1,722,240 research outputs found
Ervi, the intraspecific Barbera x Croatina crossbreed: first growing and winemaking experiences in Lombardia (northwest of Italy)
No full textBarbera and Croatina are the two most important grapevine varieties characterizing wines from several districts in North-West of Italy; they coexist on the hilly territories sited south of the Po river (historically known as “western-cispadana” area) where they are also blended together to obtain local wines such as Buttafuoco and Rosso Oltrepo Pavese in Lombardia, and Gutturnio in Emilia Romagna. Ervi is an intraspecific crossbreed between Barbera and Croatina performed in the ‘70s and selected over the last decades in order to improve some agronomical traits of both parents. The present study represents the first characterization of development, production and enological performance of the cv. Ervi in Lombardia and, more specifically, in the Oltrepo Pavese wine district. Long-term results related to a field-based assessment as well as the sensory profiling of wines produced at a micro scale are reported. When compared to Barbera and Croatina, Ervi shows improved productivity respect to Croatina and a better composition as compared to both its parents. Results recommend the introduction of the cv. Ervi in Lombardia for the production of high quality red wines
Influence of the aphid pathogen Pandora neoaphidis on the foraging behaviour of the aphid parasitoid Aphidius ervi
No full text1. The parasitoid Aphidius ervi and the entomopathogenic fungus Pandora neoaphidis both require successful invasion of an aphid host to complete their life cycle. A shorter developmental period allows P. neoaphidis to out-compete A. ervi. Aphidius ervi may reduce this fitness cost by avoiding aphid colonies containing P. neoaphidis. Here the response of A. ervi towards P. neoaphidis was assessed using sequential experiments designed to replicate different stages of parasitoid foraging behaviour. 2. Entry rate experiments showed that A. ervi entered aphid colonies containing P. neoaphidis-sporulating cadavers and that there was no significant difference in the attraction of A. ervi to aphid-damaged Vicia faba plants containing either healthy Acyrthosiphon pisum or P. neoaphidis-sporulating cadavers. 3. Observational behavioural experiments indicated that the presence of P. neoaphidis did not affect the search time or total foraging time of A. ervi on V. faba plants infested with either healthy A. pisum or P. neoaphidis-sporulating cadavers. 4. In Petri dish bioassays using aphids infected with P. neoaphidis over a period of 120 h, A. ervi showed no difference in attack rate against uninfected aphids or living aphids infected with P. neoaphidis for 1, 24, 48, 72, or 96 h. However, sporulating cadavers (120 h infection) were not attacked. 5. Aphidius ervi appears only able to detect the presence of P. neoaphidis once the host is dead and sporulation has started. The fitness of A. ervi may therefore be severely reduced when foraging in P. neoaphidis-infected aphid colonies
Responses to aphid sex pheromones by the pea aphid parasitoids Aphidius ervi and Aphidius eadyi
No full textAphidius ervi and Aphidius eadyi, two parasitoids of the pea aphid Acyrthosiphon pisum, were attracted to components of the aphid sex pheromone in laboratory bioassays. Pre-test experience with host aphids in the presence of aphid sex pheromone did not affect the response of A. ervi to pheromone in a 4-way olfactometer, compared with that of naive parasitoids. Aphidius ervi females exposed only to the pheromone prior to testing did not respond in the olfactometer, suggesting habituation to the foraging cue by the parasitoid. In a wind tunnel, aphid sex pheromone increased the attraction of A. ervi to the plant-host complex (Vicia faba/A. pisum), suggesting an additive effect when two different foraging cues are present simultaneously
LLC “Ervi I” marketing mix analysis and improvement opportunities
No full textKvalifikācijas darba temats ir SIA “Ervi I” mārketinga kompleksa analīze un pilnveides iespējas. Kvalifikācijas darba mērķis: pamatojoties uz teorijas atziņām par mārketinga kompleksu, izpētīt SIA “Ervi I” mārketinga kompleksa četrus elementus – produktu, cenu, vietu un virzīšanu tirgū, kā arī sniegt secinājumus un priekšlikumus mārketinga kompleksa pilnveidošanai. Kvalifikācijas darbs sastāv no četrām nodaļām: 1.“Mārketinga teorētiskie aspekti”, tiek apskatīti un analizēti mārketinga teorija. 2.“SIA “Ervi I” mārketinga vides analīze”, tiek analizēta saimnieciskā darbība un vide uzņēmumā SIA “Ervi I” . 3.“Uzņēmuma SIA “Ervi I” mārketinga kompleksa raksturojums”, tiek analizēts uzņēmuma SIA “Ervi I” mārketinga komplekss. 4.