2025/01/01 by Jake A. Criscuolo, Ronnie J. Dewberry, Gashaw B. Alemu +1 · 1 voice
Agricultural and Biological Sciences · Engineering · #Biofuel production and bioconversion #Plant Growth and Agriculture Techniques #Plant-Microbe Interactions and Immunity
paper · doi:10.1094/php-04-25-0121-rs
openalex publication_date 2025/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/11
The pathogenic bacterium Ralstonia solanacearum race 3 biovar 2 (R3bv2) is highly regulated because it can threaten potato production. R3bv2 can also infect geraniums, another high-value crop. Geranium cuttings infected with R3bv2 have been accidentally imported to the United States five times since 1980, triggering costly eradications. To prevent further introductions, USDA APHIS regulates offshore geranium production practices. Geraniums are typically grown from cuttings in a volcanic scoria rock medium. Reusing this growth medium saves labor and carbon. Growers must currently steam the medium at 80°C for 120 min before reuse. This required treatment is both costly and environmentally destructive. We empirically determined the conditions required to inactivate R3bv2 in infected geranium tissue with the goal of conserving resources while maintaining rigorous biosecurity. Roots of R. solanacearum-infected geraniums grown in scoria under typical production conditions were exposed to a range of time and temperatures. Surviving pathogen populations were quantified using a sensitive combination of serial dilution plating and enrichment culture. Over 99.9% of R3bv2 cells in infected roots were inactivated by exposure to 55°C dry heat for 15 min. However, these roots sometimes contained a small subpopulation of heat-resistant R3bv2 cells. The heat-resistant subpopulation was no longer detectable after infected roots were held at 75°C for 15 min. This treatment also eradicated R3bv2 cells in the stems of infected geranium plants and in infested volcanic scoria growth medium. These results demonstrate that R. solanacearum R3bv2 is eradicated from infected geranium tissue and growth media by cooler and shorter heat treatments than currently required.