Field experiments were established in the 2018/19 and 2019/20 growing seasons at the experimental station in Neu-Eichenberg, Hessen, Germany to examine the suitability of multiple wheat cultivars for intercropping with pea and the effect of mixtures on diseases. Approximately 600 wheat tillers (BBCH 49-61, depending on the year and cultivar) were sampled in each year and assessed for severity of foot (lower stem) rot symptoms. Fungi from plants with Fusarium-like symptoms exhibiting reddish-brown discolorations on the stems were isolated following the methods described in Šišić et al. (2018). Surface disinfected (3% NaOCl for 10s) wheat stems and roots were cut into three 1 cm long pieces and placed on COONS agar (Coons, 1916). Following 7 - 12 days of incubation under constant blacklight blue fluorescent light, pure cultures were generated on potato dextrose and synthetic nutrient-poor agar (Nirenberg, 1976) using the hyphal tip transfer technique, and the resulting colonies examined microscopically. Based on morphology ca 15% of all Fusarium isolates recovered belonged to a distinct taxonomic unit and were initially identified as F. sambucinum-like (Leslie and Summerell, 2006). The identity of 16 randomly selected isolates (GenBank accession numbers MW085924 - MW085939) was confirmed by sequencing a portion of the translation elongation factor 1-alpha gene region (O'Donnell et al., 1998). Blast analysis in the FUSARIUM-ID (Geiser et al., 2004) and the NCBI databases revealed >99 to 100% identity match with the Fusarium venenatum accession numbers NRRL 22196, FRC R-09186 and MRC 2394. Pathogenicity tests were conducted on wheat cultivar Torborzo using six F. venenatum isolates. Inoculum was prepared using a sterile sand-millet mix infested with six agar plugs of each of the isolates. Once fully colonized, the inoculum was mixed with sterilized sand in a 1:7 ratio (by volume), transferred to 300 ml pots and 4 surface sterilized wheat seeds (5 min 70% alcohol) were sown in each pot. Non-inoculated controls were amended with sterilized inoculum. The experiment was conducted in a greenhouse in a completely randomized design with 5 replicates. Disease symptoms were assessed after four weeks. All isolates induced reddish-brown discolorations on the lower stems similar to those observed in the field grown plants. In addition, the infected plants developed dark brown to black discolorations on the crowns and roots and showed clear signs of stunted root growth. These symptoms were further accompanied by chlorosis (yellowing) of the lower leaves starting from the leaf tip. All isolates were successfully reisolated from the infected wheat plants but not from the controls. To the best of our knowledge, this is the first report of F. venenatum causing foot and root rot of wheat in Germany. Results from field and greenhouse inoculation experiments indicate that F. venenatum may be an important pathogen of wheat in Germany. Further studies on distribution and relative abundance of the species in the Fusarium foot and root rot complex of wheat in Germany are warranted. In addition, it is important to note that our results contrast the results from previous studies (Farr and Rossman, 2021) which reported F. venenatum primarily as a soil saprophyte and presumably non-pathogenic fungus in its nature. Our findings thus, also warrant the need to further investigate pathogenic potential of this species and the role it may play on other common rotational crops in Germany.
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