根结线虫拮抗放线菌NZ-5菌株的鉴定及其发酵条件优化

以根结线虫二龄幼虫为试材,研究1株分离自土壤样本的放线菌菌株NZ-5的杀线虫活性,其发酵培养滤液对根结线虫二龄幼虫有较强的毒杀活性,24 h校正死亡率达到84.36%。为了高拮抗菌株进一步应用于田间生产实践,采用形态特征观察、培养特征观察和理化特性检测方法,结合16S rDNA基因序列分析,对其进行鉴定,同时对菌株发酵液对二龄幼虫的致死率来明确该菌株的最优发酵条件。结果表明:菌株的上述特征与链霉菌属Streptomyces中的微白黄链霉菌S.albidoflavus相似性很高,因此菌株NZ-5被鉴定为链霉菌属Streptomyces微白黄链霉菌S.albidoflavus。进一步的发酵条件优化试验发现,该菌株在以燕麦片为碳源、酵母粉为氮源、培养温度为25℃,摇床转速在210 r·min^-1震荡培养4 d,起始pH为7,装液量为75 mL时菌株发酵培养液对根结线虫的毒杀活性为93.29%,相比优化前提高了8.93个百分点,菌株NZ-5能够有效杀死根结线虫二龄幼虫,可作为优良菌株进行杀线虫生物农药的进一步研发。

Identification of Nematicidal Actinomycete NZ-5 and Optimization of Ferment Conditions

The root-knot nematodes(J2) was used as test materials.An experiment of nematocidal activities was tested using strain NZ-5,which was a kind of antagonistic actinomycete isolated from soil samples.The results showed that the strain NZ-5 had strong activities against root-knot nematodes(J2).Culture filtrate of NZ-5 could knock-down 84.36% of the J2 within 24 hours.In order to further apply the high antagonistic strain in field production practice,strain NZ-5 was identified as Streptomyces albidoflavu based on the morphological characteristics,cultural characteristics,physiological characteristics and 16 S rDNA gene sequence similarity analysis.Fermentation conditions were optimized.The optimal fermentation parameters were as follow:pH 7,4 days fermentation,210 r·min^-1,25 ℃,75 mL medium volume in 250 mL flask,oatmeal and yeast powder as carbon and nitrogen source,respectively.The toxic activity of root-knot nematode(J2) was 93.29%.The optimized fermentation products showed 8.93 percentage point higher toxicity against root-knot nematodes(J2) compared with pre-optimum.Strain NZ-5 could effectively kill root-knot nematodes(J2),and could be used as an excellent strain for further research and development of nematocidal biological pesticides.