引起水稻與茭白筍胡麻葉枯病之Bipolaris屬病原菌特性比較

Comparison of the characteristics of Bipolaris spp. causing brown spot on rice and water bamboo

前人指出引起水稻（Oryza sativa）與茭白筍（Zizania latifolia）胡麻葉枯病之病原菌分別為Bipolaris oryzae與B. zizaniae，而兩種病原菌之形態學差異在分生孢子基部臍的構造。為釐清引起臺灣水稻與茭白筍胡麻葉枯病兩種Bipolaris屬菌株間之相互關係，本研究針對兩者分生孢子形態、親和性配對、病原性測定及分子特性進行分析。形態觀察結果顯示，來自水稻或茭白筍之Bipolaris屬分生孢子形態相似，且孢子基部以直角狀臍構造為主。親和性配對試驗得知，於光照環境下，水稻與茭白筍菌株可配對產生有性世代。另接種試驗證實，分離自水稻與茭白筍之菌株均可交互感染，產生典型胡麻葉枯病病徵。分析ITS（internal transcribed spacer）與GPDH（glycerol-3-phosphate dehydrogenase）序列區間之分子親緣性，指出水稻與茭白筍之菌株於ITS序列分析形成同一分子群；而分析GPDH序列顯示水稻之菌株可分為兩群，其中一群與茭白筍菌株形成同一分子群。根據上述結果證實，引起水稻與茭白筍胡麻葉枯病之病原菌應屬同種，且分子親緣分析顯示，臺灣水稻與茭白筍胡麻葉枯病之菌株與GenBank中的B. oryzae具有高度親緣性，應屬B. oryzae。

"Bipolaris oryzae and B. zizaniae are the pathogens to cause brown spot on rice (Oryza sativa) and water bamboo (Zizania latifolia). Previous studies indicated that B. oryzae could be distinguished from B. zizaniae based on the hilum structure of conidia basal part. To understand the relationship of Bipolaris spp. causing brown spot on water bamboo and rice, the morphology, cross fertility, pathogenicity and molecular characters of Bipolaris spp. were analyzed. The observation of conidia indicated that the Bipolaris spp. isolates from rice and water bamboo showed similar morphology and rectangular hilum was the major type. The cross fertility test confirmed that the isolates from rice or water bamboo could mate successfully under light condition and produce ascospores. The pathogenicity test demonstrated that the isolates from rice or water bamboo could infect both with typical brown spot. Molecular phylogenetic analyses showed that Bipolaris isolates from rice or water bamboo formed a molecular group based on ITS (internal transcribed spacer) region. The other side, the analysis of GPDH (glycerol-3-phosphate dehydrogenase) sequence showed that isolates from rice could be separated into two molecular groups and one group isolates formed the same molecular group with isolates from water bamboo. Phylogenic analyses demonstrated that the Bipolaris spp. from rice or water bamboo were closely related to B. oryzae from GenBank. Our results suggest that the Bipolaris spp. from rice and water bamboo are same species of B. oryzae."