MATURATION AND SEASONAL DISCHARGE PATTERN OF ASCOSPORES OF ANISOGRAMMA

Authors: Pinkerton, John; JOHNSON, K - OREGON STATE UNIVERSITY; STONE, J - OREGON STATE UNIVERSITY; IVORS, KELLY - OREGON STATE UNIVERSITY

Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Eastern filbert blight has become a major constraint in the production of European hazelnut in Oregon, where 98% of US hazelnuts are grown The disea has rendered many orchards unproductive 3 to 8 years after the first infect was observed. To better understand the epidemiology of eastern filbert bl the relationship between spore maturation, environmental conditions, and release of spores was examined in diseased hazelnut orchards over a 6-year period. The maximum number of spores were observed in perithecia (the fung fruiting structure) in early winter and greater than 90% of these spores we mature. The number of spores declined until summer, after which no spores remained in the perithecia. Each years, rain catch-type spore traps were p under cankers in diseased hazelnut trees from 15 September to 30 June. Spo osamples were collected from the traps at 1 to 4 week intervals. Three patt of the seasonal release of spores were observed: in 1988-1989, > 80% of the release occurred before January; in 1989-1990, 32 to 42% of release occurr after mid-April; and in the other 4 years, releases were relatively uniform the 9-month period. The cumulative proportion of total spores collected in orchard was highly correlated with cumulative precipitation. Experiments in chambers confirmed this close relationship between the spore release and t cumulative amount of rain. A model was developed based on this relationshi that provides an estimation of the proportion of spores remaining to be rel

Technical Abstract: Maturation and release of ascospores of Anisogramma anomala were monitored a 6-yr period (1988-1995) in European hazelnut orchards located in western Oregon. Perithecia of A. anomala were dissected from stromata collected mo from September to May to determine spore maturation. Spore maturation beg late summer; by January, > 90% of spores were morphologically mature. Similarly, both the number of mature ascospores per perithecium and the proportion of ascospores that germinated increased through autumn. After January, the number of spores per perithecium declined until May, when few viable spores remained. Each of the six years, rain catch-type spore traps placed under cankers in diseased trees from 15 September to 30 June. Based dspore collection periods of 1 to 4 weeks, three patterns for the seasonal release of A. anomala ascospores were observed: in 1988-1989, > 80% of the ascospore release occurred between September and January; in 1989-1990, 32 42% of the ascospore release occurred after mid-April; and in the other 4 y releases of ascospores were relatively uniform over the 9-mo, seasonal peri Timing and amount of precipitation were the most important variables accoun for the differences among the yearly patterns of ascospore release. Over a years and sites, the cumulative proportion of total ascospores collected in orchard was highly correlated (R2 = 0.90) with cumulative rainfall. This relationship was confirmed in mist chamber experiments. A regression model