抗病及感病番木瓜品系(種)葉片感染不同木瓜輪點病毒系統後其病徵學與解剖學之研究

Symptomatology and Histology on Susceptible versus Resistant Papaya (Carica papaya L.) Cultivar/Line Infected with Papaya Ringspot Virus

湯惟真(Wei-chen Tang)

指導教授 ： 張龍生

共同指導教授 ： 林宗賢 ； 黃玲瓏 ； 洪挺軒(Ting-Hsuan Hung)

國立臺灣大學/生物資源暨農學院/園藝學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.02831

摘要

第一部分
田間抗木瓜輪點病毒之抗病品系可維持番木瓜葉片形態組織之完整性

本研究以感病品種‘台農二號’(Tainung No.2, TN2)及抗病品系‘台大十一號’(NTU hybrid 02011, NTU11)番木瓜(Carica papaya L.)為供試材料，取未罹病健康植株及田間自然感染木瓜輪點病毒(Papaya ringspot virus, PRSV)之未成熟(expanding)及完全展開(fully-expanded)之番木瓜葉片為樣本，比較其木瓜輪點病毒對番木瓜葉片形態與組織之影響。健康之‘台農二號’葉片無病徵，在光學顯微鏡下觀察其柵狀組織為單層結構，排列整齊；罹病之‘台農二號’葉片產生嚴重嵌紋、變形且有綠島(green-island)等顯著之外部病徵，其罹病之葉片上下表皮細胞異常而其柵狀組織的細胞層數則為0-3層。‘台大十一號’之健康葉片，形態與葉片組織皆與台農二號之健康葉片相似；而罹病之‘台大十一號’葉片，則呈葉脈透化之輕微病徵，病毒對其葉片組織的破壞不明顯，與健康葉片無顯著差異。以量化後的柵狀組織數據作為抗病指標，顯示‘台農二號’未成熟葉片之柵狀細胞與組織於試驗初期即持續受到病毒嚴重破壞，而病毒對完全展開葉片之破壞則於試驗第七週時顯現，表示病毒於試驗初始即影響頂芽部分之葉片，爾後此影響顯現於試驗後期之完全展開葉片。而‘台大十一號’罹病後未成熟及完全展開葉片之柵狀細胞與組織並無明顯受到病毒危害之症狀。故由顯微鏡檢結果顯示作物之抗病性不但能維持作物罹病後之形態，亦能維持組織構造之完整性，進而維持作物相對正常之生理現象。

第二部分
木瓜輪點病毒系統與寄主間之交互作用對番木瓜病害發展及微細構造之影響

經白藜三代單斑分離純化之木瓜輪點病毒(Papaya ringspot virus, PRSV) DF及SMN系統(strains)對感病品種‘台農二號’(Tainung No.2, TN2)之番木瓜(Carica papaya L.)造成不同病徵及病害發展。感染SMN系統之‘台農二號’，其病害發展曲線下面積(area under disease progress curve, AUDPC)於接種後3-4週達最大值，而感染DF系統其相對病害發展曲線下面積(relative AUDPC, RAUDPC)則為91.2%，顯著低於SMN系統，表示此二純化之病毒系統對‘台農二號’不同危害程度顯示二病毒可能具不同之毒力因子。取田間表現DF及SMN病徵之葉片作為病毒分離株(isolates)，接種DF分離株之部分‘台農二號’植株出現SMN之典型病徵，接種SMN分離株者部分也出現DF之典型病徵，顯現田間有複合感染的情況。然接種SMN分離株之‘台農二號’其AUDPC於7-8週才達最大值，與接種DF分離株之RAUDPC則無顯著差異，無法由病徵發展判斷‘台農二號’接種田間不同病徵型病毒其毒力基因之差別。且其二者之病徵發展遲緩，表示此複合感染造成病毒系統間在寄主體內彼此發生相互競爭之現象。以光學顯微鏡觀察內部病徵，量化後的柵狀組織數據則可分出此二病徵型之病毒對寄主仍具不同之危害程度。感染DF病毒之‘台農二號’葉片幾乎無柵狀組織之分化，而感染SMN病毒之‘台農二號’其柵狀組織減少為健康葉片之62.0%。以電子顯微鏡觀察柵狀細胞，受到PRSV感染之‘台農二號’以葉綠體之結構受到之影響最大。然抗病品系‘台大十一號’(NTU hybrid 02011, NTU11)之番木瓜，受PRSV感染後僅顯現輕微之嵌紋病徵，並能維持葉片組織、細胞及葉綠體與其他胞器之完整性，對不同病毒系統所導致之病徵經量化後或是利用顯微技術探討病毒對寄主細胞、組織之危害皆無顯著差異，顯示‘台大十一號’無論對最流行或是毒力最強之木瓜輪點病毒系統皆具穩定之抗病性。

