Evaluation Of Tolerance Of Different Kiwifruit Germplasm To Bicarbonate Stress

Bicarbonate stress is one of the common abiotic stresses in kiwifruit cultivation.It is easy to induce leaf yellowing,which leads to loss of yield and quality.Although soil improvement can alleviate bicarbonate stress to a certain extent,its application is limited due to high cost and short effect.Screening bicarbonate-tolerant kiwifruit germplasm is an effective strategy for environmental optimization and long-term response to this stress.However,germplasm screening of kiwifruit tolerant to bicarbonate stress is rarely reported.In this study,30 tissue culture seedlings of kiwifruit genotypes（including 4 cultivars and 26wild genotypes）were used as test materials.Sand culture was used to set control（p H=6.0±0.1）and bicarbonate stress(0.5 g L^-1Ca CO₃and 0.84 g L^-1Na HCO₃were added into the nutrient solution.p H=8.0±0.1),the responses of plant growth phenotype,biomass and physiological characteristics were observed.The key indexes of bicarbonate tolerance were screened by variance analysis and correlation analysis,and the bicarbonate tolerance of30 tested materials was evaluated by combining principal component analysis,membership function method based on weight and systematic cluster analysis.Which would contribute to providing basic materials for breeding bicarbonate-tolerant kiwifruit rootstocks and varieties and analyzing the mechanism of bicarbonate-tolerant kiwifruit.The main research results were as follows:1.The growth phenotype,biomass and physiological characteristics of 30 kiwifruit genotypes varied in response to bicarbonate stress.In terms of growth phenotype,bicarbonate stress significantly reduced stem length,leaf number,root volume and leaf area.In terms of biomass,bicarbonate treatment significantly inhibited the formation of fresh weight and dry weight,but increased the content of dry matter.In terms of physiological characteristics,bicarbonate treatment significantly inhibited root H⁺expulsion rate,iron absorption and transport,but increased the content of soluble protein in osmotic regulatory substances and the activities of SOD and CAT in antioxidant enzymes.2.Through variance analysis and correlation analysis of 38 character parameters,nine key indexes were selected from the growth phenotype,biomass and physiological characteristics:stem length,leaf area,root fresh weight,whole plant dry weight,whole plant dry matter content,root total iron concentration,ratio of total iron concentration in stem and root,total iron concentration ratio of leaf and stem,and POD activity.3.According to principal component analysis,membership function method based on weight and systematic cluster analysis,30 kiwifruit genotypes were divided into 5 groups:（1）Highly bicarbonate-tolerant,including GZ1,DE2,DE1 and DE7;（2）Bicarbonate-Tolerant,including DE6,DZ1,DE5,DE4,DZ3,DZ2,YX,DZ4,MW7 and DE3;（3）Moderate bicarbonate-tolerant,including MW1,DE8 and QM;（4）Bicarbonate-sensitive,including MW11,QH,MW8,MW9,MW4,MW10,MW5,MW2,MW12,MW6 and JM;and（5）Highly bicarbonate-sensitive,MW3 and MW13.Bicarbonate tolerance was significantly differend among kiwifruit species.2 genotypes of Actinidia chinensis belonged to sensitive type;15 genotypes of Actinidia delicisa included tolerant,moderate tolerant,sensitive and highly sensitive type;8 genotypes of Actinidia valvata had highly tolerant,tolerant and moderate tolerance type;4 genotypes of Actinidia macrosperma belonged to tolerant type;1genotypes of Actinedia polygama belonged to highly tolerant type.