The objective was to quantitatively document the pathogen community associated with the Fusarium head blight complex in Italian wheat. The observational study was prompted by increased concerns about mycotoxin contamination coupled with a surge in organically grown wheat. During the three-year survey (2004 to 2006) in three geopolitically defined zones (north, centre, south), seedborne pathogens associated with Fusarium head blight in organic bread and durum wheat were assayed by the freezing blotter method and identified to species based on morphological features. The four most abundant species overall, in order from highest to lowest, were Fusarium poae, Microdochium nivale, F. verticillioides and F. graminearum. Environment was more influential than wheat cultivar in determining the variances in seed infestation counts. Counts of infested seeds were higher (and more variable) in the north and centre zones than in the south zone. The odds of observing any seed infestation was significantly higher in both the north and centre zones (compared with the south zone) for F. avenaceum, F. graminearum, F. poae, and M. nivale in durum wheat. There was a significant nonlinear relationship between seed infestation prevalence and incidence, with evident separation of species along the prevalence-incidence curve. Species co occurrence was observed, but associations shifted with wheat type, over years, and among zones. F. poae was not positively associated with any other species.

Fusarium lateritium is a globally distributed plant pathogen. It was recently reported as the causal agent of nut gray necrosis (NGN) on hazelnut. Isolate characterization within F. lateritium was undertaken to investigate how morphological and molecular diversity was associated with host and geographic origin. Morphological studies combined with inter-simple-sequence repeat (ISSR) analysis, and phylogenetic analyses using translation elongation factor 1α (TEF-1α), β-tubulin genes, and nuclear ribosomal DNA internal transcribed spacer (ITS) sequences were conducted to resolve relationships among 32 F. lateritium isolates from NGN-affected hazelnut fruit, and 14 from other substrates or 8 from other hosts than hazelnut. Colonies of F. lateritium from hazelnut showed dark grayish-olive differing from the orange-yellow color of all other isolates from other hosts. Generally, isolates from NGN-affected fruit failed to produce sporodochia on carnation leaf agar. The influence of host and substrate on the genetic structure of F. lateritium was supported by ISSR and analyzed with principal coordinates analysis. A relationship between hazelnut and genetic variation was inferred. Phylogenetic analysis of ITS provided limited resolution while TEF-1α and β-tubulin analyses allowed a clear separation between the European and non-European F. lateritium isolates retrieved from GenBank, regardless of host. Though morphological traits of F. lateritium isolates from hazelnut were generally uniform in defining a typical morphogroup, they were not yet phylogenetically defined. In contrast, the typology related to slimy deep orange cultures, due to spore mass, grouped clearly separated from the other F. lateritium isolates and revealed a congruence between morphology and phylogeny.

Surveys on the occurrence of type A trichothecenes in wheat, and particularly for the T‐2 and HT‐2 toxins, and information on the biology and epidemiology of the causative Fusarium species (i.e. F. langsethiae, F. sporotrichioides) are scarce in Italy, as compared to the more common type B trichothecene, deoxynivalenol and its producers. This 4‐year monitoring of phytopathogenic Fusarium species on 183 seed lots of durum wheat shows wide distribution of F. langsethiae in Italy and the potential of several isolates of this fungus to produce high amounts of T‐2 and HT‐2 in wheat. Fusarium langsethiae was observed for approximately 48% of the analysed samples, with a maximum incidence for a single lot of 10.5%. Fusarium sporotrichioides was observed only in 2011, with an average incidence of 2% (range, 0–3%). A collection of F. langsethiae isolates representative of the main cultivation areas in Italy was established. These isolates showed great variability for their toxin production in vitro. Of 28 strains, all except one isolate can produce the T‐2 and HT‐2 toxins. HT‐2 was generally in greater amounts than T‐2, with an average concentration ratio for HT‐2 to T‐2 of 2.1 (range, 0.7–5.4). The artificial inoculation of wheat with three isolates of F. langsethiae produced no Fusarium head blight symptoms under field conditions. However, significantly higher incidence of F. langsethiae was seen on the kernels of inoculated plants, compared to the uninoculated controls.

No abstract

Durum wheat (Triticum durum Desf.) is one of the most widely grown crops in Italy, extending to approximately 1.5 million ha. Seedborne fungi, affecting both germination and commercial quality of the product, represent a threat to wheat production. Several Fusarium species produce mycotoxins, secondary metabolites harmful to humans and animals. In 2006, monitoring the health status of durum wheat kernels from central (Pollenza, MC) and southern Italy (Foggia; Gravina di Puglia, BA; Enna) was conducted. Kernels at the 11.3 Feeke's scale growth stage were analyzed with the deep freezing blotter test (1). Ten isolates morphologically similar to Fusarium poae were observed. For identification, monosporic isolates were transferred onto potato dextrose agar (PDA) and carnation leaf agar (CLA) to grow at 23°C with exposure to 12-h alternate cycles of darkness and near-UV light (Philips TLD 18W/08 Blacklight Blue Fluorescent Lamp, peak 360 nm). The shape and dimension of microconidia were similar to those of F. poae. The average radial daily growth rate (4.7 ± 1.0 mm day–1) of seven isolates at 23°C was significantly different (P < 0.05) from those of F. poae (8.8 ± 0.2 mm day–1) and F. sporotrichioides (9.4 ± 0.3 mm day–1). In addition to a slower growth rate, these isolates differed from F. poae because of a powdery appearance on PDA, the presence of polyphialides, the absence of macroconidia, and the lack of the peach-like odor. On the basis of the characters observed, the fungus was identified as F. langsethiae, a species recently described from several grains, including wheat (2). To confirm the diagnosis, the internal transcribed spacer (ITS) region of four isolates (ISPaVe ER-1399, ER-1400, ER-1401, and ER-1402) was amplified using universal primers ITS4 and ITS5 (3). The 546-bp product obtained was directly sequenced at the GenLab, Enea, Rome. A homology search using the BLASTn algorithm of all obtained sequences showed 100% identity with GenBank sequence AY680864, corresponding to F. langsethiae. One of these sequences (ISPaVe ER-1400) was deposited in GenBank with Accession No. EF526078. The DNAs of four isolates of F. langsethiae and one each of F. poae and F. sporotrichioides were amplified with the F. langsethiae-specific primers FlangF3 and LanspoR1 (4). The PCR conditions consisted of the initial denaturation at 94°C for 2 min, 35 cycles each of 30 sec at 94°C, 30 sec at 58°C, 1 min at 72°C, and a final extension at 72°C for 7 min. No amplification was obtained from F. poae and F. sporotrichioides, while a PCR product of the expected size (310 bp) was obtained from all F. langsethiae isolates, confirming their specific identification. To our knowledge, this is the first report of F. langsethiae on durum wheat in Italy. This species is known to produce the T2 and HT2 toxins, type A trichotecenes related to alimentary toxic aleukia in humans and haematotoxicity and immunotoxiciticy in animals. A large-scale monitoring of this fungus on durum wheat in Italy is in progress. References: (1) T. Limonard. Neth. J. Plant Pathol. 72:319, 1966. (2) M. Torp and H. I. Nirenberg. Int. J. Food Microbiol. 95:247, 2004. (3) T. J. White et al. Page 315 in: PCR Protocols, a Guide to Methods and Applications. Academic Press, San Diego, CA, 1990. (4) A. Wilson et al. FEMS Microbiol. Lett. 233:69, 2004.