The use of a chili fruit is distinguished by its capsaicinoid content, which shows many beneficial effects in food and pharmaceutical applications. However, chilies exhibit wide variations in the accumulation of capsaicinoids depending on their genotype and environmental interaction. Therefore, we conducted experiments to evaluate the capsaicinoid responses of 14 cultivars of chili across four different elevations. Experiments were conducted during the rainy season from June to Oct. 2009 at elevations of 200 m asl (Khon Kaen) and 680 m asl (Chiang Mai) in Thailand and from Apr. to Sept. 2010 at elevations of 1400 m asl (Lobesa) and 1630 m asl (Kabesa) in Bhutan. A high-performance liquid chromatography technique was used to determine capsaicin and dihydrocapsaicin. Significant differences were observed among the cultivars, the locations, and the cultivar-by-location interactions. Large variations of cultivar effects indicate that it is possible to select cultivars for capsaicinoid concentration that are adapted over a wide range of environments. Average capsaicin, dihydrocapsaicin, and total capsaicinoids were greater at higher elevations in a particular year. There was significant correlation between capsaicin and total capsaicinoid contents with elevations, but capsaicinoid yield showed negative correlation. Small-fruited cultivars with high pungency showed consistent capsaicinoid production over different environments. Dallay khorsaney, KKU-P-22006, KKU-P-31141, and KKU-P-21041 cultivars showed high stability for pungency, producing high capsaicinoids at all four locations.
Capsaicinoids are the alkaloids in hot pepper that cause the sensation of heat when eaten and are affected by a genetic and environment interaction. Drought stress is well recognized as an environmental condition that influences capsaicinoid accumulation. This investigation identified the responses of capsaicinoid accumulation in hot pepper cultivars under drought stress condition. A total of nine cultivars with a different initial pungency level, i.e., low, medium, and high, was subjected to gradual drought stress during the flowering stage. Plants in this drought stress group were supplied with reduced water applications of 25%, 50%, and 75% by volume at 10, 20, and 30 days after flowering (DAF), respectively. Leaf water potential and relative water content were recorded to measure the level of drought stress. The results indicated that all cultivars were subjected to drought stress because of their decrease in leaf water potential and changes in physiological characteristics, e.g., growth and yield performance. In addition, leaf area and shoot-to-root ratio were good criteria for identifying hot pepper cultivars under drought stress because their responses were correlated with the stress level and yield components. Yield performances of the high pungency group did not decrease under drought stress, whereas those of the low pungency group did decrease. In conclusion, capsaicinoid levels increased for all cultivars studied when subjected to drought stress, except for the cultivars in the high pungency group. A yield response under drought stress for the medium pungency group varied and was not found to be associated with drought stress.