“SIA “Ervi I” mārketinga kompleksa pilnveides iespēju izvērtēšana” tiek analizēti aptaujas rezultāti un izklāstītas mārketinga kompleksa pilnveides iespējas. Darba nobeigumā tiek uzskaitīti secinājumi un apkopoti priekšlikumi mārketinga kompleksa pilnveidošanai uzņēmumā SIA “Ervi I”. Darbs sastāv no 59 lpp., 4 nodaļām un 15 apakšnodaļām, kurās ietvertas 4 tabulas, 27 attēli. Kvalifikācijas darbam ir 37 izmantoti avoti un 2 pielikumi.The subject of the qualification paper is LLC “Ervi I” marketing mix analysis and improvement opportunities. The aim of the qualification paper is to analyze the four elements of the marketing mix of LLC “Ervi I” – product, price, promotion and place. And after that to make conclusions and suggestions for improving the marketing mix. The qualification paper is structured as follows: 1.”Theoretical aspects of marketing”, the literature review and analysis of marketing theory. 2.”Analysis of marketing environment in LLC “Ervi I””, analysis of the company’s marketing environment. 3.”Description of the marketing mix of LLC “Ervi I””, analysis of the company’s marketing mix. 4.”Chances for improvement of SIA “Ervi I” marketing mix”, author describes the results of the survey and ways to improve company’s marketing mix. At the end of the qualification paper author lists the conclusions and summarizes the proposals for improvement of marketing mix in LLC “Ervi I” The qualification paper consists of: 59 pages, 4 sections, 15 subsections with 4 tables, 27 pictures. There are 37 references and 2 attachments
Determinants of variation in the response of the aphid parasitoid Aphidius ervi to aphid sex pheromones
Get PDFVariation in parasitoid responses to semiochemicals may be influenced by genetics, phenotypic plasticity and the individual\u27s physiological state. Previous experimental work has indicated a high degree of variability among parasitoid individuals in their response to aphid sex pheromones but no work has been done to investigate the factors behind such variation. Some aspects of this variation were investigated in the aphid parasitoid Aphidius ervi (Haliday) (Hymenoptera: Braconidae) in the laboratory. Conducting behavioural experiments, the searching behaviour of females was investigated in the presence and the absence of the aphid sex pheromone (4GS,7S,7a/?)-nepetalactone, observing the same individual female parasitoids during two consecutive foraging attempts on different plants. The first set of observational experiments demonstrated the role of the pheromone as an arrestant in the searching behaviour of A. ervi and its additive effect when it was presented with other foraging cues such as aphid-induced plant volatiles. The second set of behavioural experiments showed significant differences in A. ervi responses to the pheromone depending on their physiological state. Virgin, well-fed and high egg-load females were more active in the presence of the aphid sex pheromone than mated, hungry and low egg-load females although there were no significant differences in their activities in the first foraging attempt when the pheromone was absent. The effect of the pheromone on the searching behaviour of A. ervi within different tritrophic systems was investigated. The results showed variation in this response depending on which host aphid and/or the host plant they had been reared, showing that conditioning may have an influence on this response. Using two isofemale lines and an insectary-maintained laboratory population of A.ervi, the genetic basis of this response was investigated. The behavioural experiments showed no significant differences between the three different populations in their response to aphid sex pheromones. A supportive molecular study using DNA microsatellites v/as also conducted, which revealed low genetic variability among the three studied populations. The results are discussed in the context of using the response of A. ervi to aphid sex pheromones in a strategy to manipulate natural populations of the parasitoid for the biological control of aphids and the importance of studying the variation in this response to increase the effectiveness of such strategy
Expression differences in Aphidius ervi (Hymenoptera: Braconidae) females reared on different aphid host species
