内生菌72和146对盐胁迫下大豆幼苗过氧化氢酶活性和脯氨酸含量的影响

Endophytic bacterial strains 72 and 146 affect catalase activity and proline content in soybean seedlings under salt stress

摘要:

目的 探索盐胁迫环境下大豆根瘤内生菌对大豆幼苗生长的影响，为黄河流域作物高质量发展提供参考。方法 以‘徐豆20’为实验材料，设置对照组、盐胁迫组和盐胁迫接种内生菌组3组处理，在人工气候条件下采用盆栽法探究不同盐胁迫下接种内生菌对大豆幼苗生长的影响。结果 在盐胁迫条件下，接种内生菌72时，大豆幼苗培养至21 d时，使用OD₆₀₀=0.75菌悬液(2:1)接种，当盐浓度为200 mmol/L时，过氧化氢酶(catalase, CAT)活性最高，为2.010 0 U/g FW，比盐胁迫组高出54.02%；使用OD₆₀₀=0.33的菌悬液(1:2)接种时，在盐浓度为 300 mmol/L时，脯氨酸含量最高，为0.028 6 mg/g，而在盐浓度为100 mmol/L时，脯氨酸含量比盐胁迫组高出64.38%。接种内生菌146时，大豆幼苗培养至21 d时，使用OD₆₀₀=0.50的菌悬液(1:1)接种，在盐浓度为50 mmol/L时，CAT活性最高，为1.350 0 U/g FW；培养至28 d，使用OD₆₀₀=0.75的菌悬液(2:1)接种，在盐浓度为100 mmol/L时，CAT活性比盐胁迫组高出272.73%；在盐浓度为150 mmol/L时，脯氨酸含量最高，为0.147 0 mg/g，比盐胁迫组高出860.78%。由此可见，在盐胁迫条件下，接种内生菌72和146均具有一定的修复作用。总体而言，接种内生菌146后，大豆幼苗的CAT活性和脯氨酸含量均显著高于盐胁迫组，说明内生菌146的修复作用更为明显。基于16S rRNA基因序列及系统发育分析结果，菌株72与枯草芽孢杆菌(Bacillus subtilis)最相似，相似率为99.45%；菌株146与解蛋白芽孢杆菌(Bacillus proteolyticus)最相似，相似率为100%。结论 接种内生菌可有效缓解黄河流域盐碱土壤对大豆幼苗生长的不利影响，对研发生物防治剂具有重要意义。

关键词:内生细菌;大豆幼苗;盐胁迫;过氧化氢酶;脯氨酸;修复作用

Abstract:

Objective To explore the effects of endophytic bacteria in soybean nodules on the growth of soybean seedlings under salt stress and provide reference for the high-quality development of crops in the Yellow River Basin.Methods A pot experiment was conducted with the soybean cultivar ‘Xudou 20’ under artificial climate conditions. Three groups were designed: control, salt stress, and salt stress inoculated with endophytic bacteria. The growth of soybean seedlings in each group was measured.Results Regarding strain 72, in the case of inoculation with the suspension at OD₆₀₀=0.75 (2:1) and the salt concentration of 200 mmol/L, the activity of catalase (CAT) in the seedlings of 21 days was the highest (2.010 0 U/g FW), which was 54.02% higher than that in the salt stress group; in the case of inoculation with the suspension at OD₆₀₀=0.33 (1:2) and the salt concentration of 300 mmol/L, the proline content was the highest (0.028 6 mg/g); in the case of inoculation with the suspension at OD₆₀₀=0.75 (2:1) and the salt concentration of 100 mmol/L, the proline content was 64.38% higher than that in the salt stress group. Regarding strain 146, the seedlings of 21 days in the case of inoculation with the suspension at OD₆₀₀=0.50 (1:1) and the salt concentration of 50 mmol/L had the highest CAT activity (1.350 0 U/g FW); the seedlings of 28 days in the case of inoculation with the suspension at OD₆₀₀=0.75 (2:1) and the salt concentration of 100 mmol/L had the CAT activity 272.73% higher than that in the salt stress group; the seedlings in the case of inoculation with the suspension at OD₆₀₀=0.75 (2:1) and the salt concentration of 150 mmol/L had the highest proline content of 0.147 0 mg/g, which was 860.78% higher than that in the salt stress group. The results indicated that inoculation with the endophytic bacterial strain 72 or 146 had a repairing effect. The increases in the CAT activity and proline content in the soybean seedlings inoculated with strain 146 over those in the salt stress group were generally higher than those in the case of inoculation with strain 72, indicating that the repairing effect of strain 146 was more obvious. The phylogenetic tree built based on 16S rRNA gene sequences showed that strains 72 and 146 had the highest similarity with Bacillus subtilis (99.45%) and B. protolyticus (100%), respectively.Conclusion Inoculating endophytic bacteria was of great significance for alleviating the effect of saline-alkali stress in the Yellow River Basin on the growth of soybean seedlings and developing biological repairing agents.

Key words:endophytic bacteria;soybean seedlings;salt stress;catalase;proline;repairing effect