Developmental rate models and biological parameters estimated from them, especially lower and upper temperature thresholds and optimal temperature, c

Eight new field isolates of Cydia pomonella granulovirus (CpGV) originating in Iran and Georgia and one English CpGV isolate were analysed for restriction fragment length polymorphisms (RFLPs) and by partial genome amplification and sequencing. According to the observed RFLPs, most of the predominant genotypes of these isolates could be assigned to those present in previously found isolates originating from Mexico (CpGV-M), England (CpGV-E) and Russia (CpGV-R). We suggest that these isolates should be designated genome A, B and C types, respectively. A fourth genome type was identified in three isolates and is designated D type. The isolates with A, B and D type genomes contained four open reading frames (ORFs) (ORF63–ORF66) not present in C type genomes. The lack of these ORFs in other granuloviruses suggests that the C type genome is evolutionarily ancestral to the other genome types. The B and D type genomes contained an additional insertion of a non-protein coding region of 0.7 kb, which was at different genome locations. Analysis of the partial gene sequences of late expression factor 8 (lef-8), lef-9 and polyhedrin/granulin (polh/gran) genes revealed single nucleotide polymorphisms (SNPs) that corresponded to the RFLP types. Phylogenetic analyses based on these SNPs corroborated the proposed ancestry of the C type genome. C type viruses were also less virulent to neonate codling moth larvae than the other virus types. In conclusion, the known diversity of CpGV isolates can be described by four major genome types, which appear to exist in different isolates as genotype mixtures.

Age-specific life table parameters and survivorship, adult longevity, reproduction periods, fertility, and sex ratio of the codling moth were studied at eight constant temperatures (10, 14, 20, 25, 27, 30, 33, and 35 ±0.5°C). Among the examined temperatures, the highest values of net reproductive rate, intrinsic rate of increase, and finite rate of increase were 18.28 (females/female), 0.08 (females/female/d), and 1.08 at 27°C, respectively. Similarly, the highest value of sex ratio was 0.56 [females/ (females + males)] at 27°C. The highest mean generation time and doubling time were 72.26 and 23.09 d, respectively, at 20°C. To present a suitable model for intrinsic rate of increase at different temperatures, a nonlinear Lactin model was fitted to our observations. The longest preoviposition period was 2.77 and 2.55 d at 20 and 30°C, respectively. Also, the longest oviposition period was 8.46 d at 20°C. Postoviposition period was not statistically different at examined temperatures. The Weibull frequency distribution was used to describe the age-specific survival of the female adults. Based on the Weibull distribution parameters, the survival curves were type I at all examined temperatures, which indicates that mortality mostly occurred in old individuals. These findings confirmed that temperature is a critical environmental factor affecting codling moth population growth.

Tsetse flies cause major health and economic problems as they transmit trypanosomes causing sleeping sickness in humans (Human African Trypanosomosis, HAT) and nagana in animals (African Animal Trypanosomosis, AAT). A solution to control the spread of these flies and their associated diseases is the implementation of the Sterile Insect Technique (SIT). For successful application of SIT, it is important to establish and maintain healthy insect colonies and produce flies with competitive fitness. However, mass production of tsetse is threatened by covert virus infections, such as the Glossina pallidipes salivary gland hypertrophy virus (GpSGHV). This virus infection can switch from a covert asymptomatic to an overt symptomatic state and cause the collapse of an entire fly colony. Although the effects of GpSGHV infections can be mitigated, the presence of other covert viruses threaten tsetse mass production. Here we demonstrated the presence of two single-stranded RNA viruses isolated from Glossina morsitans morsitans originating from a colony at the Seibersdorf rearing facility. The genome organization and the phylogenetic analysis based on the RNA-dependent RNA polymerase (RdRp) revealed that the two viruses belong to the genera Iflavirus and Negevirus, respectively. The names proposed for the two viruses are Glossina morsitans morsitans iflavirus (GmmIV) and Glossina morsitans morsitans negevirus (GmmNegeV). The GmmIV genome is 9685 nucleotides long with a poly(A) tail and encodes a single polyprotein processed into structural and non-structural viral proteins. The GmmNegeV genome consists of 8140 nucleotides and contains two major overlapping open reading frames (ORF1 and ORF2). ORF1 encodes the largest protein which includes a methyltransferase domain, a ribosomal RNA methyltransferase domain, a helicase domain and a RdRp domain. In this study, a selective RT-qPCR assay to detect the presence of the negative RNA strand for both GmmIV and GmmNegeV viruses proved that both viruses replicate in G. m. morsitans. We analyzed the tissue tropism of these viruses in G. m. morsitans by RNA-FISH to decipher their mode of transmission. Our results demonstrate that both viruses can be found not only in the host’s brain and fat bodies but also in their reproductive organs, and in milk and salivary glands. These findings suggest a potential horizontal viral transmission during feeding and/or a vertically viral transmission from parent to offspring. Although the impact of GmmIV and GmmNegeV in tsetse rearing facilities is still unknown, none of the currently infected tsetse species show any signs of disease from these viruses.