Abstract The patogenicity and stability of Spodoptera litura nuclear polyhedrosis Virus (S1MNPV) were affected by incubation temperature, heating, pH, chloride ion, water quality, and sunlight. The final mortality of 3rd-instr larvae of S. litura caused by S1MNPV was not significantly increased, but the incubation period was decreased at higher temperatures. The LT50 values were 3.29、5.06、5.49、8.79 and 18.93 days from 35℃ to 15℃ respectively. Histological sections showed that nuclei of epidermal cells, fat body, tracheal mermbrane, and column cells of midgut were more rapidly infected at higher temperatures of incubation. The virus in a dry powder was more thermostable than in a suspension. Of the original activity 80 percent was remained when the virus was exposured at 55℃ for 24 h. S1MNPV was not affected significantly on suspension at pH 5, 7, and 9 for 24 h, but greatly inactivated on exposure to pH 3 and 11, and to solutions containing chloride ions at high concentrations. Solar radiation was the most powerful factor that inactivated viral activity in a brief period of exposure. Uric acid provided significant protection from sunlight for S1MNPV.
摘要 斜紋夜蛾核多角體病毒 (Spodoptera litura multiple nuclear polyhedrosis virus, S1MNPV) 對斜紋夜蛾幼蟲之致病力會受到培育溫度、日照、高溫、強酸、氯離子及水質之影響。三齡幼蟲經病毒接種後在35、30、25、20、及15℃生長箱中培養發病，結果測得其半致死時間分別為：3.29、5.06、5.49、8.79、及18.93天。隨著培育溫度的下降，幼蟲發病之潛伏期及罹病死亡之時間亦明顯延長；然累記至幼蟲化蛹前，幼蟲之總罹病死亡率並不因溫度而增減，且差異不顯著。經石蠟切片觀察，病毒感染幼蟲真皮層細胞、脂肪體細胞、氣管被膜細胞、以及中腸柱狀細胞等細胞核之感染程度均隨著溫度之上升而加速其嚴重性。病毒以粉末型式較水懸液耐高溫加熱處理，經55℃處理24小時，仍保留80%以上之活性。在中性及pH值9的磷酸緩衝液中，病毒之原有活性保留百分率較高，但在強酸、強鹼及含高濃度氯離子之溶液中則極易喪失活性。在田間稀釋用水，應以中性及無氯離子之地下水為宜。病毒在自然日光之照射下很容易喪失活性，但有尿酸作為抗紫外線保護劑者，可延長病毒在甘藍葉上之持續性。
| Key words: Spodoptrera litura, nuclear polyhedrosis virus, pathogenicity, stability. | | 關鍵詞: 斜紋夜蛾、核多角體病毒、致病力、穩定性。 |
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