|Rooney, Alejandro - Alex|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/14/2012
Publication Date: 8/14/2012
Citation: O Donnell, K., Freeman, S., Sharon, M., Mendel, Z., Geiser, D.M., Kasson, M., Rooney, A.P., Aoki, T., Ploetz, R.C., White, T.L. 2012. Systematics of Fusaria associated with Ambrosia beetles [abstract]. Invasive Ambrosia Beetle Conference. Interpretive Summary:
Technical Abstract: Here, I summarize research efforts directed at characterizing ambrosia beetle-associated fusaria, including the species responsible for avocado wilt in Israel (Mendel et al., Phytoparasitica 2012) and branch dieback in California (Eskalen et al., Pl. Dis. 2012). Our multilocus molecular phylogenetic data has resolved a clade comprising four genealogically exclusive Fusarium species associated with and probably farmed by ambrosia beetles within the genus Euwallacea. These fusaria are nested within clade 3 of the F. solani species complex (sensu O’Donnell et al., J. Clin. Microbiol. 2008). To our knowledge, only one of the four fusaria, F. ambrosium, has been described. Because this species does not produce the hallmark canoe-shaped conidia typical of the genus Fusarium, F. ambrosium was originally placed in the genus Monoacrosporium based on collections from galleries made by the shot-hole borer of tea (reported as Xyleborus fornicatus) in stems of tea and castor oil tree in Sri Lanka (Gadd and Loos, Trans Br. Mycol. Soc. 1947). The three unnamed fusaria were recovered from different trees in different geographic locations. The earliest diverging lineage within the ambrosia Fusarium clade was recovered from Hevea brasiliensis (rubber tree) in North Borneo. We speculate that this Fusarium sp. is associated with ambrosia beetles because the multiseptate club-shaped conidia of this species are morphologically similar to those of the three known ambrosia fusaria, which suggests this conidial morphology may represent an adaptation to farming by ambrosia beetles. The second unnamed Fusarium sp. is vectored by E. cf. fornicatus causing avocado wilt in Israel and branch dieback in California. The avocado wilt pathogen appears to be sister to F. ambrosium and its sister Fusarium sp. from the Asian invasive tree, Ailanthus altissima (tree of heaven), in Pennsylvania (Kasson et al., in prep.). Our working hypothesis is that the ambrosia-associated fusaria are farmed by and may have coevolved with different species of Euwallacea in Asia. To advance our understanding of the epidemiology of this outbreak, we have developed a molecular diagnostic assay for the detection and identification of the avocado wilt pathogen so that it can be rapidly distinguished from the other fusarial pathogens.