ABSTRACT
Diseased mulberry grafted saplings caused by R. oryzae (A-C) and the morphology (D-I). Echinulate sporangium (D), subglobose columella (E), sporangiophore with basal rhizoid and collapsed apical sporangium (F), colony on potato-sucrose agar plate (G), chlamydospores (H), and sporangiospores. Mortierella species were found not pathogenic to cucumber seedlings by the soil-over agar-culture method. Mortierella species were applicable to the diseased soil directly by sowing the artificially infested cucumber seeds. These Mortierella species were antagonistic against the damping-off pathogens of Pythium and Rhizoctonia species. Pathogenicity of soil fungi may be simply determined by the soil-over-agar culture inoculation method using 21 Mortierella and 52 Pythium strains isolated in the Ogasawara Islands. None of 21 Mortierella isolates, and three uninoculated controls were pathogenic to cucumber seedlings, and the seedlings that emerged were all healthy, even though some plates were covered with abundant mycelia.