關鍵字

抗病性 ； 木瓜輪點病毒 ； 番木瓜 ； 組織完整性 ； 病毒-寄主交互作用 ； 微細構造

並列摘要

Section 1
Field Papaya Resistance to Papaya Ringspot Virus by Maintaining the Integrity of Tissue Morphology

Histological effects of leaf structure that papaya (Carica papaya L.) naturally infected by Papaya ringspot virus (PRSV) in the field were compared between susceptible cultivar ‘Tainung No.2 (TN2)’ and resistant line ‘NTU hybrid 02011 (NTU11)’. Expanding and fully-expanded leaf sections were observed by light microscope. The palisade tissue of healthy ‘TN2’ was well-ordered arrangement with single layer of palisade cells. PRSV-infected ‘TN2’ leaves were severe mosaic, deformed, and with green -island; the epidermal cells was abnormal and the palisade tissue was 0-3 layers. The healthy lamina of ‘NTU11’ was similar to healthy ‘TN2’. The infected one was vein clearing, but the leaf structure was as normal as healthy ones. To quantify palisade tissue, the parameters of expanding leaf of PRSV-infected ‘TN2’ decreased continually through the periods, and the parameters of fully-expanded leaf remained then rapidly dropped at the 7th week. That revealed PRSV caused damage of ‘TN2’ leaves near shoot apex at the first beginning of experiment. However, the parameters of ‘NTU11’ remained as good as healthy control. The microscopic observation revealed that viral resistant crop can keep relatively normal morphology, maintain integrity of leaf tissues, then let physiological parameters function normally.

Section 2

Disease Progress and Ultrastructural Changes between the Interaction of Papaya Ringspot Virus Strains and Hosts

Distinct DF and SMN strains of Papaya ringspot virus (PRSV) caused different symptoms in the susceptible papaya cultivar ‘Tainung No.2 (TN2)’. The area under disease progress curve (AUDPC) of SMN strain-infected ‘TN2’ was maximum 3-4 week after inoculation (w.a.i.), and the relative AUDPC (RAUDPC) of DF strain was 91.2% which was significantly lower than that of SMN strain. It revealed that two PRSV strains have different virulence to papaya hosts. Strains competition between DF and SMN isolates seemed to occur in the field. Symptom development in the TN2 host infected by SMN isolate was maximum 7-8 w.a.i., which was not significantly different from that infected by DF. Quantitative histological changes in palisade parenchyma also showed the different severity of damage between 2 strains. Palisade cells were almost absent when the plant was infected by DF isolate, and the DF-infected palisade tissue was decreased to 62.0% of healthy lamina. In the cytopathological study, severe damage of chloroplast structure was observed in PRSV-infected ‘TN2’. However, PRSV-infected ‘NTU11’ only produced mild mosaic symptoms and kept almost intact tissues, cells and organelles. Compared to the healthy control, both DF and SMN-infected ‘NTU11’ papaya did not show apparent external symptoms and histological damages. ‘NTU11’ papaya is therefore considered to be resistant to various strains of PRSV with horizontal resistance.

並列關鍵字

Carica papaya ； Papaya ringspot virus ； resistance ； integrity of tissue morphology ； virus-host interaction ； ultrastructure

參考文獻

Choy, M. W. and L. S. Chang. 1995. Characteristics of papaya ringspot virus-type P. J. Chinese Soc. Hort. Sci. 41(3): 147-160.

Agrios, G. N. 1997. Plant diseases caused by viruses. p.479-563. In: Plant Pathology. 4th ed. Academic Press, U.S.A.

Alberts, B., D. Bray, A. Johnson, J. Lewis, M. Raff, K. Roberts, and P. Walter. 1998. Membrane structure. p. 347-369. In: Essential Cell Biology: an introduction to the molecular biology of the cell. Garland, New York.

Allen, T. C. 1972. Subcellular responses of mesophyll cells to wild cucumber mosaic virus. Virol. 47: 467-474.

Atkinson, P. H. and R. E. F. Matthews. 1970. On the origin of dark green tissue in tobacco leaves infected with tobacco mosaic virus. Virology 40: 344-356.