辣椒镰孢根腐病防病促生细菌的筛选及其效应

【目的】筛选辣椒(Capsicum annuum L.)根腐病防病促生细菌并明确其防病促生效应。【方法】采集健康辣椒根围土壤样品，以辣椒根腐病病原真菌茄镰孢(Fusarium solani)和尖镰孢(Fusarium oxysporum)为指示菌，采用平板对峙法筛选生防细菌，采用选择性培养基筛选溶无机磷、溶有机磷、固氮菌和解钾菌等促生菌，钼锑抗比色法测定溶磷量，凯氏定氮法测定固氮量，火焰原子吸收光谱法测定解钾量。对特性良好组合的菌株进行16S rDNA序列分析鉴定并制作菌剂，最后采用盆栽法测定菌剂防病促生效果。【结果】共筛选得到323株特性良好的功能菌株，拮抗菌78株，溶有机磷菌87株，溶无机磷菌107株，固氮菌128株，解钾菌123株，部分菌株同时具有多个功能特性。互作组合得到6个特性良好的菌株组合，包括8株功能菌株，鉴定发现XP271和XP181为枯草芽胞杆菌(Bacillus subtilis),XP125为特基拉芽胞杆菌(Bacillus tequilensis),XP236为耐盐芽胞杆菌(Bacillus halotolerans),XP79为巨大芽胞杆菌(Bacillus ...

The Fusarium root rot-controlling effect and growth-promoting effect of the bacteria in the rhizosphere of Capsicum annuum

[Objective] To screen out the bacterial strains that can control the Fusarium root rot and promote the growth of Capsicum annuum L. and clarify their disease-controlling and growth-promoting effects. [Methods] The soil samples were collected from the rhizosphere of healthy C.annuum plants, and then plate confrontation method was employed to screen the biocontrol bacteria with Fusarium solani and F.oxysporum as the indicator fungi. After that, selective media were used to screen the growth-promoting bacteria with inorganic phosphorus-solubilizing, organic phosphorus-solubilizing, nitrogen-fixing, or potassium-solubilizing activities. Further, the disease-controlling and growth-promoting effects of the selected strains were determined qualitatively and quantitatively. The amount of phosphorus solubilized, nitrogen fixed, and potassium solubilized were respectively determined by molybdenum-antimony anti-colorimetric method, Kjeldahl method, and flame atomic absorption spectrometry. We then determined the 16S rDNA sequences of the strains with excellent characteristics and prepared the bacterial inoculants with different combination formula. Finally, pot experiments were carried out to measure the disease-controlling and growth-promoting effects of the inoculants. [Results] We screened out 323 strains with excellent functions, including 78 antagonistic strains, 87 organic phosphorus-solubilizing strains, 107 inorganic phosphorus-solubilizing strains, 128 nitrogen-fixing strains, and 123 potassium-solubilizing strains. Some strains had multiple functions, and 6 combinations with excellent characteristics were obtained, which involved 8 strains. Strains XP271 and XP181 were identified as Bacillus subtilis, XP125 as B.tequilensis, XP236 as B.halotolerans, XP79 as B.megaterium, XP171 as B.circulans, XP248 as Cellulosimicrobium funkei, and XP167 as Pseudomonas synxantha. The inoculants were prepared according to two combination formula, which demonstrated the best controlling effect of 88.52% on Fusarium root rot and increased the plant height, branch number, and biomass of C.annuum by about 10 cm, 2 branches, and 5-21 g. Moreover, after the inoculation, the content of available nitrogen, available phosphorus and available potassium in the rhizosphere soil, as well as the activities of soil enzymes such as urease, sucrase, and alkaline phosphatase increased, while the activity of soil catalase decreased. Additionally, the microbial biomass carbon, nitrogen-fixing genes, and nitrogen-fixing microorganisms in the soil increased significantly. [Conclusion] The rhizosphere soil of C.annuum harbors rich bacteria with excellent disease-controlling and growth-promoting effects, which can be prepared into inoculants for the control of Fusarium root rot and the growth-promoting on C.annuum.