Fusarium spp. associated with ambrosia beetles on Acacia crassicarpa in Indonesia

Abstract

Ambrosia beetle-related diseases have increased in prevalence globally and threaten agricultural, forestry and urban landscapes. In Riau, Indonesia, a recent outbreak of ambrosia beetle infestations on exotic Acacia crassicarpa plantations, has resulted in a decrease in wood quality and yields of affected hosts. The aim of this study was to identify the ambrosia beetle species responsible for the damage, as well as their corresponding fungal associates. Beetles were extracted from three moderately infested 2 -3 year old A. crassicarpa trees collected from five geographically separated compartments. Morphological identification and phylogenetic analyses of the mitochondrial cytochrome oxidase c subunit I (COI) gene, confirmed that the primary borer Euwallacea perbrevis and the secondary borer Euwallacea similis are the most abundant beetles infesting the plantations. Fungal isolates were either obtained by direct isolation from the mycangia of mature female beetles or by culturing from the surfaces of the beetle galleries. Multi-locus phylogenetic analyses of the fungal isolates revealed a non-specific association of these two ambrosia beetles with seven novel Fusarium spp. Five of which reside within the Ambrosia Fusarium Clade (AFC) within clade 3 of the Fusarium solani species complex (FSSC) and remaining two novel species falling outside the AFC but still grouping with the larger FSSC. These seven species have been formally described within this dissertation.