First Report of Tomato Pith Necrosis Caused by Pseudomonas mediterranea in Georgia, USA

Two separate outbreaks of pith necrosis on tomato (Solanum lycospersicum L.) under conventional production were reported from Tift (3.5-ha area) and Burke (5-ha area) counties in Georgia (April 2015) with approximate disease incidence of 10 and 15%, respectively. The tomato varieties involved in pith necrosis outbreaks in Tift and Burke counties were 'Quincy' and 'BHN 640,' respectively. These fields had history of bell peppers, cantaloupe, and cotton as previous crops prior to tomato. Infected plants in field wilted and had longitudinal necrotic lesions on stem. Longitudinally cut sections of necrotic stem area displayed discolored and rotten vascular tissues with brown discolored pith with a ladder-like appearance. Bacterial isolations were made from stem sections with symptoms on King's B agar medium. After 48 h of incubation at 28[degrees]C, white round colonies with smooth margins were isolated. Isolated colonies did not fluoresce under UV light. The isolates were Gram negative, oxidase positive, negative for pectinolytic activity on potato, arginine dihydrolase positive, did not produce levan, and gave a hypersensitivity response (HR) on tobacco. Isolates utilized arabinose, sucrose, trehalose, mannitol, and cellobiose but could not utilize rhamnose, sorbitol, and benzoic acid. The 16S rRNA (Leu et al. 2010) from five isolates (15-1, 15-2, and 15-3 from Burke County; and 15-4 and 15-5 from Tift County) were amplified, and the resultant PCR products were sequenced and BLAST searched in GenBank. The 16S rRNA sequences matched Pseudomonas corrugata(Accession No. EF153018.1) and P. mediterranea(HQ242760.1) with 96 to 99% and 97 to 99% sequence identity, respectively. Representative strains from each location were submitted to GenBank (15-1, Accession No. KT211491; and 15-4, Accession No. KT211492). The five test isolates also had [< or =]90% and [< or =]95% similarity with P. corrugata and P. mediterranea, respectively, when tested with BIOLOG (Biolog, Hayward, CA). A Taqman probe based real-time polymerase chain assay with specific primers for P. corrugata and P. mediterranea resulted in amplification of isolates with P. mediterranea but not with P. corrugata primers (Licciardello et al. 2011). These observations indicate that tomato isolates were indeed P. mediterranea. In two independent experiments, 3-week-old tomato seedlings (cv. Bonny best) were injected with bacterial suspension (100 [mu]l) containing 3x10 super(8) colony forming units (CFU)/ml o