First Report of Root Rot Caused by Ilyonectria (=Neonectria) macrodidyma on Avocado (Persea americana) in Italy

During the 2009 and the 2010 growing seasons, a root rot disease has been detected on young potted Persea americana plants in two nurseries located in the Catania and Messina provinces (eastern Sicily, Italy). A Cylindrocarpon sp. was consistently recovered from pieces of symptomatic tissues on Petri dishes containing potato dextrose agar. On the basis of morphological characteristics and molecular identification by DNA sequencing and phylogenetic analysis of internal transcribed spacer and ?-tubulin gene regions, the causal agent was identified as Ilyonectria (=Neonectria) macrodidyma. Koch's postulates were fulfilled by pathogenicity tests carried out on potted P. americana seedlings. To our knowledge, this is the first to report worldwide of the occurrence of a disease caused by I. macrodidyma on P. americana.