Butcher, Justin (2012-02). Conventional Breeding and Molecular Techniques to Improve Phytochemical Concentrations in Pepper (Capsicum spp.). Doctoral Dissertation. Thesis uri icon


  • Five separate field experiments were conducted across different environmental locations in Texas for the purpose of quantifying concentrations of different phytochemical groups (ascorbic acid, capsaicinoids, and flavonoids) within various pepper species, as well as, to identify the most optimum environment to promote expression of the aforementioned phytochemical. Depending on the particular experiment, quantitative measurements were then used in more detail in one of three ways: for identification of the most superior individuals and optimum environmental locations to express elevated concentrations of a particular phytochemical (first three experiments), to calculate 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 the first experiment, significant differences in fruit weight, capsaicin, and dihydrocapsaicin (DHC) were revealed in fruit tissue of five Habanero (Capsicum chinense) hybrids in comparison to a popular, commercial check (Kukulkan F1) after being grown across three different environmental locations (College Station, Uvalde, and Weslaco). Fruit grown at the Weslaco location was found to be larger and contained more capsaicin and DHC than those produced in Uvalde or College Station. While flavonoid contents were variable and low in all genotypes and locations, a few hybrids showed some potential for use in future crossing schemes to compete against the commercial check. Our results further suggested that variation in phytochemicals in fruit tissue of Habanero genotypes can be exploited by selecting in an appropriate environment. In the second experiment, analysis of four jalapeno hybrids in comparison to three commercial checks (Dragon, Ixtapa, and J1845), as well as, two cayenne hybrids in comparison to one commercial check (Mesilla) were compared after growing in three different locations (Amarillo, College Station, and Uvalde). Results demonstrated that the College Station location contributed to production of fruit containing higher concentrations of both AA and flavonoids, while those grown in Amarillo produced fruit with higher capsaicinoids. As expected, cayenne samples contained more AA and flavonoids than jalapeno samples. In comparison to the commercial jalapeno checks, all jalapeno hybrids generally expressed less capsaicinoids. With respect to AA and flavonoid concentrations, a few jalapeno hybrids proved to have some potential to compete against their respective commercial cultivars. For the cayenne market, one genotype revealed its potential use in mild markets and for farmers interested in a new hybrid expressing both appreciable levels of phytochemicals, as well as, more visually aesthetic attributes. Statistical analyses from the third experiment found all the F-values for each characteristic to be significant except the Location x Genotype (L x G) component for fruit wall thickness. For this experiment, a total of 21 different C. annuum (jalapeno, Serrano, and cayenne) genotypes were evaluated after growing in two diverse environmental locations (Uvalde and Weslaco). In general, peppers grown in Weslaco produced fruit with higher concentrations of AA and capsaicinoids, with a few exceptions, while fruit grown at Uvalde generally was larger in size and contained higher concentrations of flavonoids. In comparison to their respective commercial checks (jalapeno - Dragon, Tormenta; Serrano - Halcon, Magnum45; cayenne - Mesilla), a few hybrids were arguably more desirable for their respective markets with respect to different fruit measurements, AA, capsaicinoid, and flavonoid concentrations. This evidence further suggested the potential benefit this material could have for growers interested in replacing current mater

publication date

  • February 2012