| China as a large agricultural country,is extremely short of water resources.Drought is not only inhibiting the sustainable development of agricultural industry in China,but also causing immeasurable losses to agricultural economy in China.Watermelon is an important economic crop in China.It is of great practical significance to study the physiological response mechanism of watermelon under drought stress,and to screen,identify and breed high-quality droughtresistant varieties.This study mainly carried out the experiment of continuous drought in pot plants at seedling stage,combining morphological indicators with physiological growth indicators,The drought resistance of each cultivar was preliminarily evaluated by the drought damage index,and then comprehensively evaluated by the membership function.The cultivars were divided into three categories of high resistance,medium resistance,weak resistance to drought by cluster analysis.Eight cultivars were further selected from the three types of resistance and compared in the field.In the field experiment,the varieties were compared from the aspects of plant photosynthetic performance and growth trend,and the economic benefits in the field were mainly evaluated based on the yield.The evaluation results of watermelon varieties at seedling stage were further verified.The main conclusions of this study are as follows:1.According to the combination of drought index and membership function,the drought resistance of the tested varieties was evaluated.Eighteen watermelon cultivars were divided into three categories: High resistance,Medium resistance and Weak resistance to drought.Highly resistant varieties include: Nonkeda No.18,Jinchen No.5,Sh102,Xinon No.8,Hongguandragon,Medial resistant variety: Redflower No.5,Nonkeda No.20,Ninnonke No.6,Nonkeda No.5,Ninnonke No.3,Ice cream,Nonkeda No.6,Lvbaojinhua No.1,Weak resistance varieties: Nonkeda No.15,Goldgirl,Jinxing No.2,Qinding No.2,Ninnongke No.5.2.After drought treatment,the contents of Fo,Fo/Fm and chlorophyll increased in different degrees.Fm,Fv,Fv/Fm and RWC decreased significantly,The content of Pro was accumulated,and the content of MDA was significantly increased.The activities of antioxidant enzymes POD,SOD and CAT varied with different watermelon varieties,The contents of POD,CAT,SOD,Pro,RWC,Fm,Fv,a n d Fv/Fm were significantly correlated with drought resistance,which could be used as the key indexes for screening high-quality drought resistant watermelon varieties.3.Based on drought resistance evaluation results of seedling stage,the field drought resistance comparison test was conducted.The yield was us as main index,the results showed that,by yield,the varieties were sorted in descending order: Jincheng No.5> Red flower No.5>Lvbaojinhua No.1> Ninnonke No.6> Nongkeda No.20>Ninnonke No.3>Nonkeda No.5.Jincheng No.5 has high resistance and strong growth potential and photosynthetic performance in the field growth process condition.This study has supplemented and improved the comprehensive evaluation system,which was purposeoriented,combined subjective and objective,and eliminated the differences between indexes and varieties,and accurately reflect the drought resistance of each variety.Our results meet the evaluation requirements of agricultural production. |
