First Report on the Occurrence of Fusarium langsethiae Isolated from Wheat Kernels in Poland.

Abstract

Numerous Fusarium species have been associated with Fusarium head blight of wheat. In Poland, Fusarium poae was reported as the dominant species isolated from wheat grain during seasons with low amounts of rainfall during anthesis (1). F. langsethiae was described as a new toxigenic Fusarium species (3) and causal agent of Fusarium head blight (2), which has been isolated from infected oats, wheat, and barley in northern and central Europe (Norway, Austria, Germany, Czech Republic, Denmark, and England) (2). On the basis of morphological similarities, F. langsethiae has long been identified as a "powdery" form of F. poae. However, F. langsethiae produces type A trichothecene toxins such as T-2, whereas F. poae produces nivalenol and other 8-keto trichothecenes, scirpentriol, and 15-acetoxyscirpenol. In 2006, we obtained several isolates of F. langsethiae from kernels collected from winter wheat ears with head blight symptoms. Isolates were collected in the central (Sobiejuchy 52°54'N, 17°43'E; Minikowo 53°29'N, 17°56'E) and northern (Radostowo 53°59'N, 18°45'E) regions of Poland. Strains were isolated on potato dextrose agar (PDA) medium (pH 5.5). Further analyses were conducted on single-spore isolates. Initial species identification of all isolates was conducted on the basis of morphological features. The strains were grown in darkness at 25°C on PDA in plastic petri dishes to diagnose colony color, odor, and growth rate. The cultures also were incubated on saltwater nutrient agar (SNA) at 25°C for 7 days in near-UV light (Philips TLD 36W/08) and darkness in a 12/12-h cycle to promote conidia formation. The calculated average mycelial growth rate per day was based on the difference in millimeters between the colony diameters after 4 and 7 days of incubation. Growth rates ranged from 5.4 to 10.3 mm/day for nine strains. Mycelium was whitish or pinkish white, sparse, and 1 to 3 mm high with no odor. All colonies showed a powdery mycelium surface. Microconidia was napiform or globose, nonseptate, sporadically 1-septate, with an average length of 6.4 μm (range 3.9 to 13.7 μm) and width of 5.6 μm (range 2.9 to 8.8 μm). Microconidia were formed in heads, borne on unbranched or branched monophialides that were 8.5 to 16.3 μm long. All strains had slim, bent monophialides, typical for F. langsethiae, and always a few, short, thick, and squat ones resembling F. poae. In young cultures, monophialides may be formed directly on hyphae. Formation of macroconidia, sclerotia, and chlamydospores were not observed after 3 weeks of incubation. Species identification was confirmed by PCR assay with the use of SCAR (sequence characterized amplified region) primers producing a 310-bp DNA fragment (4), which was deposited in GenBank (Accession No. EU088404). To our knowledge, this is the first report of F. langsethiae in Poland.