Isolation and Characterization of Indigenous Endotoxin-Forming Bacillus sp. with Insecticidal Activity from Northern Iranian Soil

The main goal of the current study was to isolate and characterize endospore-forming soil bacteria that produce parasporal crystalline proteins against larvae of Lepidoptera insects during stationary phase of growth. Two different methods were applied for the isolation of spore-forming strains. Polymerase Chain Reaction (PCR) was used for the characterization of cry gene content of the isolated strains and ۱۶S rRNA sequencing was carried out to identify bacterial strains. Efficiency of the isolates as insecticide was evaluated in a bioassay experiment using insect's larvae. Regarding presence of parasporal inclusion crystals and SDS-PAGE patterns, ۱۰ bacterial strains were isolated from about ۲۰۰ soil samples. Analysis of crystal-spore mixtures with SDS-PAGE showed a broad range of proteins with molecular weight between ۱۱-۲۳۰ kDa. Data from PCR analysis indicated that only two isolates (RIPI۶ and RIPI۱۸) may contain cry۳ gene. Isolate RIPI۲۱ and reference strain (Bacillus thuringiensis subsp. kurstaki) were positive for cry۱ gene. ۱۶S rRNA gene sequences of all isolates showed at least ۹۶% sequence match with B. thuringiensis strains deposited in the GenBank. The results of bioassay experiments showed the efficacy of strains RIPI۷, ۱۰ and ۲۲ on killing of larvae of both Anagasta kuehniella Zeller and Plutella xylostella Curt. It is concluded that there are some bacterial candidates for biological control of major agricultural pests in north of Iran.

کلیدواژه ها:

Bacillus thuringiensis ، Cry protein ، Lepidoptera ، Parasporal crystal ، Pesticidal activity. ، کریستال پارا-اسپورال ، باسیلوس تورنجیینسیس ، فعالیت آفت کشی ، فلس بالان ، پروتئین کریستالی