香蕉品種對萎縮病感病性之研究

Studies on the Susceptibility of Banana Varieties to Bunchy Top Disease

檢定香蕉品種之萎縮病感病性，於民國五十六年開始，分田間自然發病調查與人工接種試驗兩方面進行觀察研究。在田間自然環境下，供試五十五年品種中，有三十九品種罹病，十六品種未見發病。感病品種中，罹病率鷙達50%以上者有十九品種。以帶病毒香蕉蚜蟲（Petalonia nigronervasa Cog.），做人工接種，為一檢定品種萎縮病性確實可靠的方法，兩次人工接種試驗均獲得良好的成效。供試17品種除了龍芽蕉與Ambon兩個二倍體香蕉沒有發病外，其於15個品種都有感染。Ice Cream與Popul二品種的罹病率較低，祇有62.5%與50%，似具有耐病之特性，其他感病品種的罹病率都在75%以上。品種間潛伏期之長短一，差異甚大，仙人蕉的潛伏期最短，Ice Cream與Popul二品種最長。潛伏期長短與品種葉片生長的特性，或栽培環境影響葉片生長有密切的關係。葉片生長快的品種，其潛伏期較短；葉片生長慢者，其潛伏期較長。不同品種感染萎縮病後，所表現的病微大致相同，葉片上深綠色斷績條線（dark-green streaks）為最先出現的病微。罹病植株多葉片狡小直立，葉柄縮短而呈帚狀。

Bunchy top is one of the most important diseases of banana in Taiwan. It has widely distributed and often handicapped the banana industry especially in the central part of the Island. Studies on the susceptibility of banana varieties to bunchy top disease were conducted at the Chiayi Agricultural Experiment Station, TARI, from 1967 to 1969 both by observation under natural conditions and artificial inoculation. For the field observation, among the 55 entries of banana varieties 16 of these showed no diseased plants, while 39 were either susceptible or highly susceptible to bunchy top, ranged from 16.67% to 100% in their infection percentage (Table 1). Sun (1961) reported that the banana a phid (Pentilonia nigronervosa Coq) was a very efficient vector in transmitting bunchy top disease of banana in Taiwan. For the artificial inoculation trials, 20-30 aphids taken from bunchy top diseased plants were transferred to a test-plant in each variety, and successful results were obtained. Based on the results obtained from both the first and second experiments, marked difference in the susceptibility of banana varieties to bunchy top disease was clearly indicated. Among the 17 varieties tested, two of seeded varieties, Lung-ya-chiao and Ambon, Showed no diseased symptoms, while 13 varieties were highly susceptible. Varieties Ice cream and Popul gave a low infection percentage of 62.5% and 50%, respectively, seemed showing that these two varieties were slightly tolerant to the disease (Table 2 and 3) It is evident that there is a distinct difference in the incubation periods of tested varieties when it was inoculated by banana aphids which were collected from the diseased plants. The commercial variety so-called Hsien-jen-chiao had given the shortest incubation of 21-47 days in first trial and 50-71 days in second one. The varieties Ice cream and Popul given incubation periods of longer than 80-188 days and 162-254 days, respectively (Table 2 and 3). Obviously, the incubation periods are very closely related to the character of leaf development. In general, the symptoms of bunchy top appeared to be more quickly in a variety whose leaves grew up more rapidly than the variety with slow growing leaves. However, the symptoms of infection shown by the various varirous varied rather slightly. The most common symptoms were the dark-green streaks within lamina, the slender pseudostem, narrow leaves and straight with short petioles (Fig, 2-16).