Pathogenicity test
Pathogenicity was proved by artificial inoculation PHY02 into roots of pomelo seedlings (Citrus maxima) var. Khao nam Pueng (the same affected variety where PHY02 was obtained).
Root inoculation was done using the infested soil method of Zitko et al. [4]. Six-month-old pomelo seedlings were thoroughly washed to be free of potting mix and then planted in plastic tubes (10 × 15 cm) containing sterilized clay soil-sand (1 : 1) with 5 chlamydospores of PHY02 per cubic centimeter. Controls were prepared by planting the seedlings in same size tubes, but containing sterilized clay soil-sand (1 : 1) only. All pots including the controls were maintained in the green house at temperature of about 25~30℃ and flooded with water for 24 hr each week. After 6 wk, the plants were carefully removed from plastic tubes, the soil was washed out and rating was done based on degree of the root rot symptoms. The pathogen then was re-isolated from newly infected roots symptom and morphology characteristics were compared with the isolate PHY02.