Academic literature on the topic 'Population biology'

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Journal articles on the topic "Population biology"

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Rios, José M. "Population Biology." American Biology Teacher 64, no. 6 (August 1, 2002): 470–71. http://dx.doi.org/10.2307/4451341.

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Andreone, F., S. Crovella, P. Arduino, L. Bullini, G. Badino, G. Celebrano, A. Peyrot, et al. "Population biology." Bolletino di zoologia 53, sup001 (January 1986): 61–69. http://dx.doi.org/10.1080/11250008609355541.

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Stebbins, G. Ledyard. "Advanced Population Biology." BioScience 35, no. 7 (July 1985): 456. http://dx.doi.org/10.2307/1310036.

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Cohen, G. R., and N. Keyfitz. "Population and Biology." Biometrics 42, no. 3 (September 1986): 682. http://dx.doi.org/10.2307/2531228.

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Craig, Timothy P. "Parasitoid Population Biology." Ecology 82, no. 7 (July 2001): 2083–84. http://dx.doi.org/10.1890/0012-9658(2001)082[2083:ppb]2.0.co;2.

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Robinson, Clare H. "Fungal population biology." New Phytologist 146, no. 2 (May 2000): 207–8. http://dx.doi.org/10.1046/j.1469-8137.2000.00638b.x.

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Burdon, Jeremy J. "Plant population biology." Trends in Ecology & Evolution 4, no. 10 (October 1989): 309. http://dx.doi.org/10.1016/0169-5347(89)90031-1.

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PURCELL, A. H., and S. E. LINDOW. "Pathogens and Populations: Diseases and Plant Population Biology." Science 238, no. 4824 (October 9, 1987): 221. http://dx.doi.org/10.1126/science.238.4824.221-a.

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Ashman, Tia-Lynn. "PLANT POPULATION BIOLOGY SECTION." Bulletin of the Ecological Society of America 84, no. 4 (October 2003): 188. http://dx.doi.org/10.1890/0012-9623(2003)84[188a:ppbs]2.0.co;2.

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Gibson, David J. "Population Biology of Grasses." Ecology 79, no. 8 (December 1998): 2968–69. http://dx.doi.org/10.1890/0012-9658(1998)079[2968:pbog]2.0.co;2.

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Dissertations / Theses on the topic "Population biology"

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Couch, Brett Charles. "Population biology of Sclerotium cepivorum." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0004/MQ45399.pdf.

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Vella, Adriana. "Primate population biology and conservation." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245184.

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Bohan, David Andrew. "Modelling Steinernema feltiae population biology." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261776.

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Seelig, Frederik. "Population biology of Ixodes ticks." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558849.

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The hard tick Ixodes ricinus is one of the most important species of disease vectors worldwide. It transmits a variety of pathogens, including spirochaetes that are the causative agent of Lyme borreliosis (LB) in humans. This study aimed at analysing different aspects of the ecology, molecular evolution, and microbial associations of I. ricinus. A novel scheme for the phylogenetic analysis and genotyping of I. ricinus was established as part of this study. Phylogeographic clustering of I. ricinus samples fromdifferent European countries was observed, while samples from two different sites inSouthwest England did not show spatial differentiation. The ecology and host abundance in these two habitats was assessed. Differences in the density of questing ticks and in the abundance of rodent hosts were observed. Both sites exhibited low densities of rodents and of ticks infesting them. A blood meal analysis revealed high proportions of mixed feedings and showed artiodactyls to be a main host group for immature I. ricinus ticks from Britain. The prevalence rates of Wolbachia endobacteria in British I. ricinus samples were higher than rates found in samples from other European countries. The unique endosymbiont Midichloria was detected in all female I. ricinus ticks that were screened. A newly developed multi gene analysis of Midichloria samples from six European countries showed a largely coordinated phylogeography with their tick hosts. Taken together, the findings of this thesis demonstrate that British I. ricinus ticks differ from their European counterparts in several ways, which has implications for the epidemiology of infectious diseases transmitted by this vector.
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Silva, Mónica Almeida e. "Population biology of bottlenose dolphins in the Azores archipelago." St Andrews : University of St Andrews thesis, 2007. https://research-repository.st-andrews.ac.uk/handle/10023/215.

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Kennaway, Gabrielle M. A. "The population biology of freshwater phytoplankton." Thesis, Bangor University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236909.

