Carbon utilization profiles of Fusarium virguliforme isolates

Fusarium virguliforme is the cause of sudden death syndrome in soybean. Physiological variability among isolates of the fungus is unknown. One way to measure physiologic variability is to analyze growth on different carbon sources. The carbon source utilization profiles of 18 F. virguliforme isolates were examined using the Biolog FF 96-well microplate, which contains 95 different carbon sources. The utilization of dextrin,D-mannitol, maltotriose,D-lactic acid methyl ester, N-acetyl-D-galactosamine, salicin, D-trehalose, and L-alanine differed significantly among isolates (P = 0.05). Carbon sources were grouped into 3 clusters based on their ability to promote growth of F. virguliforme, after calculating Euclidean distances among them. About 12% of the carbon sources promoted a high amount of mycelial growth, 39% promoted a medium amount of growth, and 49% promoted a low amount of mycelial growth; the latter was not significantly different from the water blank control. A hierarchical tree diagram was produced for the 18 isolates based on their carbon source utilization profiles using Ward's hierarchical analysis method. Two main clusters of isolates were formed. One cluster represented greater average mycelial growth on all of the carbon sources than the other cluster. In this study, variability in carbon source utilization among F. virguliforme isolates was evident, but the results were not associated with geographic origin of the isolates, year collected, or published data on aggressiveness. Additional research is needed to determine if these carbon utilization profiles are associated with other biological characteristics, like spore germination, propagule formation, and saprophytic competitiveness.