Characterization and Biocontrol Potential of Fungal Isolates Associated with Eldana saccharina Walker (Lepidoptera: Pyralidae) in Sugarcane in Côte d'Ivoire
Ouattara Dadjo *
UFR Biosciences, Laboratory of Biotechnology, Agriculture and Valorisation of Biological Resources, Research Unit of Plant Physiology and Pathology, Félix Houphouët-Boigny University, 22 BP 582 Abidjan 22, Côte d'Ivoire.
Kouamé Konan Didier
UFR Biosciences, Laboratory of Biotechnology, Agriculture and Valorisation of Biological Resources, Research Unit of Plant Physiology and Pathology, Félix Houphouët-Boigny University, 22 BP 582 Abidjan 22, Côte d'Ivoire.
Ouattara Migninlbin Marcel
WASCAL/CCBAD-Center of Excellence on Climate Change, Biodiversity and Sustainable Agriculture, Félix Houphouët-Boigny University, 01 BP V 34 Abidjan 01, Côte d’Ivoire.
Yao Kouakou
Department of Agricultural Studies, Sucrivoire, BP 100, Borotou-Koro, Côte d'Ivoire.
Koné Daouda
UFR Biosciences, Laboratory of Biotechnology, Agriculture and Valorisation of Biological Resources, Research Unit of Plant Physiology and Pathology, Félix Houphouët-Boigny University, 22 BP 582 Abidjan 22, Côte d'Ivoire and WASCAL Capacity Building Department, West African Science Service Center on Climate Change and Adapted Land Use, Headquarters Accra, Ghana.
*Author to whom correspondence should be addressed.
Abstract
Eldana saccharina Walker (Lepidoptera: Pyralidae) is the main stem borer of sugarcane and causes substantial economic losses in the sugarcane-growing areas of Côte d'Ivoire. This study, conducted at the Zuénoula integrated agricultural unit, aimed to identify the fungi naturally associated with E. saccharina larvae and to assess their potential as biological control agents. Larvae were collected from 39 plots and reared in the laboratory. Fungi were isolated from dead larvae, purified and identified on the basis of their macroscopic and microscopic characteristics. Twenty fungal isolates were obtained, of which 16 were assigned to four genera: Aspergillus, Fusarium, Trichoderma and Mucor. Aspergillus spp. were dominant (50 % of isolates), followed by Fusarium spp. (20 %). Fusarium isolates showed similar mycelial growth on potato dextrose agar (PDA) and Czapek-glucose agar (CGA), with identical growth rates (about 1.2 cm day−1). Sporulation peaked on day 14 of incubation and was significantly higher in potato dextrose liquid (PDL) medium than in Czapek-glucose liquid (CGL) medium (7.05 × 106 versus 3.39 × 106 spores mL−1). Fusaric acid production was confirmed by spectrophotometry, with higher concentrations on CGA medium (mean 3.6 mg mL−1) than on PDA (3.1 mg mL−1); however, toxin content decreased progressively with incubation time. These results indicate that several fungi are naturally associated with E. saccharina larvae. Fusarium spp. are of particular interest for future biological control applications owing to their production of fusaric acid, a toxic metabolite whose accumulation dynamics remain to be controlled.
Keywords: Sugarcane, stem borer, entomopathogenic fungi, fungal toxins