香蕉束顶病的研究 Ⅱ.病害的症状、传播及其特性

香蕉束顶病病株叶片边缘轻度黄化,略向上卷曲,叶背或叶片主脉背面和叶柄上出现断断续续的浓绿色条斑,即“青筋”,长短不一,短的不到1mm,长的尤其是叶片主脉和假茎上的可达30-50cm或更长,病后植株长出的叶片一片比一片小,病株外观矮化,呈束顶。病害的潜育期与侵染时蕉株大小和温度高低有关,最短的19d,最长的可达216d,病害由香蕉交脉蚜传播,最短获毒时间30min,最短接毒时间15min,循回期在ld左右,一次获毒后可保毒14d.带病吸芽也能传病。汁液摩擦和土壤不能传播,病健根部自然交接和菟丝了均没有传播成功

Studies on Banana Bunchy Top Ⅱ.Symptoms and Transmission of the Disease

Banana plants infected with banana bunchy top showed slightly marginal yellowing of their leaves,curling upwards slightly and dark green streaks with various length,from less than lmm to 30-50 cm even longer especially in the midrib or pecudostem,and width in the leaf veins,midribs and petioles.The sub- sequent leaves became progressively dwarfed and the whole plant showed a bunchy-top appearance.Its la- tent period from the shortest of 19 days to the longest of 216 days depended upon the temperature and plant height when infected.The disease was transmitted by the banana aphid,Pentalonia nigronervosa,with its shortest acquisition feeding period of c.30 minutes,shortest inoculation feeding period of c.15 minutes,la- tent period ofc.l day,and retaining infectious up to 14 days once acquiring the disease agent and by infected banana suckers as well,but not by sap inoculation,soil and natural roots interweaving of diseased-and healthy plants and Cuscuta chinensis.The significance of these detailed investigations in China was also dis- cussed.