Influence of soil quality factors on capsaicin biosynthesis, pungency, yield, and produce quality of chili: An insight on Csy1, Pun1, and Pun12 signaling responses

Hotness or pungency is the major trait of genetically diverse and economically valuable chili (Capsicum sp.) cultivars. However, little is known about the influence of soil characteristics on genetic regulation of pungency vis-a-vis capsaicin formation in endemic chilies. Hence, the present work was conducted by growing two endemic chili cultivars in two types (alluvial and lateritic) of soil. Capsaicin content, pungency, and capsaicin synthase activity were significantly greater in chilies grown in alluvial soil than in lateritic soil. Correspondingly, Csy1, the gene that encodes capsaicin synthase, was significantly upregulated in alluvial soil grown plants. Interestingly, upregulation of Pun1, the gene responsible for capsaicin accumulation in fruits, was more in lateritic soil than in alluvial soil; but pungency was inhibited in lateritic soil by the overexpression of Pun1(2), a recessive allele of Pun1 locus. Statistical analyses revealed that high organic C, microbial activity, and NPK status in alluvial soil were responsible for high pungency, capsaicin synthase activity, capsaicin accumulation, and suppression of Pun1(2). Fruit yield, dry matter, crude protein, titratable acidity, and soluble solids were also significantly high in chilies grown in alluvial soil. Therefore, we postulate that soil quality attributes play vital roles in genetic regulation of pungency, capsaicin biosynthesis, fruit yield, and produce quality of endemic chili cultivars.