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First report of powdery mildew caused by Oidium neolycopersici on tomato in China

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A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases

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

[1] Henan
Date: September 2008
Source: The American Phytopathological Society, Plant Disease 2008; 92(9): 1370 [edited]
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-92-9-1370C>

[Ref: CW Li et al: First report of powdery mildew caused by _Oidium neolycopersici_ on tomato in China. Plant Dis 2008; 92(9): 1370; DOI: 10.1094/PDIS-92-9-1370C]

Tomato powdery mildew can cause remarkable reduction in fruit size and quality. In March of 2008, powdery mildew appeared as circular, white colonies on leaves, petioles, and stems of tomato plants grown in greenhouses in Shangqiu, Henan Province, China. The pathogenic fungus had unbranched conidiophores, conidia were hyaline, elliptical, and were borne singly. Average length and width of conidia were 30.6 and 15.1 micrometer, respectively. Germ tubes were straight and formed at the ends or very close to the ends of conidia.
_Chasmothecium_ was not found in the collected samples.

Different tomato cultivars and species, including _Lycopersicon esculentum_ cultivars, _L. peruvianum_, and _L. hirsutum_, were inoculated with a conidial suspension. Plants developed powdery mildew symptoms as early as 4 days after inoculation. Symptoms developed on all _L. esculentum_ cultivars, while _L. peruvianum_ and _L. hirsutum_ displayed complete resistance, which is similar to previous results. Morphological characteristics of the pathogen on susceptible genotypes were similar to those from naturally infected plants.

On the basis of the characteristics of the asexual stage, the pathogen was identified as an isolate of _Oidium neolycopersici_, which was confirmed by internal transcribed spacer (ITS) sequence analysis. The nucleotide sequence had a 100 percent homology with 10 ITS sequences of _O. neolycopersici_ in GenBank [data base].

In Asia, the spread of this pathogen has been recently reported in Japan. To our knowledge, this is the 1st report of tomato powdery mildew in China.

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ProMED-mail
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[2] Changchun
Date: January 2008
Source: British Society for Plant Pathology, New Disease Reports (NDR) vol. 16 [edited]
<http://www.bspp.org.uk/ndr/jan2008/2008-03.asp>

[Ref: SY Liu et al: Powdery mildew on tomato caused by _Oidium neolycopersici_ in Changchun in China. BSPP New Disease Reports vol. 16]

A powdery mildew was observed on tomato (_Solanum lycopersicum_, formerly _Lycopersicon esculentum_) in greenhouses in Changchun in September 2006. Mildew first appeared as white circular patches on the adaxial leaf surface (Fig.1). As the disease progressed, abaxial leaf surface, stems, and petioles were covered by cotton-like masses of mycelia and conidia. Yellow lesions appeared on the abaxial surfaces, which turned necrotic and led to defoliation. Young plants (cotyledon period) through to flowering plants were affected, while the fruits remained free from infection. The latent period of this disease was 5-7 days. The fungus from tomato also infected tobacco
(_Nicotiana tabacum_) by inoculation but the symptoms on tobacco were usually small and localized.

The morphological characteristics of the fungus fit _Oidium neolycopersici_. In June 1988, tomato powdery mildew was found in Xinjiang, and the pathogen was identified as _Oidiopsis taurica_. _Oidium neolycopersici_ clearly differs from _Oidiopsis taurica_ by its ectophytic nature. In 1991, tomato powdery mildew was found in Shengyang and the pathogen identified as _Erysiphe polygoni_. In 2003 tomato powdery mildew in Shengyang was identified as _Oidiopsis lycopersici_. _Oidium neolycopersici_ sometimes forms conidiophores with pseudo-chains in humid conditions, and has been confused with _Oidiopsis lycopersici_ with conidia produced in chains. This is the 1st report of tomato powdery mildew caused by _Oidium neolycopersici_ in Changchun in China.

Figure 1: Symptoms of tomato powdery mildew.
<http://www.bspp.org.uk/ndr/jan2008/2008-03-1.jpg>
Figure 2: Conidia (A) and conidiophore (B) of Oidium neolycopersici.
<http://www.bspp.org.uk/ndr/jan2008/2008-03-2a.jpg>  and
<http://www.bspp.org.uk/ndr/jan2008/2008-03-2b.jpg>

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[Powdery mildews are a group of fungi causing similar symptoms on a range of host plants. The group includes many species in a number of genera. Generally, each fungal species is confined to a number of host species it affects. The pathogens cause serious losses in many important crops including cereals, hops, canola, sugar beet, and a number of vegetable crops. Leaves heavily infected by powdery mildew have reduced photosynthetic ability resulting in decreased plant vigour. Spores are spread mainly by splashing rain, wind, or mechanical means. The fungus overwinters in infected leaves on the ground. The disease can be extremely serious and cause severe crop losses. It is usually controlled with fungicides.

It appears that item [2] was published earlier but was missed when item [1] was written and published. Item [2] appears to be really the 1st report of _Oidium neolycopersici_ in China.

Maps
China:
<http://www.chinapage.com/map/map.html> and
<http://healthmap.org/promed?v=36.5,103.9,4>
Chinese provinces via:
<http://www.maps-of-china.com/>

Pictures of _O. neolycopersici_ on tomato leaves:
<http://plante-doktor.dk/Oidium%20neolycopersici%201.jpg>,
<http://botany.upol.cz/atlasy/system/images/ascomycetes/erysiphales/oidium-neolycopersici2.jpg>

Links
Powdery mildews of tomato:
<http://www.ipm.ucdavis.edu/PMG/r783100411.html>,
<http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7406.html> and
<http://www.oisat.org/pests/diseases/fungal/powdery_mildew.html>
General information on powdery mildews:
<http://plantclinic.cornell.edu/FactSheets/powdery/powdery.htm>,
<http://www.ext.colostate.edu/pubs/garden/02902.html>  and
<http://gardening.about.com/od/gardenproblems/a/PowderyMildew.htm>
_O. neolycopersici_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=467775>. 
- Mod.DHA]

[see also in the archive:
Mildews, grapevine - USA: new strains 20080327.1152
Fungal pathogens, wheat - UK (England) 20080319.1055
Fungal diseases, grapevine - Australia, South Africa 20080310.0969
2007
----
Foliar diseases, brassica crops - UK 20070913.3037
Cercospora & powdery mildew, sugar beet - UK 20070801.2478
Downy and powdery mildews, grapevine - France (02) 20070724.2368
Downy & powdery mildews, grapevine - France 20070720.2323
Fungal diseases, sugar beet and barley: alert 20070628.2078
Powdery mildew, mango - Pakistan 20070611.1900
Fungal pathogens, wheat - United Kingdom: new races 20070523.1652
Powdery mildew, watermelon - USA: resistance breeding 20070422.1320
2006
----
Cereal diseases, fungal - Russia, Kazakhstan 20060816.2298
2005
----
Powdery mildew, tomato, pepper - Bolivia : 1st report 20050628.1830
2004
----
Powdery mildew, race 2, melon - Brazil (SP) 20041128.3179
Powdery mildew, canola - Argentina 20041101.2956
Powdery mildew, sugar beets - USA (NE) 20040825.2375
Powdery mildew, Podosphaera sp., cowpea - Turkey 20040118.0200
2003
----
Powdery mildew, pepper - Canada (BC) 20030820.2089
2001
----
Powdery mildew, pepper - USA (New York) 20011101.2711]

 

 

 

 

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