关键词: 谷子, 盐胁迫, 萌发期, 综合评价, 保护酶

Abstract:

【Objective】The purpose of this study was to select germplasms tolerant to salt at germination stage, to establish an evaluation criterion for salt tolerance, and to investigate the effect of salt stress on protective enzyme system of different genotypes of foxtail millet at seedling stage. The results could propose an identification method and excellent genetic resources for research on salt-tolerant mechanisms of foxtail millet.【Method】54 foxtail millet varieties from different eco-regions were applied as experimental materials. Salt stress was implemented by adding 1.5% NaCl solution, and distilled water was used as the control. A petri dish based germination method was used to assess the salt tolerance of foxtail millet varieties in artificial climate incubator. Six salt-tolerant indexes were investigated in each treatment, including relative germination potential, relative germination rate, relative coleoptile length, relative radical root length, relative radical root / coleoptiles, and relative salt damage rate. A comprehensive analysis of the salt tolerance of different varieties was conducted via correlation analysis, principal component analysis and clustering analysis. Furthermore, pot experiment was conducted to cultivate selected varieties with different salt tolerance under both salt stress and normal conditions, and superoxide dismutase (SOD) activity, peroxidase (POD) activity, and catalase (CAT) activity in shoot were analyzed. And then the differences of physiological responses between those genotypes under salt stress were analyzed.【Result】Under salt stress of 1.5% NaCl , a significant positive correlation was detected between relative germination potential and relative germination(r=0.51, P<0.01) and relative coleoptile length (r=0.54, P<0.01). There was a significant positive correlation between relative coleoptile length and relative radical root length (r=0.64, P<0.01), while the relative salt damage rate showed a significant negative correlation with relative germination rate (r=-0.37, P<0.01) and relative coleoptile length (r=-0.51, P<0.01). Principal component analysis transformed the six single indexes in the salt-stressed germination stage of foxtail millet to three independent comprehensive indexes. Subordinate function analysis was conducted to obtain the comprehensive assessment value (D-value) of salt tolerance of different varieties at germination stage. 54 foxtail millet varieties were classified into five salt tolerant types based on clustering analysis, including extremely salt sensitive, salt sensitive, moderate salt tolerance, salt tolerance and high salt tolerance. The varieties with high salt tolerance were Yangu 13, Longgu 3 from spring sowing region of northwest China, and Jigu 16, Ai88 from summer sowing region of north China. The activities of SOD, POD, and CAT were increased and then decreased under salt stress condition. SOD, POD, and CAT in shoot increased in response to salt stress, and the activity of those enzymes in Jigu 16 was significantly higher than that in Lugu 1.【Conclusion】Remarkable variations in salt tolerance were detected among the 54 genotypes of foxtail millet. The systematical and clear results can be obtained by membership function analysis, and the salt tolerance of foxtail millet can be evaluated objectively and comprehensively. The leaf protective enzymes are important for the adaptability of foxtail millet to salt stress in seedling stage.

Key words: foxtail millet (Setaria italica L.), salt-stress, germination stage, comprehensive evaluation, protective enzymes