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First Report of Sudden Death Syndrome of Soybean Caused by Fusarium virguliforme in New York

Cummings, J. A., Myers, K. L., Bergstrom, G. C.
Plant disease 2018 v.102 no.10 pp. 2036
Fusarium virguliforme, Glycine max, ambient temperature, chlorosis, conidia, crop production, cultivars, culture media, death, developmental stages, discoloration, disease resistance, ethanol, genes, genetic databases, greenhouses, growers, growing season, leaves, neomycin, nucleotide sequences, pathogenicity, peptide elongation factors, photoperiod, planting, potting mix, roots, rye, sand, saturated conditions, seed treatment, seeds, sequence analysis, sodium hypochlorite, soybean sudden death syndrome, soybeans, species identification, streptomycin, tissues, weather, Michigan, New York
Sudden death syndrome (SDS) of soybean (Glycine max [L.] Merr.), incited by Fusarium virguliforme Aoki, O’Donnell, Homma, & Lattanzi, is an economically important disease found in many soybean production regions of the United States (Aoki et al. 2003). This disease can be a major contributor to yield loss in years with conducive weather conditions (Hartman et al. 2015). In late August of the 2017 growing season, soybean plants at growth stage R1 were submitted from Wayne County, NY, for diagnosis to determine the cause of interveinal chlorosis of the leaves. Inspection of the roots revealed vascular discoloration. Cut pieces of roots and crowns were surface sterilized in 0.5% NaOCl, followed by 95% ethanol, rinsed in sterile distilled water, and incubated on potato dextrose agar (PDA) amended with neomycin (0.12 g/liter) and streptomycin (0.2 g/liter) antibiotics at room temperature (24 to 26°C) with a 12-h photoperiod under black light for 7 days. Blue-pigmented Fusarium colonies were observed growing from the root tissues. These were transferred to PDA, and monosporic isolates were obtained. Macroconidia were morphologically consistent with those described for F. virguliforme, measuring 3.8 to 5.0 × 34 to 66 µm and three to five septate (Hartman et al. 2015). Pathogenicity of an isolate collected from one of those colonies was confirmed by planting into infested potting mix. Briefly, seeds of the susceptible cultivar Essex were sown into 10 6-in. pots containing a sand and potting mix blend, each inoculated with 25 g of pathogen-infested rye grains. Pots were incubated in a greenhouse with a 14-h photoperiod and irrigated regularly to maintain saturated conditions. Ten noninoculated controls of the same variety were included but were amended with noninfested rye grain. Foliar symptoms of small chlorotic spots and interveinal chlorosis were visible 4 weeks after planting. At that time, root discoloration was also observed in most inoculated plants, and F. virguliforme was reisolated from those roots, using the same method as described above. The noninoculated plants remained symptomless. A portion of the translation elongation factor (TEF1) gene was sequenced from the isolate used for inoculation to confirm species identification (O’Donnell et al. 1998). The isolate (accession no. MG470654) shared 100% nucleotide sequence identity with F. virguliforme accession number HM453329 (Michigan) in the NCBI GenBank database. SDS has not been reported previously on soybean in New York, although it is suspected to be more widespread within the state. We have made tentative diagnoses of SDS in plants from several counties in New York since 2013, but this was the first time that Koch’s postulates were fulfilled with a New York isolate of F. virguliforme. This confirmation of SDS in New York indicates that soybean growers in this state should consider planting varieties with resistance to this disease and utilizing seed treatments in areas where it is identified.