First report of Chalara elegans on squash in Italy

In February and March 2007 and 2008 unusual symptoms of stunting associated with severe leaf chlorosis were observed in some squash (Cucurbita pepo L.) crops near Sabaudia (Latium, Southern Italy). Roots of diseased plants showed a reduced growth, brown root rot and premature death. Microscopic observations symptomatic roots showed the presence of Chalara elegans Nag Rai & Kendrik. The same fungus was consistently isolated on potato dextrose agar (PDA) from diseased roots. To verify the pathogenicity of two fungal isolates, disks of 8-day-old colonies, 5 mm in diameter, were placed on the collar of 15 seedlings in which small lesions were made with a sterile needle. Control plants were treated with sterile PDA. The seedlings were grown in a greenhouse at 20±2°C with 14 h photoperiod. After four weeks only the inoculated plants showed the same symptoms observed in the field. C. elegans was successfully reisolated from the inoculated plants, proving that this fungus is the causal agent of black root rot of squash. C. elegans has been recorded in Italy from a wide range of important hosts, in both protected and open field crops. The occurrence of this new disease could be due to the inoculum persisting in soils where other susceptible species were previously grown in which chlamidospores can survive for more than 5 years. To our knowledge this is the first report of C. elegans on squash in Italy.