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: March 6, 2009
Source: University of Arkansas, Division of Agriculture News
[edited] <http://www.uaex.edu/news/march2009/0306riceseed_importation.htm>
University warns of disease problems if California rice seed
imported
A shortage of medium grain rice seed in Arkansas has prompted
some desperate dealers and growers to search for other seed
sources out of state, including California. The problem is that
there is a quarantine on seed imports from California because of
bakanae disease, according to Dr Rick Cartwright, University of
Arkansas.
"This is a seed-borne disease of rice common in Asia, and first
noted in California in 1999. It is not known to be present in
Arkansas or other southern rice states," Cartwright said.
The disease is caused by a fungus that, once it becomes
established, can't be eliminated, Cartwright said. The seed
can't be effectively cleaned of infection, he said. The disease
builds up in seed and mainly causes problems for seed producers.
He said, importing and planting California grains will represent
high risk to the Arkansas's rice industry. "We're not sure if
other states are preventing this risky seed movement at this
time, although our State Plant Board is advising them to be
aware of the situation."
The California varieties aren't adapted to Arkansas growing
conditions. "They will get killed by rice blast, a major
Arkansas rice disease," he said. California varieties are
extremely susceptible to the races of the blast fungus present
in Arkansas, Cartwright noted, and in the 1990's were heavily
damaged by it. He said the leaves were dead within 7 days and
fungicide applications were ineffective. "California rice
breeders have been working on blast resistance, but it's only to
the race they have."
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[Bakanae disease of rice (also called foot rot in some Asian
countries) is caused by the fungus _Gibberella fujikuroi_ and
can cause significant crop losses of up to 20 percent. The
fungus also affects other crops, including barley, maize,
sorghum, sugarcane, tomato, banana, and cowpea. Symptoms on rice
include abnormal growth patterns, death of seedlings, reduced
tillering, and partially filled or empty seed heads. The fungus
infects plants through roots or crowns and later becomes
systemic. Seeds are usually infected during the flowering stage
and the disease is primarily seed-borne. The fungus survives
under adverse conditions in infected seeds and diseased plant
parts. Disease management is difficult and includes use of
certified clean seeds and fungicides, however rapid development
of pathogen resistance has been observed.
Rice blast is caused by the fungus _Magnaporthe grisea_
(synonyms _Pyricularia grisea_, _P. oryzae_) with potential
yield losses of more than 50 percent. The fungus can affect
leaves, neck, collar, and nodes. Spread occurs with infected
plant material, by mechanical means, water, and wind. Disease
management may include fungicides and cultural practices, but
relies mainly on resistant varieties.
However, the fungus is highly variable and this favours the
emergence of new strains with increased virulence. For more
information on rice blast see links and previous posts below.
Maps
USA:
<http://www.mapsofworld.com/usa/usa-road-map-enlarge-view.html>
and <http://healthmap.org/r/006o>
US states:
<http://www.census.gov/geo/www/us_regdiv.pdf>
Pictures
Bakanae symptoms and fungal spores:
<http://plantpro.doae.go.th/diseasegroup/rice/bakanae/bakanae.jpg>
Rice blast symptoms:
<http://www.imtech.res.in/raghava/rbpred/lesion.jpg>
(leaf), <http://www.plantpath.ksu.edu/FCKUploads/Image/ValentLab/Neck-Blast-web.jpg>
(neck), and
<http://www.knowledgebank.irri.org/ricebreedingcourse/blast.jpg>
(leaf, collar, node, and neck)
Links
Bakanae disease fact sheet (with pictures):
<http://www.knowledgebank.irri.org/RiceDoctor/Fact_Sheets/Diseases/Bakanae.htm>
_G. fujikuroi_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=265414>
Rice blast fact sheets (with pictures):
<http://www.knowledgebank.irri.org/ricedoctor/default.htm#Fact_Sheets/Diseases/Rice_Blast.htm>
and
<http://www.knowledgebank.irri.org/RiceDoctor/Fact_Sheets/Diseases/blast.htm>
Information on rice blast:
<http://www.ikisan.com/links/ap_riceDetailedStudyofDiseases.shtml>,
<http://www.imtech.res.in/raghava/rbpred/home.html>
and <http://ascus.plbr.cornell.edu/blastdb/about.html>
_M. grisea_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=317113>
University of Arkansas, Plant Pathology:
<http://aaes.uark.edu/plpt.html>.
