Infectivity Studies of a New Baculovirus Isolate for the Control of the Diamondback Moth (Plutellidae: Lepidoptera)

Abstract

This study describes a new baculovirus isolate recovered from infected larvae of the diamondback moth, Plutella xylostella (L.), and identified as a multiple nucleopolyhedrovirus (MNPV). The plaque purified isolate designated as PxMNPVCL3 was found to be pathogenic to P. xylostella, Heliothis virescens (F.), Trichoplusia ni (Hübner), H. subflexa (Guenée), Helicoverpa zea (Boddie), Spodoptera exigua (Hübner), and S. frugiperda (J. E. Smith) larvae in decreasing order of susceptibility. The LC50 for diamondback moth, the most susceptible, was 6 occlusion bodies (OB)/cm2, whereas the most resistant species, namely S. frugiperda, was 577 OB/cm2. PxMNPVCL3 was more pathogenic to diamondback moth by 3-4 log cycles as compared with 2 broad-spectrum baculoviruses, namely Autographa california (alfalfa looper) MNPV and Anagrapha falcifera (celery looper) MNPV. The 3 baculoviruses were compared with each other and characterized by restriction endonuclease (REN) analysis, hybridization, and neutralization tests. Fragmentation profiles generated by REN showed that the 3 baculoviruses shared some fragments in common. Hybridization studies employing digoxigenin labeled PxMNPVCL3 DNA as a probe revealed the close but distinct relationship of these 3 viruses. Neutralization tests confirmed the hybridization studies, namely that the 3 viruses although genetically similar are distinguishable from each other.

Genomic sequence analysis of a nucleopolyhedrovirus isolated from the diamondback moth, Plutella xylostella

“…Viral DNA was purified by phenol-chloroform extraction and ethanol precipitation. The identity of the viral DNA was confirmed by digestion of DNA with restriction enzymes, agarose gel electrophoresis, and comparison of the restriction fragment patterns with previously published restriction digests for this virus [9,11].…”

“…The AcMNPV isolate C6 [12] and PlxyMNPV isolate CL3 [9] were propagated in the Spodoptera frugiperda Sf9 cell line [13] and titered by plaque assay. Sf9 cells were grown in TNM-FH medium (SAFC Biosciences) supplemented with 10% fetal bovine serum (Invitrogen), antibiotics (10 U penicillin, 0.1 mg streptomycin, and 0.25 lg amphotericin B/mL; Sigma), and 0.1% Pluronic F-68 (SAFC Biosciences).…”

“…Although the Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is infectious towards P. xylostella, it exhibits a relatively low level of virulence towards this species [7,8]. A nucleopolyhedrovirus previously had been isolated from infected larvae of P. xylostella [9]. This virus, Plutella xylostella multiple nucleopolyhedrovirus isolate CL3 (or PlxyMNPV-CL3), is significantly more virulent against P. xylostella larvae than both wild-type AcMNPV [9] and an isolate of AcMNPV selected for enhanced activity against P. xylostella [10].…”

“…This virus, Plutella xylostella multiple nucleopolyhedrovirus isolate CL3 (or PlxyMNPV-CL3), is significantly more virulent against P. xylostella larvae than both wild-type AcMNPV [9] and an isolate of AcMNPV selected for enhanced activity against P. xylostella [10]. Restriction enzyme digest and Southern blot analysis indicate that PlxyMNPV-CL3 is genetically very similar to AcMNPV [9,11].…”

Biological control of the diamondback moth,Plutella xylostella: A review

“…Based on relative differences in LC 50 values, PxMNPV was three to four log cycles more potent against DBM than either AcMNPV or AfMNPV (Kariuki & McIntosh 1999). The NPVs isolated from Anagrapha falcifera (Kirby) (AfMNPV), Autographa californica (Speyer) (AcMNPV), and Galleria melonella (L.) (GmMNPV) were also infectious to DBM (Kadir et al 1999b) but their potency was moderate to low, even after serial passage in this insect (Farrar & Ridway 1999).…”