Endophytic fungi isolated from sugarcane and pathogenicity in adults of Sphenophorus levis Vaurie (Coleoptera: Curculionidae)

Abstract

Sphenophorus levis Vaurie (Coleoptera: Curculionidae)

Some of the most common genera of endophytic fungi found in sugarcane are: Trichoderma sp., Fusarium sp., Beauveria sp., and Cordyceps sp. The aim of this study was to prospect endophytic fungi from commercial sugarcane fields and to evaluate their pathogenicity against Sphenophorus levis. In 2022, two sampling campaigns of leaves and roots were carried out in three regions of the State of São Paulo: Sertãozinho, Araras, and Paraguaçú Paulista. The samples were taken to the laboratory and subjected to surface sterilization followed by deep disinfection. Subsequently, segments of leaves and roots were placed on Petri dishes containing PDA (Potato Dextrose Agar) and incubated in a BOD growth chamber at 26±1°C for up to five days. Fungal isolates were initially classified based on macroscopic characteristics and later identified through molecular techniques. Pathogenicity tests were conducted using S. levis adults aged between 10 and 40 days. Three bioassays were performed, each using the same experimental design: five treatments (including the control), with five replicates per treatment and five beetles per replicate. The fungal suspension concentrations used were: T1 = sterile water (control), T2 = 1×10⁶, T3 = 1×10⁷, T4 = 1×10⁸, and T5 = 5×10⁸ conidia/mL. The following species were identified: Beauveria bassiana, Fusarium oxysporum, Penicillium chrysogenum, Trichosporon asahii, Aspergillus sojae, and Fusarium andiyazi. S. levis mortality was assessed daily for seven consecutive days. After exposure, insects were placed in a humid chamber and incubated at 26±1°C in a BOD chamber. Data were subjected to ANOVA followed by Tukey’s test (p > 0.05), using RStudio software. The best performance was for Fusarium oxysporum with higher mortality at all concentrations tested.