Effects of exogenous MeJA on fruit ripening and quality of overwintering pepper in greenhouse

<bold>Objective</bold> Vegetable quality has a significant impact on its sales and market value.This study aims to investigate the effect of methyl jasmonate（MeJA）on fruit ripening and quality of overwintering pepper in solar greenhouse. <bold>Method</bold> In this study，‘Huamei105’ pepper was used as experimental material，and 7 treatments of MeJA solution with different concentrations（0，25，50，100，150，200，250 µmol/L）were sprayed on the leaf surface to determine the relevant indexes of pepper fruit quality，the optimal concentration of MeJA was identified to promote fruit ripening and quality formation of overwintering pepper. <bold>Result</bold> The results show that the quality indexes of pepper fruit are the best when treated for 30 days.Compared with CK，exogenous spraying of different concentrations of MeJA solution had different effects on fruit development and quality formation of overwintering stubble peppers in solar greenhouses.Among them，single fruit length，single fruit diameter，fresh weight，cohesiveness，vitamin C and soluble protein contents of pepper fruit were increased by 7.83%，9.24%，11.45%，27.58%，10.90% and 7.72%，respectively，after exogenous application of 100 µmol/L MeJA solution.The hardness and chewiness were significantly reduced by 35.60% and 29.58% respectively，which promoted the development and ripening of pepper fruit.After treatment with 150 µmol/L MeJA solution，capsaicin and dihydrocapsaicin contents in pepper fruit significantly were increased by 262.45% and 253.81%，respectively.The contents of naringenin，gallic acid，cinnamic acid，lutein，zeaxanthin，<italic>α</italic>-carotene and <italic>β</italic>-carotene were significantly increased by 70.61%，29.36%，25.65%，234.99%，215.60%，84.16% and 68.47%，respectively，which improved the fruit quality of pepper.Whereas，after treatment with 250 µmol/L MeJA solution，single fruit length，single fruit diameter，fresh weight，dry weight，vitamin C and soluble protein contents of pepper fruit were reduced by 5.04%，7.21%，7.23%，11.37%，34.86% and 6.28%，respectively，compared with CK. <bold>Conclusion</bold> In summary，leaf spraying with appropriate concentration of MeJA solution can increase the single fruit length，single fruit diameter and fresh weight of overwintering pepper fruit in solar greenhouse，reduce the hardness and chewiness of pepper fruit，and increase the contents of capsaicin，dihydrocapsaicin，vitamin C，soluble protein，some phenolic compounds and carotenoid in fruit，thus promoting the development of pepper fruit，accelerating fruit ripening and improving fruit quality.Principal component analysis shows that 150 µmol/L MeJA treatment has the best effect.