A Method of Evaluating Postemergence Damping-Off Pathogens of Bedding Plants

Abstract

An inoculation method was developed to allow rapid assay examination of the pathogenicity of numerous fungal isolates [Pythium spp. and Rhizoctonia solani] inducing damping-off on many plant types. Seeds of host plants were thickly sown in rows in pots containing a moistened peat-vermiculite mix. Inoculum as a 12 .times. 12-mm agar disk removed from a petri plate culture of the fungus, was buried at the end of the seedling row at seedling emergence. The pots were placed in plastic bags and incubated on a shaded greenhouse bench at 26 .+-. 2.degree. C. After 9 days, the length of seedling row in which damping-off occurred was measured. This method maximized the amount of damping-off, minimized variability among replicates, and adequately revealed pathogenic isolates and susceptible hosts. Furthermore, the test conditions closely approximate seedling germination and early growth conditions prevalent in Ohio [USA] greenhouses. [Test plants included tomato (Lycopersicon esculentum ''Early Girl''), pepper (Capsicum frutescens ''California Wonder''), cabbage (Brassica oleracea var. capitata ''Golden Acre''), celosia (Celosia argentea ''Red Fox''), ageratum (Ageratum houstonianum ''Blue Blazer''), impatients (Impatiens wallerana ''Dwarf Blaze''), salvia (Salvia splendens ''Fireball''), eggplant (Solanum melongena var. esculentum ''Black Beauty'') and vinca (Vinca major ''Little Blanche'')].