BACTERIAL LEAF BLIGHT, RICE - PAKISTAN (SINDH, PUNJAB)
- BACTERIAL LEAF BLIGHT, RICE - PAKISTAN (SINDH, PUNJAB)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Wed 3 Oct 2007
Source: The News International [edited]
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 ,
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.
[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,
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
BLB symptoms on leaves and whole plants via:
Comparison of BLB effect on resistant and susceptible cultivars:
BLB disease information:
Comprehensive BLB review:
Information on rice diseases, including BLB:
Information on rice bacterial leaf streak:
Genus _Xanthomonas_ taxonomy and species list:
Details of rice varieties:
Information on Punjab:
<http://pportal.punjab.gov.pk/portal>. - Mod.DHA
Information on Sindh:
<http://www.sindh.gov.pk/>. - CopyEd.MJ]
Rana Jawad Asghar MD. MPH.
Coordinator South Asian Public Health Forum
Typhoid Net http://www.typhoid.net