Comprehensive evaluation and prediction of ultraviolet radiation resistance of pepper at seedling stage

【Objective】 The ultraviolet radiation(UV)resistance of 9 pepper varieties(Capsicum annuum L.)at seedling stage was evaluated comprehensively,and the mathematical model for predicting UV resistance of pepper varieties was established.【Method】 The morphological indexes,antioxidant enzyme activity and photosynthetic characteristics of 9 varieties of pepper seedlings were measured under UV-B radiation dose of 28.56 kJ/(m²·d)and natural conditions(control) to calculate the UV resistance coefficient. Principal components were analyzed,and the UV resistance of 9 pepper varieties according to α combined membership function and cluster analysis were compared.Then,the mathematical model of predicting UV resistance of pepper varieties was established by integrating comprehensive membership function value (D)and UV resistance coefficient.【Result】 After exposure to UV-B radiation,9 pepper varieties showed different degree of leaf appearance damage at the end of treatment,among which Huamai 105 had the most serious damage,Ledu long pepper had a little change. Peroxidase(POD),catalase(CAT)and superoxide dismutase(SOD)activities of the leaves of Ledu long pepper and YTS2013-13 showed an increasing trend under UV-B radiation,while those of Huamei 105 showed a decreasing trend,and the decreasing range was the largest among the 9 varieties. The photosynthesis of 9 varieties was inhibited under UV-B radiation,among which Huamei 105 was the most seriously affected on photosynthetic characteristics,while Ledu long pepper was the least affected. According to principal component analysis,the indicators of maximum fluorescence (F_m),SOD,stomatal conductance (G_s),primary light energy conversion efficiency (F_v/F_m),net photosynthetic rate (P_n)and carotenoid (Car)have great influence on the UV resistance of pepper at seedling stage. Two varieties with strong UV resistance,three varieties with medium UV resistance and four varieties with UV sensitivity were screened out by combined membership function and cluster analysis. The optimal mathematical model of UV resistance was established by stepwise regression analysis:D=0.037SOD+1.123P_n-0.228(R²=0.913, P=0.01). the prediction accuracy of the mathematical model of UV resistance evaluation was 92.642%.【Conclusion】SOD and P_n can be used for breeding and screening of UV resistance varieties of pepper. In addition,the UV resistance of Ledu long pepper seedlings is much stronger than other varieties,so it can be considered as the main pepper variety in plateau area to ensure the high quality production of pepper.