Efficacy of nano-silver in alleviating bacteria-related blockage in cut rose cv. Movie Star stems

Postharvest treatments with nano-silver (NS) significantly improve water relations and therefore prolong the vase life of several cut flowers, including rose (Rosa hybrida cv. Movie Star). The efficacy of NS in alleviating bacterial related blockage in the stem-ends of cut cv. Movie Star was further investigated. Four dominant bacteria strains Pseudomonas fluorescens, Aeromonas sp., Comamonas acidovorans and Chryseomonas luteola were isolated from the stem-ends of cut roses. High numbers of the isolated bacteria at 10(8) colony forming units mL(-1) vase solution led to a sharp reduction in vase life, flower fresh weight, and water uptake. In vitro assessments of the antibacterial activity of NS against the four bacterial strains was >80% at 5 mg L-1 and nearly 100% at 50 mg L-1. Bacterial blockage in the stem-ends of cut cv. Movie Star roses with and without NS pulse treatments was assessed during the vase period using scanning electron microscopy. Following a 50 mg L-1 NS pulse treatment, there were few bacterial cells on the cut surface of the stems even on day 7. Moreover, no obvious bacterial blockage was observed inside the xylem vessels. In contrast, the cut surface of control stems was covered with bacteria and associated amorphous substances, and numerous bacteria were found in the xylem vessels. (C) 2012 Elsevier B.V. All rights reserved.