Complete Sequence, Analysis and Organization of the Orgyia leucostigma Nucleopolyhedrovirus Genome

The complete genome of the Orgyia leucostigma nucleopolyhedrovirus (OrleNPV) isolated from the whitemarked tussock moth (Orgyia leucostigma, Lymantridae: Lepidoptera) was sequenced, analyzed, and compared to other baculovirus genomes. The size of the OrleNPV genome was 156,179 base pairs (bp) and had a G+C content of 39%. The genome encoded 135 putative open reading frames (ORFs), which occupied 79% of the entire genome sequence. Three inhibitor of apoptosis (ORFs 16, 43 and 63), and five baculovirus repeated ORFs (bro-a through bro-e) were interspersed in the OrleNPV genome. In addition to six direct repeat (drs), a common feature shared among most baculoviruses, OrleNPV genome contained three homologous regions (hrs) that are located in the latter half of the genome. The presence of an F-protein homologue and the results from phylogenetic analyses placed OrleNPV in the genus Alphabaculovirus, group II. Overall, OrleNPV appears to be most closely related to group II alphabaculoviruses Ectropis obliqua (EcobNPV), Apocheima cinerarium (ApciNPV), Euproctis pseudoconspersa (EupsNPV), and Clanis bilineata (ClbiNPV)

Development of economic thresholds for semiloopers (Lepidoptera: noctuidae) on four soybean cultivars in Zimbabwe

Soybean leaf consumption for the most common semilooper species, Trichoplusia orichalcea (F.) was established in the laboratory using a leaf area meter. The total consumption per larva was 120,85 cm$sp2$. The yield reduction of our soybean cultivars (Glycine max (L.) Merrill) being Duiker, Gazelle, Roan and SCS1 was measured in relation to different levels of defoliation. The defoliation was induced manually singly or sequentially over three different growth stages.At soybean maturity, counts of pods per plant, number of seeds per plant, weight per 100 seeds and weight of seeds per plant were obtained. Yields were converted to a percentage of yield and linear regressions fitted to the relationship between percentage yield and defoliation. The percentage yield was influenced by the cultivars, the levels of defoliation, and the timing of defoliation.The most critical growth stage for defoliation was the seed development stage, but the differences between them were small and not significant. SCS1 was the most resistant cultivar to defoliation, while Duiker was the most susceptible to single defoliation.The economic thresholds were determined for the soybean cultivars demonstrating significant linear relations between percentage yield and single defoliation. Based on three insecticides and two application methods, the economic thresholds were determined at the flowering stage for Duiker, at the pod development stage for Duiker and Roan and at the seed development stage for Duiker, Gazelle, Roan, and SCS1 cultivars. The numbers of semilooper caterpillars per metre of row required to reach the economic thresholds, are generally higher than the natural levels of infestation

Impact des variables et pratiques agronomiques sur la réduction des dommages : le cas de la pomme de terre au Québec

Impact of agronomie and management variables on damage reduction in potato production in Quebec This study proposes an approach similar to that of Lichtenberg and Zil-berman to model the impact of control agents (pesticides , herbicides) on potato production. We estimate simultaneously a marketable output equation as well as three damage abatement functions. Empirical results show that fertilising elements (nitrogen, phosphorus, potassium and magnesium) do not have statistically significant impacts on the potential output of potatoes. Significant effects are obtained in the damage abatement functions but only for phosphorus and potassium. These latter variables show opposite effects in altering damages caused by the small size of the tuber. Hence phosphorus increases them while potassium reduces them. Several variables reflecting alternative management practices have also been included in the model but only few of them are statistically significant.La présente étude propose une approche similaire à celle de Lichtenberg et Zilberman pour modéliser l'impact d'intrants qui agissent comme agents de contrôle (insecticides, fongicides, herbicides) sur la production de pomme de terre. Dans cette perspective, nous estimons, à l'aide de procédures économétriques, un système d'équations simultanées expliquant la production commercialisable de pommes de terre et trois types de dommage. Les résultats empiriques montrent que les effets des éléments fertilisants (azote, phosphore, potassium et magnésium) sur la production potentielle de pomme de terre ne sont pas statistiquement significatifs. En revanche, des impacts significatifs se retrouvent dans les fonctions de réduction des dommages pour le phosphore et le potassium. Ces derniers résultats montrent des effets antagoniques sur les pertes causées par le faible calibre des tubercules : ainsi, le phosphore contribue à les augmenter tandis que le potassium joue un rôle opposé. Plusieurs variables traduisant les pratiques culturales ont également été incorporées dans le modèle mais peu d'entre elles se sont avérées comme étant significatives.Romain Robert, Lambert Rémy, Michaud Renée, Lapointe Claude. Impact des variables et pratiques agronomiques sur la réduction des dommages : le cas de la pomme de terre au Québec. In: Cahiers d'Economie et sociologie rurales, N°64, 3e trimestre 2002. pp. 57-82

Impact des variables et pratiques agronomiques sur la réduction des dommages: le cas de la pomme de terre au Québec.

