Extraits de l'évolution de l'entomologie appliquée au Québec : emphase sur la phytoprotection

Le développement de l’entomologie au Québec comme science naturelle a commencé avec des naturalistes érudits comme William Couper, Léon Provancher et Henry Lyman qui ont observé abondamment et décrit l’entomofaune du Québec, fondé des sociétés professionnelles et rédigé les premiers ouvrages scientifiques sur les insectes du Québec. Au début du XXe siècle, l’importance économique des plantes agricoles et des essences de coupes forestières a atteint un niveau favorisant la naissance de l’entomologie appliquée. Son développement initial est marqué par la fondation de la SPPQ, la création du premier programme d’études supérieures en entomologie, ainsi que le recrutement d’entomologistes professionnels dans les institutions publiques de protection des plantes contre les ravageurs. Les entomologistes en chef James Fletcher au gouvernement fédéral et Victor Huard au gouvernement provincial, ainsi que les professeurs William Lochhead du Collège Macdonald et Georges Maheux de l’École forestière de l’Université Laval, sont des figures remarquables de cette époque. Les entomologistes publient abondamment sur le cycle de vie des insectes nuisibles, sur les dommages causés et sur les moyens de lutte efficaces avec des insecticides encore primitifs et dangereux. Pendant plusieurs décennies, Ernest-Melville DuPorte se trouve au Collège Macdonald au centre des études supérieures et de la recherche en entomologie au Québec. Après la Seconde Guerre mondiale, la demande en denrées alimentaires et en fibre ligneuse croît à un rythme sans précédent, de même que la lutte aux ravageurs, à l’ère nouvelle des produits chimiques de synthèse, notamment des insecticides comme le DDT. En agriculture, les entomologistes actifs en phytoprotection se regroupent au laboratoire de recherche de Saint-Jean-sur-Richelieu et au Service de la protection des cultures du MAPAQ, ainsi que dans leurs stations de recherche de terrain. La recherche en entomologie forestière se développe à Québec autour du laboratoire fédéral des Laurentides et à la Faculté d’arpentage et de génie forestier (aujourd’hui la Faculté de foresterie, de géographie et de géomatique) de l’Université Laval. Sous la pression de l’industrie forestière, les arrosages aériens aux insecticides deviennent systématiques et sont surtout régis par l’abondance cyclique de la tordeuse des bourgeons de l’épinette. À la fin des années 1960, l’entomologie appliquée prend lentement un virage écologique, ouvert au contrôle naturel des ravageurs et aux idées de la résistance des plantes et de la stimulation de l’impact des agents biologiques de répression. La recherche et la formation aux études supérieures en entomologie connaissent un essor marqué dans les centres universitaires établis et nouvellement créés. La fin du XXe siècle est marquée par l’arrivée des plantes transgéniques résistantes aux ravageurs et les conséquences prévisibles du réchauffement climatique sur l’abondance et la diversité des ravageurs. L’entomologie comme activité scientifique professionnelle s’est enrichie de l’arrivée de nombreuses femmes dans les centres de recherche et les universités, bien qu’affectée par le ralentissement du recrutement d’entomologistes professionnels dans les services publics et les universités et l’incertitude des conditions économiques futures.The development of entomology as a natural science in Quebec first involved naturalist erudites such as William Couper, Léon Provancher and Henry Lyman, who abundantly observed and described the Quebec entomofauna, founded societies of professional entomologists, and wrote the first scientific documents about the insects of Quebec. At the turn of the 20th century, the economic importance of agricultural and forest products had reached a sufficient level for applied entomology to develop its own identity. This is evidenced by the birth of the Québec Society for the Protection of Plants, the creation of the first higher education program in entomology, and the establishment of professional entomologist positions in the plant protection services of the federal and provincial governments. Entomologists abundantly published on the life cycle of insect pests, their damages, and early efficient insect pest control using what were then primitive and dangerous insecticides. Entomologists in chief James Fletcher, at the federal level, and Victor Huard, at the provincial level, as well as entomology professors William Lochhead of Macdonald College and Georges Maheux of the École forestière de l’Université Laval, are important figures who initially guided the development of applied entomology in Quebec. For decades, Ernest-Melville DuPorte, while working at Macdonald College, was at the centre of higher education and fundamental research in entomology in Quebec. Following the Second World War, the demand for food products and wood fibre grew at an unprecedented rate, and so did the need to control insect pests, in the new era of synthetic chemicals such as the DDT insecticide. Entomologists active in agriculture were mainly regrouped around the Saint-Jean-sur-Richelieu Research Station and at the MAPAQ’s Service of Plant Protection, and at their experimental field stations. Research in forest entomology developed itself in Quebec City at the Laurentians federal laboratory and at the Faculté d’arpentage et de génie forestier (known today as the Faculté de foresterie, de géographie et de géomatique) de l’Université Laval. Due to pressure from the forest industry, the spraying of Quebec forests with chemical insecticides expanded systematically and, for decades, was mainly determined by the cyclic abundance of the spruce budworm. At the end of the 1960s, applied entomology in Quebec slowly took an ecological turn, marked by environmental concerns about chemical insecticides, more attention given to natural control, and a renewed interest in biological control agents. Fundamental research on insects and higher education in entomology expanded in both established and newly created university centres. The recent decades were marked by the arrival of genetically modified crops that are highly resistant to target pests, and the imminent consequences of global warming on the abundance and diversity of insect pests. Entomology as a professional activity benefited from the arrival of many women in research centres and universities; however, there is now some concern about the noticeable decline in the recruitment of specialized entomologists in public services and universities, and an uncertain economic future

