Chili pepper belongs to genus Capsicum in the Solanaceae family, the only plant genus known to produce capsaicinoids. Capsaicinoids are acid amides of vanillylamine and C9 to C11 branched-chain fatty acids and are responsible for pungency of the chili fruits. The major analogs are capsaicin and dihydrocapsaicin, accounting for more than 90% of the total capsaicinoid content in the majority of Capsicum spp. (Nunez-Palenius and Ochoa-Alejo, 2005). Genetically, capsaicinoid production is inherited as a dominant trait and is controlled by the Pun1 locus (Blum et al., 2002). In their homozygous recessive state, pun1/pun1, capsaicinoids are not produced by chili peppers. The degree of pungency is also regulated by environment and by genotype–environment interaction; therefore, high variation of pungency level is found between and within genotypes (Harvell and Bosland, 1997; Zewdie and Bosland, 2000). The variation is attributable to pungency being a polygenic trait (Otha, 1962). Although chili peppers are considered autogamous, high rates of cross pollination (7% to 90%) have been recorded, which could lead to genetic variation of cultivars (Bozokalfa et al., 2009) and greater heterogeneity in pungency, especially in local cultivars. Pungency increases with environmental stress such as high temperature (Otha, 1960), water stress (drought or flooding) (Bosland and Votava, 2002; Sung et al., 2005), and soil fertility imbalances (Johnson and Decoteau, 1996; Medina -Lara et al., 2008; Montforte-Gonzalez et al., 2010). Medina-Lara et al. (2008) reported that nitrogen fertilizer significantly increased plant growth and fruit yield while maintaining high levels of capsaicin and that application of potassium has no effect on growth or productivity. Iwai et al. (1979) suggested that light exposure may be an important factor in the formation and accumulation of capsaicinoids. In their survey of wild Capsicum chacoense, Tewksbury et al. (2006) reported that the total capsaicinoid content increased significantly with increasing elevation.
Innovative applications of capsaicinoids in the pharmaceutical industry have stimulated interest in the use of capsaicinoids, and more information is needed on the genotype and environmental effects on this important trait. The information will aid in selecting the variety and manipulating the environment to maintain the pungency according to market demand. Therefore, the objectives of our experiments were to evaluate the effects on capsaicinoids of the environment at different elevations and to identify cultivars suitable for production of capsaicinoids.
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