Priming Bean Seedlings to Boost Natural Plant Defenses Against Common Bacterial Wilt: Leaf Architecture, Leaf area, Foliage Water Content, and Plant Biomass Results (Part 3)

Abstract

This greenhouse study evaluated the effects of two chemicals for priming kidney bean seedlings against bacterial wilt disease (Curtobacterium flaccumfaciens pv. Flaccumfaciens) (CFF). The premise of this study was that the oxidant properties of chlorine dioxide would mimic the signaling properties of radical oxygen species thereby initiating a cascade of molecular plant defenses. The factorial study included two levels for the foliar chlorine dioxide treatment, two levels for the bacterial wilt inoculation treatment, and two optional treatments. The biomass variables included oven dry total plant biomass, oven dry fruit biomass, and oven dry leaf biomass. Also, foliage and total plant water content data was collected, as well as total leaf area. Specific leaf area (SLA) was estimated from the leaf area and biomass data. The primers had equivalent leaf area, plant and fruit biomass as the water control for the CFF wilt inoculated plants. The EB 400 mg/l primer reduced SLA for the CFF inoculated plants. Both EB formulations increased aboveground water content in the CFF wilt inoculated plants. Multivariate tables revealed several significant correlations among leaf architecture, plant tissue water content, and biomass growth parameters for the EB primers and the water control treatment for the two CFF wilt treatments. Re-allocation of plant resources from plant growth to plant defenses due to chemical primers were estimated and discussed to determine the tradeoffs between plant yield and enhanced plant defenses. The three articles in this study show that chlorine dioxide primers can initiate a series of ROS and salicylic acid signals. This interplay of ROS signals and salicylic acid signals generated by the chlorine dioxide primers activates a long-term SAR response that protects plants against future pathogen attacks. In addition, interaction of the ROS and salicylic acid signals activates a suite of defense mechanisms that provide universal, multifaceted plant immunity that can be sustained across a crop season.