Study of sugarcane borer Diatraea saccharalis (Lepidoptera: Crambidae) and opportunist fungi Colletotrichum falcatum and Fusarium verticillioides interaction

Author(s)

Diego Zanardo Gallan

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2019-04-26

Examining board members

Marcio de Castro Silva Filho; Jose Mauricio Simoes Bento; Daniel Scherer de Moura; Flávio Henrique da Silva

• Advisor: Marcio de Castro Silva Filho

Abstract

In sugarcane, stem colonization by opportunistic fungi, such as Fusarium verticillioides and Colletotrichum falcatum, is directly linked to the attack of Diatraea saccharalis (Lepidoptera: Crambidae) caterpillar. Two proteins, SUGARWIN1 and SUGARWIN2 are produced in sugarcane, in response to mechanical damage and attack of D. saccharalis, however these proteins do not affect the insect, but cause physiological and morphological changes in F. verticillioides and C. falcatum, causing the death of these fungi by apoptosis. Artificial diets supplemented with these opportunistic fungi caused the weight gain of D. saccharalis. These data indicate a more intimate interaction between the insect and the sugarcane pathogens. In this study, we sought to identify symbiotic relationship among individuals, analyzing whether the transmission of these fungi is mediated by D. saccharalis. The results showed the presence of F. verticillioides in all stages of D. saccharalis development after contact with the fungus, in the 4th instar. The caterpillars remained infect by the fungus throughout the pupal and adult phase, in both sexes. In addition, F. verticillioides was transmitted to D. saccharalis offspring, being detected in eggs, an original case of vertical transmission. Through the microscopy results, it was also possible to verify the high intensity of F. verticillioides inside the intestines of caterpillar. These data infer in a symbiotic relationship between F. verticillioides and D. saccharalis, where the symbiont is transferred vertically to the offspring. The responses obtained with C. falcatum differed from those obtained with F. verticillioides, since the presence of the fungus was not detected from the pupal phase. In this case, the symbiont relationship between fungus and insect can result in a horizontal transmission. With this study was possible to identify different forms of fungi transmission by D. saccharalis. These data change the way the transmission of F. verticillioides by D. saccharalis in sugarcane is viewed, and may influence the management of Fusarium rot and sugarcane borer attack in sugarcane. (AU)

• FAPESP's process: 17/08026-0 - Study of the interaction between sugar cane, D. saccharalis, C. falcatum and F. verticillioides
• Grantee: Diego Zanardo Gallan
• Support Opportunities: Scholarships in Brazil - Master