芋頭疫病菌的交配型分佈、抗藥性及親緣關係之研究

"Mating Type Distribution, Fungicide Sensitivity, and Phylogenetic Relationships of Phytophthora colocasiae"

從1997到2011年，在夏威夷的歐胡島、可愛島、莫洛凱島及大島蒐集罹患芋頭疫病的葉片組織，總共分離到218個芋頭疫病菌菌株，其交配型經測試皆為A2型。將2011年由四個島嶼十二區共二十個田區所蒐集的141菌株進行對殺菌劑滅達樂的抗性測試，由可愛島、莫洛凱島及大島蒐集的菌株對滅達樂皆無抗藥性發生，然而，在歐胡島上蒐集的菌株約有百分之二十五對滅達樂具有抗藥性；其中112個菌株在V8培養基上培養四天，平均生長速度介於13到17公釐，依其生長於V8培養基之菌落形態可分為二群，一群僅有稀疏的氣生菌絲，另一群菌絲生長較密，具有棉花狀氣生菌絲；所分離的芋頭疫病菌菌株並無產生厚膜孢子。以轉錄區間核糖核酸（ITS）進行親緣分析，有18個菌系的轉錄區間核糖核酸序列與南太平洋及東南亞國家的菌株相近；另外一個由大島及二個由可愛島分離的菌株則與中國、印度的菌株具有高度的相同性，因此推論夏威夷的芋頭疫病菌菌株可能源自於二個不同地區。

"From 1997 to 2011, Phytophthora colocasiae was isolated from taro leaf blight samples, collected from the islands of Oahu, Kauai, Molokai, and the Big Island of Hawaii. A total of 218 isolates were obtained and all were of the A2 mating type. Isolates collected in 2011 from 20 farms in 12 districts of the 4 islands were also tested for metalaxyl resistance. No resistant isolates were found from Kauai, Molokai or the Big Island of Hawaii. However, 25 percent of the isolates from Oahu were resistant to metalaxyl. Radial growth of 112 isolates tested ranged from 13 to 17 mm on V8 agar after 4 days at 24°C. Two types of colony morphology were observed: one with sparse aerial mycelia, and the other with dense, cottony aerial mycelia. No chlamydospores were observed in either type. Eighteen of 21 isolates from Hawaii clustered with isolates from South Pacific, and South East Asia, in phylogenetic analysis of the rDNA internal transcribed spacer (ITS). Given that only three isolates from Big Island and Kauai shared higher sequence identities to isolates from the China and India. It is possible that P. colocasiae in Hawaii are from two origins."