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Vàrkonyi, Gergely. "Population biology of periodic Xestia moths." Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/mat/ekolo/vk/varkonyi/.

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Bottomley, Herbert Christian. "The population biology of multispecies helminth infection." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1445327/.

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Vertebrate hosts are frequently infected with multiple helminth species. There is a body of experimental evidence to suggest that infection with one parasite species can have either an antagonistic or synergistic effect on another species such interactions may occur through parasite establishment, survival and fecundity. The extent to which such interactions are involved in the organization of helminth communities is largely unknown. Mathematical models based on Markov processes are used to explore two themes: 1) The effect of interspecific interactions on the joint distribution of helminth par asites in a population of hosts, and 2) conditions under which interacting species can coexist. To explore the former, models are formulated that describe the pro cess by which helminths of two species are acquired and lost in a cohort of ageing hosts. In these models, the interspecific interaction occurs at the point of parasite establishment within the host such that the rate of establishment depends on the current worm burdens of the two species. The results are used to highlight some of the difficulties associated with inferring interspecific interactions from ecological data. The relationship between competition and species coexistence is investigated us ing models of the long-term dynamics of interacting species. Models are developed in which there is a free-living larval stage whose population size is dependent on the size of the adult worm population. The models are analyzed using 'hybrid' and 'moment-closure' approximations the former involves replacing stochastic com ponents of the model with deterministic approximations, and the latter assumes a functional relationship between higher and lower order moments based on a specified distribution. The Lotka-Volterra model of competition is derived for the case where hosts are equally exposed to parasites of the same species. Coexistence of two compet ing species is promoted by heterogeneous host exposure to each parasite species, provided that the rates of exposure to the two parasite species are not perfectly, positively correlated, and provided that the degree of heterogeneity in host expo sure is similar for both species. In addition, it is shown that the conditions required for coexistence are the same regardless of whether competition occurs at the point of parasite establishment within the host or via parasite fecundity. These results are discussed within the context of helminth community ecology.
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Li, Yifei. "Nonlinear diffusion in mathematical biology." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/234381/1/Yifei_Li_Thesis.pdf.

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Reaction-diffusion models with nonlinear diffusion are widely used for studying population dynamics in biology and ecology. Yet, the relationship between nonlinear diffusion mechanisms in populations and the behaviours of individuals is hard to be intuitively interpreted in classical models. To address this problem, we develop a discrete-continuum modelling framework, where the movement of individuals influenced by crowding effects is connected to the nonlinear diffusivity functions in a well-defined continuum limit. Using this framework, we explore the influence of nonlinear diffusion on population extinction, and analyse the existence and stability of travelling waves in continuous equations which model the invasion process.
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Banks, John E. "The effects of landscape heterogeneity on insect populations : a study of pattern and scale /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/5166.

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Books on the topic "Population biology"

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Wöhrmann, K., and S. K. Jain, eds. Population Biology. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-74474-7.

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Hastings, Alan. Population Biology. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4757-2731-9.

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Jain, S. K., and L. W. Botsford, eds. Applied Population Biology. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-0-585-32911-6.

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E, Hochberg Michael, and Ives Anthony R. 1961-, eds. Parasitoid population biology. Princeton, N.J: Princeton University Press, 2000.

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1934-, Jain Subodh K., Botsford Louis W, and Alfred P. Sloan Foundation, eds. Applied population biology. Dordrecht [Netherlands]: Kluwer Academic Publishers, 1992.

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1957-, Cheplick G. P., ed. Population biology of grasses. New York: Cambridge University Press, 1998.

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Zhao, Xiao-Qiang. Dynamical Systems in Population Biology. New York, NY: Springer New York, 2003. http://dx.doi.org/10.1007/978-0-387-21761-1.

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Zhao, Xiao-Qiang. Dynamical Systems in Population Biology. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56433-3.

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Blondel, Jacques, Andrew Gosler, Jean-Dominique Lebreton, and Robin McCleery, eds. Population Biology of Passerine Birds. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-75110-3.

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Hastings, A. Population biology: Concepts and models. New York: Springer, 1997.

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Book chapters on the topic "Population biology"

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Zotz, Gerhard. "Population Biology." In Plants on Plants – The Biology of Vascular Epiphytes, 149–66. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-39237-0_6.

