GERMINABILITY OF TILLETIA SPP TELIOSPORES AFTER HYDROGEN-PEROXIDE TREATMENT

Three methods of hydrogen peroxide treatment tested to control germina tion of teliospores of Tilletia spp. contaminating wheat or barley see ds 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-inj ection system (VHP) that includes control of vapor moisture content. T eliospores 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-sa turated hydrogen peroxide Vapors for as long as 15 min. Teliospores on the surface of wheat seed would not germinate after treatment for 5 m in in the VHP system at 46-48 C. Germination was reduced 95-99% by tre atment for 1 min in the VHP system. The system was equally effective w hen applied with deep (38 mm Hg) or shallow (680 mm Hg) vacuum. The tr eatment did not wet wheat or barley seeds or influence their germinabi lity even if applied for more than 30 min. Barley malting quality was not influenced by VHP system treatment. When intact sori were fumigate d, however, most teliospores within the sori of both fungi survived. S imilar results were obtained with T. fusca var. guyotiana and T. f. br omi-tectorum. Although the VHP system has insufficient activity for qu arantine purposes if sori are present, it may be a practical seed-surf ace disinfestation process for nonhost seeds, such as barley, where co ntaminating teliospores from grain handling equipment are borne superf icially on seed and sori are rarely or not present. The potency of hyd rogen peroxide vapors from the VHP system was equivalent to brief imme rsion 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.