Airborne Alternaria conidia in Mediterranean rural environments in SW of Iberian Peninsula and weather parameters that influence their seasonality in relation to climate change

Alternaria genus is an important pathogen in plants, and their allergens are one of the most important causes of respiratory allergic diseases in Europe. Alternaria fungal spore concentrations were studied in the air of Don Benito, Plasencia and Zafra (SW Iberian Peninsula), from February 2011 to December 2014, using Hirst spore traps. Daily and hourly data distribution and their correlations with meteorological parameters were analyzed statistically, according to Spearman's test. Daily average concentrations of 38 spores m(-3) in Don Benito, 11 spores m(-3) in Plasencia and 17.0 spores m(-3) in Zafra were recorded, with peaks of 923 spores m(-3) on the October 9, 2012 (Don Benito), 334 spores m(-3) on the June 1, 2011 (Zafra), and 165 spores m(-3) on the August 25, 2011 (Plasencia). Airborne conidia levels showed the highest values in spring (May and June) and autumn (September and October), and the lowest in winter, showing a bimodal seasonal distribution at the beginning of the period (2011), modified by weather toward an isolated concentration peak in autumn during the next years (2012-2014). Hourly distribution showed concentration peaks between 17:00 and 20:00 h, and the lowest values from 06:00 to 08:00 h. Land uses distribution also showed influence in some cases, such as irrigated crops and pastures versus olive crops and oak forests that provided higher levels of spore concentrations. The highest concentrations of spores were obtained with temperatures of 20-30 A degrees C. For a predicted increase in temperature in a climate change scenario, Alternaria spore production is foreseen to increase as temperatures reach optimal growing conditions in the two seasonal growing periods in Mediterranean climate.