SEASONAL AND DIURNAL-VARIATION OF AIRBORNE BASIDIOMYCETE SPORE CONCENTRATIONS IN MEXICO-CITY

Seasonal and diurnal changes in concentrations of airborne basidiomycete spores (basidiospores, rusts, smuts) were studied, using Burkard volumetric spore traps, in two areas of Mexico City with different degrees of urbanization and related to changes in climatic variables through 1991. Basidiomycete spores formed a large component of the total airborne fungal spore load in the atmosphere of Mexico City. They were the second most abundant spore type after Deuteromycotina (Hyphomycetes), forming 32% of the total fungal spores trapped in an urban-residential area and 28% in an urban-commercial area. The most abundant basidiomycete spores were basidiospores although smut-type spores were trapped on more days than basidiospores and rusts on fewer. Basidiospores occurred in concentrations up to 2,000 spores m-3 in the urban-residential area. Basidiospores showed a marked seasonal distribution, especially in the southern area, with their greatest abundance during the wet season. The correlation coefficients associated with regressions between basidiospore concentration and some environmental factors were increased when a lag period of 2 to 4 days was used between environmental measurements and the day of spore collection. Basidiospore concentrations exceeded the 75 percentile concentration (>400 spores m(-3)) most often when rainfall was up to 6 mm and relative humidity was >70%. Basidiospores showed a diurnal periodicity with greatest concentrations in the early morning. The most common basidiospore type was Coprinus which formed 67% of basidiospores trapped in the southern area and 63% in the central area. Smut spores were trapped on 87% of days through the year while rust spores occurred in only 35%. Both rusts and smuts were present in only small concentrations.