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United States Department of Agriculture

Agricultural Research Service

Title: Phoma Spot

Authors
item Krupinsky, Joseph
item Cline, Erica

Submitted to: American Phytopathological Society Press
Publication Type: Book / Chapter
Publication Acceptance Date: June 20, 2006
Publication Date: January 31, 2010
Citation: Krupinsky, J.M., Cline, E. 2010. Phoma spot. p. 42. IN: 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.

Interpretive Summary: Phoma species infect wheat in India, Mexico, Australia and parts of South America, and have been reported as secondary invaders in the United States and Germany. The pathogens are widely distributed on numerous hosts but relatively rare on wheat. Most of the Phoma species reported on wheat are opportunistic parasites: Phoma glomerata is associated with leaf spots and blights, Phoma subglomerata acts as an opportunistic parasite causing leaf spots during wet periods, Phoma macrostoma var. macrostoma causes leaf spots, and Phoma americana is associated with nematode cysts. Phoma sorghina is a seed-borne pathogen causing minor leaf spots. In experiments, Phoma triticina was reported to cause moderate damage, but it is unclear how damaging it is under natural conditions. Phoma lophiostomoides occurs on wheat in Australia and Europe, but its disease characteristics have not been reported. Phoma subglomerata, Phoma sorghina, Phoma triticina, and Phoma americana, are restricted to grasses, while the other Phoma species infecting wheat occur on a wide range of plant hosts. Phoma sorghina infects wheat heads in India, causing oval, brown lesions. Wheat and triticale in Mexico occasionally show dark brown lesions on leaf sheaths caused by Phoma glomerata. Prolonged periods of continuous wetting are required for infection and symptom development.

Technical Abstract: Phoma species invade wheat in India, Mexico, Australia and parts of South America, and have been reported as secondary invaders in the United States and Germany. The pathogens are widely distributed on numerous hosts but relatively rare on wheat. Most of the Phoma species reported on wheat are opportunistic parasites: P. glomerata (Corda) Wollenw. & Hochapfel is associated with leaf spots and blights, P. subglomerata Boerema, Gruyter & Noordel. acts as an opportunistic parasite causing leaf spots during wet periods, P. macrostoma var. macrostoma Mont., a wound parasite found on weakened hosts, causes leaf spots, and P. americana Morgan-Jones & J.F. White is associated with nematode cysts. Phoma sorghina (Sacc.) Boerema, Dorenb. & Kesteren (reported under the synonymous names P. insidiosa Tassi and P. indianensis [K.B. Deshp. & Mantri] Boerema, Dorenb. & Kesteren) is a seed-borne pathogen causing minor leaf spots. In inoculation experiments, P. triticina E. Müll. was reported to cause moderate damage, but it is unclear how damaging it is under natural conditions. Phoma lophiostomoides Sacc. occurs on leaves and culms of wheat in Australia and Europe, but its disease characteristics have not been reported. Phoma subglomerata, P. sorghina, P. triticina, and P. americana, are restricted to Poaceae (grasses), while the other Phoma spp. infecting wheat are plurivorous, occurring on a wide range of hosts from multiple plant families. P. sorghina invades wheat glumes and awns in India, causing oval, brown lesions, with pycnidia in their centers. Wheat and triticale in Mexico occasionally show dark brown lesions on leaf sheaths caused by P. glomerata. Prolonged periods of continuous wetting are required for infection and symptom development. Controls are not prescribed, but cultivars ranging from highly resistant to highly susceptible have been identified in greenhouse tests.

Last Modified: 9/2/2014
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