APS Abstracts of Presentations

Potential alternate sources of inoculum for causal agents of esca (black measles) of grapevine in California
S. ROONEY-LATHAM (1), A. Eskalen (1), L. L. Gallegos (1), W. Gubler (1)
(1) Department of Plant Pathology University of California-Davis, Davis, CA, USA
Phytopathology 96:S99

Togninia minima (anamorph: Phaeoacremonium aleophilum) is one of the primary pathogens associated with esca disease of grapevines. It has been suggested that infections occur following rainfall, which triggers ascospores to be forcibly discharged and land on pruning wounds. In this study, pruning wounds of seven different hosts were shown to be susceptible to infection by T. minima. Thirty months post-inoculation, T. minima was shown to infect peach, oak, cherry, apple, maple, walnut and almond. Peach, oak, cherry and apple were found to be the most susceptible. Furthermore, in vitro pairings using compatible isolates of T. minima from grapevine can form perithecia bearing viable ascospores on wood of twelve different hosts. The largest numbers of perithecia were formed on apple, peach, oak and alder. Additional in vitro pairings showed that perithecial formation is temperature dependent, occurring only at temperatures ranging from 15 to 30°C. Two other Phaeoacremonium species associated with grapevine and ash declines, P. angustius and P. mortoniae (teleomorph: Togninia fraxinopennsylvanica), were also isolated from an apple orchard in Mendocino Co., CA. This research suggests the importance of other hosts as potential sources of inoculum for esca pathogens in California.

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