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The Glycine max N23674 cultivar (Lishui, Jiangsu province, the salt sensitive), the salt-born Glycine soja BB52 population (Kenli, Shandong province, the salt tolerant) and their 4 hybrid strains (F4-5):4013,4035,4076 and 4111 were used as the experimental materials in this study. Their seedling salt tolerance, agronomic traits (such as the plant height, branch No., node No. of stem, pod No. per plant, weight per 100 seeds) and seed quality (such as the protein and fat contents, composition of amino acids and fatty acids) were analyzed and compared. Then taken the hybrid 4111 strain as the representative, the physiological mechanism of salt tolerance in parents of cross N23674×BB52 and their hybrids was investigated. The results showed as follows:Under the NaCl solution stressed, the indexes such as the salt tolerant coefficient, dry matter and relative growth rate of seedlings of the hybrid strains were between their parents, especially 4076 and 4111 were almost eaqual to their male parent, and which indicated that, the degree of salt injury or growth inhibition of the hybrids were lighter than their female parent. When compared the contents of K+, Na+ and Cl- in roots, stems and leaves of the seedlings, more Na+ and Cl- were found to be mainly accumulated in roots and stems than in leaves of seedlings of the hybrids and their male parent, and the Na+/K+ ratio in roots, stems and leaves were also kept at lower levels.As for the agronomic traits and seed quality, the agronomic traits of 4 F4 hybrids were all between their parents, the seed quality was obviously improved as compared with their male parent BB52, The contents of protein, most of the essential amino acids and sulfur-containing amino acids, and total amino acids exceeded the two parents; the contents of fat were between their parents and nearly closed to those of N23674. The saturated fatty acids, i.e. palmitic acid (C16:0) and stearic acid (C18:0), were almost equal to their parents, but the unsaturated oleic acid (Cl8:1), linolenic acid (C18:3) and the IUFA (index of unsaturated fatty acids) were all between the parents, the contents of linoleic acid (C18.2) in 4076 and 4111 strains were already more than those in two parents.When the seedlings of the hybrid 4111 strain and their parents (N23674, BB52) were stressed for 6 d with 130 mmol·L-1 NaCl solution, the content of K+, water content, osmotic potential in leaves of the three experimental materials were all significantly decreased, and the content of Na+, Cl-, MDA, the ratio of Na+／K+ and relative electrolytic leakage were obviously increased in comparison with the control. The contents of chlorophyll, carotenoid and the ratio of chla/chlb were reduced in the female parent N23674, while those in the male parent BB52 and the hybrid 4111 all ascended. The photosynthetic parameters, such as Pn, Gs, Ci and Tr remarkably decreased with the exception of the increase of Ls, the changes in BB52 and 4111 were relatively smaller than those in N23674. In regards with Fv/Fm value, the significant drop was observed in N23674, but no obvious change was displayed in BB52 and 4111.
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