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Leaf rust on soybean in Mato Grosso do Sul, Brazil


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: Tue 30 Dec 2014

Source: AgroNews, AgroPages.com report [edited] <http://news.agropages.com/News/NewsDetail---13871.htm>

Soybean rust develops partial resistance to fungicides

------------------------------------------------------

In Mato Grosso do Sul the Asian rust [has] developed gene alterations after application [of] fungicides belonging to the strobilurin group [chemical group of fungicides]. DuPont [chemical company] reported the detection of a mutation in the position 129, replacing the amino acid phenylalanine with leucine. This features [as] "partial resistance"

when controlling the rust disease. The problem was announced in a meeting set by the Chapadao Foundation with farmers, farm managers, and consultants from the Chapadao region that is in the border of the state of Mato Grosso do Sul, Goias and Mato Grosso.

Among the [plant] population tested, resistant individuals to strobilurins have not been found, despite [the] mutation. Embrapa (Brazil's National Agricultural Research Company), however, verified that some products have [shown] diminished performance throughout recent years.

There are several solutions that could be adopted, for example an increase of product dose, complementation with other fungicides, and rotation of products. Soybean is Brazil's main commodity and rust is its main disease.

--

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

[Leaf rust (also called soybean rust, Asian rust) caused by the fungus _Phakopsora pachyrhizi_ can result in yield losses of soybean crops of up to 90 percent. It is widespread in Asia and Africa and spreading in the Americas, but data are lacking on its establishment in Europe.

Besides soybean, over 30 other species in the family of _Fabaceae_ can also be affected and may serve as pathogen reservoirs. The related species _P. meibomiae_ is also found in South America and the Caribbean causing similar symptoms, but is less virulent and considered of lesser economic significance.

Spores are spread locally by splashing rain, or by wind over long distances. Several epidemic cycles may occur in one cropping season.

In Brazil, volunteer soybeans as pathogen reservoirs have been identified as a threat to new crops (ProMED-mail post 20120911.1287887). Fungicides may be used in disease management, but timing of applications is considered important. Partially resistant soybean lines are available. However, new fungal strains with increased virulence and fungicide resistances are emerging in soybean producing countries, including Brazil (ProMED-mail post 20090501.1644).

Strobilurins are strongly antifungal agents produced by fungi. Being derived from natural products, they are considered environmentally safe and are used against most major fungal crop diseases. Therefore, pathogen resistance is of major concern to many primary industries worldwide. Rotating or mixing chemical classes of fungicides is used to extend the useful life of the compounds.

Maps

Brazil:

<http://en.18dao.net/images/9/96/Map-Brazil.jpg> and <http://healthmap.org/promed/p/6632>

Brazilian states and regions:

<http://www.v-brazil.com/>

 

Pictures

Leaf rust on soybean:

<http://www.ent.iastate.edu/images/plantpath/soybean/asianrust/asian_soyrust_lesions.jpg>,

<http://www.state.nj.us/agriculture/plant/soybeanrust.jpg>, and <http://www.wbhm.org/pics/features/soybean-icon.jpg>

Electron microscopy of leaf rust spores:

<http://www.wbhm.org/pics/features/soybean-spores.jpg>

 

Links

Information on soybean leaf rust:

<http://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/SoybeanRust.aspx>

and

<http://nt.ars-grin.gov/taxadescriptions/factsheets/index.cfm?thisapp=Phakopsorapachyrhizi>

Disease history and pathogen evolution:

<http://www.scielo.br/scielo.php?pid=S1415-47572008000500020&script=sci_arttext>

_P. pachyrhizi_ taxonomy:

<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=121037>

_P. meibomiae_ taxonomy:

<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=102469>

Information on strobilurins:

<http://www.ibwf.de/ibwf_his&act_en.htm>,

<http://www.answers.com/topic/strobilurin>, and <http://grounds-mag.com/mag/grounds_maintenance_strobilurin_fungicides_natures/index.html>

- Mod.DHA]

 

[See Also:

2012

----

Leaf rust, soybean - Brazil: (MT), pathogen reservoirs

20120911.1287887

2010

----

Nematodes, white mould, rust, soybean - Brazil: (BA, MT)

20100408.1128

Frogeye & leaf rust, soybean - Argentina, Brazil 20100207.0420 Asian leaf rust, soybean - Cuba: 1st rep. 20100204.0374

2009

----

Fungal diseases, soybean - USA 20090817.2912 Leaf rust, soybean - Brazil: new strains 20090501.1644 Leaf rust, soybean - USA: update 20090428.1594 Leaf rust, soybean - Australia: (NSW) alert 20090407.1351

2008

----

Soybean diseases - USA: (LA) 20081012.3231 Asian soybean rust - USA, Mexico: update 20080928.3070

2007

----

Asian soybean rust - USA: 2007 final report 20071230.4184 Asian soybean rust - Canada: 1st report, (ON) 20071120.3751 Asian soybean rust - Congo DR: 1st report 20070917.3086 Asian soybean rust - Ghana: 1st report 20070820.2710

2006

----

Soybean rust, Asian strain - Brazil 20060611.1628 Soybean rust - Mexico: 1st report 20060219.0546 and older items in the archives] 



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


Website: http://www.isid.org

Published: January 2, 2015

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