Fungal endophytes and pathogens in Picea abies (L.) Karsten in natural and urban sites.

A study was carried out to determine the endophytic and pathogenic fungi of Picea abies grown in northern Italy. Samples were collected, in spring, summer and autumn, in five locations, two natural stands (near Sondrio) and three urban localities (two in Milan and one in Pavia). Results showed the presence of 48 fungal taxa in Picea abies, 34 of which in natural stands and 36 in urban localities. Some of these (Alternaria alternata, Aspergillus spp., Aureobasidium pullulans, Cladosporium spp., Penicillium spp.), known to have saprotrofic behaviour, are common in all localities, mainly in the urban ones. Other taxa (Cryptosporiopsis abetina, Fusarium spp., Geniculosporium sp., Phomopsis spp., Sirococcus sp., Sphaeropsis sapinea, Tiarosporellaparca, and Zythiostroma pinastri) are know as fungal endophytes able, in some conditions, to act as pathogens, affecting the growth of some conifers. Zythiostroma pinastri and Tiarosporella parca are abundant in natural stands. The latter species is known to cause stem and branch canker in Siberian conifer stands and some isolates are able to produce inhibiting terpenoids. Tiarosporella parca is the commonest endophyte in Swiss forests. Colonisation was higher in natural stands than in urban sites, showing an increase in summer and a decrease in autumn. In natural stands, needle colonisation, increased with time until the needles became fiveyearold when it reached a plateau. No comparable colonisation behaviour was observed in urban sites.