Archivio Journal of Plant Pathology

Abstract:

In 2014, Albizia julibrissin trees located in gardens at Logroño municipality (La Rioja, Northern Spain) showed wilt symptoms, including defoliation, internal black streaks and, finally, tree death. Necrotic wood samples were surface disinfected for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, plated onto potato dextrose agar (PDA) amended with streptomycin sulfate (0.5 g l–1), and incubated at 25°C in the dark. Fusarium colonies were consistently isolated and transferred to Spezieller Nährstoffarmer agar (SNA). Ten days after incubation at 25oC, all isolates were identified as F. oxysporum, based on the presence of short monophialides, abundant microconidia produced in false heads (length 7.5 to 12.5 μm, average 9.20 μm) and chlamydospores, and sparse, usually three-septate, macroconidia (length 21.25 to 40 μm, average 29.70 μm) (Leslie and Summerell, 2006). The translation elongation factor 1-alpha gene (TEF) region of the isolates was amplified with primers EF1 and EF2 (O’Donnell et al., 1998). Sequences showed 99% identity with a sequence of F. oxysporum f. sp. perniciosum (FJ985413). One sequence was deposited into GenBank (accession No. KU050689). Pathogenicity of isolates GIHF-019 and GIHF-021, was determined on one-year-old A. julibrissin plants grown in sterile peat moss, which were inoculated by watering the roots with 100 ml of a conidial suspension (106 conidia ml–1). Plants were maintained at 25oC in a growth chamber under a photoperiod of 12 h. Two months after inoculation all inoculated plants wilted and the fungus was reisolated from them. To our knowledge, this is the first report of F. oxysporum f. sp. perniciosum in Spain.