The host range of Fusarium virguliforme on rotational crops and common plant species and its survival and growth on crop residue.

Abstract

Sudden death syndrome (SDS), caused by Fusarium virguliforme (Fv), is an important soybean (Glycine max) disease. Crop rotation is not an effective management strategy, suggesting that the pathogen may survive long periods in the soil or may infect or be sustained on weeds or crops other than soybean. Minimal research has been conducted to understand Fv survival or its host range and ability to grow on different plants. The objectives of this thesis research were to determine the host range of Fv, the best methods for extracting Fv DNA from crop residue and macrocondia, and to determine how long Fv DNA can be detected on crop residue after burial in a field. Fifteen plant species were inoculated in a greenhouse to determine the host range of Fv. In at least one experiment, soybean, alfalfa (Medicago sativa), pinto bean and navy bean (Phaseolus vulgaris), white clover (Trifolium repens), red clover (T. pretense), pea (Pisum sativum), and Canadian milk vetch (Astragalus canadensis) developed foliar and/or root symptoms. In at least one experiment, corn (Zea mays), wheat (Triticum aestivum), ryegrass (Lolium perenne), pigweed (Amaranthus retroflexus), sugar beet (Beta vulgaris), lambsquarters (Chenopodium album), and canola (Brassica napus) appeared to be asymptomatic hosts for Fv. Thus, multiple plant species may be negatively affected by Fv and/or promote its survival and growth. Three commercial DNA extraction kits were compared to determine which would yield the greatest purity and quantity of Fv DNA from crop residue and macroconidia. The FastDNA® kit was generally most effective for extracting Fv DNA from crop residue and the MO BIO PowerSoil™ kit was superior for extracting Fv DNA from macroconidia. This knowledge was used to determine if Fv DNA can be detected on soybean, corn, alfalfa and wheat residue over time after placement in three crop fields and whether different inoculation methods influence the duration of detection. Soybean and corn tissue that was infected while growing retained detectable amounts of Fv DNA for at least 8 months after burial in the field. Dead tissues inoculated with Fv macroconidia typically did not retain quantifiable amounts of Fv DNA after burial. Results from this study suggest that the inoculation method is important for survival and detection of Fv DNA, and that Fv DNA remains detectable on crop residue from fall into the following summer.