This study proposes an approach similar to that of Lichtenberg and Zilberman to model the impact of control agents (pesticides, herbicides) on potato production. We estimate simultaneously a marketable output equation as well as three damage abatement functions. Empirical results show that fertilising elements (nitrogen, phosphorus,;potassium and magnesium) do not have statistically significant impacts on the potential output of potatoes. Significant effects are obtained in the damage abatement functions but only for phosphorus and potassium. These latter variables show opposite effects in altering damages caused by the small size of the tuber. Hence phosphorus;increases them while potassium reduces them. Several variables reflecting alternative management practices have also been included in the model but only few of them are statistically significant

Comparative genome sequence analysis of Choristoneura occidentalis Freeman and C. rosaceana Harris (Lepidoptera: Tortricidae) alphabaculoviruses.

The complete genome sequences of Choristoneura occidentalis and C. rosaceana nucleopolyhedroviruses (ChocNPV and ChroNPV, respectively) (Baculoviridae: Alphabaculovirus) were determined and compared with each other and with those of other baculoviruses, including the genome of the closely related C. fumiferana NPV (CfMNPV). The ChocNPV genome was 128,446 bp in length (1147 bp smaller than that of CfMNPV), had a G+C content of 50.1%, and contained 148 open reading frames (ORFs). In comparison, the ChroNPV genome was 129,052 bp in length, had a G+C content of 48.6% and contained 149 ORFs. ChocNPV and ChroNPV shared 144 ORFs in common, and had a 77% sequence identity with each other and 96.5% and 77.8% sequence identity, respectively, with CfMNPV. Five homologous regions (hrs), with sequence similarities to those of CfMNPV, were identified in ChocNPV, whereas the ChroNPV genome contained three hrs featuring up to 14 repeats. Both genomes encoded three inhibitors of apoptosis (IAP-1, IAP-2, and IAP-3), as reported for CfMNPV, and the ChocNPV IAP-3 gene represented the most divergent functional region of this genome relative to CfMNPV. Two ORFs were unique to ChocNPV, and four were unique to ChroNPV. ChroNPV ORF chronpv38 is a eukaryotic initiation factor 5 (eIF-5) homolog that has also been identified in the C. occidentalis granulovirus (ChocGV) and is believed to be the product of horizontal gene transfer from the host. Based on levels of sequence identity and phylogenetic analysis, both ChocNPV and ChroNPV fall within group I alphabaculoviruses, where ChocNPV appears to be more closely related to CfMNPV than does ChroNPV. Our analyses suggest that it may be appropriate to consider ChocNPV and CfMNPV as variants of the same virus species

Pathology of a Gammabaculovirus in Its Natural Balsam Fir Sawfly (Neodiprion abietis) Host

The Neodiprion abietis Gammabaculovirus (Baculoviridae: NeabNPV) is virulent, highly contagious, and infects only midgut epithelial cells of balsam fir sawfly larvae, but infections can carry through to adult sawflies in the midgut. Larval infections are characterized by hypertrophy of midgut epithelial cell nuclei, where virogenic stromata develop to produce nucleocapsids that are singly enveloped before occlusion into occlusion bodies. Infected, occlusion body-laden cells slough from the midgut epithelium as a result of a dissolution of the basal lamina. Infected cells undergo lysis, and viral occlusion bodies exit affected larvae in a watery diarrhea to infect other balsam fir sawfly larvae. A budded virus stage was not observed, but nucleocapsid and occlusion body formation resembled the development of occlusion-derived virions and occlusion bodies in lepidopteran alphabaculoviruses

Dot matrix analysis of three <i>Choristoneura</i> NPV genomes.

<p>The plots were generated using blastN global genome alignment and compare; A) ChocNPV and CfMNPV, B) ChroNPV and CfMNPV, and C) ChroNPV and ChocNPV genomes. All genomes show a high degree of co-linearity.</p

Phylogenetic tree for eukaryotic initiation factor 5 (eIF-5). Homologues of ChroNPV eIF-5 were obtained from NCBI database using BLASTP.

<p>The tree was generated based on concatenated amino acid sequences of ChroNPV eIF-5 and of other eukaryotic organisms available in the database. GenBank accession number for some analyzed taxa is shown beside those taxa. The analysis was conducted in MEGA 5 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068968#pone.0068968-Tamura1" target="_blank">[41]</a> and inferred using the UPGMA method <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068968#pone.0068968-Sneath1" target="_blank">[42]</a>. The bootstrap test values (1000 pseudo-replicates) are shown next to the branches <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068968#pone.0068968-Felsenstein1" target="_blank">[43]</a>.</p

Features of ChocNPV and ChroNPV <i>hrs.</i>

<p>Features of ChocNPV and ChroNPV <i>hrs.</i></p