内生放线菌gCLA4对辣椒疫病的防治研究

通过皿内对峙试验从242株供试内生放线菌中筛选到辣椒疫霉病菌拮抗菌62株，抑菌带宽度≥5mm的24株，占试验总菌株的10%，分别分离自黄瓜、牛蒡等9种植物的根部、茎部和叶片。用管碟法进行抑菌活性复筛，发现其中6株的无菌滤液对辣椒疫霉病菌和大豆疫霉病菌的抑菌圈直径≥20 mm，其中gCLA4的抑菌活性最强。进一步的研究结果表明，该菌株的无菌滤液能够强烈抑制病菌孢子囊的形成及游动孢子的释放，原液对孢子囊形成及游动孢子释放的抑制率分别高达100%和96.2%，稀释50倍后的抑制率仍分别达95.3%和85.6%，并且对其菌丝生长也有明显的抑制作用。温室盆栽试验结果表明，菌株gCLA4对苗期的辣椒疫病有较好防效。接种疫霉菌前48 h2、4 h和0 h以20 mL/盆（2株/盆）浇灌gCLA4菌株无菌滤液于辣椒苗基部土壤，接种后7 d调查病株率，其防效分别达100%、92.3%和80.8%，而接种14 d后分别为77.8%、55.6%和36.1%，说明该菌株无菌滤液具有开发成生防制剂的潜力。

Study on Biocontrol of Pepper Phytophthora Blight by Endophytic Actinomycetes gCLA4

Screening of 242 endophytic actinomycetes in plate showed that 62 strains were antagonistic against Phytophthora capsici. Of which 24 strains showed more than 5 mm inhibition zone. These, isolated from 9 plant species, including cucumber, burdock et al, were 10% of the total strains tasted. Re-screening by the cup-plate method, the free-cell fermentation of 6 strains were both antagonistic a- gainst P. capsici and P. sojae. Their diameter of inhibition zone were exceeded 20 mm. Further investigation showed that the strain gCLA4 inhibited sporangia and zoospores production of P. capsici, respectively 100% and 96. 2%. The inhibitory effect of 50 times dilute of the cell-free filtrate of gCLA4 fermentation were 95. 3% and 85. 6% respectively. Pot experiments in greenhouse showed that the cell-free filtrate of gCLA4 fermentation have a good control efficacy to the pepper phytophthora blight in seedlings after inoculated with pathogen. Using gCLA4 cell-free filtrate 48 h, 24 h and Oh before inoculation, the bio-control efficacy were 100%, 92.3% and 80.8% respectively investigated 7 d after inoculation. The bio-control efficacy were as high as 77.8%, 55.6% and 36.1% respectively 14 d after inoculation. The result showed that endophytic actinomycetes strain gCLA4 wasapotential bio-control agent in pepper Phytophthora blighl control.