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Multi-year study of Ganoderma aerobiology
Rebekah L. Craig & Estelle Levetin
Faculty of Biological Science, University of Tulsa, Oklahoma, USA

Abstract
Ganoderma basidiospores are dominant members of the airspora in many regions of the world and are considered important airborne allergens. The aerobiology of Ganoderma spores in the Tulsa, Oklahoma area was examined using Burkard Volumetric Spore Traps from 1987–1996. Ganoderma spores were present in the atmosphere on more than 95% of the days from June through October with peak concentrations generally occurring from late August to mid-October.
The data showed marked interannual variation, with seasonal totals in 1994 and 1995 significantly higher than other years. Stepwise backward multiple regression showed that cumulative season total was significantly related to June temperature and May through August precipitation (R2 = 0.97, p < 0.01). Abbreviations: CST – cumulative season total. Basidiomycetes are a complex group of organisms within the Kingdom Fungi consisting of approximately 25,000 species. Almost all of the known edible and poisonous mushrooms are contained within this subdivision, along with all the bracket fungi and other large fleshy fungi.

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At least nine species of Ganoderma thrive in North America. Typically, these polypores are found growing on dead or living hardwood and conifers. Ganoderma applanatum, G. lucidium, and G. curtisii can all be found in Oklahoma. The spores are easily recognizable with a smooth transparent outer wall and golden brown inner wall. Interwall connections and a prominent germ pore with truncated apex are also distinctive features (Levetin, 1989). Studies from various parts of the world have clearly implicated Ganoderma spores as aeroallergens (Tarlo et al., 1979; Hasnain et al., 1984). Evidence from New Zealand; Ontario, Canada; and Delhi, India have reported atmospheric concentrations of Ganoderma ranging from 6% to 34% of the air spora (Tarlo et al., 1979; Hasnain et al., 1984, Cutten et al., 1988; Singh et al., 1995). In various reports, 10–48% human sensitization in skin prick tests has been attributed to Ganoderma spores (Tarlo et al., 1979; Butcher et al., 1987; Hasnain et al., 1993; Singh et al., 1995). It is well known that weather conditions influence the day-to-day variability as well as seasonal levels of atmospheric spore concentrations. For instance, variations in precipitation and temperature can influence Ganoderma spore release (McCracken, 1987). During routine aerobiological analysis of Burkard slides, it appeared that Ganoderma spores were more abundant during certain years; however, these spores had not been itemized for the whole period. The present study was undertaken to specifically determine the daily concentration of airborne Ganoderma spores from 1987 to 1996 and to identify the meteorological factors that contributed to the yearly fluctuations.
Weather conditions in the months prior to the season peak may be important for determining the cumulative season total. Data indicate that June temperature and May through August precipitation influence the magnitude of Ganoderma spore levels during the season extending from June 1 to October 31. It is likely that the relationship with precipitation and temperature reflects fungal requirements for optimum growth within the substrate. The concentrations reported in this 10 year study were daily averages; however, hourly concentrations also differ throughout the day. Ganoderma spore release follows a diurnal rhythm with peak concentration at approximately 04:00 hours and lowest levels at 16:00 hours.

Ganoderma aerobiology

A similar early morning maximum was observed by Haard and Kramer (1970) at 06:00 hours. Mean temperature and relative humidity during daily peak concentrations were about 22'C and 79%, respectively. These results are consistent with those reported by McCracken who found that periods of maximum daily spore release were related to mean temperature of 17'C and mean relative humidity of 77% (McCracken, 1987). In conclusion, this study showed that (i) in northeastern Oklahoma the season for airborne Ganoderma spores lasts from June through October; (ii) there has been a significant difference among years in cumulative season total; (iii) June temperature and May through August precipitation were important predictors for cumulative season total. Additional years of data could provide a more accurate determination of any variation in spore concentration over time.

 

Ganoderma aerobiology Ganoderma aerobiology
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