Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/25/2000
Publication Date: 4/1/2004
Citation: Li, S., Tam, Y., Hartman, G.L. 2004. Molecular differentiation of fusarium solani f. sp. glycines from other f solani and their phylogenetic relationships inferred from mitochondrial small subunit rdna sequences. Phytopathology. 90:491-497. Interpretive Summary: Sudden death syndrome (SDS) is one of the most important fungal disease of soybean. The causal organism is Fusarium solani (Mart.) Sacc. f. sp. glycines, a soilborne fungus. Previously, nomenclature designated F. solani Form A (FSA) for the SDS-causing F. solani, and Form B (FSB) for the F. solani seedling/root rot pathogen that did not cause SDS. In the past, identification of F. solani f. sp. glycines has relied on variable morphological and cultural characteristics. The objectives of our study were to analyze the molecular differences and relatedness between F. solani f. sp. glycines and other F. solani isolates. The isolates from the fungus that causes SDS were genetically all alike. Two major lineages occurred in F. solani non-SDS-causing isolates. Based on molecular genetics, the isolates were divided into three groups. Understanding the molecular relationship between F. solani f. sp. glycines that causes SDS and other F. solani will provide insight in the specific identification an detection of F. solani f. sp. glycines. This study is important to plant pathologists and molecular biologist that work with soybean pathogens and has the potential to be the basis for further work on detection of the pathogen in different environments.
Technical Abstract: To differentiate between Fusarium solani f. sp. glycines that causes soybean sudden death syndrome and other F. solani isolates, a partial sequence of the mitochondrial small subunit (mtSSU) rDNA gene was PCR-amplified and sequenced from 38 isolates including 14 F. solani f. sp. glycines and 24 F. solani non-SDS-causing isolates 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 occurred in F. solani non-SDS-causing isolates distinguished by sequence divergence, and the presence/absence of multiple insertions. Genetic divergence ranged from 0.016 to 0.048 between F. solani f. sp. glycines and other F. solani isolates. Cladistic analysis produced one most pasimonious tree with three major clades. The first clade contained all F. solani f. sp. glycines isolates, which formed a sister clade with the second clade that grouped all F. solani isolates with only a single nucleotide insertion. The third clade was formed by five F. solani isolates with multiple insertions. Based on the sequence data, it is likely that F. solani non-SDS causing isolates with multiple insertions have a longer evolutionary history than F. solani f. sp. glycines and other F. solani non-SDS-causing isolates which possessed only a single nucleotide insertion.