Biodiversity of lepidopteran pests and their parasitoids in organic and conventional cranberry crop

A 2-year study was conducted in the main cranberry (Vaccinium macrocarpon Aiton) growing region of Québec to determine the biodiversity of lepidopteran pests and their parasitoids, which may differ in organic and conventional integrated pest management (IPM) systems. We also aimed to compare densities and parasitism on five caterpillar pest species of primary economic importance: Macaria sulphurea (Packard), Macaria brunneata (Thunberg), Xylena nupera (Lintner), Rhopobota naevana (Hübner) and Sparganothis sulfureana (Clemens), which accounted for more than 80% of the pest community each year. The lepidopteran pest communities clearly varied between the two pest management systems, suggesting efficacy differences among them. Rhopobota naevana was dominant on organic farms, whereas conventional farms had greater pest richness and evenness, with M. sulphurea, M. brunneata and X. nupera being the most abundant. Based on laboratory rearing of field collected caterpillars, the parasitoid community was composed of 25 species or taxa (22 from primary pests) and communities were not significantly different between the two farming regimes. The most common species belonged to the braconid genera Aleiodes, Meteorus, Microplitis, Oncophanes; ichneumonids Hyposoter, Exetastes, Phytodietus; and tachinids Campylocheta, Nemorilla. Of the five primary pests, X. nupera was the most parasitized, while no parasitoids were reared from M. brunneata. Annual parasitism rate of the primary pests ranged 20–40% and data showed that it was explainable by host availability rather than farming system

Species indicators of ecosystem recovery after reducing large herbivore density: Comparing taxa and testing species combinations

Indicator species have been used successfully for estimating ecosystem integrity, but comparative studies for defining optimal taxonomic group remain scarce. Furthermore, species combinations may constitute more integrative tools than single species indicators, but case studies are needed to test their efficiency. We used Indicator Species Analysis, which statistically determines the association of species to one or several groups of sites, to obtain indicators of ecosystem recovery after various deer density reductions. We used five taxonomic groups: plants, carabid beetles, bees, moths and songbirds. To test whether species combinations could complement single indicator species, we used plants as a model taxon and examined the indicator value of joint occurrence of two or three plant species. Our study relies on experimental controlled browsing enclosures established for six years on Anticosti Island (Quebec). Four levels of deer density (0, 7.5 and 15 deer km−2 and natural densities between 27 and 56 deer km−2) were studied in two vegetation cover types (uncut forests and cut-over areas), in a full factorial design for a total of eight experimental treatments. For all taxa but bees, we tested 54 treatment groups consisting in one specific density or in a sequence of two or more consecutive deer densities in one or both cover types (ten groups for bees, sampled only in cut-over areas). We found 12 plants, 11 moths and one songbird to be single species indicators of ecosystem conditions obtained under 12 different treatment groups. Six treatment groups were indicated by plants and six different ones by moths, of which one group was also identified by a songbird species. Moths were thus worth the extra sampling effort, especially since the groups they indicated were more treatment-specific (mainly one or two deer density treatments). We tested the same 54 treatment groups for plant species combinations represented by two or three co-occurring species. Plant combinations efficiently complemented plant singletons for detecting ecosystem conditions obtained under various deer densities. In fact, although singletons were highly predictive, 17 additional treatment groups were identified exclusively with two- and three-species combinations, some being more treatment-specific. Our findings show that plants and moths provide complementary indicators of ecosystem conditions under various deer densities, and that computing species combinations increases our capacity to monitor ecosystem recovery after reducing herbivore densities.Funding was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC)-Produits forestiers Anticosti Industrial Chair to SDC, the Ministère des Ressources Naturelles et de la Faune du Québec, the Canadian Forest Service of Natural Resources Canada and an NSERC scholarship to MB and NSERC DG to MP and SP. We are grateful to the Centre de la Science de la Biodiversité du Québec and Centre d’études nordiques for scholarships

Function of TFIIIC, RNA polymerase III initiation factor, in activation and repression of tRNA gene transcription

