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

Seasonal and diurnal changes in concentrations of airborne basidiomyce te spores (basidiospores, rusts, smuts) were studied, using Burkard vo lumetric spore traps, in two areas of Mexico City with different degre es of urbanization and related to changes in climatic variables throug h 1991. Basidiomycete spores formed a large component of the total air borne fungal spore load in the atmosphere of Mexico City. They were th e second most abundant spore type after Deuteromycotina (Hyphomycetes) , forming 32% of the total fungal spores trapped in an urban-residenti al area and 28% in an urban-commercial area. The most abundant basidio mycete spores were basidiospores although smut-type spores were trappe d on more days than basidiospores and rusts on fewer. Basidiospores oc curred in concentrations up to 2,000 spores m-3 in the urban-residenti al area. Basidiospores showed a marked seasonal distribution, especial ly in the southern area, with their greatest abundance during the wet season. The correlation coefficients associated with regressions betwe en basidiospore concentration and some environmental factors were incr eased when a lag period of 2 to 4 days was used between environmental measurements and the day of spore collection. Basidiospore concentrati ons exceeded the 75 percentile concentration (>400 spores m(-3)) most often when rainfall was up to 6 mm and relative humidity was >70%. Bas idiospores showed a diurnal periodicity with greatest concentrations i n the early morning. The most common basidiospore type was Coprinus wh ich formed 67% of basidiospores trapped in the southern area and 63% i n the central area. Smut spores were trapped on 87% of days through th e year while rust spores occurred in only 35%. Both rusts and smuts we re present in only small concentrations.