Impact of Water Supply and Harvest Period on Photosynthesis-Related Traits and Phytonutrient Content of Chili Pepper Varieties

Global warming and uneven rainfall distribution make it necessary to study not only yield but also crop quality when growing chili peppers. The yield of four chili pepper varieties (Hetényi Parázs, Unikal, Unijol and Habanero) and the changes in chlorophyll fluorescence (Fv/Fm), relative chlorophyll content (SPAD), capsaicin (CAP), dihydrocapsaicin (DC) and vitamin C content during fruit ripening were investigated in an open field experiment. The experiment covered two years of cultivation (dry and rainy years), three different water supply conditions and annual harvests. The aim of the experiments was to determine the most favourable harvest time for the yield of varieties under different environments, and explore the relationship between photosynthesis-related traits (SPAD and Fv/Fm) and bioactive compounds during fruit ripening. Three irrigation treatments were used: regular irrigation (I100 corresponds to 100% ET), deficit irrigation (I50 represents half of I100) and no irrigation (I0). The water supply had less influence on the CAP content but the DC content was higher under water scarcity. Late harvest resulted in low yield and high CAP and vitamin C content but differences were observed between varieties depending on water supply. During the ripening of the fruits, a negative relationship was observed between SPAD and the levels of capsaicin and dihydrocapsaicin, while the relationship between SPAD and vitamin C was positive. These correlations indicate that changes in SPAD during ripening are associated with changes in bioactive compounds, making it possible to identify the stages associated with better fruit quality.