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Petracco, Marcelo, Guilherme Nascimento Corte, Daiane Aviz, Rayane Romão Saad Abude, Matheus Augusto, Carlos Henrique Soares Caetano, Ricardo Silva Cardoso, and Tatiana Medeiros Barbosa Cabrini. "Population Biology." In Brazilian Sandy Beaches, 159–98. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-30746-1_6.

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Sutton, Julian. "Population Ecology." In Biology, 433–47. London: Macmillan Education UK, 1998. http://dx.doi.org/10.1007/978-1-349-15201-8_26.

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Hastings, Alan. "Population Genetics." In Population Biology, 41–80. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4757-2731-9_3.

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Hastings, Alan. "Introduction." In Population Biology, 1–5. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4757-2731-9_1.

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Hastings, Alan. "Diseases and Pathogens." In Population Biology, 189–200. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4757-2731-9_10.

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Hastings, Alan. "Coda." In Population Biology, 201–3. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4757-2731-9_11.

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Hastings, Alan. "Density-Independent Population Growth." In Population Biology, 9–40. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4757-2731-9_2.

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Hastings, Alan. "Density-Dependent Population Growth." In Population Biology, 81–106. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4757-2731-9_4.

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Hastings, Alan. "Evolution of Life Histories." In Population Biology, 107–16. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4757-2731-9_5.

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Conference papers on the topic "Population biology"

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Zhao, Changjian. "On a model in population of biology." In 2010 3rd International Conference on Biomedical Engineering and Informatics (BMEI). IEEE, 2010. http://dx.doi.org/10.1109/bmei.2010.5639725.

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Thukral, A. K., B. P. Singh, Kamel Ariffin Mohd Atan, and Isthrinayagy S. Krishnarajah. "Population Growth and National Population Policy of India." In INTERNATIONAL CONFERENCE ON MATHEMATICAL BIOLOGY 2007: ICMB07. AIP, 2008. http://dx.doi.org/10.1063/1.2883834.

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Stollenwerk, Nico, Pablo Fuentes Sommer, Luis Mateus, Bob Kooi, and Maíra Aguiar. "Stochastic Hopf and torus bifurcations in population biology." In INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2015 (ICNAAM 2015). Author(s), 2016. http://dx.doi.org/10.1063/1.4952186.

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Singh, A., and J. P. Hespanha. "Moment closure techniques for stochastic models in population biology." In 2006 American Control Conference. IEEE, 2006. http://dx.doi.org/10.1109/acc.2006.1657468.

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BEREC, L. "POPULATION DYNAMICS ON COMPLEX FOOD WEBS." In International Symposium on Mathematical and Computational Biology. WORLD SCIENTIFIC, 2010. http://dx.doi.org/10.1142/9789814304900_0012.

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Belotelov, N. V., I. A. Konovalenko, and V. M. Nazarova. "Group dynamics in the agent model of the population." In Mathematical Biology and Bioinformatics. Pushchino: IMPB RAS - Branch of KIAM RAS, 2018. http://dx.doi.org/10.17537/icmbb18.109.

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Frisman, E. Ya, K. V. Shlufman, and G. P. Neverova. "Dynamics of satellite population related species with cyclic dynamics." In Mathematical Biology and Bioinformatics. Pushchino: IMPB RAS - Branch of KIAM RAS, 2018. http://dx.doi.org/10.17537/icmbb18.68.

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Yamaguchi, H., Y. Ueda, Y. Kanno, and T. Matsuishi. "Population assessment using a length-based population analysis for the Japanese hair crab (Erimacrus isenbeckii)." In Crabs in Cold Water Regions: Biology, Management, and Economics. Alaska Sea Grant, University of Alaska Fairbanks, 2002. http://dx.doi.org/10.4027/ccwrbme.2002.36.

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HERNÁNDEZ, ISAIAS CHAIREZ, J. NATIVIDAD GURROLA REYES, CIPRIANO GARCIA GUTIERREZ, and FRANCISCO ECHAVARRIA CHAIREZ. "GRASSHOPPER DENSITY POPULATION CLASSIFICATION WITH NEURAL NETWORKS." In International Symposium on Mathematical and Computational Biology. WORLD SCIENTIFIC, 2008. http://dx.doi.org/10.1142/9789812812339_0016.

