Abstract
Soybean sudden death syndrome (SDS), caused by Fusarium virguliforme, is an economically important soilborne disease and is a major risk to many soybean [Glycine max, (L.) Merr.] production regions worldwide. Two-year studies were conducted in a greenhouse and in fields to examine survival of the fungus in corn-soybean residues. Corn kernels consistently showed significantly (P<0.05) higher F. virguliforme colony-forming units per gram of dry soil (CFU/g) in a greenhouse and in field micro-plots compared to no additional residue added treatment (control). None of the soil samples from commercial fields in Iowa showed significant (P<0.05) difference in F. virguliforme CFU/g within year of sampling, but between years there were numerical differences but not statistically different in samples if the previous crop had been corn, compared with winter wheat or soybean. In Fusarium spp. not causing SDS, CFU/g were significantly (P<0.05) higher in micro-plots amended with six different corn-soybean residue treatments compared with the control in 2008, while in 2009, only corn stock spread on soil showed significant (P<0.05) difference over the control. Our results suggest that a clean corn harvest could reduce SDS risk by reducing colonization of corn kernels that supports survival of F. virguliforme, while a considerable corn loss during harvest could increase SDS risk.
Highlights
Sudden death syndrome of soybean [Glycine max, (L.) Merr.], caused by Fusarium virguliforme O’Donnell & T
In soil samples collected from nine crop residue treatments in 2008 across dilutions, the coarse-ground corn kernel treatment showed significantly (P
In 2008, plots amended with coarse-ground corn kernels, corn roots, and soybean stalks did not differ significantly (P
Summary
Sudden death syndrome of soybean [Glycine max, (L.) Merr.], caused by Fusarium virguliforme O’Donnell & T. The disease was first observed by H.J. Walters in Arkansas in 1971 [1], but it was only in 1983 that the disease was named as sudden death syndrome (SDS) of unknown etiology [2]. After the disease was first noticed in Iowa in 1993 [5], an extensive investigation confirmed SDS in 28 counties by 1996 [6]. By 2010, the disease had spread to 96 of the 99 counties in Iowa This spread of SDS suggested that F. virguliforme may have been present in most Iowa soils in previous years, but had not been detected in several counties because of low inoculum densities and/or unfavorable environmental conditions [7]. Yield losses due to SDS vary widely depending on agronomic practices, like planting dates, row spacing, maturity groups and cultivar selection [10], as well as climatic and environmental trends in the growing season [7]
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