Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae), the sugarcane borer, spends most of its life cycle inside the galleries it burrows into sugarcane stalk, where two rot-causing fungi Colletotrichum falcatum (Went, 1893) and Fusarium verticillioides (Nirenberg, 1976) are commonly found. Results have shown that microbiota harbored by D. saccharalis inhibits the growth of F. verticillioides and C. falcatum. D. saccharalis larvae were collected from chemical-free field plants, and yeast and bacteria from third and fourth-instar D. saccharalis regurgitate were isolated onto appropriate media. The percentage of F. verticillioides and C. falcatum mycelial growth inhibition was recorded. Out of 32 yeast isolates, 9 exerted 30 to 40% growth inhibition of C. falcatum or F. verticillioides. When 24 bacterial isolates were confronted with rot-causing fungi, six inhibited C. falcatum growth by 30 to 60%, and 24 isolates inhibited 30 to 60% of F. verticillioides growth. Bacteria and yeast isolates were identified through DNA sequencing of part of 16S rDNA and part of ITS1-5.8S-ITS2, respectively, revealing an abundance of isolates with sequence similarity to Klebsiella and Bacillus and Meyerozyma, which have been used as biological control agents and their ability to promote plant growth has been demonstrated. We have shown that microorganisms from borer regurgitate inhibit phytopathogen growth in vitro. Still, further investigation of the possible functions of D. saccharalis-associated microorganisms may help understand their ecological role in plant-insect-phytopathogen interaction.
Keywords: Antifungal properties; Arthropod-associated microbiota; Growth inhibition; Insect microbiota function; Insect-associated microbiota ecological role; Regurgitate microbiota.
© 2021. Sociedade Brasileira de Microbiologia.