Friday, September 14, 2018

PRO/PL> Blast & bacterial leaf blight, rice - India

BLAST DISEASE AND BACTERIAL LEAF BLIGHT, RICE - INDIA
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In this posting:
[1] Bacterial leaf blight - Kerala
[2] Blast disease - Jammu and Kashmir

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[1] Bacterial leaf blight - Kerala
Date: Mon 10 Sep 2018 06:05 AM IST
Source: New Indian Express [edited]
<http://www.newindianexpress.com/states/kerala/2018/sep/10/crop-disease-deals-a-double-blow-to-kerala-peasants-1869846.html>


[In] Kerala, post the devastating floods, leaf blight disease
inflicted severe damage on paddy crops. Crops grown using an overdose
of nitrogen fertilisers had been affected the most as the bacterial
disease will be more virulent. The Agriculture Department found it
[in] crops which reached the booting and flowering stage.

"Even in the crops which survived the vegetative phase, the yield
could be very low," said M C Narayanankutty, Regional Agriculture
Research Station. The standing crop has been damaged along with seed
nurseries and beds. The rice from the affected areas will be broken
and the hay will also be in truncated form.

[Byline: A Satish]

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[2] Blast disease - Jammu and Kashmir
Date: Thu 13 Sep 2018
Source: Greater Kashmir [edited]
<https://www.greaterkashmir.com/news/business/rice-blast-disease-affects-paddy-in-karnah-areas/296261.html>


Farmers in Kupwara [district] expressed their resentment over outbreak
of rice blast disease in their area. A delegation said 75 per cent of
their paddy crop has been damaged by the disease. They accused [the]
Agriculture Department. "The department failed to provide necessary
chemical sprays to overcome rice blast," they said.

[Byline: Peerzada Sayeed]

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Communicated by:
ProMED-mail
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[Leaf blight
-----------
Bacterial leaf blight (BLB) of rice is caused by _Xanthomonas oryzae_
pv. _oryzae_ (Xoo). In Asia, millions of hectares of rice paddies are
severely affected every year, with reported yield losses of up to 60
per cent. The pathogen causes yellowing and drying of leaves and
wilting of seedlings. Blight lesions caused by severe strains elongate
over the entire length of the flag leaf, giving a striped appearance.
Severe strains may also affect panicles. Mild strains cause only small
leaf lesions and may not lead to any detectable yield loss. Various
saprophytic fungi may invade the lesions, contributing to the damage.
Field patches infested with bacterial blight have a whitish, ragged
appearance.

BLB is favoured by rain, high levels of fertilizer, high humidity,
standing pools of water and warm temperatures. The bacterium is
short-lived in soil and suspected to be seed borne 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 or by high insect activity).

Disease management usually includes phytosanitation (control of weed
and volunteer rice reservoir hosts, removal of contaminated
materials), cultural measures (optimal plant spacing and fertilizers)
and use of resistant crop varieties. Control of insect populations by
insecticides may help reduce the unspecific spread of bacteria via
their scratching and sucking wounds. Antibacterial sprays containing
antibiotics are rarely used because they often provide little benefit,
and agricultural application of antibiotics is strictly regulated in
most countries. The related _X. oryzae_ pv. _oryzicola_ causes
bacterial leaf streak of rice.

Blast
-----
Rice blast is caused by the fungus _Pyricularia oryzae_ (previously
_Magnaporthe oryzae_). It is one of the most destructive diseases of
the crop worldwide, with potential yield losses of more than 50 per
cent. Symptoms include lesions on all parts of the shoot, as well as
stem rot and panicle blight. When nodes are infected, all plant parts
above the infection die and yield losses are severe. When infection
occurs at the seedling or tillering stages, plants are often
completely killed; infection late in the growth cycle generally leads
to less severe damage. Depending on which plant parts are affected,
the disease may manifest itself as leaf, collar, node or neck blast.
More than 50 species of grasses and sedges can be affected by related
pathogens, but most strains isolated from rice can only infect a
limited number of cultivars.

The fungus also causes wheat blast (for example, see ProMED-mail posts
http://promedmail.org/post/20170306.4883233 and
http://promedmail.org/post/20170123.4784298). Although the pathogens
are currently classified as the same species, the wheat blast pathogen
is a distinct population (referred to as _P. oryzae_ Triticum
population) and does not cause disease in rice.

Symptom severity and spread of the blast fungus are influenced by
climatic conditions, including high humidity. The disease is also
favoured by high nitrogen levels (for example from fertilizers). The
fungus is spread by infected plant debris, mechanical means (including
insect activity), 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. Use of certified
clean seed is essential, and farm saved seed poses a high risk of
carry-over of the fungus to subsequent crops.

