Occurrence of Puccinia spp. spores in Madeira Island and their phytopathological importance

The genus Puccinia represents rust infections, which are responsible for great productivity losses in crops of commercial and ornamental plants worldwide. This work is aimed at determining the occurrence of Puccinia spp. spores in Madeira Island in order to infer the exposure risks from a phytopathological point of view. A phytopathological analysis was performed in 203 local plant samples between January 2003 and December 2012. During the same period the airborne concentrations of rust spores were monitored following well-established guidelines. Aerobiological data was compared with meteorological records. Based on macro and microscopic analyses, five species of rusts were identified: P. horiana, P. buxi, P. porri, P. pelargonii-zonalis, and P. sorghi, and they were found mostly in spring and summer. A total of 20 samples out of 203 analysed plants (9.8%), were infected with Puccinia spores, i.e., P. horiana (5.9%), P. buxi (1.47%), P. porri and P. pelargonii-zonalis (0.98%), and P. sorghi (0.5%). During the studied period Puccinia spores attained an annual average concentration of 126 spores m−3 and most of them were recorded between March and October. Meteorological factors were determinant in fluctuations in spore concentration. Relative humidity was the parameter that favoured the biggest release and dispersal of the rust spores, whereas rainfall revealed a significant negative effect. Rusts do not represent an important plant pathogen in Madeira Island, as shown by the low infection frequencies and levels of airborne spore concentrations.