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: Sun 12 Mar 2023
Source: Farmers Weekly [summ. Mod.DHA, edited]
https://www.fwi.co.uk/arable/crop-management/disease-management/brown-rust-risk-highlighted-for-key-group-4-wheat


The AHDB [Agriculture and Horticulture Development Board] has released its 1st brown rust watch list. The list aims to highlight any wheat varieties that appear to be becoming more sensitive to the disease. Growers are urged to be vigilant about the new races of brown rust being seen in some parts of the country and not miss later fungicide applications.

The new list includes wheat variety Theodore, one of 2 varieties with a brown rust resistance score of 8 (on a scale from 1 to 9, where 9 shows the most resistance). In Dorset county, infection levels of 3% have been observed, in addition to relatively high disease levels (up to 10%) in some patches. This is much higher than would be expected for a variety with a disease rating of 8, said the AHDB. Growth room screening tests suggest that the Dorset isolate may be able to unlock a specific host resistance gene.

[Byline: Richard Allison]

--
Communicated by:
ProMED

[Leaf rust (also called brown rust) of wheat is caused by the fungus _Puccinia recondita_ (synonym _P. triticina_). Related pathogens affect barley and rye. The disease reduces the photosynthetic potential of the plant and can cause serious yield losses of over 40% in individual fields. Symptoms include brick-red pustules on leaves, stems, and later on heads. Infection of the host can occur in as little as 4 hours in favourable conditions. Epidemic severity increases exponentially over time and may appear to "explode" suddenly during favourable weather.

Spores are produced as the crop ripens and are spread by wind and mechanical means. The fungus needs living tissue to survive between seasons and cannot survive on seed or stubble or in soil. Volunteer cereal plants and certain wild grasses may generate a "green bridge" providing inoculum to infect new crops. Disease management relies mainly on timely fungicide applications, choice of crop cultivars, and control of volunteer crop plants. Crop monitoring is important for early discovery of infection so action can be taken to limit pathogen spread as well as build-up of inoculum.

New strains of leaf rust with increased virulence are emerging worldwide. These include strains that show additional fungicide resistances and/or the ability to break down genetic resistance of specific host varieties (as in the report above). Monitoring programmes have been established in different countries for early detection of new rust strains. They are often linked to regional resistance breeding programmes to attempt to stay ahead of pathogen evolution.

Maps
UK:
https://www.worldometers.info/img/maps/unitedkingdom_physical_map.gif and
https://maps.lib.utexas.edu/maps/europe/united_kingdom.gif (with counties)

Pictures
Wheat leaf rust symptoms:
http://www.forestryimages.org/images/768x512/5187012.jpg,
http://www.forestryimages.org/images/768x512/5154036.jpg and
http://www.forestryimages.org/images/768x512/1493026.jpg

Links
Information on wheat leaf rust:
https://agriculture.vic.gov.au/biosecurity/plant-diseases/grain-pulses-and-cereal-diseases/leaf-rust-of-wheat,
https://doi.org/10.1111/j.1364-3703.2008.00487.x,
https://www.agric.wa.gov.au/mycrop/diagnosing-leaf-rust-wheat and
https://www.ars.usda.gov/midwest-area/stpaul/cereal-disease-lab/docs/cereal-rusts/wheat-leaf-rust/
_P. recondita_ taxonomy and synonyms:
http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=145187 and
http://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=145187
Wheat rusts overview, including epidemiology and spore types:
http://www.fao.org/3/y4011e/y4011e0g.htm
Wheat rusts global tracking, current race analysis and distribution:
https://rusttracker.cimmyt.org/ and
https://agro.au.dk/forskning/internationale-platforme/wheatrust/
Global Rust Initiative:
https://bgri.cornell.edu/
Updates on other wheat diseases in UK:
https://www.pressandjournal.co.uk/fp/business/farming/5481595/growers-warned-of-high-risk-wheat-disease/ (stripe rust) and
https://www.thescottishfarmer.co.uk/news/23377597.septoria-risk-september-down-wheat-mitigated-revystar-xe (septoria)
AHDB:
https://ahdb.org.uk/
- Mod.DHA]

See Also

Multiple diseases, cereal crops - Australia: (QL,NS) alert 20230309.8708826
2022
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Stripe & leaf rusts, wheat - Pakistan: (PB) 20220210.8701378
2021
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Stripe, stem & leaf rusts, wheat - Ethiopia 20210212.8186216
2016
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Leaf rust, wheat - UK: (eastern) 20160621.4299957
Fungal diseases, wheat & oilseed rape - UK: alert 20160128.3971413
2015
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Leaf rust, barley - Australia: (WA) 20150811.3571139
Leaf rust, wheat - Australia: new strain, spread (VI) 20150312.3226745
2014
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Leaf rust, wheat - USA: races 20140411.2396698
2013
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Leaf rust, wheat - Australia: new strain (NS) 20131003.1981154
2012
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Leaf & stripe rusts, wheat - UK: new strains 20120208.1036727
2011
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Leaf rust, wheat - UK: new strain 20110801.2315
2010
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Leaf rust, wheat - New Zealand: new strain susp. 20101213.4428
Leaf rust, wheat - Mexico: (SO) 20100201.0344
and older items in the archives

Website: http://www.isid.org

Published: March 24, 2023