First report of Verticillium dahliae Kleb. on squash (Cucurbita pepo L.) in Italy.

During field surveys in February and March 2007 and 2008, unusual symptoms of wilting were observed on squash plants (Cucurbita pepo L.) cultivated near Fondi (Latium-Central Italy) in two commercial plastic houses. Due to the very high incidence of the disease (between 20 and 30%), we performed specific diagnostic assays. The infected plants showed yellowing, stunting, vascular discoloration and premature death of leaves. A fungus was consistently isolated on potato dextrose agar (PDA) from stems showing discoloured vascular tissues. According to the typical morphology of the isolates (one celled conidia 1-2 μ) and colonies features observed, the fungus was identified as Verticillium dahliae Kleb. (1). To verify the pathogenicity of three fungal isolates, 2-week-old seedlings (15 plants/isolate) were inoculated by dipping the roots in a suspension of 105 conidia per ml for 30 s. Inocula were obtained from 2-week-old fungal cultures grown on PDA at 20±2 °C. Roots of 15 control plants were dipped in water. The seedlings were transplanted into pots containing peat and river sand (1:1, v/v) and placed in a greenhouse at 20-25 °C. One month after inoculations, all fungal isolates caused wilting while no symptoms were observed on control plants. The morphological features of the reisolated fungus, obtained only from the inoculated plants, were identical to the original isolates. Based on morphological and pathogenicity test, we can conclude that V. dahliae is the causal agent of the disease. V. dahliae is a well known polyphagus fungus recorded in Italy on a number of other plants can survive in soil for more than 5-10 years in absence of susceptible hosts. To our knowledge this is the first report of V. dahliae on squash in Italy. Recently the same fungus was recorded for the first time on Cucurbita pepo L. in Trinidad.