Abstract
Pathogenicity of 23 Pythium isolates from soils of Shikoku Island was tested by two methods. Of the 13 isolates of six taxa tested, three isolates of P. aphanidermatum and two of P. spinosum were pathogenic to potted cucumber seedlings, but other eight isolates were slightly pathogenic or nonpathogenic. Of the 23 isolates tested by the soil-over agar culture inoculation method, eight isolates including P. ultimum and P. aphanidermatum were most pathogenic, and damage rates of inoculated komatsuna seedlings were over 20%. To Japanese black pine seedlings, two isolates each of P. aphanidermatum and P. spinosum, and one isolate of P. sylvaticum were rather consistently pathogenic, but damage rates were below 25%. The rest of isolates were slightly pathogenic or nonpathogenic.
