APS Abstracts of Presentations

Dip inoculation technique to identify resistance to soybean sudden death syndrome. S. S. NAVI and X. B. Yang. Iowa State University, Dept. of Plant Pathology, Ames, IA 50011. Phytopathology 93:S65. Publication no. P-2003-0469-AMA.

A technique to measure relative disease resistance of soybean varieties in greenhouse to Fusarium solani f. sp. glycines (FSG), was developed based on our finding that radicle infection is critical to FSG colonization in taproot. A precise relationship between inoculation and early infection was established. The technique involves: seed germination, dip inoculation of germinated seeds with 1-11/2 cm radicle in FSG spore suspension, transplanting and evaluation. Using this technique three experiments were conducted: (1) planting 2-varieties in clay pots, (2) 12 varieties in cone cells and (3) 24 varieties in plastic cups. In all three experiments, inoculated seeds were transplanted in pre-irrigated containers filled with steam sterilized vertisol and sand 2:1ratio (v/v) and on the top of it one inch height peat mix and organic soil 1:1 ratio (v/v). Plants were incubated in greenhouse at 20-22°C with 12 h light cycle for a month. Mean % incidence and severities differed significantly (P < 0.05%) among varieties. Method demonstrated no variation in symptom expression vs use of containers apart from consistency in repetition.