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: April 14, 2008
Source: UN Integrated Regional Information Networks (IRIN)
[edited]
<http://www.irinnews.org/Report.aspx?ReportId=77752>
Over the past week the retail price of rice has held steady. But
in Dhaka long queues continued outside government open market
sales centres. Although this month's [April 2008] 'boro' rice
harvest, which accounts for some 60 percent of the country's
yield, is expected to be a bumper one, severe crop losses as a
result of monsoon floods last year [2007], coupled with a
devastating cyclone, have helped keep stocks low.
Bacterial leaf blight (BLB), a serious rice disease, also poses
a threat to stocks, but agriculture adviser CS Karim was
optimistic this week, saying 'boro' production would exceed the
target this year [2008] thanks in part to proper remedial
measures having been taken.
His optimism was echoed by researchers and agricultural experts
at Bangladesh Agricultural University who said the BLB outbreak
in many areas would probably not cause extensive damage to the
'boro' yield.
However, Bangladesh's is far from being out of the woods, with
government officials predicting the "crisis" likely to last
quite some time. "Bangladesh could have a food surplus if
different rice strains were grown properly. Good seeds, good
plants, balanced growth of crops, and efficient irrigation at
the right time can produce 6 to
7 metric tonnes of food grains per hectare," MA Hamid, a
scientist at the International Rice Research Institute [IRRI],
said.
--
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 first 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.
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. Mild strains may not cause
any detectable yield loss. Various saprophytic fungi may invade
the lesions, contributing to the damage. Panicles may also be
infected by 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 fertiliser, high humidity, standing pools of
water, and temperatures above 25 deg C (77 deg F).
Boro rice is an irrigated, high-yielding, cold-tolerant,
relatively pest-free, and photoperiod-insensitive rice
cultivated during the winter months in India and Bangladesh.
Other types of rice grown in the region are 'amon' and 'aus'. In
addition to BLB, these have been reported to be currently
affected in Bangladesh by other diseases as well (see
ProMED-mail post no. 20071030.3524). Recent outbreaks of BLB
have also been reported from India and Pakistan (see previous
ProMED-mail posts listed below).
Maps
Bangladesh:
<http://www.lib.utexas.edu/maps/middle_east_and_asia/bangladesh_pol96.jpg>
and <http://healthmap.org/promed?v=23.8,90.3,5>
Districts and cities:
<http://www.mapsofworld.com/bangladesh/bangladesh-political-map.html>
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/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>
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>
Bangladesh Rice Research Institute:
<http://brri.gov.bd/>
IRRI:
<http://www.irri.org>. -
Mod.DHA]
[see also in
the
archive:
2007
----
Rice diseases - Bangladesh 20071030.3524 Bacterial leaf blight,
rice - Pakistan (Sindh, Punjab) 20071005.3293 Bacterial leaf
blight, rice - India (Punjab) 20070824.2775
2005
----
Flag smut, bacterial leaf blight, rice - India (Punjab &
Haryana) 20050927.2841]