嗜线虫致病杆菌对小菜蛾的致死和亚致死效应室内评价

嗜线虫致病杆菌是与昆虫病原线虫共生的细菌,对小菜蛾等多种害虫具有广谱的杀虫活性。为了深入了解该菌的杀虫活性,在室内测定了嗜线虫致病杆菌HB310 ( 简称 Xn HB310)菌株对小菜蛾幼虫的致死和亚致死效应以及持效期。结果表明, Xn HB310菌液对小菜蛾2龄和3龄幼虫72 h的LC50值分别是3.32×104 和8.56×104 CFU/mL,其活性组分主要存在于菌株细胞和经50 kDa超滤膜超滤后的上清液中。此外, Xn HB310菌液对小菜蛾幼虫还表现出明显的拒食活性,其2龄和3龄幼虫的拒食中浓度(AFC50)分别为4.03×105和8.48×105 CFU/mL。将2.24×106 CFU/mL菌液喷施到甘蓝苗上,其在室内的持效期为3~4 d。用亚致死剂量(LC30和LC50)的菌液饲喂小菜蛾2龄幼虫,存活幼虫的生长发育指标、蛹重、雌虫寿命以及成虫产卵量均明显下降,推测这可能导致小菜蛾下一代种群数量减少。研究结果表明,嗜线虫致病杆菌HB310菌株具有开发成为杀虫剂的潜力。

Lethal and sublethal effects of Xenorhabdus nematophila on Plutella xylostella larvae in laboratory

Xenorhabdus nematophila is a broad-spectrum of entomopathogen that lives symbiotically with entomopathogenic nematode.In order to understand the insecticidal activities of X.nematophila,the toxicity and the sublethal effects of X.nematophila ( Xn ) HB310 strain on Plutella xylostella were assayed in laboratory.The bioassay results indicated that Xn HB310 culture broth had high lethal activities against 2^nd instar and 3^rd instar larvae of P.xylostella, with LC₅₀ values of 3.32×10⁴ CFU/mL and 8.56×10⁴ CFU/mL respectively,at 72 h.The insecticidal ingredient existed in bacterial cells and the free-cell supernatant by 50 kDa ultra-filtration.Furthermore, Xn HB310 also showed obvious antifeedant activity on 2^nd instar and 3^rd instar larvae of P.xylostella, and the AFC₅₀ values were 4.03×10⁵ CFU/mL and 8.48×10⁵ CFU/mL respectively.When the 2.24×10⁶ CFU/mL Xn HB310 culture broth was directly sprayed on the cabbage seedling,the persistence of the culture broth was up to 3-4 days.After feeding the 2^nd instar larvae of P.xylostella with cabbage leaves treated by sublethal concentration of Xn HB310 culture broth,the survival rate and developmental rate of larvae,as well as pupa weight,adult longevity and fecundity decreased significantly as compared to that of control. Xn HB310 showed not only high lethal and antifeedant activities but also obvious sublethal effects on P.xylostella, which illustrated that Xn HB310 has potential to control P.xylostella as insecticidal agent.