Induced Systemic Acquired Resistance, after Applying Two Oxidant Based Disinfectants to Kidney Beans (Phaseolus vulgaris) Seedlings, Followed by a Bacterial Wilt Disease Inoculation

Phytophthora ramorum is a major risk to interstate trade of nursery stock originating in the western USA. Improving the Systemic Acquired Resistance (SAR) activities in nursery plants against P. ramorum fungal attacks may decrease the need for repeated fungicide applications while growing susceptible species in western nurseries. The goal of this study was to determine whether an oxidant based disinfectant would induce SAR functionality in kidney bean seedlings after inoculation with a bacterial wilt. Foliar application of a commercial ClO₂ (Electro-Biocide) formulation, when combined with or without a sarcosinate surfactant may induce temporal changes in plant defense/SAR biomarkers such as salicylic acid (SA), jasmonic acid (JA), superoxide dismutaste (SOD), and glutathione reductase (GHR). Induced SAR responses may pre-condition plant defenses, thereby reducing the protein production cost to defend the plant and reverting resources back to plant growth and vigor after a pathogen attack. A greenhouse study was conducted to test the effects of Electro-Biocide, applied at four concentrations, for inducing SAR responses in 22 day old kidney bean seedlings. Four days after Electro-Biocide was applied the plants were inoculated with Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), which is a bacterial vascular wilt disease.  The plants were then sampled the following day for leaf tissue analysis for the four SAR biomarkers. Leaves were collected from each plant, at two hour intervals for six collection times, starting at 16 hours after the plants were sprayed with Electro-Biocide.  The leaf tissue was analyzed at the Colorado State University, Center for Environmental Medicine laboratory. Salicylic and jasmonic acid proteins (free and total protein structures) were analyzed using a validated, tandem liquid chromatography, mass spectrometry/mass spectrometry instrument (LC/MS/MS) laboratory method. Superoxide dismutaste and glutathione reductase were analyzed with a validated, immunoassay kit method. The leaf tissue analyses show that the total SA concentrations were higher for the control treatment, compared to the Electro-Biocide treatments.  Also, the free form of SA did show a dynamic pattern of increasing then decreasing over the 12 hour leaf collection time period. The SAR biomarker tests for SOD and GHR are still being planned for the spring of 2014.