Summary auto-generated
This study examined genetic variation among Cydia pomonella granulosis virus (CpGV) isolates from multiple geographic sources. Researchers compared seven CpGV samples using restriction enzyme analysis, finding that most were identical to the Mexican isolate (CpGV-M). Only Russian (CpGV-R) and English (CpGV-E) isolates showed minor differences. The English isolate proved to be a mixture of two variants: CpGV-E1 (identical to CpGV-M) and CpGV-E2 (genetically distinct but unstable). The authors constructed the first physical map of a granulosis virus genome for CpGV-M using five restriction enzymes (EcoRI, BamHI, HindIII, SmaI, and ApaI), establishing a genome size of approximately 126 kilobase pairs. They mapped the granulin gene location using a cloned probe from Trichoplusia ni granulosis virus. Comparative mapping showed CpGV-R contained a 2.4 kilobase deletion relative to CpGV-M, while CpGV-E2 had a 1 kilobase insertion with an additional EcoRI site. Bioassays using a standardized LC50 method revealed no significant differences in virulence among the three isolates for neonate codling moth larvae, contrasting with previous reports claiming CpGV-R was 70-fold less virulent.
Key findings
- Most CpGV isolates worldwide are genetically identical to the Mexican strain isolated in 1963, with only Russian and English isolates showing minor variation
- The English isolate (CpGV-E) is a mixture of two variants: CpGV-E1 (identical to Mexican strain) and CpGV-E2 (carries 1 kb insertion with extra EcoRI site)
- The Russian isolate contains a 2.4 kilobase deletion compared to the Mexican strain but shows similar restriction patterns overall
- CpGV-M has a genome of approximately 126 kilobase pairs with mapped restriction sites for five enzymes; the granulin gene is located at the BamHI K-I junction
- No significant difference in virulence was detected among the three isolates for neonate larvae, contradicting earlier reports of reduced infectivity in the Russian variant
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Abstract
Cydia pomonella granulosis viruses (CpGV) from seven different sources in Europe, America and New Zealand were compared by restriction enzyme analysis. Most samples were indistinguishable from the Mexican isolate (CpGV-M). Isolates from Russia (CpGV-R) and England (CpGV-E) showed small genotypic differences. CpGV-E was shown to be a mixture of two variants, E1 and E2. CpGV-E1 was indistinguishable from CpGV-M. A physical map of CpGV-M was constructed for the enzymes EcoRI, BamHI, HindIII, SmaI and ApaI. A comparison of fragment profiles allowed construction of maps for CpGV-R and CpGV-E2. Relative to CpGV-M, CpGV-R had a single deletion of 2.4 kbp and CpGV-E2 was modified in one area resulting in an additional EcoRI site, a shift in a BamHI site and in total about 1 kbp more DNA. The map was orientated by locating the granulin gene using the cloned granulin gene from Trichoplusia ni GV as a probe. There was no significant difference between the infectivities of the Mexican, Russian and English isolates for neonate larvae.