Abstract
Exobasidium vexans causes blister blight, a serious disease on tea plants. Establishment of cultures on media is important to clarify its characteristics and to develop useful control methods. Other Exobasidium species, but not E. vexans, can grow on common fungal agar media. However, E. vexans can grow on home-made potato dextrose broth plus edible agar. Elemental analyses of edible agars suggested that more than 0.6 % calcium content in the agar was responsible for colony formation of E. vexans. Potato dextrose agar (PDA) amended with 100 mgL-1 calcium (equivalent to 0.7 % calcium concentration and 15 gL-1 of agar) achieved the successful culture of E. vexans. Among 7 calcium salts tested, calcium chloride, calcium chloride dihydrate, calcium carbonate, calcium hydrogen phosphate, calcium hydroxide, calcium nitrate tetrahydrate, and calcium sulfate dihydrate, 5 isolates of E. vexans were able to grow on PDA amended with calcium carbonate or calcium hydrogen phosphate, with calcium carbonate being most effective. The pH of the amended PDA ranged from 5.35 to 7.56. We successfully established and maintain E. vexans on media for the first time. Basidia and basidiospores were observed on the colony of E. vexans after 23 days of incubation. A commercial potato dextrose broth plus strip agar or commercial PDA amended with 100 mgL-1 calcium (equivalent to 0.7 % calcium concentration and 15 gL-1 of agar) can help to grow pure cultures of E. vexans.
