Preliminary Observations on Varietal Reaction to Cercospora Leaf Spot of Banana

Abstract

葉斑病為本省香蕉主要病害之一， 全年危害各地蕉園， 尤以雨季流行最速。葉斑病發生嚴重時，香蕉葉片被毀，影響果實產量與品質甚鉅。為了選擇抗病性優良品系以根本解決葉斑病為害，並檢定各品系之抗病性，進而研究選育抗病性品系，作者自民國五十五年九月開始，在嘉義農業試驗分所進行觀察杳蕉品系葉斑病感應性，初步所獲結果如下：（一）供觀察香蕉品系55種中，在田間自然發病環境下，有25品種未發現有感染葉斑病之病徵；另外 Boyang 和紅皮蕉二種，僅發現在少數老葉上有病斑可能亦具有抗病性；其餘28品系則顯示對葉斑病具有感病性或高度感病性，感病指數在0.63 -1.19之間。仙人蕉之感病指數為所有品系中最高者，足見仙人蕉為一高度感病性品種。 （二）由高屏地區仙人蕉品種中選取之優良母株106株調查對葉斑病之感應性結果， 未見有抗病性者存在，植株間對葉斑病感應性差異不大。根據觀察結果，顯示由仙人蕉品種內進行抗病性優良系統選種之期望很少，但因此項觀察株數不多，今後擬增加選種株數或於病害嚴重流行時，直接到香蕉各主要產地進行選種，冀可獲得具有抗病性優良之突變系統。 （三）葉斑病之發生與氣候因子有密切關係，本項觀察期間，因氣候乾旱，病害發生並不嚴重，因正在感病性品系所示之感病指數都不高。品系間抗病性之差異除繼績在田間進行觀察外，並將利用人工接種方法以檢定具有抗病性之品系。 Observations on the varietal reaction to Cercospora leaf spot of banana were conducted at the Chiayi Agricultural Experiment Station, Taiwan Agricultural Research Institute from September, 1966 to February, 1967. Fifty-five banana varieties/clones including the materials collected from native and Tropical Asia, and 106 plants selected from the Hsien-ien-chiao variety were used in this observations. According to the preliminary results obtained, it is evident that there is a distinct difference in the reactions of the observed varieties to leaf spot of banana ranging from highly resistant to highly susceptible. Among the 55 entries, 25 of these showed no attacked symptom, while 28 were either susceptible or highly susceptible, and another two varieties, namely, Boyang and Hung-pi-chiao, giving a low infection index may be classified as resistance (Table 1). Furthermore, no plant was observed among the 106 plants selected from the commercial variety, Hsien-ien-chiao, to be resistant to the disease (Table 2). Unfortunately, the Hsien-jen-chiao variety gave the highest infection index among the varieties tested, and, it was proved very susceptible to leaf spot. Since the weather condition during the observation period was not favorable to take place the disease seriously, therefore, the infection indices are very low as shown in all the diseased varieties. However, the disease was greatly influenced by the climatic factors, and a close relation was found between plant infection index and relative humidity (Fig. 1). More studies on the susceptibility of banana varieties/clones to leaf spot are in progress.