Comparative study on the susceptibility of cutworms (Lepidoptera: Noctuidae) to Agrotis segetum nucleopolyhedrovirus and Agrotis ipsilon nucleopolyhedrovirus

The common cutworm (Agrotis segetum) and the black cutworm (Agrotis ipsilon) are serious soil pests of many vegetable and field crops all over the world. We have demonstrated the cross-infectivity of two baculoviruses, A. segetum nucleopolyhedrovirus (AgseNPV) and A. ipsilon nucleopolyhedrovirus (AgipNPV) for these two insect pests. The susceptibility of A. segetum to AgipNPV was confirmed by DNA restriction endonuclease analyses of DNA isolated from virus harvested from infected A. segetum larvae. For an initial comparison of both viruses, partial polyhedrin sequences were amplified by PCR, cloned, and sequenced. Both viruses shared a very similar polyhedrin gene sequence resulting in only three amino acid substitutions. Phylogenetic analyses clearly demonstrated that both viruses belong to NPV group II and are most closely related to a clade consisting of Spodoptera exigua NPV, Spodoptera frugiperda NPV, and Spodoptera littoralis NPV. Since AgipNPV shows high virulence for both cutworm species, it appears to be a suitable candidate as a single biological control agent of A. segetum and A. ipsilon.     

Appetitive flight patterns of male Agrotis segetum moths over landscape scales

An analysis is presented of the first harmonic radar studies of pheromone-plume locating flights of male Agrotis segetum moths over distances of up to 500 m. Upon release most moths flew in a direction having a downwind component. The first significant changes in flight orientations occur in the immediate vicinity of a pheromone source. Moths that were initially flying downwind change course and start flying crosswind whilst those that initially flew crosswind change course and start flying upwind. It is shown that such behaviour is consistent with the adoption of an effective plume-location strategy, and conditions are identified when downwind flights would be more advantageous than crosswind ones. Additionally, some of the complex flight patterns that can arise at later times are shown to be compatible with the adoption of an optimal biased scale-free (Lévy-flight) searching strategy. It is found that disruptive doses of sex pheromone can have a marked influence upon male moth flight patterns.     

Responses in highly selective sensory neurons to blends of pheromone components in the moth Agrotis segetum

Pheromone detecting sensory neurons in moths are known to be highly sensitive and selective. Female-emitted sexual pheromones are normally mixtures of a few to several components. However, not much is known about how receptor neurons respond to blends of compounds. In the present study we investigated how four physiological types of pheromone component-selective neurons responded to binary mixtures or to the complete blend in the turnip moth Agrotis segetum. We found that responses to mixtures only rarely differed from that to the excitatory component alone. The mixture interactions were exclusively suppressive and occurred only at high concentrations. Therefore we conclude that the, in A. segetum, commonly observed mixture interactions observed in higher brain centra are mainly the result of central nervous processing and that information about the pheromone components reaches the antennal lobes virtually unaltered. In addition, we found a physiological type of receptor neuron, responding selectively to one of the female-emitted pheromone components, that has previously not been observed in the Swedish population.     

The significance of shelter for young cutworms (Agrotis segetum)

The importance of shelter for young Agrotis segetum Schiff. (Lep. Noctuidae) larvae was investigated using caged carrots (Daucus carota L.) with the soil surface covered only by paraffin wax, or with a layer of vermiculite resembling dry soil on top of a layer of paraffin wax. In the vermiculite treatment, most cutworms were found in the vermiculite with only a small proportion on the plant foliage, whereas in the paraffin wax treatment, the majority was found on the foliage. Larval growth rate was higher and mortality lower among the cutworms which could shelter in the vermiculite than amongst those with no shelter. These results agree with those from previous investigations which showed that moist soil prevented the larvae from sheltering in it. The importance of shelter in dry soil cannot be fully explained, but it may provide a more favourable temperature for larval development.

