APS Abstracts of Presentations

Ascospore discharge and occurrence of Togninia minima (anamorph = Phaeoacremonium aleophilum) in California vineyards. S. R. LATHAM, A. Eskalen, and W. D. Gubler. University of California, Davis, Davis, CA. Phytopathology 94:S57. Publication no. P-2004-0384-AMA.

Species of Phaeoacremonium cause both Petri disease on young grapevines and esca (Black measles) on old grapevines. The most common species present in California vineyards is P. aleophilum. Recently, the teleomorph for this fungus was produced in-vitro and identified as Togninia minima (Calosphaeriales). As perithecia of T. minima and other species of Togninia mature in-vitro, sticky droplets containing masses of ascospores can be seen at the tips of perithecial necks. Therefore, it was speculated that ascal deliquescence occurs in the perithecium. Our findings, however, demonstrate that after dried T. minima perithecia are remoistened, ascospores are capable of being forcibly discharged from asci immediately after exiting the ostiole. Furthermore, spore release data collected from infected vineyards throughout California in 2002 and 2003 suggest that spore release is associated with rainfall. Although naturally occurring perithecia have not yet been found in nature, perithecia have been produced in the laboratory by moist incubation of naturally infected grapevine wood. These results represent the first report of how ascospores of T. minima are released and lead us to believe that ascospores serve as an important inoculum source in infected California vineyards.

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