Kumar Ch Sridhar, Ranga Rao G V, Sireesha K, Kumar P Lava
Entomology Unit, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, 502324 Andhra Pradesh India.
Indian J Virol. 2011 Jun;22(1):29-36. doi: 10.1007/s13337-011-0029-0. Epub 2011 May 22.
Baculoviruses were isolated from three major lepidopteran pests, Helicoverpa armigera, Spodoptera litura and Amsacta albistriga in the semi-arid tropics during natural epizootic conditions at ICRISAT fields, Patancheru, Andhra Pradesh, India. Biological, morphological and biochemical analysis identified these isolates as Nucleopolyhedroviruses (NPVs). Scanning electron microscopy of the occlusion bodies (OBs) purified from diseased larvae revealed polyhedral particles of size approximately 0.5-2.5 μm [Helicoverpa armigera Nucleopolyhedrovirus (HearNPV)], 0.9-2.92 μm [Spodoptera litura Nucleopolyhedrovirus (SpltNPV)] and 1.0-2.0 μm [Amsacta albistriga Nucleopolyhedrovirus (AmalNPV)] in diameter. Transmission electron microscopy of thin sections of OBs of the three isolates revealed up to 5-8 multiple bacilliform shaped particles packaged within a single viral envelope. The dimensions of these particles were 277.7 × 41.6 nm for HearNPV, 285.7 × 34.2 nm for SpltNPV and 228.5 × 22.8 nm for AmalNPV. Each of HearNPV and AmalNPV contained up to 6 nucleocapsids and SpltNPV contained up to 7 nucleocapsids per envelope. The estimated molecular weights of the purified OB (polyhedrin) protein of the three NPVs were 31.29-31.67 kDa. Virus yield (OBs/larva) was 5.18 ± 0.45 × 10(9) for HearNPV, 5.73 ± 0.17 × 10(9) for SpltNPV and 7.90 ± 0.54 × 10(9) for AmalNPV. The LC50 values of various NPVs against 2nd and 3rd instar larvae indicated 2.30 × 10(4) and 1.5 × 10(5) OBs/ml for HearNPV, 3.5 × 10(4) and 2.4 × 10(5) OBs/ml for SpltNPV and 5.6 × 10(4) and 3.96 × 10(5) OBs/ml for AmalNPV. The lethal time required to cause 50% mortality (LT50) for these three species were also defined. This study has shown that the NPVs infecting three major lepidopteran pests in India are multiple NPVs, and they have good potential to use as biocontrol agents against these important pests.
在印度安得拉邦帕坦切尔的国际半干旱热带作物研究所（ICRISAT）田间自然流行疫病的情况下，从三种主要鳞翅目害虫棉铃虫、斜纹夜蛾和白纹灯蛾中分离出杆状病毒。通过生物学、形态学和生化分析，确定这些分离株为核型多角体病毒（NPV）。对从患病幼虫中纯化的包涵体（OB）进行扫描电子显微镜观察，发现其多面体颗粒直径约为0.5 - 2.5μm[棉铃虫核型多角体病毒（HearNPV）]、0.9 - 2.92μm[斜纹夜蛾核型多角体病毒（SpltNPV）]和1.0 - 2.0μm[白纹灯蛾核型多角体病毒（AmalNPV）]。对这三种分离株的OB薄片进行透射电子显微镜观察，发现单个病毒包膜内包裹着多达5 - 8个杆状颗粒。这些颗粒的尺寸分别为：HearNPV为277.7×41.6nm，SpltNPV为285.7×34.2nm，AmalNPV为228.5×22.8nm。每个HearNPV和AmalNPV包膜内最多含有6个核衣壳，SpltNPV包膜内最多含有7个核衣壳。三种NPV纯化后的OB（多角体蛋白）估计分子量为31.29 - 31.67kDa。病毒产量（OBs/幼虫）：HearNPV为5.18±0.45×10⁹，SpltNPV为5.73±0.17×10⁹，AmalNPV为7.90±0.54×10⁹。各种NPV对2龄和3龄幼虫的LC50值表明：HearNPV分别为2.30×10⁴和1.5×10⁵OBs/ml，SpltNPV分别为3.5×10⁴和2.4×10⁵OBs/ml，AmalNPV分别为5.6×10⁴和3.96×10⁵OBs/ml。还确定了这三种害虫达到50%死亡率所需的致死时间（LT50）。这项研究表明，感染印度三种主要鳞翅目害虫的NPV是多粒NPV，它们具有作为生物防治剂防治这些重要害虫的良好潜力。
