The dual role of Bacillus thuringiensis RZ2MS9: its effectiveness as an entomopathogen and a plant growth promoter in vitro and in field conditions.

Abstract

Bacillus thuringiensis RZ2MS9, a plant growth-promoting rhizobacterium isolated from the rhizosphere of guarana plants, has shown significant growth enhancement in both soybean and maize crops. To explore its full potential, we investigated RZ2MS9's entomopathogenic properties against Lepidoptera and Coleoptera larvae in vitro, and against Hemiptera populations in both in vitro and field conditions. The strain was evaluated for insecticidal crystal proteins, which were found in cuboid and spherical forms. Comparative genomic analysis revealed that while RZ2MS9 did not share significant pesticidal protein genes with B. thuringiensis HD1, it has unique genes related to plant growth promotion and nutrient acquisition. RZ2MS9 also exhibited chitinolytic activity, linked to the presence of the chitosanase coding gene (chP). Under laboratory conditions, the larvae mortality under RZ2MS9 treatment was 90% for sugarcane borer (Diatraea saccharalis), 92.5% for old-world cotton bollworm (Helicoverpa armigera), 30% for Agrotis ipsilon, and 87.5% for Anthonomus grandis. In addition, RZ2MS9 caused severe wing deformities in 40% of Spodoptera frugiperda moths and repelled Piezodorus guildinii from its food source. In field trials, soybean plants inoculated with RZ2MS9 exhibited significative increased length. P. guildinii was more prevalent in the inoculated plants, while the incidence of Euchistus heros remained unchanged.