Study On Salt Tolerance Of Four Different Rootstock-scion Apple Combinations

Salt stress was one of the major environmental factors that inhibited fruit growth and reduced fruit yield,and the grafting as main apple breeding method had an important influence on apple salt tolerance.Studying the growth and physiological variation of different rootstock-scion combinations stressed by NaCl was great significance in elucidating the mechanism of salt damage and screening of strang salt tolerance of apple rootstock-scion combinations.Four groups of three years old apple tree cultivated in the pot with different rootstock-scion combinations were stressed by NaCl with different concentration (0,0.2%,0.4% and 0.6% NaCl) in the treated soil and shoot growth rate,leaf area growth,cell membrane permeability,Chlorophyl,MDA,soluble protein, SOD and the photosynthetic capacity were investigated. The results showed that shoot growth rate,leaf area growth, chlorophyll content reduced when the stress concentration of NaCl and stress time increased, and were negatively correlated with the stress concentration and time;cell membrane permeability and MDA content increased with the stress concentration and time increased, but MDA content reduced in the end of stress;soluble protein content and SOD activity increased firstly and then decrease with the stress concentration and time increased.The effect of NaCl stress after 14 days to the photosynthetic capacity were investigated and the result showed that net photosynthetic rate (Pn),stomatal conductance (Gs),transp iration rate (Tr),the content of chlorophyll b(chlb)and leaf growth reduced,but cell membrane permeability increased when increasing salt stress.The photosynthesis decline in the low-salinity stress was principally influenced by stomatal limitation,and in the middle and high salinity stress, stomatal limitation and non-stomatal limitation plays a role commonly.Different rootstock-scion combinations shewd different sensitivity to NaCl stress,also different indicators of growth and physiological were different. Comprehensive principal component analyse of 8 indicators showed that shoot growth rate, leaf growth and chlorophyll b content was in the stronger correlation between salt tolerance than soluble protein and SOD activity,and the strength of salt tolerance of rootstock-scion combination were M26/ChangFu2,Malus/Gala, M26/FuHungZaoGa, Malus/ShanFu3 in descending.