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: January 2017
Source: Plant Disease [edited]
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-04-16-0448-RE>
[Ref: S Sun et al (2017): An emerging disease caused by _Pseudomonas syringae_ pv. _phaseolicola_ threatens mung bean production in China.
Plant Disease 101, 95-102; doi: 10.1094/PDIS-04-16-0448-RE]
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An emerging bacterial disease with symptoms resembling those of halo blight is threatening mung bean production in China. This study was conducted to investigate the disease's geographic distribution in China using consecutive multiyear field surveys and to confirm the causative agents' identity.
The surveys were conducted in 15 provinces covering 7 geographic regions from 2009 to 2014. The survey results revealed that the emerging mung bean disease has rapidly spread and is prevalent in 3 of the main Chinese geographic regions, which contain more than 90 per cent of the mung-bean-growing areas in China.
To confirm the causal agent, diseased mung bean leaves were collected from the surveyed fields and used to isolate the pathogen. A bacterium was consistently isolated from all of the collected leaves. Based on the phenotypic characteristics, the physiological and biochemical properties, pathogenicity tests, and fatty acid composition, in combination with specific polymerase chain reactions and 16S-23S ribosomal DNA sequence analyses, the bacterium was identified as _Pseudomonas syringae_ pv. _phaseolicola_.
To our knowledge, this is the 1st report of _P. syringae_ pv. _phaseolicola_ causing halo blight on mung bean in China. The results indicate that [the bacterium] is likely of epidemiological significance on mung bean in China.
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Communicated by: ProMED-mail <promed@promedmail.org>
[Halo blight (or grease spot) caused by the bacterium _Pseudomonas syringae_ pv. _phaseolicola_ affects a range of legumes, including species of _Phaseolus_ (common, French, runner, Lima beans), _Vigna_ (cowpea, mung bean), peas, and soybean.
Symptoms of halo blight may include water soaked leaf spots which develop into brown necrotic spots with a yellow halo, water soaked
("greasy") and later necrotic spots on pods, defoliation, as well as stem cankers which may kill the plant. Seeds may be shrivelled, but heavily contaminated seeds may also appear healthy. The disease is favoured by humid conditions.
The pathogen overwinters mainly on seed, but also on undecomposed plant debris. It is seed transmitted and also spread by water (rain, irrigation), wind, mechanical means (including animal and human activities), plant material and equipment. Disease management may include cultural practices, crop rotation and phytosanitation to prevent spread. Use of certified clean seed is essential. Chemical control (copper compounds, antibiotics) may be effective, but resistant strains have emerged for some of the pathovars. Varieties with different levels of resistance are available, at least for some of the _Phaseolus_ hosts.
Over 40 different pathovars of _P. syringae_, grouped into several races, are known. The pathogens can affect a wide variety of plants and new diseases are emerging frequently. Symptoms may include leaf specks, blights and cankers on crops such as tomato, maize, mango, soybean, citrus, sweet chestnut and stone fruit.
Maps
China:
<http://geology.com/world/china-map.gif> and <http://healthmap.org/promed/p/155>
China provinces:
<http://www.diversechina.com/images1/chinamap.jpg>
Pictures
Halo blight symptoms on bean pods:
<http://vegetablemdonline.ppath.cornell.edu/Images/Impt_Diseases/5C_Bean_Halo.jpg>
and
<http://vignette2.wikia.nocookie.net/gardener/images/1/1a/French_Bean_Halo_Blight.jpg/revision/latest?cb=20100720214457>
Leaf symptoms of halo blight:
<http://www.infonet-biovision.org/res/res/files/1033.400x400.jpeg>
and
<http://cropgenebank.sgrp.cgiar.org/images/management/common_bean_smogs/halo%20blight.png>
Links
Information and hosts for halo blight:
<http://cropgenebank.sgrp.cgiar.org/index.php?option=com_content&view=article&id=535&Itemid=727#bacterial_halo_blight>,
<http://tinyurl.com/zqaqpyt>,
<http://cropwatch.unl.edu/plantdisease/drybean/halo-blight>, and <http://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=44987>
Bean bacterial diseases, including halo blight:
<http://mtvernon.wsu.edu/path_team/FS038E-CommonBacterialBlightAndHaloBlight.pdf>,
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Bean_List.htm>,
and
<http://ipm.illinois.edu/diseases/series900/rpd921/>
_P. syringae_ pv. _phaseolicola_ taxonomy:
<http://www.uniprot.org/taxonomy/319>
- Mod.DHA]
[See Also:
2012
----
Curtobacterium wilt, soybean - Germany: 1st rep, (TH)
http://promedmail.org/post/20120809.1235745
2010
----
Halo blight, broad bean - Spain: (AS)
http://promedmail.org/post/20100812.2763
2005
----
Soybean rust, Asian strain, kudzu control http://promedmail.org/post/20051006.2914]
Topics
Species
