Fitness-related traits of entomopoxviruses isolated from Adoxophyes honmai (Lepidoptera: Tortricidae) at three localities in Japan Jun Takatsuka * , Shohei Okuno 1 , Takayoshi Ishii 2 , Madoka Nakai, Yasuhisa Kunimi Department of Bioregulation and Biointeraction, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Saiwai, Fuchu, Tokyo 183-8509, Japan article info Article history: Received 5 February 2010 Accepted 27 April 2010 Available online 4 May 2010 Keywords: Adoxophyes honmai Adoxophyes orana Entomopoxvirus Fitness Homona magnanima Fatal infection Tortricidae Variation Viral yield abstract Three entomopoxviruses (EPVs) isolated from diseased Adoxophyes honmai larvae at different localities (Tsukuba, Itsukaichi, and Miyazaki) in Japan were compared for biochemical identity and key parameters of virus fitness, fatal infection, speed of kill, and virus yield. When the structural peptides of occlusion bodies (OBs) and occlusion-derived viral particles were compared using sodium dodecyl sulfate–poly- acrylamide gel electrophoresis, no difference in banding patterns was observed. However, DNA restric- tion endonuclease analysis showed that the three isolates were genotypically different, but many commonly sized DNA fragments were observed. Five tortricid species, A. honmai, Adoxophyes orana, Adox- ophyes dubia, Homona magnanima, and Archips insulanus were susceptible to all isolates. No significant differences in the key viral fitness parameters were detected among the isolates in A. orana. However, the Miyazaki isolate had a different effect on H. magnanima; it allowed infected insects to survive longer and develop to a larger size, but had a lower yield of OBs per larva at any given time to death. OB yields per unit cadaver weight for the Miyazaki isolate, which indicate the conversion rate of the insect to virus, were lower over time compared to the other two isolates. The implications for selecting a candidate iso- late to control tortricid pests are discussed. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction Entomopoxviruses (EPVs) are large oval-shaped viruses with a linear double-stranded DNA genome and a molecular weight of 200–240 kbp. EPVs belong to one of two Poxviridae subfamilies: Entomopoxvirinae, which are insect poxviruses, or Chordopoxvirinae, which are vertebrate poxviruses (King et al., 1998). Entomopoxviri- nae is divided into three genera according to viral morphology, host range, and genome size: Alphaentomopoxvirus, Betaentomopoxvirus, and Ganmaentomopoxvirus. Alphaentomopoxvirus comprise viruses infecting coleopterans, Betaentomopoxvirus infects lepidopterans and orthopterans, while those from Ganmaentomopoxvirus infect dipterans (Buller et al., 2005). Although recent sequencing studies have shown that all members of the two Poxviridae subfamilies have several conserved genes, EPVs are believed to be specific to in- sects. EPV virions are embedded in occlusion bodies (OBs) or spher- oids composed mainly of a highly expressed protein called spheroidin. After ingestion by the insect host, OBs are dissolved by the alkaline-reducing conditions in the midgut and release viri- ons, resulting in viral replication in the midgut epithelial cells, fol- lowed by transmission to the internal tissues. Deleting the spheroidin gene has no effect on viral replication in vitro (Palmer et al., 1995); however, spheroidin should have an important func- tion in the viral life cycle in nature by protecting virions from envi- ronmental asperity, similar to the polyhedrins of baculoviruses or cypoviruses. EPV pathology depends on the insect host, but the infection course is generally slow (Arif, 1995). For example, larvae of the lepidopteran Choristoneura fumiferana infected with C. fumif- erana EPV show few symptoms until late in the infection and die in 1–3 weeks (Palli et al., 2000). The EPV-infected orthopteran Locusta migratoria shows a decreased developmental rate and eventually dies 20–60 days after infection (Jaeger and Langridge, 1984). In the dipterans, Chironomus attenuatus and Goeldichironomus halop- rasimus, EPV-infected larvae appear to survive up to 8 weeks after infection (Huger et al., 1970). EPV-infected coleopterans may sur- vive for up to 40 weeks (Goodwin and Roberts, 1975). The potential use of EPVs as microbial control agents has at- tracted attention (Mason and Erlandson, 1994; Wegensteiner et al., 1996; Woods et al., 1992). Microbial control agents have been used for integrated pest-management programs with differ- ing strategies (Fuxa, 1987). For example, a pathogen that can kill its insect host shortly after infection could be used in place of a chemical insecticide. In contrast, an appropriate use of a pathogen 0022-2011/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.jip.2010.04.010 * Corresponding author. Present address: Forestry and Forest, Products Research Institute, Matsunosato 1, Tsukuba 305-8687, Japan. Fax: +81 29 874 3720. E-mail address: junsan@ffpri.affrc.go.jp (J. Takatsuka). 1 Present address: Arysta LifeScience Corporation, 8-1 Akashi, Chuo-ku, Tokyo 104- 6591, Japan. 2 Present address: Oonuma-machi, Kodaira-shi, Tokyo 187-0001, Japan. Journal of Invertebrate Pathology 105 (2010) 121–131 Contents lists available at ScienceDirect Journal of Invertebrate Pathology journal homepage: www.elsevier.com/locate/jip