Morphological and Molecular Characterization of Beauveria bassiana Isolates and Assessment of Their Pathogenic Effects On Bemisia tabaci

Bemisia tabaci (Hemiptera: Aleyrodidae), is one of the most destructive agricultural pests worldwide. Traditional control of B. tabaci has relied heavily on chemical pesticides. However, their indiscriminate use has led to the development of resistance. There is an urgent need to explore alternative, sustainable pest management strategies to mitigate pesticides and their ecological impacts.

Eight isolates of Beauveria bassiana (J02, J05, J12, J15, J20, J28, J31, and J36) were collected from different localities of China. Morphological studies indicated that these eight strains exhibited fundamentally similar morphological characteristics. After seven days of cultivation, the colonies were white or light yellow, with septate hyphae measuring 0.8–2.0 μm in diameter, and single-celled conidia that were spherical or oval, with a diameter of 1.8–2.2 μm. Genomic identification results confirmed that the strains (J02, J05, J12, J15, J20, J28, J31, and J36) were B. bassiana, with NCBI blast results showing 98%–100% similarity to another strain of B. bassiana. The newly identified strains demonstrated pathogenicity against the whitefly under laboratory conditions. Furthermore, strain J36 exhibited the highest virulence against immature life stages of B. tabaci, with median lethal concentrations (LC₅₀) values of 6.54 × 10⁹, 8.79 × 10⁶, 3.16 × 10⁶, 3.43 × 10⁶, and 3.13 × 10¹² conidia/mL against eggs, first instar, second instar, third instar, and fourth instar nymphs, respectively after seven days of application.

The newly isolated strains of B. bassiana show promise as biological insecticides against B. tabaci, but further field trials and the development of suitable formulations are necessary to validate their effectiveness.