Conventional breeding and molecular techniques to improve phytochemical concentrations in pepper (Capsicum spp.).

摘要

Five separate field experiments were conducted across different environmental locations in Texas for one of three purposes: for identification of the most superior individuals and optimum environmental locations to express elevated concentrations of different phytochemicals within various pepper species (first three experiments), to calculate broad sense heritability and % heterosis estimates for various fruit characteristics and phytochemical levels (fourth experiment), or for use in a specific biotechnology technique to potentially identify a molecular marker linked to elevated levels of ascorbic acid (AA) and flavonoids (quercetin and luteolin) (fifth experiment). In each of the three phytochemical experiments, significant differences were observed not only for fruit measurements but also for expression of the various phytochemicals in comparison to their respective commercial checks. From these experiments, we were able to confirm our hypotheses and identify different genotypes that were capable of expressing better traits for consumption. In addition, we were also able to identify an optimum environmental location in each experiment that contributed to production of fruit with better traits. In the fourth experiment, results confirmed our hypotheses that paprika type material has higher AA and flavonoid concentrations than serrano peppers, while the opposite is true for capsaicinoid expression. From our correlation analyses, we were also able to identify the presence of several significant associations between the various characteristics we evaluated. In all, our results were able to reveal how effective certain combinations of parent material are towards production of offspring with improved traits expressing better fruit characteristics and elevated phytochemical concentrations. Finally, the quantitative measurements produced in our F2 molecular marker experiment found significant amounts of variation for both flavonoids and AA expression. We also were able to identify a significant association between quercetin and luteolin, quercetin and total flavonoids (quercetin+luteolin), as well as, luteolin and total flavonoids. In addition, three candidate primers were eventually identified for their potential polymorphic expression. Although one of the three primers was identified as expressing a significant association, the value still represented a relatively low amount of variability with respect to luteolin. From our results, we were able to arguably conclude that an environmental component may serve a more essential role in activating the necessary physiological processes to produce specific secondary metabolites.