- Mod.DHA]
[see also
in the
archive:
2008
----
Blast disease, rice - India (02): (HAR) 20081224.4051 Foot rot &
false smut, rice - India 20080929.3080 Blast disease, rice -
India: (JK) 20080919.2935 Blast disease, rice - Guyana
20080812.2491 Yellow mottle & blast diseases, rice - Uganda
20080504.1527 Blast disease, rice - Kenya (02): (CP)
20080421.1413 Blast disease, rice - Kenya (CP) 20080402.1211
Virus & blast diseases, rice - Viet Nam (Mekong Delta)
20080204.0454
2005
----
Rice blast fungus, genome sequence - China 20050424.1147
2001
----
Magnaporthe grisea, rice blast - Vietnam 20010214.0298 2000
----
Rice blast: new method of control (02) 20000928.1678 Rice blast:
new method of control 20000825.1419
1998
----
Rice blast - USA (California) 19980224.0361]
Date: Sun 15 Mar 2009
From: Jack Woodall <woodall@promedmail.org>
On 6 Mar 2009, the University of Arkansas, Division of
Agriculture, put out a warning of potential problems because of
bakanae disease if Californian rice seed is imported into
Arkansas to replace a shortage of local seed [ProMED-mail post
no. 20090313.1029].
It was said that this is a seed-borne disease and not known to
be present in Arkansas or other southern states. The fungus
poses a high risk to rice and also affects other crops. Letting
it loose in Arkansas would be a major, irrecoverable disaster.
On top of that, Californian rice varieties would be useless due
to their high sensitivity to Arkansas rice blast strains.
What concerns me is the further statement, "We're not sure if
other states are preventing this risky seed movement at this
time, although our State Plant Board is advising them to be
aware of the situation."
I recall the sad story of the attempted eradication of _Citrus
tristeza virus_ [CTV] in California, where citrus growers
refused to fell their trees in order to protect their neighbors'
orchards, so that now the disease is endemic (see ProMED-mail
post no.
20080305.0899). In that update ProMED commented: "It appears
that a short sighted decision 10 years ago has led to the
present problem.
As a result of ignoring scientific advice at the time, much more
expensive measures are now necessary to ameliorate the effect of
CTV on the industry than would have been needed to maintain the
CTV-free status of the trees used for providing budwood."
Are we going to see the same short-sighted, self-serving actions
from Arkansas rice growers, who may be willing to risk importing
diseased seed rather than having no rice crop, regardless of
what they will let loose in the state, which could spread to
other crops there besides rice, and to every other rice-growing
state? Are other states going to refrain from somehow obtaining
Californian seed and passing it off to Arkansas as local grown?
Is there going to be an efficient plant quarantine this time?
Precedent does not encourage optimism.
Perhaps concerned ProMED-PLANT readers would care to contact
state agricultural officials and insist on a properly supervised
[quarantine] ban. ProMED-mail would be interested to hear of any
developments regarding this particular problem.
--
Jack Woodall
Associate Editor, ProMED-mail
Rio de Janeiro
Brazil
<woodall@promedmail.org>
[To prevent introductions of plant pathogens or to attempt
eradication of new incursions, any official measures cannot be
effective without the informed cooperation and positive support
of growers and the general public (for example, see ProMED-mail
post no. 20090206.0528 on successful eradication of citrus
canker in Australia). These are long-term commitments for the
benefit of national agricultural industries and depend on the
individual as much as governments. - Mod.DHA]
[see also
in the
archive:
Rice diseases - USA: quarantine 20090313.1029
Citrus canker - Australia: (QLD) eradicated 20090206.0528
2008
----
Citrus tristeza - USA: research station (CA), update
20080305.0899
2007
----
Citrus tristeza virus, research station - USA (CA)
20070528.1710]
