FIRST REPORT OF JUJUBE DIEBACK CAUSED BY FUSARIUM SOLANI

Abstract

In spring 2010, a severe branch dieback was observed in jujube (Ziziphus jujuba) orchards of the Sarbishah region of southern Khorasan (Iran). Symptoms included twig dieback, blackish discoloration of wood and foliage, and wilting followed by leaf shedding. Samples of symptomatic tissues, including discoloured wood and cambium from twigs and branches, were excised, surface-sterilised, plated onto Petri dishes with potato dextrose agar (PDA), and incubated in the dark at 25°C for 10 days. On PDA, the colonies presented a cream-coloured mycelium with yellow pigmentation and a creamy reverse. On carnation leaf agar, macroconidia were abundant, thick walled, 4 to 6 celled, hyaline, fusoid, and measured 5-7×20-37.5 μm. Microconidia, which were formed in false heads developing on long monophialides, were oval, reniform and fusiform, had 0 to 2 septa and measured 2.5-5×7-15 μm. Chlamydospores were single, double or several in chain, and measured 5-7.5×5-9 μm. Based on these morphobiometric and cultural characteristics, the fungus was identified as Fusarium solani (Demicri and Maden, 2006; Leslie and Summerell, 2006). For pathogenicity tests, normal and wounded shoots of three 6-year-old jujube trees were inoculated with 5 mm diameter mycelium disks from two 10day-old single-spore isolates. Inoculation sites were covered with moistened cotton wool and parafilm. Control inoculations were made with sterile PDA. Disease symptoms, including tissue discoloration, were first observed 14 days after inoculation of the shoots, from which the fungus was reisolated. Controls did not develop symptoms. F. solani is frequently found associated with damage or stress events caused by other biotic or abiotic agents (Booth, 1971). This represents the first evidence of F. solani pathogenicity to Z. jujuba.