Efficacy of Orange, Cinnamon, and Ginger Oils in Emulsion and Nano-emulsion Forms on Potato Bacterial Wilt Caused by Ralstonia solanacearum

Abstract

Antibacterial activity of essential plant oils ex. orange, cinnamon, and ginger in normal nano-emulsion forms against potato bacterial wilt disease caused by Ralstonia solanacearum was screened in vitro and in vivo. All treatments revealed inhibitory effects in vitro on growth of R. solanacearum compared to the control treatment. In this respect, 0.05% ginger nano-emulsion oil (GIN-NE) increased the bacterial inhibition zone to 18.5 mm, followed by cinnamon essential oil ex. CIN-NE and CIN-EO (15.5 and 11.5 mm, respectively) while, the inhibition zone of bacterial growth recorded the greatest inhibition of 22.0 mm followed by 21.0 mm in reaction to 0.10% cinnamon nano-emulsion oil (CIN-NE) and ginger nano-emulsion (GIN- NE) oil comparing with control treatments. The bacterial inhibition zone of R. solanacearum was inhibited to 27.5, 25.8, and 21.5 mm in response to 0.20% GIN-NE, CIN-NE, and CIN-EO, respectively. Applying 0.20% concentration of each tested essential plant oil as foliar spray on Cara and Spunta cvs. reduced disease severity index % in comparison to control. All tested treatments decreased bacterial wilt disease assessment than control treatment. The treatment effect on the Spunta cultivar was more effective in decreasing disease severity index % of bacterial wilt disease than the Cara cultivar. All tested treatments increased potato yield. Relative expression profiles of Serine protease, glutathione S-transferase, catalase, and peroxidase genes in Cara and Spunta cultivars after inoculation with R. solanacearum showed positive transcriptome alterations in response to essential oils at 0.20% concentrations in normal and nano-emulsion form in comparison to the positive control.

Keywords

• ralstonia solanacearum
• essential oils
• gene expression
• nano-emulsion