Diseases

Botryotinia fuckeliana (de Bary) Whetz. (teleomorph); Botrytis cinerea Pers. (anamorph) - Gray Mould of Sunflower

Systematic position.

Class Ascomycetes, order Helotiales, family Sclerotiniaceae, genus Botryotinia.

Biological group.

Facultative parasite.

Morphology and biology.

B. fuckeliana in his cycle of development forms exophitic septate mycelium, conidia, microconidia, sclerotia, and apothecia with ascospores. The reproductive body is the apothecium to 5 mm in diameter and to 4 mm in height; it is forming on sclerotia in shape of elevated rounded formations widening upward; the asci with ascospores are located in their stroma. Microconidia function as spermatozoons at forming the perfect stage. Sources of the infection are sclerotia on crop debris in soil, mycelium in infected seeds, conidia, and ascospores. The disease pathogen affects seedlings of sunflower, leaves and stalks after flowering, heads during maturing more intensively. Gray Mould of Sunflower is characterized by the gray scurf of fungal conidia on affected tissue. It is especially characteristically pronounced on lower side of heads as dark-brown necroses, where it forms concentric circles of conidial sporification of gray color. Further on shallow spherical or oblong black sclerotia are forming on plants. The greatest harm the pathogen causes to sunflower heads, sometimes it affects seedlings.

Distribution.

The Gray Mould of Sunflower is spread in Russia and other countries of the former USSR everywhere.

Ecology.

The occurrence of disease is more intensively connected to cold wet weather. Mass sporification of the disease happens at temperature 12.C to 22.C. The optimal relative air humidity for spore germination of the fungus 85% to 100%. The mass development of Gray Mould on sunflower heads occurs, when Hydrothermic Coefficient reaches 1.2 and more.

Economic significance.

Gray Mould causes losses of sunflower yield to 50% and more. The greatest damage is observed in East Kazakhstan, Western Siberia, in Central Cernozem region and Northern Caucasus of Russia, in Ukraine and Moldova. In these places the epidemics of Gray Mould of sunflower take place 2-4 times per 10 years. Control measures includes optimal crop rotation, the use of less affected varieties and hybrids, presowing seed dressing and fungicide treatment of the growing plants, and also preharvresting desiccation.

Related references:

De Bary A. 1866. Morphologie und Physiologie der Pilze, Flechten und Myxomyceten. Engelmann, Leipzig.
Esimov A.D. 1990. Harmfulness of Gray Mould of Sunflower. Tezisy dokl. Respublikanskoi konferentsii, posvyashch. 60-letiyu Kazakhskogo selskokhozyaistvennogo instituta, Alma-Ata, p. 125-126 (in Russian).
Faretra F., Grindle M. 1992. Genetics studies of Botryotinia fuckeliana (Botrytis cinerea). Recent advances in Botrytis research. Proc. of the 10th International Botrytis Symposium, Heraklion, Crete, Greece, 5 -10 April 1992. Wageningen, p. 7-21.
Kukin V.F., Gavinskaya N.A. & Artemenko U.R. 1982. The short-range forecast of development of Gray Mould of Sunflower in the south of Ukraine. Nauchno-tekhnicheskii byul. Vsesoyuznogo selektsionnono-geneticheskogo instituta, 1, p. 43 (in Russian).
MacFarlane H.H. 1968. Plant host - pathogen index to volumes 1-40 (1922-1961). Review of Applied Mycology. Commonwealth Mycological Institute. Kew, 820 p.
Jarvis W.R. 1977. Botryotinia and Botrytis species: taxonomy, physiology and pathogenicity. Canada, 195 p.
Persoon C.H. 1801. Synopsis methodical fungorum. H.Dieterich, Gottingen.
Tikhonov O.I. 1975. Diseases of sunflower. In: Sunflower. Moscow, Kolos, p. 401-409 (in Russian).
Yakutkin V.I. & Milyutenkova T.I. 1990. Forecast of White Rot and Gray Mould of sunflower for optimization of the protective methods. The methodical recommendations. St.Petersburg, 17 pp. (in Russian).
Yakutkin V.I. & Milyutenkova T.I. 1991. The account, forecast of White Rot and Gray Mould of Sunflower. The methodical recommendations. St.Petersburg, 36 pp. (in Russian).
Yakutkin V.I. 2001. Diseases of sunflower in Russia and their control. Zashchita i karantin rastenii, N10, p. 26-29 (in Russian).

© Yakutkin V.I.