Isolation of Densovirus and Picornavirus from natural field populations of Spodoptera littoralis Boisd. (Lep. Noctuidae) in Egypt

Two natural viral strains belonging to the Parvoridae (Densovirus) and the Picornaviridae (Picornavirus) families were isolated from larvae of the Egyptian cotton leafworm #Spodoptera littoralis. The strains were sampled from natural infestation of cotton field in Kafr El-Sheikh Governorate in May 1997. Electron microscopy observations revealed the presence of icosahedral particles with 22 nm in diameter for the viral capside related to the Densovirus (DNV), and 29 nm for the second one as a Picornavirus (PV). For the DNV four capsid proteins of 91,63, 53 and 47 KDa have been separated, and were undifferentiated from that of the unique published Densovirus isolate from Egypt, the #Mythimna loreyi DNV (MIDNV). PV capsids contain three major structural proteins of 30, 32 and 33 KDa resembling the Drosophila C virus (DCV), a very well known Picornavirus of insect. The DNV genome consists of a single stranded DNA molecule of size 5.95 Kb. It was characterized using 12 restriction endonucleases. The DNA restriction profiles were identical with these of MIDNV. The PV contain a single stranded RNA genome of size 9.4 Kb as the different reported isolates of DCV. Using rabbit antisera, immunological comparison revealed a complete homology between the DNV and IDNV, as well as, the PV isolated from #S. littoralis shows a complete serological identity with the DCV. These results suggest that we can register the DNV isolated from #S. littoralis as a strain of MIDNV and the small RNA virus as an Egyptian strain of DCV. Larvae of #S. littoralis$ reared on artificial diet in the laboratory were susceptible to these two viruses. (Résumé d'auteur

Proceedings of the first regional symposium for applied biological control in Mediterranean countries

Trois ravageurs principaux en Egypte, #Phthorimaea operculella, #Spodoptera littoralis et #Sesamia cretica$ sont infectés naturellement par un granulovirus spécifique mais aussi par des nucleopolyhedrovirus. Cette situation locale et l'existence de plusieurs isolats de ces différents virus, offrent des potentialités pour le développement d'études génétiques grâce notamment à la disponibilité de lignées cellulaires susceptibles à ces virus. Les recombinaisons expérimentales entre GVs mais aussi entre GVs et NPVs doit permettre l'étude des facteurs qui régulent la spécificité virale, pour étudier les différentes propriétés biologiques des baculovirus, et pour augmenter leurs potentiels. (Résumé d'auteur

Isolation of Densovirus and Picornavirus from natural field populations of Spodoptera littoralis Boisd. (Lep. Noctuidae) in Egypt

Two natural viral strains belonging to the Parvoridae (Densovirus) and the Picornaviridae (Picornavirus) families were isolated from larvae of the Egyptian cotton leafworm #Spodoptera littoralis. The strains were sampled from natural infestation of cotton field in Kafr El-Sheikh Governorate in May 1997. Electron microscopy observations revealed the presence of icosahedral particles with 22 nm in diameter for the viral capside related to the Densovirus (DNV), and 29 nm for the second one as a Picornavirus (PV). For the DNV four capsid proteins of 91,63, 53 and 47 KDa have been separated, and were undifferentiated from that of the unique published Densovirus isolate from Egypt, the #Mythimna loreyi DNV (MIDNV). PV capsids contain three major structural proteins of 30, 32 and 33 KDa resembling the Drosophila C virus (DCV), a very well known Picornavirus of insect. The DNV genome consists of a single stranded DNA molecule of size 5.95 Kb. It was characterized using 12 restriction endonucleases. The DNA restriction profiles were identical with these of MIDNV. The PV contain a single stranded RNA genome of size 9.4 Kb as the different reported isolates of DCV. Using rabbit antisera, immunological comparison revealed a complete homology between the DNV and IDNV, as well as, the PV isolated from #S. littoralis shows a complete serological identity with the DCV. These results suggest that we can register the DNV isolated from #S. littoralis as a strain of MIDNV and the small RNA virus as an Egyptian strain of DCV. Larvae of #S. littoralis$ reared on artificial diet in the laboratory were susceptible to these two viruses. (Résumé d'auteur

Multiplication of Spodoptera littoralis granulosis virus in a cell line established from Phthorimaea operculella

A complete replication of the #Spodoptera littoralis granulosis virus (SpliGV) was obtained in vitro by both virus infection and DNA transfection in the ORS-Pop-95 (Pop-95) cell line established from embryonic cells of the potato tuber moth, #Phthorimaea operculella. SpliGV multiplied significantly during several passages in Pop-95 cells at 19°C. When the cells were infected and kept at 19°C for the first 4 hrs and then at 27°C for the rest of the experiment (20 days), the viral multiplication proceeded at the same rate. Comparison of SpliGV progenies, multiplied either in vivo or in vitro, using electron microscopy and restiction profile analysis, showed their identity. (Résumé d'auteur

Effects of some insecticides on the division of a Spodoptera littoralis cell line and on the replication of Sl baculovirus (NPV)

Quatre insecticides chimiques (Chloropyrifos, Fenitrothion, Cypermethrin, Carbaryl) appartenant à 3 groupes de pesticides ont été utilisés sur des cellules de #S. littoralis$in vitro. Le Chloropyrifos induit une augmentation de 25$ NPV est augmentée avec augmentation du titre montrant un effet synergique comme celui observé in vivo. Le modèle pourrait permettre de mieux comprendre l'impact des insecticides et leur mode d'action. (Résumé d'auteur