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Résumé L'importance des abris pour les jeunes chenilles d'A. segetum a été examinée en utilisant des carottes (Daucus carota) dans des cages dont le sol était recouvert d'une couche de paraffine ou d'une couche de vermiculite mimant du sol sec au-dessus de la couche de paraffine. La plupart des vers gris ont été trouvés dans la couche de vermiculite contre une faible proportion dans le feuillage, tandis qu'en absence de vermiculite la majorité a été retrouvée dans le feuillage. La croissance larvaire était meilleure et la mortalité plus faible avec la vermiculite. Ces résultats sont conformes à des observations antérieures qui avaient montré qu'un sol humide empechait les chenilles de s'y abriter. L'importance de l'abri en sol sec n'est pas entièrement expliquée, mais celui-ci pourrait assurer une température plus favorable au développement larvaire.

     

First Record of Steinernema kraussei (Rhabditida: Steinernematidae) from Turkey and Its Virulence against Agrotis segetum (Lepidoptera: Noctuidae)

During a survey of entomopathogenic nematodes (EPNs) in the eastern Black Sea region of Turkey in 2009–2012, a steinernematid species was recorded and isolated using the Galleria-baiting method. The isolate was identified as Steinernema kraussei based on its morphological and molecular properties. The analysis of the ITS rDNA sequence placed the Turkish population of S. kraussei in the “feltiae-kraussei” group in the clade that contains different isolates of the species. This is the first record of S. kraussei from Turkey. The efficacy of S. kraussei was tested on Agrotis segetum (Lepidoptera: Noctuidea) larvae at different densities (100, 300, and 500 infective juveniles (IJs) g⁻¹ dry sand ) in laboratory conditions at 25 °C. The highest mortality (98%) was obtained with 500 IJs g⁻¹ dry sand within 7 d after inoculation. Our results indicate that the new isolate is a highly promising biological control agent against A. segetum, one of the most serious soil pests of agricultural area and fruits worldwide.     

Fine-structural characteristics of the antennal sensilla of Agrotis segetum (Insecta: Lepidoptera)

Summary The turnip moth Agrotis segetum possesses seven different types of sensilla: four single-walled (SW), one double-walled (DW), one terminal-pore (TP), and one poreless sensilla (NP).The SW 1 and SW 2 sensilla have the same external appearance, being long and slender, but differ in the branching pattern of the sensory processes: unbranched and branched in SW 1 and SW 2, respectively. The SW 3 sensilla are shorter, sickle-shaped, and contain a large number of branches from the sensory processes. These three sensillar types are innervated by 2–3 sensory cells. The SW 4 sensilla are raisin-shaped and possess three profusely branched sensory processes. The DW sensilla are short and have apical slit-like pores. This sensillar type has 5–6 sensory processes. The TP sensilla possess five sensory processes, one of them terminates basally in a tubular body, the others in the apical part of the long cuticular bristle. The NP sensilla are stout and have apical conelike structures. Two of the sensory processes terminate in the apical part, the third proximally. The third sensory process has a lamellar pattern. The fine structure indicates the following functions: SW and DW sensilla: chemoreception; TP sensillum: chemoreception and mechanoreception; NP sensillum: thermoreception and hygroreception.Supported by joint grants from the Swedish Council for Planning and Coordination of Research, the Swedish Natural Science Research Council, and the Swedish Council for Forestry and Agricultural Research     

Characterization and polyhedrin gene cloning of Lymantria xylina multiple nucleopolyhedrovirus

A baculovirus has been isolated from infected larvae of the casuarina moth, Lymantria xylina Swinehoe (Lepidoptera: Lymantriidae) in Taiwan. Ultrastructural observation revealed that this virus is a multiple nucleopolyhedrovirus (MNPV), and the name L. xylina MNPV (LyxyMNPV) was proposed. Restriction endonuclease (BamHI, EcoRI, and EcoRV) profiles of LyxyMNPV genome differed from those of other known NPVs. The size of the LyxyMNPV genome was estimated to be 154+/-1.26 kbp (mean+/-SE). The polyhedrin gene is located in the BamHI-D, EcoRI-C, and EcoRV-K fragments of LyxyMNPV genome. The gene organization of the LyxyMNPV EcoRV-K fragment and the phylogenetic analysis based on the polyhedrin gene sequences showed that LyxyMNPV is closely related to the L. dispar MNPV (LdMNPV). Furthermore, a rapid assay method was developed to distinguish LyxyMNPV from LdMNPV based on PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) analysis of polyhedrin genes.     

