Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/19/1997
Publication Date: N/A
Technical Abstract: The phytotoxicity of culture filtrates from Fusarium solani isolates, cause of soybean sudden death syndrome (SDS), was tested using a vital staining and a stem-cutting assay. Two week-old soybean suspension cultured cells (SCC) from a SDS-susceptible cv. Williams 82 were stained with 0.1% phenosafranin after exposure to cell-free culture filtrates from three soybean and three non-soybean isolates of F. solani. Dead cells stained red and were clearly differentiated from nonstained live cells. The percentage of dead cells increased with time and at higher concentrations of the culture filtrates. The culture filtrate of soybean SDS-causing isolates had a significantly (P<0.001) higher toxicity to soybean SCC than those from non-soybean isolates. For the stem-cutting assay, stems of soybean seedlings were cut and immersed in culture filtrates from soybean and non-soybean isolates. All soybean isolates caused typical SDS foliar symptoms including leaf drop while non-soybean isolates caused either atypical SDS symptoms or no symptoms. Both vital staining and stem-cuttings can be used as rapid methods to determine the phytotoxicity of fungal culture filtrates and may be useful in identifying culture filtrate fractions for toxin(s).