''Ascochyta sorghi'' is a
fungal
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
plant pathogen
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...
. It causes
Ascochyta leaf spot (also known as rough leaf spot) on
barley
Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...
that can also be caused by the related fungi ''
Ascochyta hordei
''Ascochyta hordei'' is a plant pathogen that causes Ascochyta leaf spot on barley, which can also be caused by the related fungi ''Ascochyta graminea, Ascochyta sorghi
''Ascochyta sorghi'' is a fungal plant pathogen. It causes Ascochyta leaf ...
,
Ascochyta graminea
''Ascochyta graminea'' is a plant pathogen that causes Ascochyta leaf spot on barley which can also be caused by the related fungi '' Ascochyta hordei'', ''Ascochyta sorghi
''Ascochyta sorghi'' is a fungal plant pathogen. It causes Ascochyta ...
'' and ''
Ascochyta tritici
''Ascochyta tritici'' is a fungal plant pathogen that causes Ascochyta leaf spot on barley, wheat and maize
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian En ...
''. It is considered a
minor disease of barley.
Hosts and symptoms
''Ascochyta sorghi'' infects grain crops such as sorghum (''
Sorghum bicolor
''Sorghum bicolor'', commonly called sorghum () and also known as great millet, broomcorn, guinea corn, durra, imphee, jowar, or milo, is a Poaceae, grass species cultivated for its grain, which is used for food for humans, animal feed, and ethan ...
''), Johnson grass (''
Sorghum halepense
Johnson grass or Johnsongrass, ''Sorghum halepense'', is a plant in the grass family, Poaceae, native to Asia and northern Africa. The plant has been introduced to all continents except Antarctica, and most larger islands and archipelagos. It re ...
''), Sudan grass (''
Sorghum sudanense
''Sorghum'' () is a genus of about 25 species of flowering plants in the grass family (Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species is grown for grain, while many other ...
''), and barley (''
Hordeum vulgare
Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...
'').
["Rough Leaf Spot of Sorghum (Ascochyta Sorghi)." ''Plantwise Knowledge Bank''. N.p., n.d. Web. 23 Oct. 2016. .] It can also infect wild sorghum species.
[Kucharek, Tom. "Foliar and Head Diseases of Sorghum in Florida." EPPO Bulletin 41.3 (2011): 266-68. Web. 23 Oct. 2016. .]
Symptoms of rough leaf spot can appear on leaf blades, leaf sheaths, peduncles, stalks, and glumes of susceptible species.
On sorghum, symptoms are usually noted on leaf blades beginning as small red lesions.
Lesions expand over time, becoming broadly-elliptical up to one inch in length.
Spots usually develop a tan interior bordered by a dark red to purple color, but can remain a uniform dark color.
The presence of black pycnidia exposed on the surface of the lesions give the leaf a rough, sandpapery feeling, hence the name “rough leaf spot.”
[Das, I.K.H, and P.G Padmaja. ''Biotic Stress Resistance in Millets''. Amsterdam: Academic, an Imprint of Elsevier, 2016. Print.] Rough leaf spot can eventually lead to leaf senescence.
Management
''Ascochyta sorghi'' is controlled through host plant resistance, cultural practices, and chemical application when necessary. Varieties of sorghum are not generally susceptible to rough leaf spot, although exceptions do exist.
Cultural practices include crop rotation, deep plowing, and avoiding field operations when leaf surfaces are wet.
As ''Ascochyta sorghi'' survives in plant debris and pycnidia in the soil, crop rotation and deep plowing allow for the avoidance of potential inoculum sources.
[Singh, D.S., and M.S. Pavgi. “Perpetuation of Two Foliicolous Fungi Parasitic on Sorghum, in India / Sopravvivenza Di Due Funghi Fitopatogeni Che Attaccano Le Foglie Di Sorgo, in India.” ''Phytopathologia Mediterranea'', vol. 21, no. 1, 1982, pp. 41–42. www.jstor.org/stable/42685858.] Other sanitation, such as using clean seed and removing alternate hosts, such as wild sorghum species, can reduce disease incidence.
Spores are spread from water splash, and can also be transmitted through contact with field equipment, especially when leaves are wet, so delaying field operations until plants are dry can help prevent spread of the pathogen.
If necessary, the application of fungicides can help limit disease severity.
Importance
''Ascochyta sorghi'' is found in all sorghum growing areas.
Throughout most areas of the Americas, Asia, Africa, and Europe, ''Ascochyta sorghi'' causes little crop loss and is considered to have a very low overall impact on sorghum production.
[Plant Health Australia Ltd (Version 1, May 2014) ''Generic contingency plan – Exotic foliage affecting necrotrophic pathogens affecting the grains industry''. Plant Health Australia, Canberra, ACT. Web. 23 Oct. 2016.] The lack of economic importance of rough leaf spot is thought to be due to the prevalence of resistant varieties.
However, there are a few areas where it may be more prevalent. Some states in India, such as Madhya Pradesh, have seen severe outbreaks of ''A. sorghi'', where it has the potential to become epidemic.
[ICRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1980. Proceedings of the International Workshop on Sorghum Diseases, sponsored jointly by Texas A & M University (USA) and ICRISAT, 11–15 December 1978, Hyderabad, India. (Available from ICRISAT, Patancheru, A.P., India 502 324.)] Weimer et al. (1937) reported that A. sorghi had the capacity to become damaging in Georgia.
Historically, rough spot has been responsible for crop losses between 3 and 10% in French Equatorial Africa.
See also
*
List of ''Ascochyta'' species
References
{{Taxonbar, from=Q4803970
Fungal plant pathogens and diseases
Barley diseases
sorghi
Fungi described in 1878