Diseases

Aspergillus Link spp., Penicillum Link. spp., Trichothecim roseum Fr., Mucor mucedo Fres, Rhizopus nigricans Ehr. - Moulds of wheat seeds.

Systematic position.

Causal agents of moulds of wheat seeds are Mitosporic fungi of the genera Aspergillus (A. milchelii, A. candidis, A. fumigatus, A. glaucum, A. niger), Penicillum (P. cyclopium, P. glaucum, P. rudilosum et all.), Trichothecim (T. roseum) and fungi of the class Zygomycetes, order Mucorales (M. mucedo, R. nigricans ).

Biological group.

Saprotrophs.

Biology and morphology.

Mould saprotroph fungi belong to surface microflora of wheat seeds. Grain may be infected in maturing period under high humidity conditions at low temperature, but more often moulds develop during storage. A. fumigatus forms light-violet or brown mycelium. Conidiophores are 300 by 2-8 um in size, with bladder-like inflation on top, 20 to 30 um in diameter. Sterigmas are mononuclear, located on upper part of bladder-like inflation. Conidia are mononuclear, ellipsoidal or spherical, smooth or spinose, 2.5 to 3 um in size. A. glaucum forms friable yellow-green mycelium. Conidiophores are unbranched, bloated on top, bearing sterigmas that branch off radially and diverge at apices like chains. Conidia are spherical, bristly, green, 7 to 15 mkm in diameter. P. cyclopium forms mycelium of light-blue to dark-green colors. Conidiophores are single, 200-400 by 3-3.5 um in size, rough, sometimes smooth, with one or more branchlets. 4 to 8 sterigmas in fascicle are 7-10 by 2.2-2.8 um in size, with truncated top. Conidia are spherical, 3.3 to 4 um in diameter or elliptical, 3.3-4 by 2.5 um in size. P. glaucum forms green-gray mycelium; conidiophores have branched racemule; apical branches bear chains of small-sized round uncolored spores (2 to 4 um in diameter each). T. roseum forms dense felt mycelium; conidiophores are unbranched, bearing bulb-shaped and bicellular spores on top, 12-18 by 8-10 um in size. M. mucedo forms dark-red mycelium with black dots (sporangia); sporangiophores are brown, gathered in fascicles (3 to 5), 4 mm in height. Sporangium is spherical, 100 to 200 um in diameter; spores are unicellate, spherical or ellipsoidal, 8-14 by 6-11 um in size, with gray wrinkled surface. Spores of mould fungi are preserved in granaries, and under favorable conditions may cause mass infection of seeds.

Distribution.

Disease occurs everywhere, but it is more significant in irrigated part of Volga region, East and West Siberia, Central Black Earth region and North-West region.

Ecology.

Moulds develop in field under conditions of high air humidity during harvesting time only. Active mould development is observed in granaries, if storage requirements are not followed.

Economic significance.

Causal agents occur on Poaceae species, on different substrates, and in soil. Moulds reduce seed quality and germination and weaken the plants. Protection measures include keeping optimal grain storage conditions and seed chemical dressing.

Reference citations.

Bel.kov G.A. 1983. Mold seeds infection under conditions of different agricultural growing practices of winter wheat. Collection of scientific reports of Odessa agricultural institute: Biological and agrotechnical basis of growing practices of cereal and leguminous crops on south of Ukraine. ?dessa. 93-96 p. (In Russian)
Chernyshova .P. 1991. Phytosanitary estimation of winter wheat seeds in different nature-climatic zones of Stavropol. Territory. Proceedings of science-practical conference: Agrometeorological resources and productive process in crop production; 1991 Mar 18-21; Kiev. 108-109 p. (In Russian)
Ilukhina, Fedorova R.N. 1989. About species composition of microorganisms on wheat seeds growing in Central Black Earth Region. Plant protection in intensive technology of agricultural crops growing. Voronezh: All Russian Institute of Plant Protection (VIZR). 114-121 p. (In Russian)
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 p. (In Russian)
Peresypkin V.F. 1989. Agricultural Plant Pathology. Moscow: Agropromizdat. 480 p. (In Russian)
Potlaichuk V.I., Semenov Ya. 1977. Seeds microflora of spring wheat and rice in different growing zones. Byulleten. VNII zashchity rastenii, 40: 40-44. (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)
Semenov A.Ya., Fedorova R.N. 1984. Infection of grain seeds. Moscow: Kolos. 96 pp. (In Russian)
Zhukova V. 1982. Some Penicillum species found in wheat seeds. Ikologiya i fitopatologiya, 16(3): 491-495. (In Russian)

© Gultyaeva E.I.