Biologically active phytochemicals of sweetpotato
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Flavor quality is one of the most important traits to select in food crop breeding programs due the large number of sensory panelists required, the small number of samples can be evaluated/day and the subjectivity of the results. Using sweetpotato [Ipomoea batatas (L.) Lam.] as a model, the flavor chemistry was ascertained and a rapid analytical method was developed to accurately screen large numbers of progeny for flavor. The identity and contribution of 37 odor-active volatile compounds to the aroma of the baked sweetpotato were determined by employing GC, GC-MS, GC-olfactometry, and aroma extract dilution analysis (AEDA). Clones exhibiting distinctly different flavors were analyzed for sugars, nonvolatile acids and aroma compounds. Using the intensity of the aroma/Fl for each of the 17 most important aroma-active compounds and the relative sweetness of individual sugars × their respective concentrations, principal component and cluster analyses were used to accurately classify the clones according to flavor type. Use of this method to assess flavor would greatly facilitate the accurate evaluation of large numbers of progeny, the selection of multiple flavortypes simultaneously, and the development of superior new cultivars for a wide cross-section of food crops. In that host-plant phytochemicals play critical roles in insect behavior, the volatile chemistry of the sweetpotato and its role in the sweetpotato weevil’s [SPW; Cylas formicarius elegantulus (Summers)], host finding behavior were studied. Thirty-three compounds were identified, among them 23 were terpenes. Three oxygenated monoterpenes (nerol, Z-citral, and methyl geranate) were identified as attractants. The sesquiterpene volatile fraction was repellent to female SPW with a-gurjunene, a-humulene, and ylangene active in a concentration range comparable to that emanating from storage roots. The relative attraction of storage roots from 4 cultivars to female SPW was negatively correlated with the composite concentration of headspace sesquiterpenes. Selection for clones with decreased volatile attractants and/or increased deterrents using an analytical means of quantification may significantly facilitate developing resistance to the SPW.