The entomogenous nematode Neoaplectana bibionis as a biological control agent of Agrotis segetum in lettuce

Biological control of the soil-inhabitating larvae (cutworms) of Agrotis segetum Schiff. using the entomogenous nematode Neoaplectana bibionis Bovien was investigated under field conditions. Cutworms were introduced to plots planted with lettuce, Lactuca sativa L. After planting and infection with cutworms the plots were treated with either N. bibionis, the insecticide endosulfan or water. The trials were sited on locations with loamy and sandy soil. Adequate control of cutworms was obtained using 2.5×10⁵ nematodes/m² on sandy soil and 1×10⁶ nematodes/m² on loamy soil. Effects of these treatments with nematodes were equal to the effect of endosulfan.

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Neoaplectana bibionis ein entomophager nematode zur biologischen bekämpfung von Agrotis segetum an salat

Zusammenfassung Unter Freilandbedingungen wurde die biologische Bekämpfung von Erdraupen (Agrotis segetum Schiff., Lepidoptera, Noctuidae) mit dem entomophagen Nematoden Neoaplectana bibionis Bovien geprüft. Mit Salat bepflanzte Parzellen wurden mit Erdraupen besetzt. Anschliessend wurde auf die Parzellen N. bibionis, das Insektizid Endosulfan oder Wasser ausgebracht. Die Versuche wurden in Gebieten mit lehmigen und sandigen Böden durchgeführt. Für eine ausreichende Bekämpfung der Erdraupen waren auf dem sandigen Boden 2.5×10⁵ Nematoden/m² und auf dem lehmigen Boden 1×10⁶ Nematoden/m² erforderlich. Die Wirkung dieser Behandlungen entsprach der mit Endosulfan.

     

Postembryonic development of leucokinin I-immunoreactive neurons innervating a neurohemal organ in the turnip moth Agrotis segetum

Summary In the abdominal ganglia of the turnip moth Agrotis segetum, an antibody against the cockroach neuropeptide leucokinin I recognizes neurons with varicose fibers and terminals innervating the perisympathetic neurohemal organs. In the larva, the abdominal perisympathetic organs consist of a segmental series of discrete neurohemal swellings on the dorsal unpaired nerve and the transverse nerves originating at its bifurcation. These neurohemal structures are innervated by varicose terminals of leucokinin I-immunoreactive (LKIR) fibers originating from neuronal cell bodies located in the preceding segment. In the adult, the abdominal segmental neurohemal units are more or less fused into a plexus that extends over almost the whole abdominal nerve cord. The adult plexus consists of peripheral nerve branches and superficial nerve fibers beneath the basal lamina of the neural sheath of the nerve cord. During metamorphosis, the LKIR fibers closely follow the restructuration of the perisympathetic organs. In both larvae and adults the LKIR fibers in the neurohemal structures originate from the same cell bodies, which are distributed as ventrolateral bilateral pairs in all abdominal ganglia. The transformation of the series of separated and relatively simple larval neurohemal organs into the larger, continuous and more complex adult neurohemal areas occurs during the first of the two weeks of pupal life. The efferent abdominal LKIR neurons of the moth Agrotis segetum thus belong to the class of larval neurons which persist into adult life with substantial peripheral reorganization occurring during metamorphosis.     

Characterization of a nucleopolyhedrovirus of Epinotia granitalis (Lepidoptera: Tortricidae)

A nucleopolyhedrovirus (NPV) from the cypress bark moth Epinotia granitalis Butler was partially characterized. Electron microscopy indicated that E. granitalis NPV (EpgrNPV) is a singly embedded nucleocapsid NPV with a relatively small polyhedron, ranging from 480 to 1100nm in diameter. Phylogenetic analysis revealed that EpgrNPV is a Group II NPV that is related to but distinct from Adoxophyes honmai NPV. The LC(50) against third instar E. granitalis larvae was 10(5.5) polyhedral occlusion bodies per gram (OBs/g diet), and the average time to death was 14 days. E. granitalis was the only EpgrNPV-susceptible species in a series of infection tests using insect species belonging to the family Tortricidae. Other test species, including Eucoenogenes ancyrota, A. honmai, Adoxophyes dubia, Pandemis heparana, Homona magnanima, and Archips insulanus, were not susceptible to the infection.     

