بررسی اندوفیتیسم باکتری Bacillus thuringiensis در کلم‌چینی به منظور اعمال حشره‌کشی علیه بید‌کلم

Plants from the Brassicaceae family with more than 3500 species, including various oilseed crops, root, and leafy vegetables, are of great economic importance. One of the most destructive pests of these plants in many regions worldwide is the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), which can cause significant economic loss from seedling to adult plant stages. This insect has developed resistance to many chemical insecticides, while the use of these insecticides also has harmful effects on the environment and human health. Bacillus thuringiensis (Bt) is one of the most successful entomopathogens. Bt produces toxic proteins that are harmful to a wide range of insect pests. Previous studies have shown that Bt can also act as an endophytic bacterium in plant tissues and induce plant growth and resistance against pests and pathogens. In this study, the insecticidal property of a commercial formulation of Bt was assessed against diamondback moth larvae using the leaf-dipping method. Accordingly, The LC50 and LC90 values were determined to be 9×105 and 7×106 CFU/ml, respectively. To further evaluate the endophytic potential of Bt, 5 ml of bacterial suspension of spores and crystals containing 1/4×107 CFU/ml concentration of Bt was inoculated into 4-week-old Chinese cabbage plants through irrigation and foliar spray. We monitored the presence of Bt in plant tissues at different intervals (7, 14, 21, and 28 days) post-inoculation. It was found that the foliar spray method resulted in highest number of bacteria in plant tissues by the 7th-day post-inoculation. The role of endophytic bacteria in altering plant growth characteristics and its effects on the mortality and fitness of Plutella xylostella is under investigation.