Study On Physiological Response Of Shine Muscat Grape Grafted Seedlings With Different Rootstocks To Salt And Low Temperature Combined Stress

Grape is one of the largest fruit trees in China,which has important economic value and is widely planted in China.Northwest China,as one of the main producing areas of grape planting in China,is often subjected to various abiotic stresses such as cold,drought,soil salinization,which affect the yield and quality and hinder the development of grape industry.China’s grape grafting cultivation started late,mainly focused on the breeding of cold-resistant rootstocks and the evaluation of single resistance of rootstocks.There is a lack of systematic research on the stress resistance and compound stress of grafted seedlings.Therefore,it is of great significance to study the response of grafted seedlings to combined stress and its mechanism to promote the sustainable development of grape industry in Northwest China.In this study,four rootstock-scion combinations（shine muscat/5BB,shine muscat/SO4,shine muscat/Kangzhen No.3,shine muscat/101-14）and self-rooted seedlings of shine muscat were treated with salt stress,low temperature stress and salt and low temperature stress.The physiological and biochemical indexes such as relative water content,relative electric conductivity,malondialdehyde,chlorophyll,chlorophyll fluorescence parameters,photosynthetic gas exchange parameters,proline,soluble sugar,soluble protein and antioxidant enzyme activity were measured.Finally,the comprehensive evaluation of lowtemperature and salt tolerance was carried out by principal component analysis and membership function analysis.The main results are as follows:1.Under salt stress,compared with the self-rooted seedling,the relative water content of four grafted seedlings decreased significantly,the conductivity and malondialdehyde showed an upward trend,the contents of chlorophyll,proline,soluble sugar and soluble protein increased,and there were significant differences,the photosynthetic gas exchange parameters and chlorophyll fluorescence parameters showed a decreasing trend,and the activities of catalase,peroxidase and superoxide dismutase increased significantly.Combined with the results of principal component analysis and membership function analysis,the order of salt tolerance of five kinds of sunshine muscat grapes was shine muscat/SO4>shine muscat/101-14>shine muscat/Kangzhen No.3>shine muscat/5BB>shine muscat self-rooted seedling.2.Under low temperature stress,the change trend of physiological and biochemical indexes of grafted seedlings and self-rooted seedlings was similar to that of salt stress,but the amplitude of variation was significantly different,among which shine muscat/5BB showed stronger low temperature resistance.Comprehensive analysis concluded,the tolerance ability of low temperature resistance of five kinds of shine muscat grapes was shine muscat/5BB>shine muscat/Kangzhen No.3>shine muscat/SO4>shine muscat/101-14>shine muscat self-rooted seedling.3.Under the combined stress of salt and low temperature,the change trend of physiological and biochemical indexes were similar to that of salt stress and low temperature stress.The MDA content of shine muscat/SO4 under combined stress was 4.06μmol·g^-1,which was significantly lower than that under salt stress and low temperature stress.The contents of three organic osmotic adjustment substances were significantly higher than those under salt stress and low temperature stress.The activities of CAT and POD were also significantly higher than those under salt stress and low temperature stress.The other grafted seedlings and self-rooted seedlings were similar.Comprehensive analysis concluded,the tolerance ability order of five kinds of shine muscat grapes to salt and low temperature combined stress was shine muscat/SO4>shine muscat/5BB>shine muscat/Kangzhen No.3>shine muscat/101-14>shine muscat self-rooted seedling.4.In this experiment,correlation analysis,grey correlation analysis,principal component analysis and membership function analysis were carried out on the physiological indexes related to stress resistance.Under the combined stress of salt and low temperature,the results showed that the cell membrane permeability changed little,the photosynthetic gas exchange parameters and chlorophyll fluorescence parameters decreased slightly,and the organic osmotic adjustment substances and antioxidant enzyme activities increased greatly.Among them,malondialdehyde,relative electric conductivity and proline can be preferentially used as indicators for evaluating grape stress resistance.In summary,SO4 is the rootstock with the highest resistance to salt and low temperature combined stress.The tolerance ability of potted shine muscat grafted seedlings under combined stress is higher than that under single stress,that is,when shine muscat grafted seedlings are under salt stress and then placed in low temperature stress,their resistance will be enhanced.