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FONTANARI, J. F. "A POPULATION DYNAMICS APPROACH TO LANGUAGE EVOLUTION." In International Symposium on Mathematical and Computational Biology. WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789814271820_0010.

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Reports on the topic "Population biology"

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Sandercock, Brett K. Environmental Impacts of Wind Power Development on the Population Biology of Greater Prairie-Chickens. Office of Scientific and Technical Information (OSTI), May 2013. http://dx.doi.org/10.2172/1220108.

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Sandercock, Brett K. Environmental Impacts of Wind Power Development on the Population Biology of Greater Prairie-Chickens. Office of Scientific and Technical Information (OSTI), May 2013. http://dx.doi.org/10.2172/1080446.

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Grumet, R., J. Burger, Y. Tadmor, A. Gur, C. Barry, A. Schäffer, and M. Petreikov. Cucumis fruit surface biology: Genetic analysis of fruit exocarp features in melon (C. melo) and cucumber (C. sativus). Israel: United States-Israel Binational Agricultural Research and Development Fund, 2020. http://dx.doi.org/10.32747/2020.8134155.bard.

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The fruit surface (exocarp) is a unique tissue with multiple roles influencing fruit growth and development, disease susceptibility, crop yield, post-harvest treatments, shipping and storage quality, and food safety. Furthermore, highly visible exocarp traits are the consumer's first exposure to the fruit, serving to identify fruit type, variety, attractiveness, and market value. Cucurbit fruit, including the closely related Cucumis species, melon (C. melo) and cucumber (C. sativus), exhibit tremendous diversity for fruit surface properties that are not present in model species. In this project, we identified genetic factors influencing Cucumis fruit surface morphology with respect to important quality determinants such as exocarp and flesh color, cuticle deposition, and surface netting. We employed a combination of approaches including: genome-wide association studies (GWAS) utilizing an extensive melon population and the U.S. Plant Introduction (PI) collection for cucumber to identify genomic regions associated with natural variation in fruit surface traits; bulked segregant RNA-seq (BSR-seq) analysis of bi-parental F2:3 or RIL (recombinant inbred line) populations to genomic regions and candidate genes segregating for fruit surface traits; and comparison of syntenic genomic regions and identification of homologous candidate genes. Candidate genes were examined for sequence and/or expression differences during fruit development that correspond with phenotypic differences. Primary outcomes of the work included identification of candidate genes influencing cuticle deposition, epidermal cell structure, surface netting, and intensity of rind and flesh color. Parallel studies identified mutations within the cucumber and melon homologs of the transcription factor WIN1 (WAX INDUCER1) as a significant factor influencing these surface properties. Additional QTL (quantitative trait loci) were identified in both species, and candidate genes in melon include a novel beta-glucosidase involved in lignin production and an integral membrane protein potentially involved in cuticle metabolism. Genetic resources and biochemical approaches have been developed to study cuticle and wax deposition in both species: segregating populations of melon were developed and sequenced for bulked segregant analysis and samples collected for metabolic analysis; an isolation procedure was developed for lipid droplets from cucumber peel and metabolomic analyses have been initiated. Genetic studies in melon identified mutations in a candidate gene (APRR2), associated with light immature rind, and further indicated that this gene is also associated with color intensity of both mature rinds and flesh, making it a good target for breeding. GWAS studies utilizing the cucumber core diversity population are being performed to identify additional sources of variation for fruit surface properties, map QTL, and examine for synteny with melon. Collectively these studies identified genetic regions associated with important quality traits and contributed to our understanding of underlying biological processes associated with fruit surface development. Knowledge of genetic control of these characteristics can facilitate more efficient breeding for important fruit surface traits.
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Gottlieb, Yuval, Bradley Mullens, and Richard Stouthamer. investigation of the role of bacterial symbionts in regulating the biology and vector competence of Culicoides vectors of animal viruses. United States Department of Agriculture, June 2015. http://dx.doi.org/10.32747/2015.7699865.bard.