Mating Behavior and Reproductive Potential in the Turnip Moth Agrotis segetum (Lepidoptera: Noctuidae)

We investigated the lifetime mating potential and the reproductive behavior of male and female turnip moths Agrotis segetum (Schiff.) under field and laboratory conditions. The sex ratio was 1 : 1 in a lab-reared population as well as in two wild populations. Males were capable of mating repetitively a relatively large number of times (mean of 6.7 ± 2.7 matings) when given access to new virgin females throughout their lifetimes. Females seldom mated more than once (mean ± 1.3 ± 0.6 matings), indicating a male-biased operational sex ratio. The mean potential lifetime mating was five times higher in males, while the coefficient of variance was lower in males. There was no differences in longevity between animals that were allowed to mate and animals not allowed to mate, indicating no direct costs or benefits of mating in physiological terms. In males, the number of matings was positively correlated with longevity, but this was not the case in females. Nor was there a correlation between the number of female matings and the number of fertilized eggs. There was a negative correlation between the number of eggs fertilized and the number of times males had previously mated, indicating that male ejaculates were limited. Male spermatophore size also decreased with number of achieved matings. Laboratory-reared females attracted males in the field throughout their lifetimes, with a peak at 3–7 days of age. Wild males, allowed to choose between pairs of caged females in the field, were attracted in equal numbers to females of different ages. Females did not show any mate-rejection behavior in the field. They mated with the first male that courted them. No incidence of mate replacement by males arriving later to already courted females were recorded.     

New cell lines derived from the black cutworm, Agrotis ipsilon, that support replication of the A. ipsilon multiple nucleopolyhedrovirus and several group I nucleopolyhedroviruses

New cell lines were recently developed from the embryos of the black cutworm, Agrotis ipsilon (Lepidoptera: Noctuidae). A primary culture was initiated from 4-day-old A. ipsilon eggs in ExCell420 medium supplemented with 5% fetal bovine serum. This initial culture produced sufficient cell growth to allow subcultivation and eventually led to the establishment of eight distinct strains. Two of these strains (AiE1611T and AiEd6T) were selected for further characterization. Extracts of these strains were compared to an extract from A. ipsilon eggs by isozyme analysis and shown to be from the same species. Both strains were susceptible to infection by the A. ipsilon multiple nucleopolyhedrovirus (AgipMNPV), as well as to lepidopteran group I NPVs from A. californica, Anagrapha falcifera, Anticarsia gemmatalis, Galleria mellonella, Helicoverpa armigera, Plutella xylostella, and Rachiplusia ou, with large numbers of occlusion bodies produced in most of the inoculated cells. The cell lines did not support the replication of group II NPVs from Helicoverpa zea, Lymantria dispar, and Spodoptera exigua. Both cell lines produced confluent monolayers in plaque assays and supported the formation of plaques upon infection with AgipMNPV and Autographa californica (Ac)MNPV. Twenty AgipMNPV plaques were picked from either AiE1611T or AiEd6T monolayers, and the plaque isolates were serially passaged three times through A. ipsilon cells. Only one isolate from AiE1611T cells exhibited genotypic variation in the form of an altered restriction fragment profile. Our results suggest these new lines can be useful in the study of AgipMNPV and A. ipsilon cellular and molecular biology.     

黄地老虎颗粒体病毒cDNA文库的构建

以感染黄地老虎颗粒体病毒(Agrotis segetum ganulosis virus,AsGV)的黄地老虎幼虫为材料提取总RNA、分离mRNA,并反转录合成cDNA,构建了包括黄地老虎(Agrotis segetura,As)幼虫和黄地老虎颗粒体病毒的cDNA文库.用EcoR Ⅰ和HindⅢ限制性内切酶酶切AsGV基因组DNA,制备地高辛探针,与上述总RNA、mR-NA、cDNA杂交,从文库中筛选出AsGV的阳性克隆1081个,经cDNA测序,cDNA编码序列与基因组编码序列相符.并根据基因组阅读框序列合成引物,PCR扩增出59个阅读框的编码基因,也完全与基因组序列相符.     

