Abscisic Acid Alleviates Tobacco Bacterial Wilt by Regulating Plant Water Potential and Inducing Systemic Resistance

Abstract

Tobacco will present typical dehydration and wilting symptoms after infected with Ralstonia solanacearum (R. solanacearum). At present, many studies have only reported that the Abscisic acid (ABA) can regulate the transportation of plant water or enhance plant disease resistance. However, the role of ABA-mediated plant water potential and plant resistance in process of R. solanacearum infection remains unclear. This study examined the variations of plant water potential and ABA content after inoculation R. solanacearum, and the effects of ABA application for plant resistance. The results showed that the ABA content in leaves corresponded to leaf water potential, and ABA content of resistant tobacco cultivar K326 were higher than the susceptible cultivar Yunyan 87. After spraying Na2WO4 of ABA synthesis inhibitor, the disease index of tobacco infected by R. solanacearum was also higher than CK (DI water), and leaf water potential was low. Additionally, 0.78 mg/L ABA promoted plant height (or leaf area), activated the activities of defense enzymes (PAL, POD, SOD, and PPO), and inhibited the expression of jasmonic acid antagonist gene JAZ3, ethylene synthesis gene EFE26, and salicylic acid synthesis pathway gene NPR1. Moreover, incidence of tobacco bacterial wilt was dramatically decreased by spraying ABA, with the control efficiency reaching up to 54.94% at 11 dpi, significantly higher than benzothiazole (19.33%). Furthermore, spraying ABA reduces the infection of R. solanacearum by promoting stomatal closure and decreasing transpiration rate. In summary, this study provides a different consequence for ABA controlling tobacco bacterial wilt by regulating leaf water potential and enhancing plant resistance.

Keywords: abscisic acid, plant water potential, induced resistance, tobacco bacterial wilt, R. solanacearum