Screening Of Low Temperature And Weak Light Resistance Of Pepper Cultivars And Its Physiological Mechanism

Pepper is the main vegetable crop in China.Due to its thermophilic nature,it is often caused by low temperature and low light stress in low yield and even death in actual agricultural production.Related studies found that the damage caused by low temperature and low light to cold sensitive plants is far greater than the single stress of low temperature,however,in the actual production process,low temperature and low light often have synergistic effects,so this study is mainly on screening of pepper cultivars to low temperature and low light condition.The identification of low temperature and low light stress ability of plants involves many aspects such as plant morphology,physiology and biochemistry.The commonly used identification indexes include stress index,root vigor,chlorophyll content,membrane lipid peroxidation level,protective enzyme system activity and soluble protein content,and so on.The experimental materials of this study used 8 kinds of pepper cultivars provided by Yancheng Agricultural Science Institute as material.The seedling stage was carried out for 18 d at a temperature of 15℃/6℃(day 12 h/night 12 h),light intensity 100 μmol·m-2·s-1 low temperature and low light treatment,and simultaneous control treatment.Apparent observation recordings and determination of chlorophyll content and fluorescence parameters were performed during the treatment.After the treatment,some pepper plants were sampled for subsequent measurement and the other part was moved to the greenhouse for recovery.The measured indexes of the collected samples were biomass,photosynthetic parameters,soluble protein content and several major antioxidant enzyme activities,which was compared with the control group.The recovered plants were subjected to trait and photosynthetic assays after 40 d,and fruit determination and yield calculation were performed after the results.The main results are as follows:(1)The order of chilling injury index of all pepper varieties from low to high is:cultivar 4,17<cultivar 18<cultivar 6<cultivar 3<cultivar 1,19<cultivar 24.The selected cultivars 4 and 17 were the most resistant to low temperature and low light intensity.After 18 days of low temperature and low light treatment,the external symptoms of pepper were not damaged,and the chilling injury index was 0,but the growth of both plants existed significant difference.(2)Low temperature and low light treatment resulted in a decrease in the maximum photon yield(Fv/Fm)and actual photon yield(Yield)of all pepper seedling leaves,and the decrease range increased with the decrease of its tolerance.In addition,the contents of chlorophyll a and chlorophyll b in different cultivars showed a different degree of decline,and the most sensitive variety 24 had the largest decline,while the variation trend of carotenoid content varied greatly,which needs further study.(3)The effect of low temperature and low light on the growth and development of pepper roots was greater than that of the upper part,and had no significant effect on the water content of the aboveground tissues.Under the low temperature and low light treatment,the content of soluble protein increased in different degrees,and the increase range was related to the difference and tolerance of the variety.(4)Superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),peroxidase(POD)and catalase(CAT)in the leaves of pepper seedlings were determinated to be significantly different due to differences in variety and tolerance,and the varieties with high tolerance and the varieties with poor tolerance showed significant differences.(5)After 40 days of recovery treatment,Variety 18 grew best,and its resistance to low temperature and weak light stress and recovery were strong.Fruit determination showed that the low temperature and low light treatment had a great damage to the growth and development of the fruit of Variety 3,so its reproductive growth recovery ability was poor.In summary,the order of low temperature and low light stress tolerance of all pepper varieties from high to low is:cultivar 4,17>cultivar 18>cultivar 6>cultivar 3>cultivar 1,19>cultivar 24.There were correlations between the indicators and the cultivar characteristics and low temperature and low light tolerance of each pepper cultivar.