Relationship of Micro-Organisms to sporulation of Phytophthora cinnamomi rands

摘要

Abstract The effect of soil extracts on sporulation of Phytophthora cinnamomi Rands has been investigated. Non-sterile soil extracts from different soil types and from soils under different plant species all supported sporulation, stimulatory activity being markedly reduced only after 1,000-fold dilution. Autumn soil was most active in stimulating sporulation, whereas summer soil was inactive. When peptone was added to summer soil, the stimulatory activity of the extract was restored. A wide variety of materials added to distilled water failed to stimulate sporulation. Soil extract lost its stimulatory properties after sterilisation by autoclaving, steaming, Seitz or sintered glass filtration, dialysis, ultrasonic disintegration, ultracentrifugation, or treatment with propylene oxide or alcohol. Root exudates and micro-organisms other than bacteria had no effect on sporulation. Fifty-nine bacterial cultures classified in 15 genera stimulated sporulation on one or more occasions when transferred from nutri...