Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/21/2005
Publication Date: 3/17/2006
Citation: Rolshausen, P.E., Mahoney, N.E., Molyneux, R.J., Gubler, D.W. 2006. Systematics of the causal agent of eutypa dieback of grapevine. Phytopathology. 96:369-377. Interpretive Summary: Dying-arm disease is a serious disease in grapevines caused by infection by a fungus (Eutypa) that enters the vine through pruning wounds. Economic losses from this disease in California have been estimated to be $260 million per year. The fungus is difficult to control because it is slow-growing and difficult to detect. Moreover, it is similar in appearance to others that cause different grapevine diseases. This research reports a method to definitely identify the Eutypa fungus and distinguish it from others with which it could be confused.
Technical Abstract: Eutypa dieback is a vascular disease of several cultivated crops and trees worldwide. The attribution of the name to the agent responsible for branch dieback is ambiguous. Pathogenicity of Eutypa was first reported on apricot and the causal agent was named E. armeniacae. However, no morphological differences were reported with E. lata, previously described in the literature, and some authors considered both species synonymous. Others regarded them as distinct species on the basis of pathogenesis and molecular analysis, and (concluded to their occurrence B unclear) on grapevines in California. We further investigated the relatedness of both species by phylogenetic analysis of the ITS region, alpha-tubulin gene and the combined datasets, that included several other taxa placed in the same family, the Diatrypaceae. Results were compared to secondary metabolites profile and conidia length of isolates. Tree reconstruction yielded three monophyletic groups. The isolates referred to as E. lata in previous work clustered with one group that included Diatrype stigma, which confirmed the presence of other diatrypaceous species on grapevines. Secondary metabolites production was observed in another group indicating the synapomorphy of this character. The results also supported the polyphyletic origin of the genus Eutypa and the synonymy of E. lata and E. armeniacae.