ProMED
http://www.promedmail.org

Source: Rising Kashmir [summ. Mod.DHA, edited]
https://risingkashmir.com/fungal-disease-hits-paddy-crops-in-trals-amirabad-village/
A disease has affected paddy fields in south Kashmir. Farmers say that their crops have shown symptoms of green panicles turning whitish. A local agriculture extension officer reported that the affected crops displayed symptoms similar to rice blast disease and that symptoms were confined to a few patches of land.
A fungicide spray was applied to the affected areas. The presence of bacterial blast in the paddy crop was ruled out because the affected crops showed signs of improvement following the fungicidal treatment. Experts have been invited to examine the disease further and assist in its identification.
[Byline: Javid Sofi]
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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 may 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; 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 infect only a limited number of cultivars.

The fungus also causes wheat blast (e.g., see ProMED post 20240207.8714710). 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 (e.g., 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 defence-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. 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).

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:
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
Blast symptoms on wheat:
https://chainpure.files.wordpress.com/2012/04/wheat-blast.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 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
Research on rice blast host resistance:
https://doi.org/10.1016/j.pbi.2019.03.015 (review) and
https://doi.org/10.1371/journal.pone.0211061
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://openwheatblast.net/ and
http://wheat.org/wp-content/uploads/sites/4/2016/04/Wheat-Blast-Priority-Brief-web-07Apr2016.pdf
_P. oryzae_ taxonomy and synonyms:
https://www.indexfungorum.org/names/NamesRecord.asp?RecordID=224486 and
https://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=224486
- Mod.DHA