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International Society for Infectious Diseases <http://www.isid.org>
Date: February, 2008
Source: The American Phytopathological Society, Plant Disease
2008; 92(2): 313 [edited]
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-92-2-0313C>
[Reference: AM Al-Sa'di, et al: First report of _Pythium
splendens_ associated with severe wilt of muskmelon (_Cucumis
melo_) in Oman.
Plant Dis 2008; 92(2): 313; DOI: 10.1094/PDIS-92-2-0313C]
Muskmelon (_Cucumis melo_ L.) is one of the most important
vegetable crops in Oman. In the fall of 2004, sudden wilt was
observed in muskmelon grown in a field at Sultan Qaboos
University, Muscat. The disease was characterized by rapid
collapse of vines and muskmelon plants at the fruit production
to maturation stage, associated with brown to dark brown rotted
primary and secondary roots. The disease resulted in death of
more than 85 percent of muskmelon plants in that field.
_Pythium_ spp. were consistently isolated from crowns and roots
of plants showing wilt symptoms. Further identification of 5
isolates of _Pythium_ produced a nucleotide sequence 806
basepairs long, which was identical among all isolates.
Comparison with sequences deposited at the National Center for
Biotechnology Information revealed 100 percent nucleotide
similarity to a previously published sequence of an isolate of
_P. splendens_ from cucumber from Oman, for which identification
has also been confirmed by morphological characteristics.
In pathogenicity tests conducted in a greenhouse, _P. splendens_
induced damping-off symptoms on 7-day-old muskmelon seedlings
and also reproduced the same wilt symptoms observed in the field
when 2-month-old muskmelon plants were inoculated with 3-day-old
_P. splendens_ cultures. To our knowledge, this is the 1st
report of association of _P. splendens_ with wilt of muskmelon
in Oman.
--
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[Fungal diseases called sudden or severe wilt of melon occur in
many areas of the world, particularly in arid and semi-arid
areas, and can cause severe yield losses. The term is a generic
name for plants that suddenly die at or around fruit filling and
is associated with fungal root infection and plant stress
occurring at fruit set. Several
soil-borne fungi can be associated with the symptoms, including
several species of _Pythium_, which destroy the plant feeder
roots and invade larger roots, thus restricting water uptake.
The high demand for water during fruit enlargement cannot be met
following this invasion, and the vine wilts and plant death
follows with immature fruits. The fungi can be spread by soil
and infected plant material. Disease management includes
cultural practices and use of resistant varieties. Soil
fumigation and some fungicide treatments have been found to be
of limited use.
_P. splendens_ is found in many areas of the world on a wide
range of hosts, including crops such as taro and oilpalm, but
has rarely been reported as being associated with sudden wilt of
cucurbits. It has, however, been reported as one of the main
causal agents of melon wilt in Japan.
Maps of Oman:
<http://meteorites.wustl.edu/oman.jpg>
and
<http://healthmap.org/promed?v=20.6,56.1,5>
Pictures of sudden wilt symptoms on melon:
<http://www2.dpi.qld.gov.au/images/8223.jpg>,
<http://www2.dpi.qld.gov.au/images/8222.jpg>
and
<http://www2.dpi.qld.gov.au/images/8170.jpg>
Links
General information on sudden wilt diseases of melons:
<http://www2.dpi.qld.gov.au/horticulture/11648.html>
_P. splendens_ causing melon wilt in Japan:
<http://sciencelinks.jp/j-east/article/200702/000020070207A0024751.php>
and
<http://www.niast.go.kr/workpds/workpdsDown.asp?idx=3378&tG=1>
Biocontrol of _P. splendens_ on melon:
<http://www.fao.org/agris/search/display.do;jsessionid=790E8046426152BA03116FAE1B4540AA?f=./2004/v3005/IT2004060931.xml;IT2004060931>
Information on _Pythium_ species:
<http://taropest.sci.qut.edu.au/LucidKey/TaroPest/Media/Html/Fungi/Pythium/Pythium3.htm>
_P. splendens_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=278667>.
- Mod.DHA]
