Biological Characteristics of Experimental Genotype Mixtures of Cydia Pomonella Granulovirus (CpGV): Ability to Control Susceptible and Resistant Pest Populations

Abstract

The detection of resistance in codling moth (Cydia pomonella) populations against the Mexican isolate of its granulovirus (CpGV-M), raised questions on the sustainability of the use of this biological insecticide. In resistant host cells, CpGV-M is not able to complete its replication cycle because replication is blocked at an early step. Virus isolates able to overcome this resistance have been characterized—among them, the CpGV-R5 isolate. In mixed infections on resistant insects, both CpGV-M and CpGV-R5 viruses replicate, while CpGV-M alone does not induce mortality. Genetically heterogeneous virus populations, containing 50% of each CpGV-M and CpGV-R5 appear to control resistant host populations as well as CpGV-R5 alone at the same final concentration, even if the concentration of CpGV-R5 is only half in the former. The use of mixed genotype virus preparations instead of genotypically homogeneous populations may constitute a better approach than traditional methods for the development of baculovirus-based biological insecticides.

Using Next Generation Sequencing to Identify and Quantify the Genetic Composition of Resistance-Breaking Commercial Isolates of Cydia pomonella Granulovirus

“…The mean mortality of CpRR1 infected with either CpGV-R5 or CpGV-0006 (98% mortality) appeared to be higher, though statistically not significant, than obtained with single genome groups A and E (11% and 72%, respectively) [ 35 ], suggesting some synergistic effect, when A and E are combined. Similar effects were also identified in the larvae of the resistant CM strain RGV from France, where some synergy of mixed application of CpGV-M and the resistant-breaking CpGV-R5 in infection experiments were noticed [ 52 ]. We assume that CpGV-0006 and CpGV-R5 were selected in CM populations with type I resistance.…”

A Third Type of Resistance to Cydia pomonella Granulovirus in Codling Moths Shows a Mixed Z-Linked and Autosomal Inheritance Pattern

“…For CpRR1, it was demonstrated that resistance-breaking properties of the CpGV isolates depended on the lack of an insertion of 24 bp in the open reading frame (ORF) pe38 in CpGV-M (group A), which is missing in all resistance-breaking isolates of genome group B to E CpGVs (6). By registration of some of these isolates, a successful commercial control of the type I resistance in C. pomonella was eventually reestablished in Europe (23)(24)(25)(26)(27)(28).…”

Novel Diversity and Virulence Patterns Found in New Isolates of Cydia pomonella Granulovirus from China

“…This hypothesis is supported by the observation of an LC 50 of isolate CpGV-ZY which was lower than that of CpGV-WW on CpRR1 at 7 and 14 dpi (Table 1). A mixture of CpGV-M and -R5 (each at 50%) induced mortality in resistant CM strain R GV (type I resistance strain) larvae that was similar to that caused by the resistance-breaking isolate CpGV-R5 alone (33). Interestingly, although pe38 of CpGV-WW comprised only one type of pe38 containing no 2 ϫ 12-bp-repeat insertion, its virulence against CpRR1 was reduced or at least delayed (Fig.…”

“…The LC 50 at 7 dpi could not be determined for CpGV-ALE due to the very low mortality, whereas the LC 50 value at 14 dpi was significantly higher than those of CpGV-ZY and -WW (Table 1). The viral gene pe38 was confirmed as a target of type I resistance (13), and this gene has also been used as a genetic marker to distinguish between CpGV isolates prone to this type of resistance or able to break it (13,33), depending on the presence of a 2 ϫ 12-bp-repeat insertion that is found in CpGV-M and other CpGVs of genome group A but not in resistance-breaking isolates like CpGV-E2, -S, and others.…”