Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691.
Seed treatment with a 2,4-diacetylphloroglucinol (DAPG)-producing Pseudomonas strain ameliorated abiotic stress disorder in corn caused by growth in a low-pH soil. In two consecutive growing seasons, Wood1R-treated seed gave rise to plants that grew taller (P ≤ 0.05), had fewer foliar lesions (P ≤ 0.10), and provided greater yields (P ≤ 0.1) than the negative controls when grown in soil with a pH < 5.0. Under controlled conditions, seed treatment with Wood1R also reduced foliar lesion severity (P ≤ 0.05 in two of three experiments) but failed to increase shoot or root growth in young seedlings grown in acidic soil. Significant (P ≤ 0.05) patterns of altered mineral nutrient uptake (i.e., generally increasing P and Mg while reducing Al) were observed to occur as a result of Wood1R seed treatment under both sets of growing conditions. In contrast, suppression of seedling damping-off disease was not indicated in this low-pH soil, because no difference in crop stand was observed for any experiment. Additionally, Wood1R-mediated growth inhibition of seedling pathogens was reduced in vitro at pH < 5.0, indicating that secretion of antifungal metabolites may not occur in low-pH soils. This is the first report of an abiotic stress amelioration of acid soil stress-related symptoms by a DAPG-producing pseudomonad.