Submitted to: Soybean Research World Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 8/5/1999
Publication Date: N/A
Technical Abstract: Fusarium solani f. sp. glycines causes sudden death syndrome (SDS) of soybean (Glycine max). F. solani f. sp. glycines isolates grew slowly and appeared reddish light blue to dark blue on PDA medium. Cultures produced macroconidia and chlamydospores. Foliar disease severity ratings and the percentage of the root with lesions were greater (P < 0.001) for F. solani f. sp. glycines than for 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 analyze the molecular relationship between F. solani f. sp. glycines and other F. solani isolates, the mitochondrial small subunit (Mt SSU) rDNA was PCR-amplified and sequenced from 38 isolates including 14 F. solani f. sp. glycines and 24 F. solani from various plant hosts. All F. solani f. sp. glycines isolates had identical sequences. A single insertion of cytosine was present in all F. solani non-SDS-causing isolates but absent in all F. solani f. sp. glycines isolates. 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 similar tree topologies. Based on the sequence data, a pair of primers, Fsg1 and Fsg2, were designed. Of 98 isolates tested, these primers specifically amplified DNA from all 37 F. solani f. sp. glycines isolates, but not from other isolates including 45 F. solani and 16 other soybean pathogens.