Get PDFabstract: The molecular mechanisms that allow generalist parasitoids to exploit many, often very distinct hosts are practically unknown. The wasp Aphidius ervi, a generalist koinobiont parasitoid of aphids, was introduced from Europe into Chile in the late 1970s to control agriculturally important aphid species. A recent study showed significant differences in host preference and host acceptance (infectivity) depending on the host A. ervi were reared on. In contrast, no genetic differentiation between A. ervi populations parasitizing different aphid species and aphids of the same species reared on different host plants was found in Chile. Additionally, the same study did not find any fitness effects in A. ervi if offspring were reared on a different host as their mothers. Here, we determined the effect of aphid host species (Sitobion avenae versus Acyrthosiphon pisum reared on two different host plants alfalfa and pea) on the transcriptome of adult A. ervi females. We found a large number of differentially expressed genes (between host species: head: 2,765; body: 1,216; within the same aphid host species reared on different host plants: alfalfa versus pea: head 593; body 222). As expected, the transcriptomes from parasitoids reared on the same host species (pea aphid) but originating from different host plants (pea versus alfalfa) were more similar to each other than the transcriptomes of parasitoids reared on a different aphid host and host plant (head: 648 and 1,524 transcripts; body: 566 and 428 transcripts). We found several differentially expressed odorant binding proteins and olfactory receptor proteins in particular, when we compared parasitoids from different host species. Additionally, we found differentially expressed genes involved in neuronal growth and development as well as signaling pathways. These results point towards a significant rewiring of the transcriptome of A. ervi depending on aphid-plant complex where parasitoids develop, even if different biotypes of a certain aphid host species (A. pisum) are reared on the same host plant. This difference seems to persist even after the different wasp populations were reared on the same aphid host in the laboratory for more than 50 generations. This indicates that either the imprinting process is very persistent or there is enough genetic/allelic variation between A. ervi populations. The role of distinct molecular mechanisms is discussed in terms of the formation of host fidelity.The final version of this article, as published in PeerJ, can be viewed online at: https://peerj.com/articles/3640
Strategies involved in the location of hosts by the parasitoid Aphidius ervi Haliday (Hymenoptera : Braconidae : Aphidiinae)
No full textThe parasitoid Aphidius ervi Haliday uses both semiochemical and physical cues to locate and recognize its main host, the pea aphid Acyrthosiphon pisum (Harris). In wind tunnel studies, it was demonstrated that plant volatiles, particularly those induced by aphid feeding, are important long-range cues in the initial stages of host location. Furthermore, A. ervi distinguished between plants damaged by Ac. pisum and those damaged by the nonhost aphid Aphis fabae (Scop.). Host-induced volatiles were emitted by young broad bean plants (Vicia faba) in sufficient quantities to elicit a flight response from female parasitoids after 40 aphids had been feeding for 72 h. Aphids confined to a single leaf caused systemic production of herbivore-induced volatiles throughout the plant. Previous experiences with hosts or host-related cues heightened parasitoid responses to host-induced volatiles and also triggered responses to other plant volatiles. This learning ability provides the parasitoid with behavioral plasticity to adapt its responses to suit prevailing foraging opportunities. A. ervi females also responded to synthetic aphid sex pheromones in wind tunnel experiments, and attempts are being made to manipulate field populations using host pheromone lures. Contact kairomones in the host cuticle and cornicle secretion appear to be involved in host recognition and acceptance by A. ervi females. In addition, visual cues play a role in host location and recognition, with color being an important short-range cue. Color alone stimulated attack responses; A. ervi females attacked green aphids in preference to brown aphids and showed attack responses toward yellow paint pigments enclosed in glass capillary tips. (C) 1998 Academic Press
The role of Aphidius ervi venom in regulating host nutritional suitability
No full textParasitoid wasps have evolved complex strategies to exploit and regulate the physiology of their hosts and
enhance their suitability for the development of their progeny, which are modulated by host regulation
factors both of maternal (venom) and embryonic (teratocytes) origin. The pea aphid, Acyrthosiphon pisum
(Homoptera, Aphididae), and its endophagous parasitoid wasp, Aphidius ervi (Hymenoptera, Braconidae),
represent a unique model system to investigate the molecular mechanisms underlying the interactions
between parasitoids, their hosts and primary symbionts. In this study, we focused on the functional role of
Ae-γ-glutamyl transpeptidase (Ae-γGT), the most abundant component of A. ervi venom which is known to
induce host castration. Using RNA interference technique, we knocked down Ae-γGT gene in newly emerged
female wasps, using microinjections of double-stranded RNA (dsRNA) in the pupal stage of the parasitoid.