Maps
India (with states):
<http://www.mapsofindia.com/maps/india/india-political-map.htm> and
<http://healthmap.org/promed/p/142>
Jammu and Kashmir districts:
<https://www.mapsofindia.com/maps/jammuandkashmir/jammuandkashmir-district.htm>

Pictures
BLB symptoms on rice leaves:
<http://agropedia.iitk.ac.in/sites/default/files/uas%20raichur/diseases%20of%20paddy/blb00.jpg>
and
<http://www.knowledgebank.irri.org/images/stories/bacterial-leaf-blight-4.JPG>
BLB affected rice plants:
<http://www.apsnet.org/edcenter/K-12/TeachersGuide/PlantBiotechnology/Article%20Images/fig34.jpg>
and
<http://www.invasive.org/images/768x512/0162037.jpg>
BLB affected rice field:
<http://www.apsnet.org/edcenter/advanced/topics/EcologyAndEpidemiologyInR/ModelingDispersalGradients/PublishingImages/BacterialBlight.jpg>
Droplets of Xoo exudate on leaf:
<http://www.invasive.org/images/768x512/0162038.jpg>
Rice blast symptoms:
<http://www.knowledgebank.irri.org/ricebreedingcourse/blast.jpg>
(different symptomatic forms) and
<http://www.imtech.res.in/raghava/rbpred/lesion.jpg>
Rice fields affected by blast:
<http://ucanr.edu/blogs/riceblog/blogfiles/22977_original.jpg> and
<https://previews.123rf.com/images/imagethink/imagethink1411/imagethink141100067/33260576-rice-blast-Stock-Photo.jpg>

Links
Aditional news story for item [2]:
<http://thekashmirimages.com/2018/09/12/continuous-water-flow-in-dobhi-canal-inundates-paddy-fields-in-tullamula/>
BLB of rice, disease information:
<http://www.knowledgebank.irri.org/decision-tools/rice-doctor/rice-doctor-fact-sheets/item/bacterial-blight>,
<http://www.cabi.org/isc/datasheet/56956> (with distribution map),
<http://www.apsnet.org/publications/PlantDisease/BackIssues/Documents/1993Articles/PlantDisease77n01_5.pdf>
and via
<http://www.oisat.org/pests/diseases/bacterial/bacterial_leaf_blight.html>
_X. oryzae_ pv. _oryzae_ taxonomy:
<http://www.uniprot.org/taxonomy/64187>
Information on rice blast:
<http://www.knowledgebank.irri.org/training/fact-sheets/pest-management/diseases/item/blast-leaf-collar>
(with pictures),
<http://www.oisat.org/pests/diseases/fungal/rice_blast.html>,
<http://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=46103>,
and
<http://www.imtech.res.in/raghava/rbpred/home.html>
Rice blast disease cycle:
<http://www.imtech.res.in/raghava/rbpred/cycle.jpg>
Impact of rice blast (and other fungal crop diseases):
<http://onlinelibrary.wiley.com/doi/10.1111/j.1364-3703.2011.00783.x/full>
_P. oryzae_ taxonomy and synonyms:
<http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=224486>
and
<http://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=224486>
- Mod.DHA]

[See Also:
Virus & blast diseases, rice - Viet Nam: (Mekong Delta)
http://promedmail.org/post/20180712.5901134
Blast disease, rice - Bangladesh: (RJ)
http://promedmail.org/post/20180419.5756531
2017
----
False smut & blast, rice - Bhutan, India
http://promedmail.org/post/20171102.5419405
Blast disease, rice - India: (JK)
http://promedmail.org/post/20170725.5202371
Blast disease, rice - Bangladesh
http://promedmail.org/post/20170428.5000484
Bacterial leaf blight, rice - Philippines: (NS)
http://promedmail.org/post/20170327.4927699
2016
----
Bacterial leaf blight, rice - India: (TN)
http://promedmail.org/post/20161228.4729157
Bacterial leaf blight, rice - Bangladesh: (RJ)
http://promedmail.org/post/20161101.4598659
Bacterial leaf blight, rice - Viet Nam: (Mekong Delta)
http://promedmail.org/post/20161014.4558824
Blast & sheath blight, rice - Philippines: (II)
http://promedmail.org/post/20160915.4489271
Blast disease, wheat & rice - Bangladesh
http://promedmail.org/post/20160419.4168271
Blast disease, rice - India (02): (JK) origin
http://promedmail.org/post/20160407.4145967
Bacterial leaf blight, rice - Peru: (PI)
http://promedmail.org/post/20160405.4138616
Blast disease, rice - India: (TN)
http://promedmail.org/post/20160108.3918812
2015
----
Bacterial leaf blight, rice - India: (TN)
http://promedmail.org/post/20151216.3868035
Neck blast, rice - India: (HR)
http://promedmail.org/post/20151014.3713941
Bacterial leaf blight, rice - Bangladesh: (DA)
http://promedmail.org/post/20151009.3702001
Blast disease, rice - Spain: (VC)
http://promedmail.org/post/20150903.3620399
Sheath blight, rice - India: (PB)
http://promedmail.org/post/20150831.3612426
Blast disease, rice - India: (TN)
http://promedmail.org/post/20150128.3124545
Rice diseases - Malaysia: (western) emerging strains
http://promedmail.org/post/20150108.3080315
2014
----
Leaf blight & sheath rot, rice - Bangladesh: (RJ)
http://promedmail.org/post/20141017.2872718
Blast disease, rice - India: (GA)
http://promedmail.org/post/20140417.2410154
Blast disease & bacterial blight, rice - Viet Nam: Mekong Delta, alert
http://promedmail.org/post/20140216.2282042
and additional items in the archives]
.................................................sb/dha/mj/jh
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