Identification and Detection of Fusarium striatum as a New Record of Pathogen to Greenhouse Tomato in Northeastern America

Abstract

Recently, a new disease was reported on greenhouse tomato plants in both Quebec, Canada and Maine, United States. Symptomatic plants bore brown lesions at graft points and pruning sites, resulting in expanding cankers with clearly delineated margins. Diseased plants eventually wilted and died within a few weeks following the appearance of the first symptoms. The symptoms are reminiscent of infection by Fusarium oxysporum f. sp. radicis-lycopersici, with the notable difference of a discoloration of the pith area rather than the vascular tissues. A homothallic Fusarium sp. was consistently recovered from these lesions. Sequencing of the internal transcribed spacer and the partial translation elongation factor 1-α gene identified the species as F. striatum. Pathogenicity tests with F. striatum isolates from diseased tissues reproduced disease symptoms in tomato similar to those observed on tomato plants in the greenhouses. Specific detection of F. striatum from mycelia and diseased and disease-free plant tissues was achieved by developing a polymerase chain reaction-based test. These results establish, for the first time, that the species F. striatum is the cause of crown and stem rot affecting tomato in North America. In addition F. striatum was detected from all sampled tissues of plants delivered by the nursery common to both growers, suggesting that the transplants would be the source of the inoculum.