Screening of Highly Virulent Beauveria bassiana Strains Against Tuta absoluta Larvae and Evaluation of Their Endophytic Colonization-Mediated Suppression in Tomato Plants

To identify highly virulent Beauveria bassiana strains against Tuta absoluta and evaluate their biocontrol potential, four strains were phylogenetically characterized via ITS sequence analysis of rDNA and assessed for virulence against second-instar T. absoluta larvae. Foliar spray and root irrigation methods were used to establish B. bassiana endophytic colonization in tomato plants, with untreated plants serving as controls. A population life table was constructed to quantify the impact of colonized plants on larval development, fecundity, and key demographic parameters. Results showed variation in virulence among the four B. bassiana strains Bb1Bm, Bb2Bm, Bb1M, and BbC with Bb1Bm exhibiting the highest pathogenicity (85.00% corrected mortality at 1 × 108 spores/mL). Maximum endophytic colonization in tomato leaves was observed 14 days post-inoculation with both foliar spray and root irrigation treatments. Life table analyses revealed that T. absoluta feeding on colonized plants exhibited significantly reduced survival rates, shorter adult lifespans, and lower female fecundity compared to controls. Key population parameters, including net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ), were significantly reduced, while mean generation time (T) was significantly prolonged. These findings highlight the dual role of B. bassiana in T. absoluta management, demonstrating its potential as both a direct pathogen and an endophytic biocontrol agent capable of disrupting pest population dynamics.