Ascochyta
| Ascochyta | |
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| Genus: | Ascochyta
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Ascochyta asparagina | |
Ascochyta is a genus of ascomycote fungi, containing several pathogens to plants. The taxonomy of this genus is still incomplete.
Some of these pathogens affect grass species, including grains.
Some species of Ascochyta
- Ascochyta asparagina, Ascochyta blight.
- Ascochyta bohemica
- Ascochyta boltshauseri
- Ascochyta caricae, Stem end rot.
- Ascochyta chrysanthemi, Ray blight.
- Ascochyta doronici
- Ascochyta fabae f.sp. lentis
- Ascochyta graminea
- Ascochyta gossypii, now Phoma exigua
- Ascochyta hordei
- Ascochyta humuli
- Ascochyta imperfecta
- Ascochyta pinodes, Ascochyta blight.
- Ascochyta pisi, Leaf and pod spot.
- Ascochyta prasadii
- Ascochyta rabiei, blight on chickpeas.
- Ascochyta rhei, Leaf spot.
- Ascochyta sorghi, Sorghum rough leaf spot.
- Ascochyta sorghina, Rough leaf spot.
- Ascochyta spinaciae, Leaf spot.
- Ascochyta tarda, Leaf blight.
- Ascochyta tritici
- Ascochyta vindobonensis
Summary
Ascochyta is a genus of Ascomycote fungi. This group contains several plant pathogens, some of which affect cereal crops. The genus was first described in 1830 by Mlle Libert, who regarded the spores as minute asci and the cell contents as globose spores. [1] Numerous revisions to the members of the genus and its description were made for the next several years. Species that are plant pathogenic on cereals include, A. hordei, A. graminea, A. sorghi, A. tritici. Symptoms are usually elliptical spots that become chlorotic and later become a necrotic brown. Management includes fungicide applications and sanitation of diseased plant tissue debris.
Hosts and Symptoms
Hosts species include wheat, barley, oats, rye, triticale, many other grass species found throughout the world. Symptoms are found on lower leaves early in the season and upper leaves later in the season. Lesions are usually elliptical and initially chlorotic until becoming brown and splitting longitudinally. Lesions have a brown margin with white center. Pycnidia within the lesions are generally black. [2]
Disease Cycle
The fungus often invades damaged leaf tissue. Infections lead to leaf spots which develop into lesions. Perithecia and pycnidia develop in lesions. Conidia from pycnidia are dispersed by rainsplash and cause secondary infections. Perithecia produce ascospores which are dispersed by air currents. The fungus overwinters as mycelium and pycnidia in host debris.
Environment
Leaf spotting is often associated with high humidity, dense foliage, and leaves in contact with soil. [3]
Management
Currently, specific controls for Ascochyta leaf spot diseases have not been clearly prescribed. [4] Controls for a similar disease, Septoria leaf blotch, would be effective on Ascochyta leaf spot disease. These include: crop rotation, fungicide application, variety selection, irrigation management, tillage to reduce residue, and good grassy weed control. [5] Fungicides that are listed as providing 'Very Good' control of Septoria leaf blotch include Azoxystrobin 22.9%, Pyraclostrobin 3.6%, and Propiconazole 41.8%. [6] Applying fungicides at the beginning of the season reduces the number of sporulating pycnidia and mycelium that overwintered. Sanitation through removing all plant debris from the field at the end of the season reduces the inoculum for the following season.
Importance
The disease is of relatively minor economic importance although in individual crops the disease is likely to add to leaf death. Symptoms are often seen later in the season towards the end of grain filling when they are unlikely to cause any yield loss. The air-borne ascospores are common in late summer, and have been implicated in late summer asthma. [7] Ascochyta Leaf Blight of turf has become a common disease of Kentucky bluegrass lawns in Colorado. [8]
References
- ^ Ascochyta Leaf Spots of Cereals and Grasses in the United States. Roderick Sprague and A. G. Johnson. Mycologia, Vol. 42, No. 4 (Jul. - Aug., 1950), pp. 523-553
- ^ Cereal Disease Encyclopedia
- ^ Asochyta leaf spot. Krupinsky, J.M., Cline, E. 2010. Compendium of Wheat Diseases and Pests, 3rd Edition. Edited by W.W. Bockus, R.L. Bowden, R.M. Hunger, W.L. Morrill, T.D. Murray, and R.W. Smiley. American Phytopathological Society Press, St. Paul. p. 18-19
- ^ USDA, Agricultural Research Service
- ^ Montana Wheat Production Guide
- ^ Montana Wheat Production Guide
- ^ Cereal Disease Encyclopedia
- ^ Colorado State University Extension. http://www.ext.colostate.edu/pubs/garden/02901.html
