In vitro sporulation of race 32 of Puccinia graminis Pers. f.sp. tritici Erikss. & Henn

Race 32 of Puccinia graminis f.sp. tritici sporulated in vitro on a chemically defined medium whose amino acid and carbohydrate composition corresponded to that of the susceptible wheat cultivar Little Club. Sporulation was affected by pH, heat-treatment of the medium and the spore-density of the inoculum. Good mycelia( growth was promoted at high inoculum density, low volume of culture medium, and when no heat treatment, or only limited heat treatment, was given during sterilization of the medium. When these conditions were reversed and at pH 5·2, sporulating colonies occurred. Under optimal conditions the first urediospore bearing colonies could be detected 10 days after inoculation of the medium. Several hundred fertile colonies could be detected up to day 20. Typical teliospores were usually found for the first time at day 30. Differentiation of infection structures had a negative effect on sporulation.