Infections of Glomerella cingulata on olive in Italy

Olive anthracnose, caused by strains or populations of Glomerella cingulata (anamorph Colletotrichum gloeosporioides) pathogenic for olive, was introduced into southern Italy before or during the 2nd World War presumably from Albania or Greece. In the following 20 years, severe outbreaks of fruit rot and dieback of twigs and branches were recorded in several areas of Puglia, Calabria, Sicilia and Sardegna. After the 1970s, the epidemics gradually regressed. At present, the disease is restricted to certain humid areas of southern Italy. Factors associated with this regression are discussed, including a supposed change in virulence of the fungus, possibly as a consequence of mixing of the introduced strains infecting olive trees with local, less pathogenic populations of G. cingulata. The first results of a comparison of olive isolates with isolates of the pathogen from citrus and Annona muricata in Calabria suggest that the population from olive is relatively homogeneous and can be distinguished from the population infecting other hosts by a number of morphological, pathogenic and biochemical characteristics.