对小菜蛾高毒的苏云金杆菌菌株筛选试验初报

A Preliminary Report on Screening for High Toxicity B. t.Strains to Diamondback Moth.

从田间自然死亡的小菜蛾虫尸中分离到Ｂ．ｔ．９４１９茵株，经复壮选育及摇瓶考核，在自选培养基上生长良好，２４ｈ孢子开始脱落形成晶体，３６ｈ全部形成晶体。晶体大、宽棱形、角尖。４８ｈ发酵液含菌量为３５亿／ｍＬ。经发酵液对小菜蛾毒力测定，４８ｈＬＣ５０：对照ＨＤ－１含菌量为２７４ｍＬ／Ｌ，而９４１９仅１２４ｍＬ／Ｌ。

Bacillus thuringinensis(B.t.)9419 strain, which was separated from the corpse of diamond-back moth(Plutella xylostella)that was natural death in the field, was growing on the selective culture medium after rejuvenation selection culturing and shaking task examination. The spores began to come off and to form a crystal in 24 hours and the crystal formation was accomplished in 36 hours. It looks big,wide rhombus with sharp angle. In 48 hours the fermented solution contained 35 hundred millions bacteri-a/mL. The toxicity test of the fermented solution against Plutella xylostella showed that LC50 of HD-1 (CK) was 274 bacteria/mL, but that of 9419 was only 124 bacteria/mL in 48 hours after treatment.