Influence of Watering Regimes on Physiological Traits, Growth, Yield, and Capsaicin Content of Chilies

Abstract

Water stress is a major limiting factor affecting the physiological processes, growth, and productivity of crop plants, including chili. This study evaluated chili plants' responses regarding physiological traits, growth, yield, and capsaicin content under different irrigation levels. The experimental design was a 2x4 factorial in CBD. A pot experiment was conducted on two species of chilies: Capsicum annuum ‘Super-Hot 2’ and ‘Huay-Siiton’ and C. frutescent ‘Prik-Kee-Nu-Suan.’ The plants were irrigated at four watering regimes such as 100%, 80%, 60%, and 40% of maximum water holding capacity (MWHC) after the anthesis through fruit development. Midday leaf water potential (LWPmd) was ranked between -1.30 MPa in 100% MWHC to -2.11 MPa in 40% MWHC indicating the level of water stress. The 40% MWHC caused a drastic decrease in LWPmd and reduced the maximum quantum yield of PSII (Fv/Fm) and growth rate in canopy width. Observed leaf greenness was maximized at 60% MWHC. The irrigation regimes also affected the yield of chili, especially the 60% and 40% MWHC, with a reduced number of fruits/plant, fruit fresh and dry weights, and fruit sizes. In the case of 40% MWHC, the dry yield was too low, and it was impossible to analyze the capsaicin content. The reduced irrigation (80% and 60% MWHC) did not significantly induce the capsaicin content or pungency of the studied chili cultivars. Thus the capsaicin yield of studied chili cultivars was reduced considerably by severe reduction of dry fruit yield under restricted water.