Physiological And Molecular Mechanisms Of Salt Tolerance In Hybrid JB185 Of Glycine Max And Salt-born Glycine Soja

The Glycine max Jackson cultivar(the salt sensitive),the salt-born Glycine soja BB52 population(the salt tolerant),and their hybrid JB185(F₅) selected for salt tolerance generation by generation were used as the experimental materials.The above seedlings were stressed for 6 d with 50,100,150 mmol·L^-1 NaCl solution,respectively. The physiological changes in water content,value of R/T,cholophyll and its fluorescence parameter,salt ion absorption and its toxicity,and molecular mechanism mainly through by EST(expressed sequence tags) were investigated.The result are as follows:After stressed for 6 d,the plant relative growth rate,water content,and dry weight of the 3 experimental materials were declined with the increase of NaC1 concentration. The value of R/T,MDA content,and relative electrolytic leakage were increased with the increase of NaCI concentration.The changes in above physiological indexes of JB185 were among its parents.The chlorophyll and carotenoid contents in leaves of Jackson and JB185 were increased under 50,100 mmol·L^-1 NaCl stress,but they were decreased under 150 mmol·L^-1 NaCl stress when compared to the control.Chlorophyll and carotenoid contents in leaves of BB52 were all increased under these NaC1 stresses.The Fv/Fm values in leaves of BB52 and JB185 were not obviously changed with the increase of NaCl concentration when compared to the control,and those in Jackson were increased under 50,100 mmol·L^-1 NaCl stresses,but it was obviously decreased under 150 mmol·L^-1 NaCl stress.The K⁺ contents in different organs or whole seedlings of 3 experimental materials were decreased with the increase of NaCl concentration,except for the enhanced K⁺ absorption in roots of BB52 seedlings under 50 mmol·L^-1NaCl stress,but the decrease of K⁺ content in BB52 was smaller than those in Jackson.The Na⁺ contents in the 3 experimental materials at different organs or whole plants were increased with the increase of NaCI concentration.The Na⁺ contents in root,stem,and whole seedling of BB52 were all fewer than Jackson,but it showed the reverse in leaf. The change in value of Na⁺/K⁺ was consistent with the change in Na⁺.The Na⁺ and K+ contents,and value of Na⁺/K⁺ in JB 185 seedlings were between its parents.One EST(expressed sequence tag) of chloride channel genes(CLCs) in soybean was assembled according to the EST database,and was confirmed in soybean cDNA by RT-PCR technique.No difference in gene copy number of the EST among the Glycine max(Jackson),Glycine soja(BB52) and their hybrid(JB185) was showed by Southern blot, its weakening transcriptional level by semi-quantitative Northern blot and RT-PCR exhibited in roots and leaves of Jackson seedlings under salt stress,while an enhanced or relatively higher trend was found in salt-stressed BB52 and JB185 seedlings,especially in JB185.Measured by photometric method,the higher CI content in plants and its larger proportion in leaves of Jackson seedlings,and lower Cl^content in plants and its larger proportion in roots in BB52 and JB185 seedlings were observed.The results of this research indicate that,the relative improved salt tolerance of the hybrid JB185 compared to its female parent Jackson can be achieved by hybridization with the salt-born BB52 population and selection for salt tolerance generation by generation,and this improved salt tolerance may be resulted from the enhanced transcriptional level of CLCs.