Studies On Appraisal Method And Index Of Low Temperature Resistance And Low-light-tolerance In Melon

Low temperature and weak light have becoming important factors to restrict the yield and quality of crops in Facility. Therefore, screening and breeding chilling-resistant and weak-light-resistant varieties have become important breeding targets for the domestic and overseas breeders. Identification of tolerance to chilling and weak-light in the basis for the mechanisms of tolerance and screening chilling-resistant and weak-light-resistant.The scientificalness and the accuracy of the identification indexes are the keys to evaluate breeding materials for chilling-and weak-light-tolerance objectively, melon which originated from Africa is widely popular warm vegetable and the growth and development is strict with temperature and light.The low temperature and weak light in Facility often inhibit the growth and development.At present,there are no agreement methods and indexes to screen and identify chilling-resistant and weak-light-resistant melon varieties.In this research, the morphology, physiology and biochemistry of three different tolerant melon varieties under low temperature and weak light stress were studied, the correlations were also analyzed between the changes of these indexes and the shoot dry matter accumulations of melon treated under weak light stress.Therefore, the optimal indexes for evaluating chilling-and weak-light-tolerant melon varieties were selected. The main results of experiment were as follows:1. From the chilling injury index of controlled low temperature conditions for seven day, the order of chilling resistance of three different melon varieties was obtained:Yi Li Sha Bai,Zhen Zhu,Su Tian1Hao,and there was difference in different varieties, this method could be used to appraise chilling resistance of melon at seedlings stage.2. Under weak light, Shoot dry matter accumulations of melon were decline than control and difference in different varieties, the order of shoot dry matter accumulations of melon was obtained:Yi Li Sha Bai,Zhen Zhu,Su Tian1Hao.3. Effect of different temperature on melon seed germination were studied.The significant correlation was obtained between relative sprouting rate, relative tendency of sprouting,relative germination index at15℃.There was obvious difference in different varieties.Therefore,these could be used to identify chilling tolerance of seed.4. Effect of different temperature, different light and different temperature and light Combination on morphology and index of biochemistry of melon were studied. Under low temperature and low temperature with weak light, Stem long and Stem diameter and RGLR were reduced gradually, electric conductivity was increasing gradually.gross Chlorophyll and Car were obvious difference in different varieties in20℃/10℃. Therefore,these could be used to identify chilling tolerance of melon. SOD and POD were no obvious difference in different varieties which were correlation with tolerance, MDA was obvious difference in different varieties in15℃/5℃. Under weak light stress,MDA and O2.-were obvious difference in different varieties. Under low temperature and weak light,MDA and O2.-were all increased in different varieties.but the trend is not obvious.5. The correlations of thirteen indexes were compared. relative sprouting rate, relative tendency of sprouting,relative germination index at15℃. Stem long in15℃/5℃,Stem diameter, RGLR,gross Chlorophyll and car in20℃/10℃, and chilling injury index had respectively better correlation with other indices.6. The correlations of seven indexes were compared, Shoot dry matter accumulations, MDA and O2.-in33μmol·m-2·s-1, Stem diameter,RGLR, MDA and O2.-in67μmol·m-2·s-1had respectively better correlation with other indices.7. The correlations of seven indexes were compared, the chilling injury index in10℃,22μmol·m-2·s-1. Stem long, RGLR and O2.-in20℃/10℃,33μmol·m-2·s-1. Stem diameter in15℃/5℃、67μmol·m-2·s-1. had respectively better correlation with other indices.