苏云金杆菌及其微胶囊剂对落叶松毛虫的毒力及抗紫外线能力

Virulence and anti-ultraviolet ability of two strains of Bacillus thuringiensis to Dendrolimus superans

从呼和浩特市大窑林场自然死亡的落叶松毛虫Dendrolimus superans幼虫体分离Bacillusthuringiensis菌株Bt-S04,通过形态观察和生理生化反应并与菌株Bt-k01进行对照,Bt-S04其精氨酸酶、尿酶和水杨苷反应均为阴性,菌膜反应和蔗糖发酵反应均为阳性,与苏云金杆菌松毛虫变种有差异。室内采用针叶给毒法,测定了Bt-S04和Bt-k01菌株对落叶松毛虫2龄幼虫的毒力,其致死中浓度LC50分别为5.493×106(1.349×106～1.698×107)CFU/mL和7.227×105(3.111×105～1.399×106)CFU/mL,Bt-k01对落叶松毛虫2龄幼虫的毒力是Bt-S04的7.6倍,致死中时间是其1/5。经紫外光照射2 h后,Bt-k01和Bt-S04活菌率分别是5.4%和8.2%,微胶囊化后菌液成活率分别是72%和76.3%,表明微胶囊剂的抗紫外线能力增强了。

A pathogenetic bacteria,Bacillus thuringiensis Bt-S04 strain was separated from Dendrolimus superans larvae of natural death in Dayao Forest Farm of Huhhot,Inner Mongolia.The culture characteristics of the bacteria was compared with the Bt-k01 strain by morphology observation and physiological biochemistry reaction.Its arginase reaction,urease reaction and salicin reaction were negative,the velum reaction and the sucrose fermentation response were positive which were different from Bacillus thuringiensis.subsp.dendrolimus.The toxicity of the two strains of B.thuringiensis to the 2nd-instar larvae of D.superans was examined in laboratory.The results showed that LC50 of Bt-S04 and Bt-k01 to the 2nd-instar larvae were 5.493×106 CFU/mL and 7.227×105 CFU/mL respectively.The toxicity of Bt-k01 was 6.6 times higher than that of Bt-S04,LT50 of Bt-k01 was 1/5 of that of the Bt-S04 strain.When exposed to ultraviolet for two hours,the survival rate of Bt-k01 and Bt-S04 were 5.4% and 8.2% respectively,but the survival rates of microcapsules of Bt-k01 and Bt-S04 were 72% and 76.3% respectively,indicating that microcapsule could enhance the ability of anti-ultraviolet of the two stains.