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Poster: Biology & Disease Mgmt: Mycology


Host colonization and substrate utilization by wood-colonizing Ascomycete fungi in the grapevine trunk disease complex
E. GALARNEAU (1), C. Wallis (2), K. Baumgartner (2) (1) University of California-Davis, U.S.A.; (2) USDA-Agricultural Research Service, U.S.A.

Grapevine trunk diseases cause chronic wood infections (cankers) in mixed infections within the same vine. To determine the synergistic interactions of trunk-pathogen communities and their impact on the host we are characterizing, on a pathogen-by-pathogen basis, fungal damage to woody cells and tissues. Our focus is on two taxonomically unrelated Ascomycetes: Botryosphaeria dieback pathogen Neofusicoccum parvum and Eutypa dieback pathogen Eutypa lata. After inoculating plants and identifying the host-defense compounds that accumulated in wood cankers, we tested their effects on fungal growth in vitro. Both fungi significantly degraded and utilized rutin, epicatechin, and piceid, suggesting that these fungi tolerate and possibly subvert the biochemical host-defense response. In contrast, fungal growth was significantly inhibited by lignin and gallic acid. Only E. lata discolored solid media amended with gallic acid, signifying phenoloxidase activity, which is consistent with its status as a soft-rot fungus. Previous work showed E. lata colonizes the ray parenchyma, xylem vessels and fibers, which we verified are also proliferated by N. parvum. The ability of these fungi to degrade wood was evaluated in planta by imaging the microscopic features of soft rot. As both fungi have similar gene families associated with cell-wall degradation and secondary metabolism, it is not surprising that they may share similar strategies for colonization and substrate utilization.