Induced systemic resistance against three foliar diseases of Agrostis stolonifera by (2R,3R)-Butanediol or an isoparaffin mixture

Abstract

Induced systemic resistance (ISR) is a type of plant defense mechanism typically activated by nonpathogenic root-associated microorganisms and systemic priming of gene expression in response to subsequent pathogen challenge. ISR was found to be activated by PC1, a mixture of food-grade synthetic isoparaffins, and (2R,3R)-butanediol, a volatile organic compound produced by bacteria. In controlled environment tests, application of PC1 or (2R,3R)-butanediol to the soil reduced the diseased leaf area of Agrostis stolonifera by 20 to 40% for the fungal pathogens, Microdochium nivale, Rhizoctonia solani or Sclerotinia homoeocarpa compared to the water control. In A. stolonifera, expression of the jasmonate synthesis-related genes, AsAOS1, encoding an allene oxide synthase, and AsOPR4, encoding a 12-oxo-phytodienoic acid reductase, and expression of a pathogenesis-related protein gene, AsGns5, encoding an acidic β-1,3-glucanase, were primed for increased expression by PC1 or (2R,3R)-butanediol when M. nivale was inoculated seven days later. However, the compounds differed in their ability to induce expression prior to pathogen challenge. PC1 induced AsAOS1 expression upon treatment, whereas (2R,3R)-butanediol induced expression of AsOPR4 and AsGns5 upon treatment. These results indicate that both (2R,3R)-butanediol and PC1 can produce ISR in A. stolonifera but may do so through different mechanisms.