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Poster: Diseases of Plants: New & Emerging Diseases


Raffaelea arxii may be the primary symbiont of Xyleborus affinis
J. SAUCEDO (1), R. Ploetz (2), D. Carrillo (2), J. Konkol (2), J. Smith (1), J. Rollins (1), S. Ochoa (3) (1) University of Florida, U.S.A.; (2) University of Florida, U.S.A.; (3) Universidad Michoacana de San Nicolás de Hidalgo, Mexico

Symbioses between fungi and ambrosia beetles are poorly understood. Most of the ambrosia beetles that have been studied have a primary fungal symbiont that predominates in a species’ mycangium and natal gallery, where it is cultivated as a food source. However, there is increasing evidence that species of fungal symbionts can be laterally transferred to other beetle species (are not uniquely associated with a single species). For example, the primary symbiont of Xyleborus glabratus, Raffaelea lauricola (cause of laurel wilt), has been found in at least nine other species of ambrosia beetle. Symbiont composition was examined in several of the latter species. Mandibular mycangia of one of the species, X. affinis reared from laurel wilt-affected logs of avocado (Persea americana), were assayed for fungal communities. Partial sequences of LSU of rDNA regions identified high concentrations of phenotypically variable populations of R. arxii in 95%, whereas Raffaelea sp., R. lauricola, and Ambrosiozyma platypodis were recovered from, respectively, 45, 20 and 15% of 20 assayed individuals. Although R. arxii was first reported in South Africa as the primary symbiont of X. torquatus (syn. X. volvulus), the abundance and persistent association between R. arxii and X. affinis suggests that R. arxii may also be the primary symbiont of X. affinis. Primary and secondary symbionts of X. affinis, X. volvulus and other potential vectors of R. lauricola will be discussed.