Regulation of <i>Botrytis cinerea</i> Infection and Gene Expression in Cut Roses by Using Nano Silver and Salicylic Acid

<i>Botrytis cinerea</i> (<i>B. cinerea</i>) is one of the necrotrophic pathogens resulting in the heaviest commercial losses in cut rose flowers, and the severity of gray mold disease partly depends on the presence of ethylene during the storage and transport. The effectiveness of nano silver (NS) and salicylic acid (SA) was assessed as a novel control agent in protecting the cut rose flowers against <i>B. cinerea</i> infection and ethylene damages. The efficacy of NS and SA was compared with an inoculated control (CON). A non-treated control (NT) was also used to evaluate the natural infection process. The results indicated that pretreatment with 20 mg L⁻¹ NS significantly reduced <i>B. cinerea</i> growth in rose petals during vase periods. NS effectively suppressed the mRNA levels of ethylene biosynthesis genes (<i>RhACS2</i>, <i>RhACS4</i>, and <i>RhACO1</i>) and the reduction in expression levels of ethylene receptor genes (<i>RhETR1</i>, <i>RhETR2</i>, and <i>RhETR5</i>) and the downstream regulator <i>RhCTR2</i> in rose petals after <i>B. cinerea</i> inoculation. NS application also decreased the expression of the <i>B. cinerea snod-prot-like 1</i> (<i>Bcspl1</i>) gene which acts as the virulence factor in cut roses. In NS flowers, the maximum quantum yield of PSII (F_v/F_m) value was higher and the leaf temperature was lower on day 1, suggesting that these factors can be used for detecting <i>B. cinerea</i> infection and water stress in cut rose flowers. Furthermore, NS improved water relations and extended the vase life of cut rose flowers by 3.3 d, compared with that of NT flowers. In contrast, SA had no inhibitive effects on both <i>B. cinerea</i> growth and ethylene response in cut roses. The findings from the present study highlight NS as a promising new candidate for preventing <i>B. cinerea</i> infection and ethylene damages and for improving the postharvest quality of cut roses exported overseas.