Studies On The Cultivation Physiology Related To High-temperature Sealing Treatment And Grafting In Cucumner

With the increasing global warming recent years,cucumber(Cucumis sativus L.)is faced with a great challenge of high temperature and global warming,which severely affect the year-round production and quality of cucumber.Improving the resistance to high temperature stress and powdery mildew in cucumber has become the focus of scholars and breeders.In this study,the resistance to different cucumber varieties to powdery mildew was identified after inoculation,planting in an intelligent illumination incubator under high-temperature sealing treatment.It was preliminary studied that growth and physiological changes of powdery mildew infected cucumber plants under high-temperature sealing treatment.The changes of growth,leaf photosynthetic,chlorophyll fluorescence parameters and physiology of self-rooted cucumber seedlings(Cucumis sativus’Chunqiuwang No.2’)and grafted cucumber(Cucurbita ficifolia Bouche,Cucurbita maxima × Cucurbita moschata,Luffa cylindrica,Benincasa hispida Cogn.)were studied under high temperature treatment in an intelligent artificial climate box.Two rootstock cultivars,Towel gourd and White pumpkin seeds showed highly resistance to high temperature stress.The effect of different rootstocks on the cucumber growth,photosynthesis,fruit yield and quality in greenhouse was studied.Growth index of plants and quality of fruits were determined.The major results were as follows:1.Activities of defensive enzymes related to powdery mildew resistance and chlorophyll fluorescence parameters were measured in leaves of cucumber varieties with different resistance levels after powdery mildew inoculation.The results showed that activities of six disease resistance-related enzymes had different degrees of increase after inoculation of powdery mildew and increased more in resistant varieties than that in susceptible varieties,indicating that disease resistance-related enzymes played an important role in cucumber resistance mechanism against powdery mildew;light use efficiency of five varieties,were significantly decreased,and reduced more in resistant varieties than that in susceptible varieties,indicating that photosynthesis in powdery mildew infected cucumber plants was inhibited,and was significantly affected in susceptible varieties.2.Using method of substrate culture and material of cucumber cultivar’Chunqiuwang No.2’,the alleviating effects of high-temperature sealing treatment on growth,chlorophyll content,chlorophyll fluorescence parameters,active oxygen metabolism and chitinase of cucumber seedlings which were infected with powdery mildew in an intelligent illumination incubator under high-temperature sealing treatment.The results showed that powdery mildew infection significantly inhibited plant growth,and decreased chlorophyll contents,light capture and conversion efficiency,but increased the activities of antioxidant enzymes and chitinase.For normal plants,high-temperature sealing treatment light use efficiency increased.For powdery mildew infected cucumber seedlings,high-temperature sealing treatment reduced the powdery mildew disease index,light use efficiency increased,and the activities of antioxidant enzymes and chitinase.The study indicated that high-temperature sealing treatment could reduce the activity of powdery mildew germs and infection,enhanced antioxidant capacity,light capture and conversion efficiency and the ability of resistance to pathogen of powdery mildew-infected cucumber seedlings.However,normal plants showed higher adaptation capacity to heat stress than plants infected by powdery mildew.3.Using self-rooted cucumber seedlings(Cucumis sativus ’Chunqiuwang No.2’)and grafted cucumber with Cucurbita ficifolia Bouche,Cucurbita maxima × Cucurbita moschata,Luffa cylindrica,Benincasa hispida Cogn.cultured in an intelligent artificial climate box,the changes of growth,leaf photosynthetic and chlorophyll fluorescence parameters in cucumber seedlings subjected to high temperature treatment were investigated.The results showed that the cucumber seedlings had different degrees of growth under high temperature.The chlorophyll content,light use efficiency increased significantly.The activities of antioxidant enzyme activity,soluble protein content and MDA content increased significantly.Taking comprehensive growth,photosynthesis and fluorescence characteristics,antioxidant enzymes activities into consideration,two grafted cucumber seedlings,Cucurbita maxima × Cucurbita moschata and Luffa cylindrical showed stronger tolerance under high temperature stress.4.Effects of high temperature stress on ascorbate-glutathione cycle in self-rooted cucumber seedlings and grafted cucumber seedlings were studied.The results showed that:(1)under high temperature stress,the content of AsA and GSH,reduced,the value of AsA/DHA,and GSH/GSSG in leaves of 4 grafted and self-rooted decreased;(2)under high-temperature stress treatment for 72 h,activity of APX,GR in leaves of 4 grafted and self-rooted increased,and gourd rootstock grafted seedlings showed a larger amplitude increase;(3)under high temperature stress for 24 h,activitives of DHAR,MDHAR increased to the highest level in leaves of 4 grafted and.self-rooted,with grafted seedlings using loofah as rootstock increased the most.The results showed that the grafted seedlings.could increase non-enzymatic antioxidant the content of AsA and GSH and activity of antioxidant enzyme and increased ascorbate-glutathione cycle capacity of scavenging reactive oxygen species,thereby alleviated damage of high temperature stress on cucumber plant.5.Four different types of rootstock were selected to graft with ’Chunqiuwang No.2’to investigate the effect of different rootstock on the cucumber growth,photosynthesis,fruit yield and quality.The results showed that the growth of seed pumpkin rootstock was higher.Seedlings with Pumpkin seeds and white gourd as rootstock had higher light use efficiency,yield per plant,fruit soluble sugar,free amino acid content than those of other plants.Therefore,towel gourd and white pumpkin seeds rootstock,to a certain extent,could improve the yield of cucumber in the high temperature season and cucumber nutritional value.