根结线虫拮抗放线菌菌株DA07118的筛选与鉴定及其发酵条件的优化

从海南东寨港红树林、尖峰岭等原始森林及黄流地区发病蕉园采集土壤样品,分离得到215株放线菌菌株。以根结线虫为靶标线虫对215株放线菌进行筛选,获得18株对根结线虫校正死亡率在80%以上的菌株。菌株DA07118抗线虫活性最强,校正死亡率达100%;经5次继代培养,仍具有稳定产生杀线虫活性物质的能力。通过形态学、生理生化反应和16S rDAN分类鉴定,将该菌株归类为链霉菌属Streptomyces。进一步的发酵条件优化试验,确定该菌株产活性物质的最佳培养基配方为（g/L）：麦芽糖10g、蔗糖25g、酵母膏20g、蛋白胨20g、K2HPO4 0.5g,初始pH7.0。发酵优化后,菌株发酵液的10倍稀释液处理后24h对根结线虫的校正击倒率从优化前的75.0%提高到93.7%。

Screening and Identification of Nematicidal Actinomycetes and Optimization of Ferment Conditions

A total of 215 actinomycetes strains were isolated from soil samples collected from Dongzhaigang mangrove and Jianfeng Mountain in Hainan province,China.By using Meloidogyne arenaria cultured in vitro as index nematodes for selecting actinomycetes against Meloidogyne,18 strains were selected,among which strain DA07118 possessed the highest nematicidal activity with lethal rate as high as 100%.The strain was identified as Streptomyces sp.through morphological observation,physiological, biochemical and 16S rDNA analyses.Ferment conditions were optimized as follow：maltose 10 g, sucrose 25 g,yeast extract 20 g,bacterial peptone 20 g,K2HPO40.5 g,and water to 1000 ml.The 10-fold diluted culture filtrate from optimized fermentation medium increased the mortality from 75.0%to 93.7%,after 24 h of treatment,on the second-stage juveniles of root-knot nematode.