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 14 Jul 2021
Source: PhysOrg, Teagasc report [abridged, edited]
https://phys.org/news/2021-07-vulnerability-upcoming-wheat-varieties-irish.html
Teagasc [Agriculture and Food Development Authority] has confirmed that Irish strains of septoria are able to overcome a source of genetic resistance present in a range of wheat varieties. Septoria blotch is the primary disease of the Irish wheat crop. In 2020, unexpected levels of the disease were observed on varieties in a number of locations, each with the variety Cougar in their background, which has levels of septoria resistance.
Initial results confirmed the strains of septoria isolated from these varieties were able to cause significant levels of disease on Cougar in glasshouse trials. Dr Steven Kildea, Teagasc, said; "Cougar derived resistance has been included in commercial breeding programs. However, our work has now confirmed that this source of resistance is vulnerable to Irish strains of septoria. With upwards of 20% of the Irish winter wheat seed available for autumn 2021 expected to be made up of varieties bred from Cougar the implications of these findings are immediate."
There is no evidence that the strains are more aggressive on other commercial varieties. Further investigations are ongoing to determine how widespread this virulence is within the Irish septoria populations. Fortunately, following intensive analysis, the strains are similar in fungicide sensitivity to the wider Irish _Zymoseptoria tritici_ population.
The risk is greatly increased in regions where septoria pressure is traditionally high, such as the South of the country. Here, even with well-timed fungicide programs, there is a concern that adequate disease control would not be achieved and growers should consider alternative varieties.
[Source publication: https://doi.org/10.1111/ppa.13432]
--
Communicated by:
ProMED
<promed@promedmail.org>
[Septoria leaf blotch of cereals is caused by fungi in the septoria species complex, which includes _Zymoseptoria tritici_ (previously _Septoria tritici_), _Mycosphaerella graminicola_, and _Phaeosphaeria nodorum_ (previously _Stagonospora nodorum_). They affect mainly wheat, but also barley, oats, occasionally rye, as well as some grass species. Symptoms on wheat and barley are very similar, they may occur at any time during the growth cycle and on any portion of the plant. They include blotches on both leaves and glumes, which reduce the photosynthetic ability of the host. Disease development is favoured by humid conditions. Up to 50 percent yield losses have been reported on susceptible varieties.
Spores can be spread by infected plant material, wind, water (rain splash), and mechanical means. The pathogens can overwinter on crop debris and on autumn sown crops or volunteers. Disease management includes fungicide treatments aimed at preventing the disease from becoming established on the upper 3 leaves of the crop canopy (where it would affect the ears most), removal of inoculum sources, and use of resistant varieties. After the cereal rusts, the septoria is considered the most important challenge to plant breeders (see ProMED post 20120831.1274190) and a threat to food security worldwide.
Pathogen strains with high levels of resistance to many fungicides are emerging in different regions (see ProMED posts 20160516.4225677, 20161031.4598540, 20140417.2410219). Furthermore, the number of fungicides available for septoria control has been decreasing in Europe and elsewhere due to withdrawal of products for environmental reasons (e.g., ProMED post 20210223.8207530).
In addition to fungicide resistant pathogen strains, host resistance breaking strains are being observed in recent years, for example also in the UK (ProMED post 20190218.6322156).
Maps
Ireland:
http://www.vidiani.com/maps/maps_of_europe/maps_of_ireland/general_map_of_ireland.jpg and
http://healthmap.org/promed/p/39
Pictures
Septoria leaf symptoms:
http://ipm.illinois.edu/bulletin/photos/septoria_wheat.jpg and
https://www.farminguk.com/images/news/44568_2.jpg
Wheat crops affected by septoria:
https://s0.geograph.org.uk/geophotos/02/98/84/2988496_24261618.jpg and
https://www.agric.wa.gov.au/sites/gateway/files/styles/original/public/septoria_nodorum_withered_leaves.jpg
Septoria diseases and pathogens, photo gallery:
http://www.forestryimages.org/browse/subimages.cfm?sub=9457
Links
Additional news stories:
https://www.irishexaminer.com/farming/arid-40335980.html and
https://www.fwi.co.uk/arable/crop-management/disease-management/septoria-disease-explosion-hits-uk-wheat-crops
Information on septoria diseases:
http://www.agroatlas.ru/en/content/diseases/Tritici/Tritici_Septoria_tritici/,
http://www.agroatlas.ru/en/content/diseases/Tritici/Tritici_Septoria_nodorum/,
https://www.apsnet.org/edcenter/disandpath/fungalasco/pdlessons/Pages/Septoria.aspx,
https://cropscience.bayer.co.uk/threats/diseases/wheat-diseases/septoria-tritici-in-wheat/,
https://cropprotectionnetwork.org/resources/articles/diseases/septoria-tritici-blotch-of-wheat,
https://ipm.ca.uky.edu/content/septoria-leaf-blotch-complex-wheat, and
https://agriculture.vic.gov.au/biosecurity/plant-diseases/grain-pulses-and-cereal-diseases/septoria-tritici-blotch-of-wheat
Taxonomy of fungal species via:
http://www.indexfungorum.org/Names/Names.asp
Teagasc:
https://www.teagasc.ie/
- Mod.DHA]
See Also
Septoria blotch, wheat - UK: latent infections, alert 20210513.8359121
Septoria blotch, wheat - UK: reduced fungicide sensitivity 20210223.8207530
2019
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Septoria blotch, wheat - UK: (DS, WL) 20190218.6322156
2017
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Septoria, wheat - Zambia: (CO) 20170914.5315295
Septoria, wheat - Australia: (VI, SA) 20170828.5280388
2016
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Septoria, wheat - Australia: emerging strains 20161031.4598540
Septoria blotch, wheat - UK: SDHI resistance 20160516.4225677
Fungal diseases, wheat & oilseed rape - UK: alert 20160128.3971413
2015
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Septoria blotch, wheat - Europe (02): (Ireland) new strains, SDHI resistance 20151214.3860515
Septoria blotch, wheat - Ethiopia: survey of incidence 20151018.3725790
Septoria blotch, wheat - Europe: fungicide resistance 20150619.3450044
2014
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Fungal diseases, cereal crops - UK: SDHI resistance, alert 20140507.2457504
Septoria blotch, wheat - New Zealand: new strains, strobilurin resistance 20140417.2410219
Septoria, wheat - Australia: new strains, alert 20140313.2329774
2011
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Fungal diseases, cereal crops - Ireland: alert 20110525.1590
and older items in the archives
Topics
Species
