Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/27/1998
Publication Date: N/A
Technical Abstract: Fusarium solani f. sp. glycines is the causal organism of sudden death syndrome (SDS) of soybean (Glycine max). F. solani f. sp. glycines isolates grew slowly and appeared reddish blue to dark blue on PDA medium. Cultures produced macroconidia and chlamydospores. Pathogenicity tests of F. solani f. sp. glycines based on foliar severity ratings and the percentage of the root with lesions differed significantly (P<0.001) from F. solani non-SDS causing isolates. Cuttings of soybean seedlings with their stems immersed in cell-free culture filtrates of F. solani f. sp. glycines isolates developed SDS-like foliar symptoms, but not when immersed in filtrates of F. solani non-SDS causing isolates. To compare the molecular difference and relatedness between F. solani f. sp. glycines and other F. solani isolates, the mitochondrial small subunit (Mt SSU) rDNA was PCR-amplified and sequenced from 35 isolates including 14 F. solani f. sp. glycines and 22 F. solani from various plant hosts. All F. solani f. sp. glycines isolates had identical sequences. Two major lineages were found in F. solani isolates in view of the nucleotide similarity, and presence and absence of insertions. Maximum parsimony analysis, UPGMA, and neighbor-joining analysis gave identical tree topologies. Based on the sequence data, a pair of primers, Fsg1 and Fsg2, were designed. Of 95 isolates tested, these primers specifically amplified DNA from all 35 F. solani f. sp. glycines isolates, but not from 45 F. solani and a 15 other soybean pathogen isolates.