The role of food plant and pathogen-induced behaviour in the persistence of a nucleopolyhedrovirus

Insect baculoviruses can survive between epidemics as infectious particles external to the host. Many pathogens persist in reservoirs, i.e., microhabitats where survival is enhanced, for example due to protection from the degrading effects of UV irradiation. However, the probability of infecting new susceptible hosts is usually reduced. Persistence of pathogens and their movement in and out of reservoirs is an important, albeit little understood, aspect of insect pathogen ecology. This study investigated interactions between the behaviour of infected insect hosts, virus distribution and plant species on the persistence of the winter moth (Operophtera brumata) nucleopolyhedrovirus. Habitat influenced the persistence of infectious baculovirus in the field: virus on Sitka spruce (Picea sitchensis) and oak (Quercus robur) in forested areas retained more infectivity than virus on heather (Calluna vulgaris) in an unshaded habitat. Plant species per se did not directly affect the persistence of virus on the foliage of potted seedlings. Virally infected insects had altered behaviour and moved down plants relative to control insects, whereas in other systems larvae show height-seeking behaviour. Consequently, the majority of virus particles were distributed on plant stems. In two experiments (one using winter moth NPV and one Mamestra brassicae NPV) virus persisted better on plant stems relative to foliage. Neonate larvae were shown to be able to acquire infections from tree stems contaminated with a low level of virus. These data suggest that plant stems may be important reservoirs for between-year persistence of this pathogen. The observed virus-induced changes in host behaviour in winter moth could enhance the viral persistence by increasing the deposition of occlusion bodies in these reservoirs.     

Analysis of rhizobial strains nodulating Phaseolus vulgaris from Hispaniola Island,a geographic bridge between Meso and South America and the first historical link with Europe

Hispaniola Island was the first stopover in the travels of Columbus between America and Spain, and played a crucial role in the exchange of Phaseolus vulgaris seeds and their endosymbionts. The analysis of recA and atpD genes from strains nodulating this legume in coastal and inner regions of Hispaniola Island showed that they were almost identical to those of the American strains CIAT 652, Ch24-10 and CNPAF512, which were initially named as Rhizobium etli and have been recently reclassified into Rhizobium phaseoli after the analysis of their genomes. Therefore, the species R. phaseoli is more abundant in America than previously thought, and since the proposal of the American origin of R. etli was based on the analysis of several strains that are currently known to be R. phaseoli, it can be concluded that both species have an American origin coevolving with their host in its distribution centres. The analysis of the symbiovar phaseoli nodC gene alleles carried by different species isolated in American and European countries suggested a Mesoamerican origin of the α allele and an Andean origin of the γ allele, which is supported by the dominance of this latter allele in Europe where mostly Andean cultivars of common beans have been traditionally cultivated.     

Claviradulomyces, a new genus of Odontotremataceae from West African rainforest

A new genus, Claviradulomyces, morphologically typical of Odontotremataceae, is proposed to accommodate the new species Claviradulomyces dabeicola. The genus is characterised by its ornamented periphysoids, and long-cylindric, sigmoid, acuminate ascospores. Genetically, C. dabeicola falls within the Ostropales, but the Odontotremataceae have been very poorly sampled genetically and their phylogenetic relationship within the order is unclear. C. dabeicola has been collected consistently and exclusively on the rainforest tree Erythroxylum mannii in the Côte d'Ivoire and Ghana, where it is associated with bark abnormalities on branches and stems of living trees.     

Molecular characterization and distribution of CYCLE protein from Athalia rosae

cDNA encoding CYCLE (CYC) from the coleseed sawfly, Athalia rosae (Hymenoptera, Symphyta), was amplified by PCR. This is a first determination of hymenopteran CYC structure. ArCYC had an overall identity of 66% with CYC of Anopheles gambiae and ca. 60% of Drosophila melanogaster. Structural investigation revealed that ArCYC contained characteristic motifs of: bHLH, PAS A, PAS B, PAC and BCTR. Detailed analysis indicated high conservation of these regions among insects. Northern blot analysis showed that the mRNA of ca. 3 kb was transcribed both in the head and in the rest of the body. Southern blot analysis suggested the presence of a single copy of the gene in the genome. Western blot indicates that the quantity of CYC protein does not fluctuate under LD 12:12 in either the head or the rest of the body. Immunocytochemical examination revealed CYC-like antigen in the pars intercerebralis, dorsolateral protocerebrum, dorsal optic tract, tritocerebrum of the brain and the subesophageal ganglion.