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Blast disease on rice in Bangladesh


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: Wed 11 May 2022
Source: Fourals [summ. Mod.DHA, edited]
https://www.fourals.com/2022/05/11/loss-of-boro-in-storm-rain-and-blast-disease/


The Naogaon District [Rajshahi division] Agriculture Extension Department said that storms and rain have created a favourable environment for rice blast. Paddy plants in affected fields have completely dried up. The disease is spreading rapidly in parts of the district as many farmers do not take effective measures in time. According to information from the farmers, due to storms and blast diseases, there is a risk of 30 percent less paddy compared to 2021.

[Byline: Brenton Herrera]

--
Communicated by:
ProMED

[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%. 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 post 20210324.8267471). 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 fertilisers). 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. Use of certified clean seed is essential, farm-saved seed poses a high risk of carry-over of the fungus to subsequent crops.

The fungus is highly variable; this favours the emergence of new strains with increased virulence, including host resistance breaking strains. Environmental factors may also affect plant resistance. Both resistance and defense-regulator genes have been found to be involved in host resistance against blast (see links below) and could potentially be combined ("pyramided") to develop rice varieties with broad-spectrum host resistance against blast that cannot be as easily overcome by the fungus as varietal resistance based on single genes.

Rice varieties have been developed by the Bangladesh Rice Research Institute (BRRI) for local conditions and have been classed according to their levels of blast resistance (see link below). However, a lower blast resistance level is considered acceptable by some farmers for the sake of higher potential yield and quality of produce (ProMED post 20210422.8321022). It is not clear from the report above if this may be a factor in the current problem.

Maps
Bangladesh:
http://www.nationsonline.org/maps/bangladesh_map.jpg and
https://promedmail.org/promed-post?place=8703232,2442
Bangladesh divisions and districts:
https://nutritionprofile.gov.bd/district/

Pictures
Rice blast symptoms:
http://www.knowledgebank.irri.org/ricebreedingcourse/blast.jpg
(different symptomatic forms) and
https://www.dpi.nsw.gov.au/__data/assets/image/0006/798765/RiceBlast5.jpg
Rice fields affected by blast:
http://ucanr.edu/blogs/riceblog/blogfiles/22977_original.jpg,
https://guardian.ng/wp-content/uploads/2019/06/Rice-Blast.jpg, and https://previews.123rf.com/images/imagethink/imagethink1411/imagethink141100067/33260576-rice-blast-Stock-Photo.jpg

Links
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
https://www.dpi.nsw.gov.au/biosecurity/plant/insect-pests-and-plant-diseases/rice-blast
Rice blast disease cycle:
https://ars.els-cdn.com/content/image/3-s2.0-B9780123820341000086-f08-05-9780123820341.jpg and https://www.researchgate.net/profile/Darren_Soanes/publication/7891924/figure/fig2/AS:271700617068555@1441789883887/Life-history-of-Magnaporthe-griseaa-Asexual-spores-called-conidia-germinate-and-develop.png
Research on rice blast host resistance:
https://doi.org/10.1016/j.pbi.2019.03.015 (review),
https://doi.org/10.1371/journal.pone.0211061, and
https://www.researchgate.net/publication/330889038_Molecular_and_field_level_screening_for_blast_resistance_gene_donors_among_traditional_rice_varieties_of_Kerala
Impact of rice blast (and other fungal crop diseases):
https://doi.org/10.1111/j.1364-3703.2011.00783.x
Information on wheat blast:
http://wheatblast.org/ and
http://wheat.org/wp-content/uploads/sites/4/2016/04/Wheat-Blast-Priority-Brief-web-07Apr2016.pdf
_P. oryzae_ taxonomy and synonyms:
http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=224486 and
http://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=224486
Information on some BRRI rice varieties via:
http://dhcrop.bsmrau.net/category/brri/
- Mod.DHA]

See Also

2021
----
Blast disease, rice - India (02): (KL) 20211116.8699708
Blast disease, rice - India: (NL) 20210728.8549976
Blast disease, rice - Bangladesh: (KH) 20210422.8321022
Blast disease, wheat - global epidemiology 20210324.8267471
2020
----
Neck blast, rice - Nepal: (CH) 20200611.7459995
Blast disease, rice - Viet Nam: alert 20200409.7202041
Blast & undiagnosed rust, wheat - Bangladesh: (RP) 20200323.7132348
Blast disease, rice - India: (TG) 20200303.7042063
2019
----
Blast & bacterial leaf blight, rice - India: (TN) 20191110.6771677
Blast disease, rice - Bangladesh: (DH) 20190506.6457423
2018
----
Blast & bacterial leaf blight, rice - India 20180914.6028737
Virus & blast diseases, rice - Viet Nam: (Mekong Delta) 20180712.5901134
Blast disease, rice - Bangladesh: (RJ) 20180419.5756531
2017
----
False smut & blast, rice - Bhutan, India 20171102.5419405
Blast disease, rice - India: (JK) 20170725.5202371
Blast disease, rice - Bangladesh 20170428.5000484
Blast disease, wheat - India: 1st rep (WB) 20170306.4883233
Blast disease, wheat - Bangladesh: (KH) 20170123.4784298
and additional items in the archives

 



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Published: May 17, 2022

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