MOLECULAR AND MORPHOLOGICAL CHARACTERS OF ISOLATES OF EUTYPA LATA
P LEETON1, M COLE2, S McLOUCHLIN3, P TAYLOR3 and I PASCOE4
1AgPath Laboratory, Wagga Wagga NSW, Australia; 2School of Wine and Food Science, Charles Sturt University, Wagga Wagga NSW, Australia; 3Department of Agriculture and Resource Management, University of Melbourne VIC, Australia; 4Institute for Horticultural Development, Knoxfield VIC, Australia
Eutypa lata (Pers: Fr.) Tul & C. Tul. (syn E. armeniacae Hansf. & M.V. Carter; anamorph Libertella blepharis A.L. Smith) is a worldwide primary vascular pathogen of many perennials. In grapevine (Vitus spp.) and apricot (Prunus armeniacae), it causes a disease known as "Eutypa dieback", or "dying arm". The fungus reproduces from perithecia in stromata which develop in old infected wood. Ascospores released from perithecia infect fresh wounds, such as those caused by pruning. Eutypa was first diagnosed in Australian grapevines in the 1970s. Infections in grapevines are easily confused with Phomopsis ("dead arm") infection; both fungi producing similar symptoms. There is a long lag period of several years between infection and the appearance of the first symptoms, and the fungus sporulates very slowly. The lack of rapid diagnostic tests for early detection allows the fungus to become well-established by the time visual symptoms are evident and control measures taken.
This research program is directed towards the early diagnosis of this disease using both RAPD-PCR techniques and improved mycological methods for the isolation and identification of the fungus. RAPD-PCR techniques are used here to distinguish initially between Eutypa lata and other fungal pathogens displaying similar symptoms in the host plant, as well as between Eutypa isolates obtained from both France and Australia. The results are compared with European data to determine whether an initial source of the Australian infection can be ascertained.
Single ascospore isolates of Eutypa lata were collected from fruiting bodies on quince and grapevine. The morphology of vegetative hyphae on various agar media was characterized to facilitate isolation and identification of the fungus from mixed cultures growing on isolation media. A method for inducing rapid sporulation of the Libertella anamorph in culture was also developed.