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Symbiotic bacteria have been shown to influence host reproduction and defense against biotic and abiotic stressors, and this relates to possible development of a symbiont-based control strategy. This project was based on the hypothesis that symbionts have a significant impact on Culicoides fitness and vector competence for animal viruses. The original objectives in our proposal were: 1. Molecular identification and localization of the newly-discovered symbiotic bacteria within C. imicola and C. schultzei in Israel and C. sonorensis in California. 2. Determination of the prevalence of symbiotic bacteria within different vector Culicoides populations. 3. Documentation of specific symbiont effects on vector reproduction and defense: 3a) test for cytoplasmic incompatibility in Cardinium-infected species; 3b) experimentally evaluate the role of the symbiont on infection or parasitism by key Culicoides natural enemies (iridescent virus and mermithid nematode). 4. Testing the role(s) of the symbionts in possible protection against infection of vector Culicoides by BTV. According to preliminary findings and difficulties in performing experimental procedures performed in other insect symbiosis systems where insect host cultures are easily maintained, we modified the last two objectives as follows: Obj. 3, we tested how symbionts affected general fitness of Israeli Culicoides species, and thoroughly described and evaluated the correlation between American Culicoides and their bacterial communities in the field. We also tried alternative methods to test symbiont-Culicoides interactions and launched studies to characterize low-temperature stress tolerances of the main US vector, which may be related to symbionts. Obj. 4, we tested the correlation between EHDV (instead of BTV) aquisition and Cardinium infection. Culicoides-bornearboviral diseases are emerging or re-emerging worldwide, causing direct and indirect economic losses as well as reduction in animal welfare. One novel strategy to reduce insects’ vectorial capacity is by manipulating specific symbionts to affect vector fitness or performance of the disease agent within. Little was known on the bacterial tenants occupying various Culicoides species, and thus, this project was initiated with the above aims. During this project, we were able to describe the symbiont Cardinium and whole bacterial communities in Israeli and American Culicoides species respectively. We showed that Cardinium infection prevalence is determined by land surface temperature, and this may be important to the larval stage. We also showed no patent significant effect of Cardinium on adult fitness parameters. We showed that the bacterial community in C. sonorensis varies significantly with the host’s developmental stage, but it varies little across multiple wastewater pond environments. This may indicate some specific biological interactions and allowed us to describe a “core microbiome” for C. sonorensis. The final set of analyses that include habitat sample is currently done, in order to separate the more intimately-associated bacteria from those inhabiting the gut contents or cuticle surface (which also could be important). We were also able to carefully study other biological aspects of Culicoides and were able to discriminate two species in C. schultzei group in Israel, and to investigate low temperature tolerances of C. sonorensis that may be related to symbionts. Scientific implications include the establishment of bacterial identification and interactions in Culicoides (our work is cited in other bacteria-Culicoides studies), the development molecular identification of C. schultzei group, and the detailed description of the microbiome of the immature and matched adult stages of C. sonorensis. Agricultural implications include understanding of intrinsic factors that govern Culicoides biology and population regulation, which may be relevant for vector control or reduction in pathogen transmission. Being able to precisely identify Culicoides species is central to understanding Culicoides borne disease epidemiology.
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Kang, Jing, Jun Zhang, Zongsheng Tian, Ye Xu, Jiangbi Li, and Mingxina Li. The efficacy and safety of immune-checkpoint inhibitor plus chemotherapy versus chemotherapy for non-small cell lung cancer: an updated systematic review and meta-analysis. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, May 2022. http://dx.doi.org/10.37766/inplasy2022.5.0156.

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Review question / Objective: Population: histologically confirmed advanced NSCLC patients; Intervention: received immune-checkpoint inhibitor plus chemotherapy; Comparison:received chemotherapy; Outcome: reported OS, PFS, ORR and TRAEs; Study design: RCT. Condition being studied: Lung cancer is the primary cause of cancer-related deaths, with an estimated 2.20 million new cases and 1.79 million deaths every year, and 85% of all primary lung cancers are non-small cell lung cancer. Eligibility criteria: Studies were considered eligible if they met the following criteria: (1) being an randomized controlled trial published in English, (2) histologically confirmed advanced NSCLC patients, (3) reported OS, PFS, ORR and TRAEs, (4) the intervention group received immune-checkpoint inhibitor plus chemotherapy, while the control group received chemotherapy, (5) When numerous papers reporting the same trial were found, the most current or most complete publications were chosen. The following were the exclusion criteria: (1) duplicate articles, (2) reviews, meta-analyses, case reports, editorials and letters, (3) molecular biology or animal research, (4) retrospective or prospective observational cohort studies.
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Lers, Amnon, Majid R. Foolad, and Haya Friedman. genetic basis for postharvest chilling tolerance in tomato fruit. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7600014.bard.

