Phenological analysis of grasses (Poaceae) as a support for the dissection of their pollen season in Perugia (Central Italy)

Grasses (Poaceae) pollen is a major cause for allergic diseases worldwide. Pollen monitoring in the atmosphere is of primary importance for symptoms interpretation and therapy planning. Microscopic pollen identification and counts do not allow the detection at species or genus level because of the stenopalynous nature of the family. Nevertheless, the assessment of the flowering phenology of different species would be important, because not all grass allergens are cross-reacting and allergic patients could be differentially sensitized. In this work, a phenological survey was carried out in five stations located on the urban territory of Perugia (Central Italy), from April to September 2015, recording the alternation between flowering phenophases of 19 grass species and estimating their contribution to the airborne pollen load of the area through the calculation of a Phenological Index. Moreover, pollen grains of the different species were collected and observed, confirming the impossibility to make a discrimination during microscope pollen counts. The prevailing grasses in terms of contribution to the pollen detection in the studied area resulted to be Dactylis glomerata and Lolium perenne during spring and early summer, and Cynodon dactylon during late summer. Data should be validated repeating the survey in successive years and possibly using biomolecular tools, but the obtained information could be relevant for diagnosis and treatment of grass pollen allergies.