Diseases
Alternaria alternata (Fr.) Keissl., Cladosporium herbarum (Pers.) Link., Epicoccum purpurascens Ehrenb., Botrytis cinerea Pers. - Black Ear of wheat.
Taxonomic position.
Pathogens of Black Ear are fungi of the class Deuteromycetes: A. alternata (syn. A. tenuis Ness, A. grossulariae Jacz., A. lini Dey.), C. herbarum, E. purpurascens (syn. E. nigrum Link), B. cinerea (syn. Haplaria grisea Link, B. vulgaris Link: Fr.).Biological group.
Saprotroph.Morphology and biology.
Disease appears in mature stage of wheat, especially on late harvests. Sporulation of fungus becomes visible on spikelets, head, and grains. A. alternata on spikelets and grains (especially in embryo) causes dark spots with olive conidial infection. Conidiophores are pale brown, smooth, 50 microns in length and 3 to 6 microns in width. Conidia form long (often branching) chains and are inversely club-shaped, ovoid or elliptic, often with conic or cylindrical neck, from pale brown to moderately golden brown, smooth or slightly warty, with lateral (to 8) and dilatational septa, 20-63x9-18 microns in size. C. herbarum on spikelets forms spreading, olive-brown, velvet mat. Conidiophores are nodose, from pale to middle olive-brown, smooth, to 250 microns in length, 3 to 6 microns in width. Conidia form long (often branching) chains, are elliptic, oblong with rounded ends, from pale- to olive-brown, slightly warty, unicellular, sometimes with septa, 5-23x3-8 microns in size, with a small scar on one or both ends. E. purpurascens on spikelets forms punctiform, pincushion-like, dark brown sporodochiums having semi-circled stromatic base, where a dense layer of short hyaline conidiophores branch from, 5-15x3-6 microns in size. Conidia are spherical, dark-brown, 15-50 microns with reticular and warty surface, sometimes with short hyaline neck. B. cinerea forms gray inoculums on spikelets. Hypha is hyaline or gray-olive, 4 to 10 microns in width. Conidiophores are 300-1,000x6-17.5 microns in size, with thick sheath; branched apical cells are denticulate and covered with tightly acervate conidia. Conidia are ovoid or elliptic, 9-17.5x6.5-10 microns in size, mostly grayish. Sclerotia are gray-white, later blackened, 2 to 7 microns in diameter, with rough surface. Pathogens keep as mycelium and conidia on infected plant residues and grain.Distribution.
Disease is widely distributed in wheat growing areas. Wheat sowings in the North Caucasus region are strongly damaged by Black Ear disease. A disease harmfulness increase is predicted in Volga, Central and Central Black Earth regions and in adjacent territories.Ecology.
Wet weather during wheat ripening period causes fast disease development and distribution.Economic significance.
Pathogens infect many plants of different families. Germinating ability of infected wheat seeds is decreased. Protective measures include well-timed yield harvesting.Reference citations:
Ainsworth G.C. 1971. Dictionary of the Fungi. Sixth edition. Commonwealth Mycological Institute Kew: Surrey. 663 pp.Ishkova T.I., Berestetskaya L.I., Gasich E.V., Vlasov D.Y. 2001. Methodical instruction for diagnostics of major cereal fungal diseases. St. Petersburg: VIZR. 22-24 pp. (in Russian).
Peresypkin V.F. 1989. Agricultural Plant Pathology. Moscow: Agropromizdat. 480 pp. (in Russian).
Sanin S.A. 2000. To increase the level of phytosanitary safety of the country. Zashchita rastenii i karantin 12: 3-7. (in Russian).
Sanin S.S., Nasarova L.N., Sokolova E.A., Ibragimov T.S. 1999. Health of cereals field. Zashchita i karantin rastenii 2: 28-31. (in Russian).
Zakharenko V.A., Kuzmichev A.A., Plotnikov V.F. 2000. Extent and trends of species composition and population structure changes, areas of harmful and useful organism complexes, and forecast of dangerous phytosanitary situations in Russian regions. St. Petersburg: RASKhN. 1-100 pp. (in Russian).