First Report of Anthracnose Caused by Colletotrichum gloeosporioides on Taxus mairei in Taiwan.

Abstract

Taxus mairei (Lemee & Levl.) S.Y. Hu ex Liu is a giant evergreen tree native to Taiwan. T. mairei and the Pacific yew, T. brevifolia, produce taxol, a highly effective antitumor drug. Anthracnose was observed on cuttings and seedlings of T. mairei in nurseries and on larger plants grown in plantations in Taiwan. Circular or irregular, brown leaf spots were associated with defoliation. Stems lesions and tip dieback were also observed. Colletotrichum gloeosporioides (Penz.) Sacc. was isolated from diseased tissues, and this fungus grew well on potato dextrose agar and malt extract agar (MEA), with a growth rate of 6.3 mm per day on MEA at 32°C in the dark. Colonies were white to grayish white and became dark gray with age. Acervuli produced on leaves were 115 to 155 μm in diameter, with one or several brown-to-black setae and pale salmon conidial masses. Conidia were guttulate, straight, cylindrical, obtuse at the apex and truncate at the base, and approximately 12 to 17 × 3.5 to 6.0 μm. The disease was reproduced by spraying T. mairei seedlings with a suspension of 104 to 105 conidia per ml, and the control plants were inoculated with distilled water. Inoculated plants were kept in a transparent moist chamber with a constant humidity near 100% (1). Symptoms appeared within 7 days when the temperature was over 32°C. When the temperature was below 24°C, symptoms were delayed. The fungus was reisolated from the inoculated plants, fulfilling Koch's postulates. To our knowledge, this is the first record of anthracnose on Taxus mairei (2), and anthracnose appears to be the most important disease on this plant in Taiwan. Voucher specimens have been deposited at the Division of Forest Protection, Taiwan Forest Research Institute as TFRIFCH Herbarium specimen 137.