Transcription of transfer RNA genes by RNA polymerase III (Pol III) is controlled by general factors, TFIIIB and TFIIIC, and a negative regulator, Maf1. Here we report the interplay between TFIIIC and Maf1 in controlling Pol III activity upon the physiological switch of yeast from fermentation to respiration. TFIIIC directly competes with Pol III for chromatin occupancy as demonstrated by inversely correlated tDNA binding. The association of TFIIIC with tDNA was stronger under unfavorable respiratory conditions and in the presence of Maf1. Induction of tDNA transcription by glucose-activated protein kinase A (PKA) was correlated with the down-regulation of TFIIIC occupancy on tDNA. The conditions that activate the PKA signaling pathway promoted the binding of TFIIIB subunits, Brf1 and Bdp1, with tDNA, but decreased their interaction with TFIIIC. Association of Brf1 and Bdp1 with TFIIIC was much stronger under repressive conditions, potentially restricting TFIIIB recruitment to tDNA and preventing Pol III recruitment. Altogether, we propose a model in which, depending on growth conditions, TFIIIC promotes activation or repression of tDNA transcription

Wounding, insect chewing and phloem sap feeding differentially alter the leaf proteome of potato, <it>Solanum tuberosum</it> L.

<p>Abstract</p> <p>Background</p> <p>Various factors shape the response of plants to herbivorous insects, including wounding patterns, specific chemical effectors and feeding habits of the attacking herbivore. Here we performed a comparative proteomic analysis of the plant's response to wounding and herbivory, using as a model potato plants (<it>Solanum tuberosum</it> L.) subjected to mechanical wounding, defoliation by the Colorado potato beetle <it>Leptinotarsa decemlineata</it> Say, or phloem sap feeding by the potato aphid <it>Macrosiphum euphorbiae</it> Thomas.</p> <p>Results</p> <p>Out of ~500 leaf proteins monitored by two-dimensional gel electrophoresis (2-DE), 31 were up- or downregulated by at least one stress treatment compared to healthy control plants. Of these proteins, 29 were regulated by beetle chewing, 8 by wounding and 8 by aphid feeding. Some proteins were up- or downregulated by two different treatments, while others showed diverging expression patterns in response to different treatments. A number of modulated proteins identified by mass spectrometry were typical defense proteins, including wound-inducible protease inhibitors and pathogenesis-related proteins. Proteins involved in photosynthesis were also modulated, notably by potato beetle feeding inducing a strong decrease of some photosystem I proteins. Quantitative RT PCR assays were performed with nucleotide primers for photosynthesis-related proteins to assess the impact of wounding and herbivory at the gene level. Whereas different, sometimes divergent, responses were observed at the proteome level in response to wounding and potato beetle feeding, downregulating effects were systematically observed for both treatments at the transcriptional level.</p> <p>Conclusions</p> <p>These observations illustrate the differential impacts of wounding and insect herbivory on defense- and photosynthesis-related components of the potato leaf proteome, likely associated with the perception of distinct physical and chemical cues <it>in planta</it>.</p

Survival to parasitoids in an insect hosting defensive symbionts: a multivariate approach to polymorphic traits affecting host use by its natural enemy.

Insect parasitoids and their insect hosts represent a wide range of parasitic trophic relations that can be used to understand the evolution of biotic diversity on earth. Testing theories of coevolution between hosts and parasites is based on factors directly involved in host susceptibility and parasitoid virulence. We used controlled encounters with potential hosts of the Aphidius ervi wasp to elucidate behavioral and other phenotypic traits of host Acyrthosiphon pisum that most contribute to success or failure of parasitism. The host aphid is at an advanced stage of specialization on different crop plants, and exhibits intra-population polymorphism for traits of parasitoid avoidance and resistance based on clonal variation of color morph and anti-parasitoid bacterial symbionts. Randomly selected aphid clones from alfalfa and clover were matched in 5 minute encounters with wasps of two parasitoid lineages deriving from hosts of each plant biotype in a replicated transplant experimental design. In addition to crop plant affiliation (alfalfa, clover), aphid clones were characterized for color morph (green, pink), Hamiltonella defensa and Regiella insecticola symbionts, and frequently used behaviors in encounters with A. ervi wasps. A total of 12 explanatory variables were examined using redundancy analysis (RDA) to predict host survival or failure to A. ervi parasitism. Aphid color was the best univariate predictor, but was poorly predictive in the RDA model. In contrast, aphid host plant and symbionts were not significant univariate predictors, but significant predictors in the multivariate model. Aphid susceptibility to wasp acceptance as reflected in host attacks and oviposition clearly differed from its suitability to parasitism and progeny development. Parasitoid progeny were three times more likely to survive on clover than alfalfa host aphids, which was compensated by behaviorally adjusting eggs invested per host. Strong variation of the predictive power of intrinsic (body color) and extrinsic traits (symbionts, host plant), indicate that host variables considered as key predictors of outcomes strongly interact and cannot be considered in isolation