Published Date: 2009-12-14 15:00:03
Subject: PRO/PL> Sudden decline, mango - Oman
Archive Number: 20091214.4240

SUDDEN DECLINE, MANGO - OMAN
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Date: Sun 13 Dec 2009
Source: Oman Tribune [edited]
<http://www.omantribune.com/index.php?page=news&id=60344&heading=Oman>


Efforts under way to protect mango farming
------------------------------------------
Researchers from Sultan Qaboos University [SQU] and experts from the
Ministry of Agriculture jointly proceed with a strategy aimed at protecting
mango farming in Oman that has been passing through a phase of attack from
fungal pathogens for the past decade.

The Al Batinah coastal region, once known for opulent mango farms, has lost
its mango splendour due to the unexpected entry of a fungal disease. Since
2000, the number of mango trees in the Al Batinah region has been reduced
by more than a half. The symptoms of the disease include sudden browning of
the part of canopy of the trees, wilting of leaves, oozing from the trunk,
blackened wood under the bark, and small holes on the stem caused by a
beetle, which acts as the vector in spreading the disease. Trees normally
die within 6 to 12 months of getting infected.

Michael Deadman, of SQU, revealed that the Omani varieties of mango are
particularly susceptible to the disease. "In Oman, the pathogen first
attacked mango trees in the region of Barka. In areas of such high
intensity, many mango trees were doomed from the beginning. Then the
disease started spreading outwards. Now almost all areas of Oman are
affected," he added.

Some fungicides were effective against the decline. However, chemicals are
expensive for farmers and difficult to apply over large areas. Molecular
studies have revealed the complex aetiology of the disease. Deadman and his
fellow researchers identified 2 new species involved in the disease in
Oman. The species were named _Ceratocystis manginecans_ (manginecans means
"mango killer") and _Ceratocystis omanensis_. "Ultimately, resistance is
the only sustainable way to combat this plant disease," Deadman said.

Exotic rootstocks have been brought from various countries, including the
United States and Brazil. They are grafted with stems of local varieties to
produce trees, which should show resistance to the pathogen. Field tests
conducted under Omani conditions will ensure that the trees will be
healthy. It is expected that in 5 years the improved trees will be
available for farmers across the country.

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[The symptoms on mango described above are usually referred to as sudden
decline (or sudden wilt) in the Asian-Pacific region or "seca" disease in
Brazil. The disease is of great economic importance since the trees die
within a very short time. The fungi _Lasiodiplodia theobromae_ or/and
_Ceratocystis fimbriata_ have been reported to be associated with this wilt
in different areas, including in Oman (before the new additional species
were identified). Both pathogens can affect a range of hosts including
important crops.

It is thought that nutrient deficiencies and environmental stress factors
may increase the susceptibility of mango trees to sudden decline.
Fungicides may be helpful in disease management if applied quickly enough,
and mango varieties with different levels of sudden decline resistance are
available for different areas. The results of the programme set up in Oman
will show whether these genetic resources will be useful against the local
form of the disease involving at least four fungal species.

It appears that the presence of the new fungi in other areas still remains
to be investigated, but it has been proposed that the pathogens originally
classed as _C. fimbriata_ may actually represent a complex including a
number of separate species.

Maps of Oman:
<http://meteorites.wustl.edu/oman.jpg>
<http://healthmap.org/r/010w>
Pictures
_L. theobromae_ associated symptoms on mango
- gummosis and vascular discolouration:
<http://www.bspp.org.uk/publications/new-disease-reports/006/2002-44-1.jpg>,
<http://www.plantmanagementnetwork.org/elements/view.aspx?ID=1916>, and
<http://www.ctahr.hawaii.edu/nelsons/mango/mango_decline_stem_gummosis_1.JPG>
- branch dieback:
<http://www.bspp.org.uk/publications/new-disease-reports/006/2002-44-2.jpg>
and
<http://www.plantmanagementnetwork.org/pub/php/diagnosticguide/2004/mango/image/dieback1sm.jpg>
Links
Additional news story:
<http://www.khaleejtimes.com/darticlen.asp?xfile=data/middleeast/2009/December/middleeast_December255.xml§ion=middleeast&col>

Information on mango sudden decline:
<http://www.plantmanagementnetwork.org/pub/php/diagnosticguide/2004/mango/>,
<http://www.pakistan.gov.pk/divisions/food-division/media/Brief%20on%20Mango%20Die%20Back.pdf>,
and
<http://www.bspp.org.uk/publications/new-disease-reports/ndr.php?id=006018>
_L. theobromae_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=188476>
Diseases caused by _C. fimbriata_:
<http://www.public.iastate.edu/~tcharrin/FimbDis.html>
_C. fimbriata_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=167245>
_C. omanensis_, information and description:
<http://cat.inist.fr/?aModele=afficheN&cpsidt=17539886>
_C. omanensis_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=357390>
_C. manginecans_, information and description:
<http://www.fungaldiversity.org/fdp/sfdp/27_13.pdf>
_C. manginecans_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=510851>. -
Mod.DHA]

See Also

Lasiodiplodia dieback, cocoa - India: 1st rep (KA) 20090814.2892
Gummosis, mango - Bangladesh: (RJ) 20090504.1669
2008
---
Fungal diseases, mango - Australia, Pakistan 20080229.0832
2007
---
Anthracnose & stem-end rot, mango - Australia (NT) 20071110.3650
2002
---
Mango sudden decline - Oman (Al Batinah Region) 20021213.6053
Mango decline - Oman 20021209.6018
1999
---
Mango tree blight - Philippines 19990203.0153
Mango tree blight - Brazil (02) 19990203.0151

.................dha/mj/sh



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