These females were used to observe phenotypic changes in parasitized hosts and the parasitoid's progeny,
as affected by a venom blend lacking Ae-γGT. We found that Ae-γGT silencing prevented the aphid castration
and enhanced the growth of both the host and parasitoid, which was supported by a higher load of the
primary bacterial symbiont Buchnera aphidicola. However, emerging adults exhibited reduced survival and
fecundity, suggesting a trade-off with body size. This demonstrates the primary role of Ae-γGT in host ovary
degeneration and suggests that this protein counterbalances the proliferation of Buchnera likely triggered by
other venom components. Our study offers a new approach to unravel the complexity of aphid parasitoid
venom in vivo and sheds light on a previously unknown role for Ae-γGT in the host regulation process
Induction and systemic release of herbivore-induced plant volatiles mediating in-flight orientation of Aphidius ervi
No full textIn-flight orientation of the braconid Aphidius ervi in response to volatiles released from broad bean plants infested by the pea aphid, Acyrthosiphon pisum, was studied in a no-choice wind-tunnel bioassay. The role of aphid infestation level and duration, systemic production of volatiles by "insect-free" parts of the plant, and the specificity of aphid-induced volatiles on the flight behavior of the foraging female parasitoids were investigated. The upper insect-free part of a three-leaved broad bean plant, which was basally infested by a population of 40 A. pisum, released synomones detectable by A. ervi females after at least 48-72 hr of infestation, resulting in both significant increases iii oriented flights and landings on the source compared with uninfested control plants. This suggests that volatiles involved in host-location by A. ervi are systemically released by broad bean plants either in response to circulation of aphid saliva, circulation of saliva-induced bioactive elicitors, or circulation of the synomones themselves. Air entrainment extracts of volatiles collected from a broad bean plant infested by the nonhost Aphis fabae or an uninfested broad bean plant elicited few oriented flights and landing responses by female parasitoids. These extracts were significantly less attractive than extracts collected from a broad bean plant infested by the host A, pisum, indieating the specificity of synomones elicited by different aphid species on the same plant species
Plant-to-plant communication mediating in-flight orientation of Aphidius ervi
No full textBroad bean plants (Vicia faba) infested by the pea aphid, Acyrthosiphon pisum, play a key role in the in-flight orientation of the parasitoid Aphidius ervi, by producing host-induced synomones (HIS). These volatiles are herbivore-specific and are systemically released from insect-free parts of an infested plant, suggesting the existence of an elicitor circulating throughout the plant. This study was designed to investigate whether the plant metabolic changes, leading to HIS biosynthesis and emission, can in some way trigger similar responses in neighboring plants through aerial and/or root communication. Uninfested broad bean plants maintained in the same pot together with plants infested by A. pisum became more attractive towards A. ervi females when tested in a wind-tunnel bioassay. This change was not observed when root contact was prevented among plants that had their aerial parts in close proximity, suggesting that an exudate from the roots of the infested plant may cause the induction of the attractive volatiles in uninfested plants. Broad bean plants grown hydroponically also produce pea aphid induced signals that attract A. ervi. When an intact (uninfested) plant was placed in a hydroponic solution previously used to grow a pea aphid-infested plant, it became attractive to parasitoids, while an intact plant placed in a solution previously used to grow an intact plant did not undergo such a change. These results indicate that plant-to-plant signaling in this tritrophic system may occur at the rhizosphere level and is most likely mediated by a systemically translocated elicitor
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