First report of Fusarium oxysporum Schlecht. emend. Snyder and Hansen causing wilt of lettuce in Bulgaria. Short Communicattion

Ivo T. Yanashkov and Tzenko D. Vatchev

Abstract: Lettuce plants (Lactuca sativa L.) showing symptoms of yellowing and wilting of folliage, stunting and death of the plants were observed in a commercial greenhouses situated near Sadovo (Sauth Central Bulgaria) in April, 2019. Roots, stems and leaves of the symptomatic plants decayed and turned reddish brown. All isolates obtained from symptomatic plants were identified as Fusarium oxysporum Schlecht. emend. Snyder and Hansen by microscopic observation of their morphological characteristics (3-4-septate macroconidia – 25.2-30.5 μm x 3.1-4.6 μm, 1-2-septate microconidia – 6.2-9.0 μm х 2.8-4.5 μm and abundant chlamydospore formation). Pathogenicity of all isolates was confirmed on lettuce cultivar Grand Rapids in pot experiments with artificially inoculated soils. Seedlings grown in inoculated soils showed wilting and root rot symptoms, identical to those observed on naturally infected plants. The inoculated pathogens were consistently reisolated from symptomatic tissues. To the best of our knowledge, this is the first report of F. oxysporum infecting lettuce in Bulgaria.

Keywords: Fusarium oxysporum; lettuce; pathogen; root rot; stem rot; wilting; yellowing

Date published: 2021-02-25