辣椒镰孢根腐病防病促生细菌的筛选及其效应

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

摘要:

【目的】筛选辣椒(Capsicum annuumL.)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 megaterium)，XP171为环状芽胞杆菌(Bacillus circulans)，XP248为芬氏纤维微菌(Cellulosimicrobium funkei)，XP167为产黄假单胞菌(Pseudomonas synxantha)。选择2种优良组合制作菌剂，测定其防病促生效果发现，对辣椒镰孢根腐病的防效达88.52%，并使辣椒株高增加10 cm左右、分枝数平均增加2个、生物量增加5–21 g；辣椒根围土壤中碱解氮、速效磷、速效钾等土壤养分含量增加，脲酶、蔗糖酶、碱性磷酸酶等土壤酶活性增加，土壤过氧化氢酶含量降低；土壤微生物生物量碳、固氮基因、固氮微生物的含量均显著增加。【结论】辣椒根围土壤中含有功能良好防病促生菌株，制成菌剂对辣椒镰孢根腐病有良好的防效且对辣椒促生性能明显。

关键词:辣椒;镰孢根腐病;拮抗细菌;促生菌

Abstract:

[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.

Key words:Capsicum annuum;Fusarium root rot;antagonistic bacteria;growth-promoting strains