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GrainGenes Pathology Report: Tan Spot

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Pathology
Tan Spot
Other Name
Yellow Leaf Spot
Yellow Leaf Blotch
Type
Fungus
Host Species
Triticum aestivum
Secale cereale
Hordeum vulgare
Causal Organism
Pyrenophora tritici-repentis
Trait
Reaction to Pyrenophora tritici-repentis
Evaluation
Tan spot, Faris95
Tan spot, WGRC
Gene Class
Insensitivity to tan spot toxin
Resistance Gene
tsn1 (Triticum)
Symptoms
Tan spot fungus over winters on infested wheat stubble or straw remaining on the soil surface. Shortened or continuous wheat rotations and reduced tillage practices favor occurrence of this disease. Sporulation occurs from spring to late summer, with infection related to periods of leaf wetness. Depending on the variety, infection requires 6 to 48 hours of canopy wetness. Spots initially appear as tan-brown flecks. Spots expand to form tan colored, elliptical shaped lesions possessing a tiny dark brown spot at the center. Lesions will often exhibit a narrow-to-broad yellow border. Lesions will continue to expand and often involve the entire leaf surface. Severe infection of the flag leaf and heads can result in 30 to 40 percent yield losses. Bromegrasses (Bromus species), wheatgrasses (Agropyron species) and rye are alternate hosts.
Image
Early leaf-spotting symptoms...
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Reference
ReferenceKephart KD (1993) Winter wheat disease management Insect and plant disease management handbook.
Reference(1987) Compendium of wheat diseases.