柑桔黃龍病菌對其媒介昆蟲柑桔木蝨生活史特徵與族群介量之影響

Abstract

本論文的目的在於藉由收集生命表資料以比較帶有柑桔黃龍病菌（Candidatus Liberibacter asiaticus, Las (+)）與健康無菌（Las (-)）之亞洲柑桔木蝨（Diaphorina citri Kuwayama）生活史特徵與族群介量之差異。生活史觀察後死亡的蟲體分別以黃龍病菌特殊引子對配合PCR法來檢測是否帶菌，收集資料再以兩性生命表分析法進行分析。結果顯示帶菌的木蝨平均壽命比健康無菌木蝨有稍長，分別為35.2及33.4天。黃龍病菌會使某些木蝨若蟲發育不正常或羽化失敗，五齡若蟲期甚至會延長至一個月之久（最大值為40天）且無法發育到成蟲期，但是外部形態與正常發育的若蟲無明顯差異。而有些可成功發育到成蟲期的帶菌木蝨在羽化後可能會具有扭曲畸形的翅，這些情況都不曾發生在健康無菌的木蝨上。在每日產卵模式觀察中，木蝨族群傾向於在陽光較弱的早晨及下午產卵，夜間較少產卵。此外，帶有柑桔黃龍病菌的雌蟲會比健康無菌者具有較長之繁殖前期（分別為10.5 及5.7天），較晚的首次繁殖日期（自出生後算起，分別為27.6 及 21.9 天）及較低的產卵力(分別為18.6 及 29.6 粒卵/♀）。在此試驗中，無論帶菌與否，雌蟲都傾向於在產卵期之前段產下絕大部分的卵。而在兩者之族群介量方面，帶菌的木蝨雌蟲平均世代時間（T）與族群倍增時間（Dt）均長於健康無菌者（依序為29.09 vs. 22.87與10.35vs. 6.36天）。就內在增殖率（rm）而言，健康無菌者為0.1112 d-1為帶菌者（0.0689 d-1）之1.61倍，淨繁殖率（R0）為1.70倍（12.27 vs.7.22 offspring/female/generation），而終極增長率（λ）則為1.04倍(1.1176 vs. 1.0712 d-1)。在帶菌與健康無菌的木蝨族群穩定齡期分佈中，未成熟期均占極大比例，分別為84.25及88.58%。在帶菌木蝨族群中，具有傳播黃龍病菌能力的四、五齡若蟲期及成蟲期共占了48.03%，遠高於無菌族群之34.08%。綜合上述，黃龍病菌的存在確實會影響柑桔木蝨生活史特徵與族群介量。不同的病菌數量會造成木蝨不同的生理反應，而此數量又與木蝨首次獲菌量有關。當田間罹病病株率高時，木蝨帶菌率會隨之增加。故在黃龍病的綜合防治方面，清除田間病株與加強若蟲的防治均不容忽視。

This research was conducted to compare the differences in the life history traits and population parameters between Asian citrus psyllids (Diaphorina citri Kuwayama) with or without citrus Huanglongbing (HLB) pathogen (Candidatus Liberibacter asiaticus) (Las). The life table data were collected and then subjected to the age-stage, two-sex life table analysis. The polymerase chain reaction (PCR) was used to monitor the pathogen at the death of each psyllid. The results showed that the life span of Las-infected (Las (+)) psyllids were relatively longer than those of Las-free (Las (-)) ones, with 35.2 and 33.4 d. The Las appeared to cause psyllids to develop abnormally or emerge unsuccessfully. It also occasionally prolonged the period of 5th instar up to 40 d, resulting in their failure to reach adulthood. Some Las (+) adults even had abnormal wings after emergence. These abnormalities had never been observed in the Las (-) adults. Adult females had the preference of laying eggs during their early reproductive period, and daily oviposition pattern occurred primarily in two periods, one morning (7:30-9:30 a.m.) and the other late afternoon (3:30-5:30 p.m.). Comparing to Las (-) females, the Las (+) females also had longer pre-oviposition period (10.5 vs. 5.7 d), late first reproduction age counted since birth (27.6 vs. 21.9 d), and lower fecundity (18.6 vs. 29.6 eggs/♀). When comparing the population parameters between psyllids with or without being infected with the pathogen, the Las (+) psyllids had a longer mean generation time (T) (29.09 vs. 22.87 d) and doubling time (Dt) (10.35 vs. 6.36 d). The intrinsic rate of increase (rm) of the Las (-) female (0.1112 d-1) was 1.61 times higher than that of the Las (+) female (0.0689 d-1); the net reproductive rate (R0) was 1.70 times higher (12.27 vs. 7.22 offspring/female/generation); and the finite rate of increase (λ) was 1.04 times higher (1.1176 vs. 1.0712 d-1). In the stable stage distribution of Las (+) and Las (-) psyllids, the total percentage of immature was 84.25% and 88.58%, respectively. And the total percentage of the Las-transmitting individuals, including the 4th, 5th instar nymphs and adults, of Las (+) psyllids was 48.03%, which was higher than that of the Las (-) ones (34.08%). It is concluded that Las amounts found in psyllids would affect their life history traits and population parameters. Different amounts of Las found in a psyllid would cause different physiological responses. These Las amounts were closely related to the amount of Las acquired in the initial acquisition period. Furthermore, when the proportion of the infected citrus trees increased, the Las (+) psyllids would also increase. Therefore, removing and destroying infected citrus plants and improving the control of psyllid nymphs were essential to an effective field management of HLB.