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New disease - Taproot decline on soybean in Mid-South USA


A ProMED-mail post <http://www.promedmail.org>
ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>

Date: Mon 25 Jan 2016

Source: Delta Farm Press [edited]
<http://deltafarmpress.com/soybeans/taproot-decline-mid-south-soybean-mystery-malady>

Soybean 'mystery malady'

The Mid-South's soybean "mystery malady" [see ProMED-mail post http://promedmail.org/post/20150609.3421625] now has a name -- taproot decline. Unfortunately, there remain many questions about treatment.

"In 2007, I received numerous calls about a root-associated soybean disease that appeared different than the other root diseases in the Mid-South," said Tom Allen, Mississippi State University. "Looking back, and based on some of the more prominent symptoms associated with this root disease, I think it was likely misdiagnosed as one of several other diseases. This new disease is interesting, because [it] can be observed at both vegetative and reproductive growth stages."

Typically, interveinal chlorosis can be observed in a single plant or small clumps of plants, scattered around in a field. On plants exhibiting symptoms above ground, "a thick black growth at the base of the stem and taproot along the soil line can often be observed. In some cases, there can be a thick, ropy white mycelium. If you cut into the stem, the vascular tissues will be brown and slightly discolored."

Allen said to date, taproot decline has been observed in all soil types throughout the Mid-South regardless of irrigation, dryland, furrow-irrigated, and variety planted.

"The 1st step is to determine the specific fungus that is causing this disease. I think we know the genus, now we'll attempt to determine if this is a new species. We're planning some field trials to determine whether some currently available soybean cultivars are more susceptible to the fungus than others."

[Byline: David Bennett]

--

Communicated by: ProMED-mail <promed@promedmail.org>

[The new disease has been reported to be widespread, for example in Mississippi (ProMED-mail post http://promedmail.org/post/20150609.3421625), with an estimated yield loss of almost 20 per cent. It occurs in the same area of a field if soybean is planted in consecutive years, and in individual plants or clusters along the same row. This would suggest soil transmission and possible mechanical transmission by farming activities.

An undescribed fungus was isolated from infected taproots previously and was found to have 97 per cent sequence similarity, based on internal transcribed spacer regions, to species within the family Xylariaceae (see link below). From the report above it appears that a likely genus has been identified now.

Maps

USA:

<http://www.mapsofworld.com/usa/usa-state-and-capital-map.html> and <http://healthmap.org/promed/p/226>

Pictures

Symptoms of the "mystery disease":

<http://www.mississippi-crops.com/wp-content/uploads/2015/05/IMG_1043.jpg>,

<http://www.mississippi-crops.com/wp-content/uploads/2015/05/IMG_1051.jpg>,

and

<http://www.mississippi-crops.com/wp-content/uploads/2015/05/DSC_0590.jpg>

Links

Previous research and news reports on taproot decline:

<http://mssoy.org/wp-content/uploads/2015/04/78-2014-PETERSON-ANN-REP-FINAL.pdf>,

<http://agfax.com/2015/12/22/soybeans-new-taproot-decline-disease-hurting-south/>,

and

<http://www.soybeansouth.com/departments/industry-news/mississippi-state-researchers-id-new-soybean-disease/>

Taxonomy and type species of Xylariaceae via:

<http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=81528>

Other fungal taxonomy via:

<http://www.indexfungorum.org/names/Names.asp>

List of major diseases and pathogens of soybean:

<http://www.apsnet.org/publications/commonnames/Pages/Soybeans.aspx>

- Mod.DHA]

[See Also:

2015

----

Undiagnosed disease, soybean - USA: (MS) http://promedmail.org/post/20150609.3421625]



More news from: ISID (International Society for Infectious Diseases)


Website: http://www.isid.org

Published: February 11, 2016

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