Bio-Priming Seed Treatment for Biological Control of Pythium Ultimum Preemergence Damping-Off in SH-2 Sweet Corn

Abstract

Sweet corn (Zea mays) with the shZ gene for enhanced sugar content is highly susceptible to preemergence damping-off, caused primarily by Pythium ultimum in Montana’s Bìtterroot Valley. Rhizosphere bacteria that adhered to hyphae of P. ultimum and were antagonistic to the growth of this pathogen were isolated from Bitterroot Valley soils. An isolate of Pseudomonas fluorescens, AB254, provided superior seed protection from Pythium damping-off in naturally infested soils. At least 1 X 100,000,000 cfu per seed of AB254 was needed to achieve maximum protection. In a process we have termed “bio-priming,” dry seed was coated with P. fluorescens AB254 and allowed to imbibe water under warm temperatures until a 35-40% moisture content was achieved. During bio-priming, bacterial populations increased from 10 to over l0,000­-fold, depending on initial inoculum level. Bio-priming provided protection against damping-off as good as or better than seed treatment with metalaxyl when the seeds were planted in cold soil. This process may be of interest and value to growers who wish to plant sweet corn or other temperature-sensitive crops into cold soils where damping-off is a problem and the use of chemical seed treatments is not desired.