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International Society for Infectious Diseases <http://www.isid.org>
October 3, 2007
Source: The News International [edited]
<http://www.thenews.com.pk/daily_detail.asp?id=74441>
Bacterial leaf blight (BLB) has attacked rice crops in the
country as 50 000 acres (20 234 hectares) of cultivated land in
Sindh and large areas of Narowal, Sheikhupura, Sialkot, and
Hafizabad districts of Punjab have been affected by the disease.
The pest attack would definitely slash production of rice in the
country this year [2007], which would eventually reduce foreign
exchange earnings.
In a statement issued on Tuesday [2 Oct 2007], Chairman of the
Rice Committee of Kisan Board Pakistan, Aman Ullah Chatha,
stated that last year (2006-07) the area cultivated with rice
crop rose 0.2 percent to 258 000 acres (about 104 410 hectares),
but production dropped by 2 percent at 5438 million tonnes
against the target of
5693 million tonnes. He said during the last 4 years, BLB had
created problems for the rice growers but the agriculturists
failed to eradicate it or overcome the disease.
He said the stockists had reduced the price of the rice variety
386 from PKR 700 (USD 11.53) per 40 kg to PKR 575 (USD 9.47).
So, like in the past they would again mint money and the growers
would fail to get advantage of their crop, he remarked. He
demanded the government take the necessary steps to stabilise
rice prices, as the stockist mafia would again create artificial
shortages like they did in the case of wheat.
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[Bacterial leaf blight (BLB) of rice is caused by _Xanthomonas
oryzae_ pv. _oryzae_ (previously _X. campestris_ pv. _oryza_).
It was 1st noticed in Japan in 1884 and has since been reported
from Asia, northern Australia, Africa, and the USA. The pathogen
causes yellowing and drying of leaves, wilting of seedlings, and
reduces yield. In Asia, millions of hectares of rice paddies are
severely affected every year with reported yield losses of up to
60 percent.
Mild strains of the bacterium are also known, for example in the
USA, which do not cause any detectable yield loss.
Blight lesions caused by severe strains of the bacterium
elongate over the entire length of the flag leaf, giving a
striped appearance to leaves. Lesions caused by mild strains are
usually only a few centimeters long. Various saprophytic fungi
may invade the lesions, contributing to the damage. Panicles may
be infected by the severe strains. Field patches infested with
bacterial blight have a whitish, ragged appearance.
The bacterium is short-lived in soil and suspected to be
seedborne, but also to be short-lived in seeds. Grassy weeds,
infected plant material, such as rice stubble or ratoons, and
contaminated irrigation systems are thought to be the primary
pathogen reservoirs.
The disease spreads by windblown rain and mechanical means (for
example when transplanting seedlings) and is favoured by rain,
high levels of fertilizer, high humidity, standing pools of
water, and temperatures above 25 deg C (77 deg F).
A different pathovar (strain) of the same species, _X. oryzae_
pv.
_oryzicola_ causes bacterial leaf streak of rice. It occurs in
Asia and West Africa and yield losses of up to 30 percent have
been recorded. Symptoms vary early on, but in the later stages
of the disease look similar to BLB.
Variety 386 is a cultivar of basmati long grain rice suitable
for rain fed cultivation in lowlands. India and Pakistan are the
largest producers of basmati rice. Basmati plants are delicate,
prone to breaking, and have a relatively low yield, but produce
high-quality grains.
Map of Pakistan
<http://www.lib.utexas.edu/maps/middle_east_and_asia/pakistan_pol_2002.jpg>
Pictures
BLB symptoms on leaves and whole plants via:
<http://www.invasive.org/browse/subject.cfm?sub=11182>
Comparison of BLB effect on resistant and susceptible cultivars:
<http://www.tari.gov.tw/tarie/photos/introduction/introduction_PPD_02.jpg>
Links
BLB disease information:
<http://www.knowledgebank.irri.org/riceDoctor_MX/Fact_Sheets/Diseases/Bacterial_Leaf_Blight.htm>
and
<http://www.oisat.org/pests/diseases/bacterial/bacterial_leaf_blight.html>
Comprehensive BLB review:
<http://www.ias.ac.in/currsci/dec101999/REVIEWARTICLE.PDF>
Information on rice diseases, including BLB:
<http://msucares.com/pubs/publications/p1840.htm>
Information on rice bacterial leaf streak:
<http://www.knowledgebank.irri.org/riceDoctor_MX/Fact_Sheets/Diseases/Bacterial_Leaf_Streak.htm>
Genus _Xanthomonas_ taxonomy and species list:
<http://www.bacterio.cict.fr/xz/xanthomonas.html>
Details of rice varieties:
<http://dacnet.nic.in/rice/Rice%20Varieties%20-%2008.htm>
Information on Punjab:
<http://pportal.punjab.gov.pk/portal>.
- Mod.DHA Information on Sindh:
<http://www.sindh.gov.pk/>. - CopyEd.MJ]
[see also in the
archive:
Bacterial leaf blight, rice - India (Punjab) 20070824.2775
2005
----
Flag smut, bacterial leaf blight, rice - India (Punjab &
Haryana) 20050927.2841]
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