Biological and molecular characterization of Spodoptera littoralis granulovirus with insecticidal activity against the cotton leafworm, Spodoptera littoralis (Boisd.)

Abstract

Granuloviruses (GVs) associated to the cotton leafworm Spodoptera littoralis, particularly type I, have been poorly examined. In this study, a field-collected baculovirus isolate, Spodoptera littoralis granulovirus (SpliGV) was characterized. Viral granules with a single rod-shaped virion with a range size of 271–358 in length and 148–171 nm in width, were detected by transmission electron microscopy. The genome pattern of SpliGV was compared to that of the sister strain Spodoptera litura granulovirus (SpltGV) isolate K1 upon restriction endonuclease digestion, and its identity was confirmed. The SpliGV isolate showed to be closed and shares a 99.07% genetic similarity with the Spodoptera litura granulovirus isolate K1, and 95.22% with Spodoptera littoralis granulovirus isolate 66, both classified as Type I granulovirus. The median lethal concentration values (LC50), measured as the concentration of viral occlusion bodied (OBs), for the SpliGV isolate against S. littoralis larvae were 1.76 × 105 OB ml-1 for second instar larvae and 2.92 × 105 OB ml-1 for fourth instar larvae ten days post-infection. Based on its host specificity and virulence traits, the SpliGV isolate is a potential bioagent candidate for the control of S. littoralis.