Abstract:
Species of Raffaelea (Ophiostomatales: Ascomycota) are obligate symbionts of ambrosia beetles, some of
which pose a substantial threat to forest trees. Leucaena leucocephala is a small mimosoid tree species that is considered
as an invasive weed in most of its introduced range globally. During a field expedition on the French island of Réunion,
dying L. leucocephala trees were observed. Samples were taken from these trees and isolations made from symptomatic
wood tissues that included beetle tunnels, but in the absence of the beetles themselves. Multiple isolates of a fungus
resembling a Raffaelea species were obtained from the discoloured wood associated with the beetle tunnels. To
determine their identity, microscopic examination was performed and DNA sequences for three gene regions (ITS, LSU,
TUB) were obtained. Phylogenetic analyses based on these gene regions revealed that the isolates represent a new
species of Raffaelea, described here as R. borbonica sp. nov. A pathogenicity test was conducted with the fungus, which
was shown to cause lesions on the inoculated seedlings, but with a low level of aggressiveness.
