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Illinois researcher zeroing in on soil condition and soybean SDS
 

 

CARBONDALE, Ill. — A Southern Illinois University Carbondale researcher has developed timely new evidence to a long-known hypothesis: Soil condition could hold the key to combating sudden death syndrome (SDS).

Ahmad Fakhoury, an associated professor of plant pathology and fungal genetics, details his theory in an article published recently in Phytobiomes, a journal of The American Phytopathological Society.

As growers know, SDS can wipe out whole fields of soybeans if left untreated, and for Illinois – the top-producing bean state for the past two years – the crop is big business, hitting nearly $6 billion in direct sales last year.

Fakhoury said his research zeros in on the condition of soil as an attack point to combating the disease. “The occurrence of SDS in fields is dependent on physical and biological factors, and the suppressiveness of soils to disease is a long-known phenomenon,” he explained.

“Promoting and sustaining the soil’s natural suppressiveness to disease can be integral to the effective, sustainable management of soilborne pathogens.”

Soil profiling has been a key tool for researchers studying SDS, but most work has focused on identifying the soil’s physical and chemical characteristics when SDS is present. Fakhoury found a new way to analyze soil to determine the incidence and severity of SDS by profiling the soil’s microbes as well as its physical and chemical properties.

In Fakhoury’s study, soil samples from 45 soybean fields in Illinois, Iowa and Minnesota were analyzed. Researchers collected samples from fields showing symptoms of SDS and from adjacent areas where SDS foliar symptoms did not develop.

Fakhoury compared microbial populations in the “healthy” and “diseased” soil to correlate the presence incidence and severity of SDS, then measured soil-related factors and used markers specific to bacteria, fungi, archaea, oomycetes and nematodes to help identify key taxonomic species associated with SDS development.

He generated more than 14 million sequences and mapped them against the National Center for Biotechnology Information’s nucleotide database, and compared them using several bioinformatics tools.

The unique method of analysis found significant differences in the bacterial and fungal structures between healthy and diseased areas of fields, suggesting the relative abundance of multiple microbial taxia in the soil as a key determinant in the incidence of SDS, Fakhoury explained.

“The work … documents the first attempt to assess the importance of biological factors in determining the incidence of SDS in soybean using metagenomics tools,” he noted. “This is basically a first attempt at resolving the complexity of the biological interactions that affect the occurrence of the disease.”

The yearlong project will lead to further research to characterize the main fungal pathogen associated with SDS – and likely lead to ways of addressing soil conditions in ways that limit or prevent the start of SDS.

“The emerging tools and techniques we used permit the differentiation of complex microbial interactions,” Fakhoury added. “This will ultimately allow us to devise and adopt more efficient and sustainable strategies to manage SDS and other diseases that are detrimental to agricultural production.”

His research can be viewed at www.phytobiomesjournal.org

11/8/2017