多功能复合菌剂的构建及盐碱胁迫下促生效果

    Constructing multifunctional composite microbial agents for promoting crop growth under saline-alkali stress

    • 摘要: 微生物对植物的生长和土壤改良起到重要作用。为改变盐碱土壤不利于作物生长的现状,该研究对盐碱土壤进行了菌群结构分析,并分离得到了有促生作用的功能微生物,利用已有拮抗菌与分离促生菌混合构建一种多功能复合菌剂,研究在盐碱胁迫下其对绿豆的促生作用。结果表明:供试土壤中具有特定的微生物群落结构,其中SI-1-3经鉴定为枯草芽孢杆菌属,具有溶解有机磷和分解钾元素的能力,能够分泌吲哚乙酸和赤霉素;酵母菌Y-2对镰孢菌等植物病原菌有抑制作用。复合菌剂在盐碱条件下对绿豆生长有明显的促进作用,且能防止病原菌的侵染,增强植物的抗逆性,从而降低植株的发病率。与无菌水对照组相比,绿豆的出苗率增长了7.44%,发病率降低了82.37%,处理后的绿豆根长、株高和茎叶鲜质量分别增长了75.24%、64.33%、66.67%;绿豆苗的叶绿素、可溶性糖和可溶性蛋白含量分别升高了71.63%、64.21%和77.87%。该复合菌剂对植株具有促生效应,有望进一步开发成为特定环境下的微生物资源。

       

      Abstract: Crops are often subjected to low survival rates in saline-alkali soil, due to the saline-alkali stress. The increasing number or variety of functional microorganisms in the saline-alkali soil can be expected to significantly promote the growth of plants. In this study, the microbial community structure of saline-alkali soil was analyzed to isolate the functional microorganisms with the growth-promoting using high-throughput sequencing. A multifunctional composite microbial agent was constructed to mix the existing antagonistic bacteria with the isolated growth-promoting bacteria. A systematic investigation was made to clarify the growth-promoting on the mung beans under saline-alkali stress. Two strains were identified by molecular biology. The phosphorus and potassium solubilization of strain SI-1-3 were verified by culture media. The Salkowski colorimetric technique was used to determine the production of the IAA (indole-3-acetic acid) product. Spectrophotometry was used to identify the secretion of GA (gibberellin). The inhibitory capability of antagonistic Y-2 against pathogenic bacteria was determined using the petri dish confrontation. The compatibility experiment among strains was conducted for the composite microbial formulation in a petri dish using the cross-line method. The saline-alkali conditions of the tested soil in the pot experiment were determined to measure the saline-alkali tolerance range of the composite microbial agent. Pot experiments were used to clarify the effects of compound strains on the emergence rate, incidence rate, growth indicators, and physiological and biochemical indicators of mung beans. The growth promotion was verified for the composite microbial agent. The results showed that Proteobacteria, Actinobacteria, and Firmicutes were the dominant bacterial communities in the soil samples, while Ascomycota shared the highest proportion of fungal communities. A bacterium named SI-1-3 was isolated with a higher isolation frequency from the dominant strains. It was identified as Bacillus subtilis, with the ability to dissolve organic phosphorus, decompose potassium elements, and secrete indole-3-acetic acid and gibberellin. According to the phylogenetic tree, the antagonistic strain Y-2 was Pichia membranifaciens. Plate experiments showed that antagonistic bacterium Y-2 shared a significant inhibitory effect on Fusarium raminearum and Pyricularia oryzae Cav. There was no antagonistic effect between the two strains through compatibility tests. They were co-cultured to construct a composite microbial formulation with a volume ratio of 1:1. The saline-alkali tolerance of the composite bacterial agent was identified to determine the best growth of the strain in the PDB medium. Therefore, a pH value of 8.5 and NaCl concentration of 5% were selected as the saline-alkali stress conditions for the subsequent experiments. The mung beans were then planted in the saline-alkali soil with the composite microbial agent. There was a certain promoting effect of composite microbial agent on the growth of mung beans under saline-alkali stress conditions with pH 8.5 and NaCl concentration of 5%. The emergence rate of mung bean increased by 7.44% in the pot experiment, whereas, the incidence rate decreased by 82.37%, compared with the control group. Additionally, the root length, plant height, and fresh weight of stem and leaf that were treated by the composite microbial agent increased by 75.24%, 64.33%, and 66.67%, respectively. At the same time, the chlorophyll, soluble sugar, and soluble protein content of mung bean seedlings increased by 71.63%, 64.21%, and 77.87%, respectively. There was the promoting effect of composite microbial agents on the plants. Thus, the finding can provide an effective microbial resource to improve the saline-alkali land and agricultural development.

       

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