Vase performance and bacterial colony dynamics at the stem-ends of cut ‘Master’ carnations pretreated with nanosilver

Vascular occlusion caused by bacterial proliferation is the primary determinant of postharvest quality deterioration in cut flowers. This study investigated the efficacy of nanosilver pretreatment on the vase performance and stem-end bacterial colony dynamics of cut carnations (Dianthus caryophyllus L. ‘Master’). Pretreatment with 75 mg L−1 nanosilver for 24 h significantly enhanced vase performance and extended vase life from 8.4 to 12.1 d. The pretreated flowers also demonstrated higher relative fresh weights and hydraulic conductivity than those in the deionised water control. Scanning electron microscopy and confocal laser scanning microscopy both demonstrated that nanosilver pretreatment effectively suppressed bacterial propagation and biofilm formation at the stem ends. Further observations revealed that nanosilver pretreatment reduced exopolysaccharide deposition and inhibited rapid bacterial biofilm formation within 24 h in vitro. High-throughput 16S rRNA sequencing revealed Enterobacter, Lactococcus, and Bacillus as the predominant genera (day 0). During subsequent vase-life stages (4 and 8 d), nanosilver pretreatment inhibited plant pathogenic bacteria, while enriching beneficial bacteria. Additionally, nanosilver pretreatment reduced bacterial abundance during the vase life of cut carnations, and altered their microbial community composition dynamics. These findings elucidate the postharvest bacterial ecology of cut flowers treated with nanosilver and contribute to the development of preservation techniques for cut flowers.