First Report of Bacterial Stem Rot of Tomatoes Caused by Pectobacterium carotovorum subsp. brasiliense in Colombia

During 2013 and 2014, farms in the municipality of La Cumbre, Valle del Cauca, that produce the ‘Calima’ hybrid tomato, Solanum lycopersicum L., were visited. Tomato plants with soft, aqueous lesions and brown lesions on the lower stem were observed. The vascular bundles were necrotic and in various states of decay, with some plants presenting cracking symptoms along the stem. At advanced stages of the disease, presence of exudates from the lesions was observed. Due to the destruction of medular tissue, the stems appeared hollow and brittle, resulting in symptoms of chlorosis and slight loss of turgidity in leaves. The incidence of the disease ranged from 5 to 80%. Isolation of the possible causal agents of this disease was done following the method described by Castaño and Mendoza (1997) and Botero et al. (2013). Seventeen bacterial isolates were obtained and were thereafter used in pathogenicity tests on 35-day-old tomato plants of the ‘Calima’ hybrid. Inoculation was performed by puncturing the stem with a bacterial suspension in sterile distilled water (10⁸ CFU/ml) using a sterile syringe. All plants were kept in a moist chamber for 48 h. After 3 days, the plants that were inoculated with isolate LCB07 showed stems with aqueous brown lesions, softening and hollowing, and presence of exudation at the site of inoculation. Control plants, which were inoculated with sterile distilled water, showed no symptoms. When the pathogen was reisolated and identified using morphological, biochemical, and molecular methods, results confirmed the originally isolated pathogen. Molecular identification of the pathogenic isolate was performed by amplifying the 16S region of rRNA using universal primers (27f/Llr), and reconfirmed by amplification of 16S-23S intergenic space region of rRNA using primers (1491f/Llr) (Fessehaie et al. 2002). Alignment of study and reference sequences deposited in the NCBI GenBank database showed that the isolate LCB07 has 98% similarity with Pectobacterium carotovorum subsp. brasiliense. Unique sequences in this study were submitted to GenBank under accession numbers KX669672.1 and KX673747.1. This is the first report of P. carotovorum subsp. brasiliense causing bacterial stem rot of tomatoes in Colombia.