Thyme oil treatment controls bacterial wilt disease symptoms by inducing antioxidant enzyme activity in Solanum tuberosum

Abstract

This study aimed to use thyme volatile oil (TVO) to control potato bacterial wilt disease caused by Ralstonia solanacearum and to explore the biochemical responses in relation to defense enzymes that induce resistance against pathogens in plants. In vitro experiments showed that all tested concentrations of TVO (1 µl, 2, 4, 6, 8, and 10 µl ml−1) significantly (P ≤ 0.05) inhibited the growth of the pathogen, with the most significant effect recorded at a concentration of 10 µl ml−1. Under greenhouse conditions, the tested concentration of TVO (10 µl ml−1) significantly (P ≤ 0.05) reduced the incidence of potato bacterial wilt and the population of R. solanacearum pathogens in potato plants. The current study also revealed that TVO (10 µl ml−1) increased the activity of antioxidant enzymes, e.g.,. peroxidase (POX) and phenylalanine ammonia-lyase (PAL), and reduced the activity of catalase (CAT) in treated potato plants. In conclusion, our results showed that TVO (10 µl ml−1) afforded a strong reduction of R. solanacearum radial growth in vitro and a high reduction in the development of potato wilt in vivo. Moreover, we demonstrated that POX and PAL activities can be used as biochemical markers for biocontrol efficacy in the control of potato bacterial wilt.