Etiology of soybean root rot caused by Fusarium solani and its effect on root and above ground plant development
F. J. SESSOMS (1), L. K. Otto-Hanson (2), J. Lencowski (2), D. K. Malvick (2), J. E. Kurle (2). (1) Department of Plant Pathology, College of Food, Agriculture, and Natural Sciences, University of Minnesota, St Paul, MN, U.S.A.; (2) Department of Plant Pathology, College of Food, Agriculture, and Natural Sciences, University of Minnesota, St. Paul,
<i>Fusarium solani</i> is an important soybean root pathogen. However, its interaction with soybean and the etiology of root rot are poorly understood. Our objectives were to determine if <i>F. solani</i> is a pathogen of soybean at different growth stages and if it affects plant growth, development and yield. Experiments were conducted in sterile phytagel and several growth media. The effects of soil temperature and moisture conditions were also tested. In phytagel, greater spore concentrations led to reduced tap root length and lateral root number, and the highest concentration (104/ml) stopped seed germination. Root lesions, initiated where lateral roots emerged, were observed in the inoculated plants, and microscopy will reveal if hyphal presence is associated with these lesions. Results indicate that most <i>F. solani </i>isolates, 11 of 18 tested, were weakly pathogenic. <i>F. solani</i> could cause severe root rot in all moisture conditions at 15ºC but not at 30ºC. Root biomass was often lower in the infected plants, but no clear negative relationship was found between discoloration percentage and shoot biomass or yield. <i>F. solani</i> DNA was detected at low levels in inoculated roots at the R1 and R4 stages using quantitative PCR, whereas it was detected at higher levels in vegetative stages. Results suggest <i>F. solani</i> infects young seedlings, causes root rot, and reduces root development that may lower the plant’s ability to overcome abiotic and biotic stresses.
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