THIELAVIOPSIS PARADOXA CAUSING NECK BENDING DISEASE OF DATE PALM IN IRAN
M.R. Mirzaee, H. Tajali, S.A. Javadmosavi
In April 2014, severe neck bending symptoms were observed on date palm (Phoenix dactylifera L.) in Tabas region of Southern Khorasan, Iran. Symptoms included inclination of the area of the uppermost portion of the trunk and internal brown discoloration of the petiole bases. A fungus with the characteristics of Thielaviopsis paradoxa (Teleomorph: Ceratocystis paradoxa) was consistently isolated on potato dextrose agar (PDA) from the symptomatic tissues. The fungus produced two types conidia, including cylindrical, hyaline to pale brown which formed endogenously in chains, 5-7.5×7.5-15 μm, and oval, thick-walled, black chlamydospores in chains from the tips of short lateral hyphae that were 7.5-15×10-25 μm.
The ITS region of rDNA was amplified using primer pair ITS1F/ITS4 and the PCR product was sequenced. Comparison of the sequence (GenBank accession No. KM519456) revealed 99% similarity to C. paradoxa (DQ318203). Date palm seedlings (cv. Kabkab) and banana fruits were inoculated with PDA plugs taken from 5-day-old single-spore isolates. Disease symptoms developed on both hosts, on banana fruits within 5-7 days and on date palm seedlings after 12 days and re-isolation from affected tissues yielded T. paradoxa. The control seedlings and fruits showed no symptoms. T. paradoxa has been reported as the causal agent of neck bending disease on date palm in Iraq and Qatar (Abbas and Abdulla, 2003) and trunk rot of Canary Island date palm and date palm from Italy (Polizzi et al., 2006). This is the first report of the disease as well as the first confirmed record of the fungus T. paradoxa in Iran.