黄河三角洲芽孢杆菌的分离鉴定及其盐胁迫下对田菁的促生作用

Bacillus strains from the Yellow River Delta: isolation, identification, and assessment of growth-promoting effect on Sesbania cannabina under salt stress

摘要:

目的 从黄河三角洲盐碱土中分离筛选具有耐盐性且促生效果良好的菌株，为作物在盐碱地高效种植提供菌种资源。方法 采用平板稀释涂布法分离芽孢杆菌，并通过浸种试验筛选出促生效果良好的菌株。对筛选出的菌株进行促生特性测定，并在盐胁迫条件下，利用田菁盆栽试验评估其促生效果。结合形态学特征、生理生化特征以及分子生物学方法，对促生效果最佳的菌株进行鉴定，并通过全基因组序列分析，挖掘与促生功能相关的基因。结果 共分离获得60株芽孢杆菌，通过浸种试验筛选出编号为M4、M5、B5、L3和Q17的菌株，这些菌株表现出优良的促生效果，具备解无机磷、解钾以及产生吲哚-3-乙酸(indole-3-acetic acid, IAA)等功能。田菁盆栽试验结果表明，在正常培养条件以及低浓度盐胁迫(NaCl浓度为100 mmol/L)培养时，接种芽孢杆菌能够显著提高田菁幼苗的株高、最大叶面积、茎秆干重和根干重(P<0.05)；高浓度盐胁迫(NaCl浓度为200 mmol/L)培养时，接种5株芽孢杆菌能够显著提高田菁幼苗茎秆和叶片的鲜重与干重(P<0.05)；接种芽孢杆菌能显著提高田菁幼苗叶片中的过氧化氢酶(catalase, CAT)、超氧化物歧化酶(superoxide dismutase, SOD)和过氧化物酶(superoxide dismutase, POD)活性，且丙二醛(malondialdehyde, MDA)含量显著降低(P<0.05)。其中，促生效果最佳的菌株M4经鉴定为苏云金芽孢杆菌(Bacillus thuringiensis)。结论 分离得到的5株芽孢杆菌均具有多种促生特性，能够促进盐胁迫下田菁幼苗的生长，缓解盐分对幼苗的抑制作用。其中促生效果最好的M4菌株经鉴定为B. thuringiensis，具备较强的开发盐碱地促生菌肥的潜力。

Abstract:

Objective To isolate and screen the salt-tolerant strains with good plant growth-promoting effect from the saline-alkali soil of the Yellow River Delta, thus providing strain resources for the efficient cultivation of crops in saline-alkali soil.Methods Bacillus strains were isolated by the dilution coating method, and the strains with good plant growth-promoting effects were further selected by the seed soaking test. The growth-promoting characteristics of the selected strains were measured, and the growth-promoting effects of the strains on Sesbania cannabina under salt stress was evaluated by pot experiments. The strain with the strongest plant growth-promoting effect was identified based on morphological characteristics, physiological and biochemical characteristics, and molecular biological evidence. Through the whole genome sequence analysis, the genes related to the plant growth-promoting function were discovered.Results A total of 60 Bacillus strains were isolated, from which strains M4, M5, B5, L3, and Q17 were screened out by the seed soaking test. These strains showed robust plant growth-promoting properties, being capable of solubilizing inorganic phosphorus, solubilizing potassium, and producing inole-3-acetic acid. The pot experiment results showed that under normal culture conditions and under low salt stress (NaCl concentration of 100 mmol/L), inoculation with Bacillus increased the plant height, maximum leaf area, stem dry weight, and root dry weight of S. cannabina seedlings (P<0.05). Under high salt stress (NaCl concentration of 200 mmol/L), the fresh and dry weights of stem and leaves of S. cannabina seedlings were increased by inoculation with five strains of Bacillus (P<0.05). In addition, inoculation with Bacillus enhanced the activities of catalase, superoxide dismutase, and peroxidase while reducing the content of malondialdehyde in the leaves of S. cannabina seedlings (P<0.05). Strain M4 with the strongest plant growth-promoting effect was identified as Bacillus thuringiensis.Conclusion All the five isolates have various plant growth-promoting properties, being capable of promoting the growth of S. cannabina seedlings under salt stress and alleviating the inhibitory effect of salt on the seedlings. Strain M4 with the robust plant growth-promoting effect is identified as B. thuringiensis, and it has the potential to be developed as plant growth-promoting bacterial fertilizer for saline-alkali soil.