The fungal pathogen Fusarium solani poses an increasing threat to tomato production in Northern China

Greenhouse cultivation conditions, such as low light intensity, high humidity and limited crop rotation, result in an increased severity of foot rot disease. Here, we isolated a fungal pathogen from tomato plants infected with foot rot disease to investigate its pathogenicity and establish an inoculation system to distinguish tomato susceptible and resistant varieties. Microscopic analyses of the fungal spores suggested that the pathogen belonged to the genus Fusarium, while polymerase chain reaction amplification of internal transcribed spacer (ITS), translation elongation factor-1 alpha (EF-1 alpha) and mitochondrial small subunit (mtSSU) rDNA fragments revealed that it was an isolate of Fusarium solani. Phylogenetic analyses indicated that the ITS, EF-1 alpha and mtSSU sequences were distinct from other isolates identified in this region, suggesting that this fungus has recently arrived here. Reinoculation of this fungus on tomato seedlings grown on Murashige and Skoog medium and in pots filled with soil resulted in foot rot disease, but disease symptoms appeared more rapidly in the medium-grown seedlings. Together, our results demonstrate that this new F. solani isolate is causing tremendous losses of tomato production in greenhouse cultivation. Fungal inoculation on both medium-grown and soil-grown seedlings will facilitate resistance screening of tomato germplasm against infection by this pathogen.