Germinability Of Tilletia Spp Teliospores After Hydrogen-Peroxide Treatment

Three methods of hydrogen peroxide treatment tested to control germination of teliospores of Tilletia spp. contaminating wheat or barley seeds were: 1) immersion in heated aqueous solutions of hydrogen peroxide, 2) exposure to water-saturated hydrogen peroxide vapors produced by bubbling air through hydrogen peroxide solutions, and 3) treatment in a chemosterilizer that produces hydrogen peroxide vapor by a pulse-injection system (VHP) that includes control of vapor moisture content. Teliospores of T. controversa and T. tritici would not germinate after immersion for 6 min in 1.0 M (3.5%, w/v) hydrogen peroxide solution at 45 or 50 C. Teliospores would germinate after treatment with water-saturated hydrogen peroxide Vapors for as long as 15 min. Teliospores on the surface of wheat seed would not germinate after treatment for 5 min in the VHP system at 46-48 C. Germination was reduced 95-99% by treatment for 1 min in the VHP system. The system was equally effective when applied with deep (38 mm Hg) or shallow (680 mm Hg) vacuum. The treatment did not wet wheat or barley seeds or influence their germinability even if applied for more than 30 min. Barley malting quality was not influenced by VHP system treatment. When intact sori were fumigated, however, most teliospores within the sori of both fungi survived. Similar results were obtained with T. fusca var. guyotiana and T. f. bromi-tectorum. Although the VHP system has insufficient activity for quarantine purposes if sori are present, it may be a practical seed-surface disinfestation process for nonhost seeds, such as barley, where contaminating teliospores from grain handling equipment are borne superficially on seed and sori are rarely or not present. The potency of hydrogen peroxide vapors from the VHP system was equivalent to brief immersion in heated hydrogen peroxide or sodium hypochlorite solutions but superior to water-saturated hydrogen peroxide vapor and to fumigants such as methyl bromide, propylene oxide, and chloropicrin.