Ascochyta
| Ascochyta | |
|---|---|
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| Subclass: | |
| Order: | |
| Family: | |
| Genus: | Ascochyta
|
| Species | |
|
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 caused by physical damage. In the spring, the primary inoculum is thought to be conidia from pycnidia which are dispersed by rainsplash and infect leaves. Infections lead to leaf spots which develop into lesions. Black pycnidia can be observed in lesions. Secondary infection occurs when pycnidia produce more conidia which are again dispersed by rainsplash. The fungus overwinters as mycelium and pycnidia in host debris. Perithecia have also been observed in lesions. Ascospores from the perithecia are dispersed by air currents and may cause primary infections.
Environment
Leaf spotting symptoms are often associated with high humidity, warm temperatures, dense foliage, and leaves in contact with soil. [3] Because the fungus overwinters in plant debris on or in the soil and conidia are dispersed by rainsplash, initial infections occur on leaves in close proximity to the soil. High humidity and temperature promote sporulation and dense foliage aids in the spread of the disease.
Management
Currently, specific controls for Ascochyta leaf spot diseases have not been clearly prescribed. [4] Effective controls for a similar disease, Septoria leaf blotch, have been prescribed for 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. Reduced irrigation prevents the spread of conidia from infected leaves to healthy leaves. Removing other grassy weeds that can harbor the pathogen reduces a source of inoculum.[7][8]
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. [9] Ascochyta Leaf Blight of turf has become a common, although minor, disease of Kentucky bluegrass lawns in the United States. [10]
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
- ^ [1]
- ^ [2]
- ^ Cereal Disease Encyclopedia
- ^ Colorado State University Extension. http://www.ext.colostate.edu/pubs/garden/02901.html
