Maritza Institute for Vegetable Crops, 32 Brezovsko shosse str., Plovdive-4003, BULGARIA
Fungi from the Genus Pythium were often isolated from diseased plants of greenhouse tomato varieties Rosela, Ramada, and Fontana, grown in district of Petrich. Cultural and morphological features of the isolates were studied according to criteria of Plaats-Niterink (1981) and Waterhouse (1967). Two different species were identified:
Pythium irregulare Buisman. Culture on corn meal agar not fluffy. Hyphe 2-4 m to 8 wide, often with hyphal swellings. Sporangia spherical pyriform and ellipsoid; terminal or intercalary; Oogonia globose to irregular, intercalary, some terminal 15-25 m diam., smooth or with finger-like projections of variable length. Antheridia monoclinous, rarely diclinous. Oospores mostly aplerotic 10-25 m diam.
Pythium vexans de Bary. Cultures on oat or corn meal agar fairly fluffy. Hyphae 2 to 5 m wide. Sporangia globose, ovoid or pyriform, terminal or intercalary in range 15-27 x 11-23 m (av. 20.1 x 17.5). Oogonia globose on short branches lateral or intercalary, 16 to 24.5 m diam. Anteridia monoclinous, sometimes diclinous; antheridial cells broad bell-shaped. Oospores globose with smooth wall, aplerotic, 14 to 20 m diam.
Neither species of fungus had been recorded on tomatoes in the country and this is the first record of P. irregulare in Bulgaria as a pathogen. Pathogenicity of the isolates was confirmed in experiments with artificial inoculation.
Literature cited:
Van Der Plaats -Niterink, A.J. 1981. Studies in Mycology, N21: 1-239.
Novotelnova, N.S. and K.A. Pystina, 1985. Flora Plantarum Cryptogamarum URSS vol. XI Fungi (3), Ordo Peronosporales, L. 1-362.
Waterhouse, G.M. 1967. Mycological Papers, no. 109:1-15.