Stenotrophomonas maltophilia - an Emerging Pathogen of Local Varieties of Tomatoes in Bulgaria

Since 2014, an unusual appearance of tomato seeds (Solanum lycopersicum) has been observed. The seeds were produced from local tomato genotypes from Bulgaria without visible symptoms of disease. The seeds exhibited small or large brown-grey spots on the surface that affected also the deeper layers. The most affected seeds lacked germinating ability or were unable to produce normal seedlings. Bacteria were derived from exudates, seed coat, endosperm, and embryo. Several tests were carried out to investigate pathogenicity - inoculation of seedlings, seeds, and plants. All isolates were identified as Stenotrophomonas maltophilia by BiologTM and after sequencing of the 16S rRNA gene region. S. maltophilia was found to be the sole causal agent of the disease in seeds. This is the first report of S. maltophilia causing disease of tomato seeds.