- 學位論文
香蕉苞葉嵌紋病毒之發病生態
Disease ecology of Banana bract mosaic virus
摘要
香蕉為世界生產量最高之全年水果，也是全世界超過一百多個熱帶國家之主食果實，臺灣也一直將香蕉視為重要出口農產品。香蕉苞葉嵌紋病毒 ( Banana bract mosaic virus, BBrMV ) 為 Potyviridae 科，Potyvirus 屬之正譯單股RNA 病毒 ((+) ssRNA virus)，可藉由無性繁殖體（如組織培養苗與吸芽）與蕉蚜 ( Pentalonia nigronervosa )、棉蚜 ( Aphis gossypii )、黍蚜 ( Rhopalosiphum maidis ) 等三種蚜蟲以非永續性方式傳播 (non-persistent transmission)。BBrMV會在香蕉苞葉上產生暗紅色紡綞型條斑，於葉子及假莖上則產生淡綠色紡綞狀嵌紋病斑。此病害已在許多熱帶國家對當地香蕉產業造成危害，且威脅日漸加深；而臺灣在過去也已經在三尺蕉 ( AAA ) 上發現得病植株，值得關注。近年來在臺灣由於香蕉黃葉病菌生理小種第四型 ( Fusarium oxysporum f. sp. cubense race 4，Foc 4) 的出現危害北蕉 ( AAA )，台灣香蕉研究所已選育出對Foc 4抗病的香蕉品系，如：寶島蕉 ( GCTCV-218 )、台蕉五號、台蕉七號、大北蕉等品系。以蕉蚜傳染試驗確認上述抗Foc 4 個品系以及台灣香蕉研究所的保存品種Umalag - V63 ( AAA ) 皆對BBrMV 感病，而原來對Foc 4感病的北蕉卻對BBrMV抗病，顯示北蕉之變異品系對BBrMV之感病性與Foc 4 之抗病性可能有所關聯（linkage）。另外以蕉蚜傳染試驗來調查BBrMV在田間可能的中間寄主，並以反轉錄聚合酶連鎖反應 (reverse transcription-polymerase chain reaction，RT-PCR) 追蹤BBrMV，結果顯示 BBrMV可成功感染紅花月桃 ( Alpinia purpurata ) 與姑婆芋 ( Alocasia odora )，並可永續於植株內部增殖。紅花月桃被感染後於葉部也會出現典型之紡錘狀淡綠色病徵；但姑婆芋被感染後則不出現病徵，為潛伏感染。野薑花 ( Hedychium coronarium ) 和美人蕉 ( Canna spp. ) 則不被BBrMV感染。選用台蕉五號測試不同株齡的植株對BBrMV是否具有成熟抗性 ( maturity resistant )，結果顯示當植株愈幼嫩，染病率較高；植株愈成熟，染病率愈低。以RT-PCR進行臺灣田間香蕉植株BBrMV的感染情形調查，發現在雲林莿桐之烏龍蕉 ( AAA )、高雄大寮大北蕉 ( AAA ) 及屏東九如之台蕉五號 ( AAA )、台蕉七號 ( AAA ) 與Saba ( ABB ) 皆有發現到BBrMV的感染株。
並列摘要
The banana is one of the most important fruits with the highest yield in the world, which is the main food source for more than 100 tropical countries. It is also an important export crop in Taiwan. Banana bract mosaic virus (BBrMV), a positive-sense single-stranded RNA virus categorized into Potyvirus, Potyviridae may be transmitted by the vegetative propagation and three aphids such as the banana aphid (Pentalonia nigronervosa), cotton aphid (Aphis gossypii) and corn leaf aphid (Rhopalosiphum maidis) with the non-persistent manner. BBrMV causes the dark purple spindle-shape mosaic symptom on flower bracts, and chlorotic spindle-shape mottling on leaves and pseudostem in bananas. This disease had already seriously impacted the banana industry in several tropical countries, and its threat is increasing. BBrMV has become a new concerned problem for the banana industry since the BBrMV-infected banana plants were ever discovered in San chi chiao (AAA) in Taiwan. Owing to the destructive damage of Fusarium oxysporum f. sp. cubense race 4 (Foc 4) on the Pei-chiao ( AAA ) banana (the most popular traditional banana cultivar), Taiwan Banana Research Institute (TBRI) had already developed several resistant banana cultivars against Foc 4 such as ‘Formosana’ (GCTCV-218), ‘Tai-chiao No. 5’, ‘Tai-chiao No. 7’ and ‘Large-pei-chiao’. In this thesis, the inoculation tests with banana aphids demonstrated that those resistant cultivars against Foc 4 mentioned above and the cultivar ‘Umalag - V63’ (AAA) preserved in TBRI were susceptible to BBrMV whereas the traditional cultivar ‘Pei-chiao’ (susceptible to Foc 4) showed resistance to BBrMV. It suggested that gene linkage probably exists between the genes governing BBrMV susceptibility and the genes responsible for the resistance against Foc 4 in those Pei-chiao-derived cultivars. In addition to various banana cultivars, several other species of plants were also inoculated with BBrMV through aphid-transmission and RT-PCR assays to test whether they are potentially alternative hosts for BBrMV. The results indicated that Alpinia purpurata and Alocasia odora had potential to be the alternative hosts whereas Hedychium coronarium and Canna spp. were immune against BBrMV. BBrMV caused the typical spindle shaped chlorosis mosaic symptom on A. purpurata and did not induce any symptom (latent infection) on A. odora though BBrMV could be detected in both of them with RT-PCR assays. Besides, the comparative inoculation tests among different ages of banana plants (Tai-chiao No.5) showed that the transmission efficiency in the younger plants were higher than those in the older plants. The field survey conducted in this study discovered that the cultivar ‘Oolong’ (AAA) collected from Yunlin, ‘Large-pei-chiao’ (AAA) collected from Kaohsiung, ‘Tai-chiao No. 5’ (AAA), ‘Tai-chiao No. 7’ (AAA), and Saba (ABB) collected from Pingtung were tested positive for BBrMV. It demonstrated again that BBrMV existed in the banana orchards in Taiwan.