Enzymatic, cellular breakdown and lysis in treatment of Beauveria Brongniartii on Spodoptera litura (Fabricius, 1775).

Abstract

The current study aimed to isolate Beauveria brongniartii conidia from forest soils, identify the fungus, and evaluate its effectiveness on the eggs, larvae, pupae, and adults of Spodoptera litura. Insect mortality rates were recorded every 3, 6, 9, and 12 days. The identification of entomopathogenic fungi was carried out using molecular techniques, including PCR, DNA sequencing, and molecular markers, to detect species-specific 18 S rDNA genetic sequences, all performed under aseptic conditions. The results indicated that higher conidia concentrations (2.7 × 10⁹ conidia/mL) exhibited greater virulence, with eggs showing a mortality rate of 98.66%, followed by larvae 96%, adults 90.66%, and pupae 77.33% after 12 days. Probit analysis revealed minimal LC₅₀ and LC₉₀ values: eggs (5.5 × 10²; 1.0 × 10⁶ spores/mL), larvae (8.2 × 10²; 1.2 × 10⁷ spores/mL), pupae (9.6 × 10⁴; 7.3 × 10¹⁰ spores/mL), and adults (1.0 × 10³; 2.0 × 10⁸ spores/mL). The total hemocyte counts and detailed observational results revealed that B. brongniartii induces cellular breakdown and cell lysis in S. litura larvae by producing enzymes that degrade the cuticle and cell membranes. Earthworm bioindicator studies showed minimal effects from B. brongniartii conidia compared to controls, while chemical treatments resulted in 96% mortality at 100 ppm. Histopathological examinations revealed no significant differences in gut tissue between earthworms treated with fungal conidia and those in the control group, unlike the substantial damage caused by chemical treatments. Biochemical analysis revealed significant alterations in enzyme activity, including reduced levels of phosphatase and catalase, as well as increased levels of lipid peroxides and superoxide dismutase. This study highlights the effectiveness of B. brongniartii in controlling S. litura, demonstrating its potential as a viable biocontrol agent and promoting eco-friendly alternatives to chemical pesticides, with no risk to non-target species or the environment.