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Date: Fri 10 Dec 2010
Leaf rust found on domestic wheat
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The Conquest milling wheat [variety] was bred 4 years ago by Plant & Food Research and is showing signs of leaf rust this season on some crops in Mid-Canterbury.
Plant & Food suspects it is the result of a new strain or pathotype of the fungal disease, but is also not ruling out weather conditions.
Federated Farmers says it's concerning for the industry as Conquest has performed very well against imported wheats.
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[Leaf rust (also called brown rust) of wheat is caused by the fungus _Puccinia recondita_. Different pathovars affect barley and rye. The disease reduces the photosynthetic potential of the plant and can cause serious yield losses of over 40 percent in individual fields.
Symptoms include brick-red pustules on leaves, stems, and later on heads. As the crop ripens, spores are produced. 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.
The fungus is not soil-borne but spores are spread by wind and mechanical means. It needs living tissue to survive between seasons and cannot survive on seed, 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.
Monitoring programmes have been established in many affected areas to detect emerging new strains. It is difficult to see how the 'weather conditions' mentioned above as a possible alternative could have been responsible for the reported resistance breakdown, but molecular data will be needed to confirm a new strain.
Maps
New Zealand:
Pictures
Links
Additional news story:
Information on wheat leaf rust:
and
_P. recondita_ taxonomy and synonyms:
Plant & Food Research NZ:
[see also:
Leaf rust, wheat - Mexico: (SO) 20100201.0344
2009
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Fungal diseases, field crops - Americas 20091025.3696 Cereal rusts - Australia: (WA) alert 20090820.2948 Fungal diseases, cereal crops - France, Germany 20090504.1668
2008
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Cereal rusts - Australia: (NSW) 20080624.1945 Leaf rust, wheat - USA: (KS, OK) 20080519.1665 Fungal diseases, cereals - UK, Ireland: update 20080428.1460 Fungal diseases, wheat - Canada, USA 20080427.1454 Fungal pathogens, wheat - UK (England) 20080319.1055
2007
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Fungal diseases, wheat & pulses - Australia (SA) 20070821.2729 Fungal pathogens, wheat - United Kingdom: new races 20070523.1652 Rust diseases, bean & wheat - UK: alert 20070512.1515
2006
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Leaf rust, wheat - Russia (Irkutsk) 20060815.2287
2005
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Leaf rust, wheat, resistance change - India 20051201.3462 Leaf rust, Septoria spp., wheat - Kazakhstan: corr. 20050825.2509 Leaf rust, Septoria spp., wheat - Kazakhstan 20050823.2488]
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