Biological, morphological, and molecular characterization of the baculovirus PlxyMNPV_LBIV-11, and its virulence towards Plutella xylostella, Trichoplusia ni, and Spodoptera frugiperda larvae.

Abstract

PlxyMNPV_LBIV-11 is an alphabaculovirus strain, isolated from Plutella xylostella larvae. This work characterized this strain at a biological, morphological, and molecular level to evaluate its similarity with other baculoviruses. Its ultrastructure showed a multiple arrangement of nucleocapsids within enveloped virions, all occluded within large cubical polyhedra. PlxyMNPV_LBIV-11 showed infectivity on the Hi5 and Sf9 cell lines, despite these being from heterologous origin. This in vitro infectivity was observed using either BVs or by transfection with genomic DNA. Restriction fragment patterns of PlxyMNPV_LBIV-11, using the enzymes EcoRI, BamHI and HindIII, showed a high relationship with those patterns shown by AcMNPV, except for one or two differential bands with each enzyme. Sequences of core genes lef-8 and lef-9 and the conserved polh gene showed identities ranging from 98 to 100% when compared with those of AcMNPV. Somewhat lower was the sequence identity of the gp64 gene (94%) as compared with those of AcMNPV and PlxyMNPV_CL3, which might be related to the difference in virulence. Besides, the presence of this gene in PlxyMNPV_LBIV-11 indicates that it belongs to group 1 of alphabaculoviruses. A phylogram was estimated with the core and conserved gene sequences, corroborating its high relationship with AcMNPV and PlxyMNPV_CL3. Bioassays were performed with P. xylostella larvae reared on a meridic diet, whose LC50 values indicated lower virulence than AcMNPV when tested against P. xylostella, Spodoptera frugiperda, and Trichoplusia ni larvae. Its virulence against S. frugiperda was only seven times lower than AcMNPV. Its potential as a biological control agent is discussed.