利用嫁接於抗病根砧防治甘藍根瘤(腫)病之研究

Abstract

甘藍[Brassica oleracea L. (Capitata group)]為臺灣與世界重要蔬菜之一。十字花科根瘤病(clubroot disease)為甘藍常見之土壤傳播性病害，好發於冷涼濕度高地區之酸性土壤。罹病植株之地下部出現不規則或紡錘狀腫狀物，地上部則萎凋，嚴重時甚至植株死亡。根瘤病之病原菌-根瘤病菌(Plasmodiophora brassicae Woronin)可存活土中達十多年之久，因此難以根除。慣行栽培甘藍因土壤酸鹼值之降低，而增強根瘤病菌之活性。常見之根瘤病防治方法為施用含鈣資材、殺菌劑等，但上述防治方法效果未必穩定。目前最有效的防治方法為種植抗病品種，但臺灣尚無根瘤病抗病品種。‘初秋’甘藍為最受臺灣消費者歡迎的甘藍品種，卻極感根瘤病。「嫁接」常被運用於果菜類作物以達到抗病目的。本研究利用套管接(tube grafting)，將‘初秋’甘藍嫁接於六個日本抗病品種甘藍，探討嫁接後甘藍對根瘤病之抗病性。試驗一配製不同濃度之根瘤病菌休眠孢子懸浮液進行人工接種，進行盆栽試驗以探討各品種甘藍實生苗之抗病性，並找出最適之人工接種濃度，接種結果顯示各抗病品種甘藍皆具根瘤病抗病性，並決定後續試驗接種濃度為105 spores·mL-1 soilless mix。試驗二採集南投縣春陽、紅香二地區之根瘤病菌，接種於特定寄主以判定根瘤病菌分群，結果顯示此二地區之根瘤病菌均屬於Hatakeyama (2004)定義之第四群。試驗三、四將‘初秋’甘藍嫁接於抗病品種，進行盆栽試驗，觀察嫁接後植株於苗期、成株之生長情形、根瘤病抗病性、葉球產量與品質，結果顯示嫁接‘初秋’甘藍於抗病根砧能顯著提高根瘤病抗病性，並可維持或提高葉球產量及品質。試驗五於南投紅香田區種植八品種甘藍實生苗，結果顯示六抗病品種甘藍皆可於田間表現根瘤病抗病性，‘初秋’與‘228’則對根瘤病敏感。綜合以上結果，春陽與紅香之根瘤病菌屬於同一群，而日本抗病甘藍可於春陽接種原之盆栽試驗及紅香田間試驗表達根瘤病抗性。將‘初秋’甘藍嫁接於抗病根砧，能有效提高甘藍對根瘤病之抗病性，且植株生長、葉球產量與品質通常能維持。

Cabbage [Brassica oleracea (Capitata group)] is one of the important vegetable in Taiwan and in the world. Clubroot disease is a common soil-borne disease of cabbage. It happens in acidic soils in cold and humid areas. The roots of infected plants appear irregular or spindle-like galls, and the shoots wilt or even die in severe cases. The pathogen of clubroot disease is Plasmodiophora brassicae Woronin. P. brassicae can survive in soil for ten years or more, therefore, it is difficult to be eliminated. Conventional farming of cabbage enhances the activity of P. brassicae due to the decrease of soil pH. The common control methods for clubroot disease are application of calcium-containing materials, fungicides, etc., but the effects of the above control methods may not be stable. Currently, the most effective control method is to culture clubroot disease-resistant (CR) cultivars, but there is no CR cultivar in Taiwan yet. ‘K-Y cross’ cabbage is the most popular cabbage among customers in Taiwan, but it is extremely susceptible to P. brassicae. “Grafting” is usually applied in fruit vegetables to achieve disease resistance. In this study, tube grafting was applied. ‘K-Y cross’ cabbage was used as scion, and grafted it onto six Japanese CR cabbage cultivars so as to discuss clubroot resistance of cabbage after grafting. In experiment one, different concentrations of P. brassicae resting spores were prepared for artificial inoculation. Pot experiment was conducted in order to discuss the resistance of different cultivars and find out optimal concentrations of P. brassicae resting spores for artificial inoculation. According to the results, all the CR cabbage cultivars are resistant to P. brassicae, and spore concentration of inoculation in subsequent experiments was also determined as 105 spores·mL-1 soilless mix. In experiment two, P. brassicae isolates from Chunyang and Hongxiang, Nantou County were collected and inoculated on specific hosts to determine the classification of P. brassicae isolates. According to the results, P. brassicae in these two areas were both classified as group 4 defined by Hatakeyama (2004) method. In experiment three and four, ‘K-Y cross’ cabbage was grafted onto the CR cultivars, and conducted pot experiment to observe the growth, clubroot disease resistance, yield and quality of leaf head at seedling and mature stage. The results showed that grafting ‘K-Y cross’ cabbage onto resistant rootstocks can significantly improve clubroot disease resistance, and also maintained or even enhanced yield and quality of leaf head. In experiment five, eight non-grafted cabbage cultivars were cultured in field in Hongxiang, Nantou County. The results showed that in Hongxiang field, all six CR cabbages performed resistance to P. brassicae, but ‘K-Y cross’ and ‘228’ cabbages were susceptible to P. brassicae. Based on the above results, P. brassicae isolates of Chunyang and Hongxiang were classified as the same group. Japanese CR cabbages performed resistance to P. brassicae in pot experiments with Chunyang isolate and in Hongxiang field trial. Grafting ‘K-Y cross’ cabbage onto CR rootstocks effectively enhanced clubroot resistance of cabbages. Furthermore, plant growth, yield and quality of leaf head can usually be maintained after above grafting.