香蕉抗黃葉病植株網室檢定法及其選種效果

A Net-house Method for the Mass Screening of Resistance to Fusarium Wilt in Banana and Its Efficiency in Clonal Selection

本研究研討利用人工接種病原菌，在網室進行香蕉抗黃葉病選種的可行性。經分離後的黃葉病菌（Fusarium oxysporum f. sp cubense, race 4）菌絲在砂－－玉米介質中培養21天後，取少量放置盤缽底部，再假植香蕉組織培養苗，經兩個月後，進行塊莖病徵檢查。試驗結果顯示，假植一個月大的幼苗經接種後，發病速度及程度均高於三個月大的幼苗。比較病原菌用量，接種全量菌種的發病速度雖較快，但在兩個月後，接種全量或半量菌種引起的發病程度，差異不大，故使用半量可達相同效果。取用上述網室接種病原菌方法對‘北蕉’進行抗病選種研究。從20,176株組織培養苗中，經單株選種，選出46個初步鑑定為具抗性的品系。再經兩次田間病圃品系抗病性鑑定，選出高抗品系GC-1089。在病園塊莖檢查GC-1089的嚴重病徵發生率約為13.1%，而抗病品種‘台蕉三號’及感病品種‘北蕉’的重病率分別為21.6及74.6%。在三個蕉農黃葉病感染的蕉園種植，GC-1089的發病率為4.6-29.8%，而抗病對照品種為10.8-23.2%。可見使用網室檢定法，不但省工簡便，同時選出的抗病系，其抗病性極其穩定。

The objective of this study is to investigate the feasibility of using artificial inoculation of the Fusarium pathogen for the mass screening of resistant clones in banana under the net-house environment. After isolation, the mycelium of Fusarium oxysporum f.sp. cubense (race 4) was cultured in the sand-maize mixture for 21 days. Small quantity of this Fusarium culture was placed at the bottom of plug-holes before transplanting the banana tissue-cultured plantlets. After 2 months of inoculation, the tip of the rhizomes were cut to examine the internal symptom of the disease. It was observed that the expression of the disease symptom in 1-month old plantlets was more prominent than that of 3-month old plantlets. In the experiment to test the amount of inoculum, development of the disease symptom was faster in the treatment using full dosage of inoculum than that of the half dosage. However, at the end of the 2-month period, the degree of disease infection in both treatments was not significantly different. Therefore, half dosage of the inoculum was used for later experiments. By using the above procedure, selection of resistant clones was made from 'Pei Chiao', a Giant Cavendish cultivar. After screening of 20,176 plants, 46 of them were selected as putative resistant plants and were used for multiplication by tissue culture. These clones were subjected to two subsequent clonal evaluations in the disease nursery. A resistant clone, designated as GC-1089 was selected. In the disease nursery, the percentage of heavily infected plants of GC-1089 was 13.1% while the percentages of the resistant and susceptible check cultivars were 21.6 and 74.6%, respectively. In three on-farm experiments, the percentages of diseased plants of GC-1089 and the resistant check cultivars were 4.6-29.8% and 10.8-23.2%, respectively. The results indicated that the net-house method for screening resistance to Fusarium wilt in banana was simple and effective. The resistance of the selected clones was stable during several generations of evaluation.