Variation assessment of airborne Alternaria and Cladosporium spores at different bioclimatical conditions F. Javier RODRI ´ GUEZ-RAJO, Isabel IGLESIAS and Victoria JATO Department of Plant Biology and Soil Sciences, University of Vigo, Campus As Lagoas, Polytechnic Building, E-32004 Ourense, Spain. Received 4 May 2004; accepted 3 November 2004. The study of mould spores is of major importance as many fungi can cause considerable economic losses worldwide acting as plant pathogens or triggering respiratory diseases and allergenic processes in humans. Knowledge of spore production relationships to different altitudes or weather patterns can be applied in a more efficient and reliable use of pesticides or improving diagnosis and treatment of respiratory allergic diseases. In this way monitoring of Cladosporium cladosporioides, C. herbarum and Alternaria spp. airborne spores during 2002 was carried out by means of three LANZONI VPPS 2000 pollen traps located in areas of north-west Spain at various altitudes and with various weather patterns. High spore counts were recorded in the late summer and early autumn, with a fairly similar hourly spore-count pattern, increasing the concentrations in the late evening (7–10 p.m.). High spore concentrations were detected in inland rural areas in front of coastal ones. As the continentality index increased, C. cladosporioides spore concentrations rose and Alternaria declined. C. herbarum concentrations increased with increasing height above sea level. The weather factor displaying the strongest positive correlation with mean daily spore counts was temperature. The optimal conditions for high airborne spore concentrations were recorded at temperatures ranging from 23–29 xC and RH values of around 80%, followed rapidly by rainfall in Vigo and Ourense and preceded by heavy rain two days prior to recording peak values in Trives. INTRODUCTION Because of their adverse effects on crops and as allergens, aerobiological monitoring of mould spores is of major importance. Most fungal species act sapro- trophically, colonising all stages of plant growth, or as plant pathogens, prompting considerable economic losses worldwide (Hjelmroos 1993, Infante et al. 1997a, b). Fungal spores can also have a serious detri- mental effect on human health, triggering respiratory diseases and allergenic processes (O’Hollaren et al. 1991, Peat et al. 1995, Ricci et al. 1995, Mitakakis & McGee 2000). Knowledge of plant pathogen spore trends and their relationship with weather variables can be used not only in the early detection of plant infections, thus allowing a more efficient and reliable use of pesticides (Montesinos et al. 1995, Bugiani et al. 1996, Dı´az, Iglesias & Jato 1998), but also, combined with clinical data, in the prevention of respiratory allergic diseases, improving diagnosis and treatment (Munuera, Carrion & Navarro 2001). Cladosporium and Alternaria are the most cosmopolitan fungi involved, particularly in temperate regions, due to their almost permanent presence in outdoor and indoor air (Infante et al. 1997a, b, D’Amato 1981, Ricci et al. 1995). The cross- reactivity of these two allergenic genera may have implications for the treatment of fungal allergies (Jones & Gerson 1971). Numerous surveys of the occurrence of Cladosporium spores in different regions of the world show their dominance in comparison with other spores (Infante et al. 1997a, b, Mitakakis et al. 1997, Stepalska et al. 1999). Since Cladosporium spores greatly outnumber those of Alternaria, this cross- reactivity is of particular significance for Alternaria- sensitive patients. The onset of allergenic symptoms in atopic subjects occurs most frequently when the concentration of Alternaria spores is equal to or greater than 100 spores m x3 (Ballero et al. 1984, Ricci et al. 1995), while the threshold Cladosporium count for evoking allergenic symptoms is estimated at 3000 spores m x3 (Gravesen 1981). Fungal spore con- centrations are governed by the nature and distance of the major sources, prevailing meteorological con- ditions and local topography (Angulo, Mediavilla & Domı´nguez 1999). Rural areas are of particular interest (Mitakakis & McGee 2000), because large amounts of conidial spores are thought to be released from crops, Mycol. Res. 109 (4): 497–507 (April 2005). f The British Mycological Society 497 doi:10.1017/S0953756204001777 Printed in the United Kingdom.