First Report of Crown Rot of Bloodroot (Sanguinaria canadensis) Caused by Fusarium oxysporum in the United States

摘要

Bloodroot (Sanguinaria canadensis L [Papaveraceae]) is a native herbaceous perennial in eastern North America, found from Nova Scotia to Florida. Although it is a common wildflower, rhizomes of double-flowered forms are sold commercially. Rhizomes planted into a wooded area in Guilford, CT produced healthy stems and flowers for a few years and then began to collapse and die in 2008. The same symptoms were observed with a new planting in 2011. Initially, leaves were dull green and were more leathery than healthy leaves. Eventually, the leaves collapsed at the junction of the petioles and the rhizomes. Vascular discoloration, if present, was obscured by the red pigmentation in the rhizome. A Fusarium sp. sporulated on the discolored tissue at the junction between healthy and rotted tissue. Stem pieces were surface disinfested (0.53% NaClO for 1 min), rinsed, and placed on Peptone-PCNB agar (2) at room temperature for 5 days. Colonies originating from single spores were subcultured on carnation leaf agar (2) and identified as Fusarium oxysporum based on falcate, thin-walled, three-septate macroconida borne in monophialides on doliform conidiophores (2). Four rhizomes of double-flowered bloodroot were planted in potting mix in the greenhouse in October 2010; sprouts were observed in March 2011. Two plants were inoculated in March 2011 by drenching the soil with 100 ml of a conidial suspension (106 spores/ml) and two control plants were treated with deionized water. Two months later, the inoculated plants were smaller than the controls. The treated plants subsequently collapsed and F. oxysporum was reisolated. Control plants remained healthy and F. oxysporum was not isolated. DNA extracted from the F. oxysporum isolates was used to obtain partial sequences of the translational elongation factor 1-alpha (tef1) gene, which were then blasted against the GenBank database. We observed a 100% similarity with F. oxysporum f. sp. lycopersici. The bloodroot isolates were compared with a known F. oxysporum f. sp. lycopersici isolate for their ability to cause disease on 2-week-old tomato seedlings (cv. Brandywine), using pathogenicity tests as described above. The known F. oxysporum f. sp. lycopersici isolate caused severe wilt and stunting of the tomato seedlings, but the bloodroot isolate caused no symptoms in inoculated seedling compared with those not inoculated. These results suggest that there may be more hosts for isolates in the F. oxysporum f. sp. lycopersici species complex than previously thought (1). An isolate (O-2603) has been deposited at the Fusarium Research Laboratory at Pennsylvania State University, University Park. Since bloodroot is now being sold commercially as an ornamental, disease management strategies may be needed. To our knowledge, this is the first report of a Fusarium crown rot of bloodroot.