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: Tue 5 Jan 2016
Source: The Hindu [edited]
<http://www.thehindu.com/news/cities/Tiruchirapalli/blast-disease-threatens-andhra-ponni-crop/article8067533.ece>
Blast disease threatens crop
Farmers blame fog for triggering the blast disease in Tiruchi district. They have complained that it has caused serious loss to the standing "BPT 5204" variety. They said farmers relied more on BPT 5204 variety as it ensured immediate marketability with good price. But the blast disease has destroyed the crop.
S.K. Selvaraj of the Tamil Maanila Congress, said the sudden fall in temperature had triggered blast disease because of fog. The tillers had grown [but] without grains inside. Farmers want a compensation.
--
Communicated by: ProMED-mail <promed@promedmail.org>
[Rice blast is caused by a fungus which has yet again been reclassified and is now called _Nakataea oryzae_ (previously _Magnaporthe oryzae_, previously classified as a strain of _M. grisea_, previously _Pyricularia oryzae_). Rice blast 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. 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.
Symptom severity and spread of the blast fungus are influenced by climatic conditions. The disease is also favoured by high nitrogen levels (for example from fertilizers) and high humidity (as stated above). 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.
An outbreak of rice blast was also reported from the same area in early 2015 (ProMED-mail post http://promedmail.org/post/20150128.3124545), but it is unclear if the same rice variety was planted then. The popular BPT 5204 (released in the 1980s) is known to be highly susceptible to a number of diseases.
Alternative varieties have been developed and are recommended by authorities (see links below).
Maps
India:
<http://www.mapsofindia.com/images2/india-map.jpg>
Tamil Nadu districts:
<http://www.mapsofindia.com/maps/tamilnadu/tamilnadu-district.htm>
Pictures
Rice blast:
<http://www.knowledgebank.irri.org/ricebreedingcourse/blast.jpg>
(different symptomatic forms) and
<http://www.imtech.res.in/raghava/rbpred/lesion.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 <http://www.imtech.res.in/raghava/rbpred/home.html>
Information on BPT 5204 and new replacement varieties:
<http://www.thehindu.com/todays-paper/tp-national/tp-andhrapradesh/two-new-rice-varieties-developed/article773478.ece>,
<http://www.thehindu.com/todays-paper/tp-national/tp-tamilnadu/farmers-take-to-new-paddy-variety/article2870870.ece>
and
<http://www.rkmp.co.in/content/samba-mahsuri-bpt-5204>
Impact of rice blast (and other fungal crop diseases):
<http://onlinelibrary.wiley.com/doi/10.1111/j.1364-3703.2011.00783.x/full>
_N. oryzae_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=802971>
and
<http://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=802971>
- Mod.DHA]
[See Also:
2015
----
Neck blast, rice - India: (HR)
http://promedmail.org/post/20151014.3713941
Blast disease, rice - Spain: (VC)
http://promedmail.org/post/20150903.3620399
Blast disease, rice - India: (TN)
http://promedmail.org/post/20150128.3124545
Rice diseases - Malaysia: (western) emerging strains
http://promedmail.org/post/20150108.3080315
2014
----
Blast disease, rice - India: (GA)
http://promedmail.org/post/20140417.2410154
2013
----
Blast disease, rice - India: (TN)
http://promedmail.org/post/20131231.2144256
Fungal diseases, rice - USA, India
http://promedmail.org/post/20130905.1926343
2012
----
Blast disease, rice - Nigeria: (KD)
http://promedmail.org/post/20121105.1391776
Blast disease, rice - Australia: (NT)
http://promedmail.org/post/20120217.1044294
Blast disease, rice - Malaysia: (KH)
http://promedmail.org/post/20120103.0015
2011
----
Blast disease, rice - Nepal: (JU)
http://promedmail.org/post/20111111.3339
Blast disease, rice - Australia: (WA)
http://promedmail.org/post/20110812.2442
Blast disease, rice - Philippines: (KA)
http://promedmail.org/post/20110801.2311
Blast disease, rice - Kenya: (CE)
http://promedmail.org/post/20110704.2025
Rice diseases - Costa Rica, Bangladesh
http://promedmail.org/post/20110425.1289
and older items in the archives]
Topics
Species
