In May 2011, samples of lavender plants (Lavandula × intermedia) showing wilt symptoms were collected from two commercial plantings in Slavonia County. Disease was observed on 20 to 30% of the plants. Symptoms of the disease consisted of chlorosis, stunting, wilting, and death. Vascular tissue of stems and roots exhibited brown discoloration. Isolations of the pathogen were made from the discolored tissues on potato dextrose agar (PDA). Colonies were initially white, but with age became red, and red pigments were produced in agar. Microconidia were pear shaped, oval, and fusoid, and ranged from 4.5 to 14.0 × 2.8 to 4.7 μm. Macroconidia were curved, mostly three septate, and ranged from 21.8 to 24.3 × 2.9 to 3.9 μm. Morphology of colonies and conidia matched the description of Fusarium sporotrichioides Sherb. (1). Identity of the fungus was confirmed by examining a portion of the EF1-α gene using the degenerated primers EF1 and EF2 (2). BLAST searches of the obtained sequences showed a 100% homology with several isolates of F. sporotrichioides from GenBank. Pathogenicity tests were conducted on 20 4-month-old rooted cuttings under greenhouse conditions. Each plant was planted in a separate pot containing 0.7 liter of sterile soil. Inoculum for artificial infection was prepared with sterilized mixtures of wheat and barley seeds (10 g of each). Seeds were inoculated with a F. sporotrichioides spore suspension (106 conidia/ml) and incubated at 22°C for 10 days. Noninoculated seeds served as controls. Ten seeds were placed under the soil surface around the root of each plant. Plants were irrigated and placed in a greenhouse (22°C and a 12-h day/night photoperiod). Sixteen days after inoculation, 80% of inoculated plants were wilted. Symptoms on infected plants were similar to those observed in the field. The pathogen was reisolated and confirmed from the infected vascular tissue, thus fulfilling Koch's postulates. A previous paper reported lavender as host of F. solani in China (4) and F. oxysporum in Saudi Arabia (3). To our knowledge, this is the first report of Fusarium wilt of lavender caused by F. sporotrichioides.
References: (1) J. F. Leslie and B. A. Summerell. Page 256 in: The Fusarium Laboratory Manual. Blackwell Publishing Professional, Hoboken, NJ, 2006. (2) K. O'Donnell et al. Appl Biol. Sci. 95:2044, 1998. (3) K. Perveen and N. Bokhari. Plant Dis. 94:1163, 2010. (4) Y. Z. Ren et al. New Dis. Rep. 15:55, 2007.