in the other genotypes), demonstrating the importance of foliar acidity values of sesame as resistance mechanisms against whiteflies.