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ABSTRACT Postharvest losses of fresh produce are estimated globally to be around 30%. Reducing these losses is considered a major solution to ensure global food security. Storage at low temperatures is an efficient practice to prolong postharvest performance of crops with minimal negative impact on produce quality or human health and the environment. However, many fresh produce commodities are susceptible to chilling temperatures, and the application of cold storage is limited as it would cause physiological chilling injury (CI) leading to reduced produce quality. Further, the primary CI becomes a preferred site for pathogens leading to decay and massive produce losses. Thus, chilling sensitive crops should be stored at higher minimal temperatures, which curtails their marketing life and in some cases necessitates the use of other storage strategies. Development of new knowledge about the biological basis for chilling tolerance in fruits and vegetables should allow development of both new varieties more tolerant to cold, and more efficient postharvest storage treatments and storage conditions. In order to improve the agricultural performance of modern crop varieties, including tomato, there is great potential in introgression of marker-defined genomic regions from wild species onto the background of elite breeding lines. To exploit this potential for improving tomato fruit chilling tolerance during postharvest storage, we have used in this research a recombinant inbred line (RIL) population derived from a cross between the red-fruited tomato wild species SolanumpimpinellifoliumL. accession LA2093 and an advanced Solanum lycopersicumL. tomato breeding line NCEBR-1, developed in the laboratory of the US co-PI. The original specific objectives were: 1) Screening of RIL population resulting from the cross NCEBR1 X LA2093 for fruit chilling response during postharvest storage and estimation of its heritability; 2) Perform a transcriptopmic and bioinformatics analysis for the two parental lines following exposure to chilling storage. During the course of the project, we learned that we could measure greater differences in chilling responses among specific RILs compared to that observed between the two parental lines, and thus we decided not to perform transcriptomic analysis and instead invest our efforts more on characterization of the RILs. Performing the transcriptomic analysis for several RILs, which significantly differ in their chilling tolerance/sensitivity, at a later stage could result with more significant insights. The RIL population, (172 lines), was used in field experiment in which fruits were examined for chilling sensitivity by determining CI severity. Following the field experiments, including 4 harvest days and CI measurements, two extreme tails of the response distribution, each consisting of 11 RILs exhibiting either high sensitivity or tolerance to chilling stress, were identified and were further examined for chilling response in greenhouse experiments. Across the RILs, we found significant (P < 0.01) correlation between field and greenhouse grown plants in fruit CI. Two groups of 5 RILs, whose fruits exhibited reproducible chilling tolerant/sensitive phenotypes in both field and greenhouse experiments, were selected for further analyses. Numerous genetic, physiological, biochemical and molecular variations were investigated in response to postharvest chilling stress in the selected RILs. We confirmed the differential response of the parental lines of the RIL population to chilling stress, and examined the extent of variation in the RIL population in response to chilling treatment. We determined parameters which would be useful for further characterization of chilling response in the RIL population. These included chlorophyll fluorescence Fv/Fm, water loss, total non-enzymatic potential of antioxidant activity, ascorbate and proline content, and expression of LeCBF1 gene, known to be associated with cold acclimation. These parameters could be used in continuation studies for the identification and genetic mapping of loci contributing to chilling tolerance in this population, and identifying genetic markers associated with chilling tolerance in tomato. Once genetic markers associated with chilling tolerance are identified, the trait could be transferred to different genetic background via marker-assisted selection (MAS) and breeding. The collaborative research established in this program has resulted in new information and insights in this area of research and the collaboration will be continued to obtain further insights into the genetic, molecular biology and physiology of postharvest chilling tolerance in tomato fruit. The US Co-PI, developed the RIL population that was used for screening and measurement of the relevant chilling stress responses and conducted statistical analyses of the data. Because we were not able to grow the RIL population under field conditions in two successive generations, we could not estimate heritability of response to chilling temperatures. However, we plan to continue the research, grow the RIL progeny in the field again, and determine heritability of chilling tolerance in a near future. The IS and US investigators interacted regularly and plan to continue and expand on this study, since combing the expertise of the Co-PI in genetics and breeding with that of the PI in postharvest physiology and molecular biology will have great impact on this line of research, given the significant findings of this one-year feasibility project.
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7

Zchori-Fein, Einat, Judith K. Brown, and Nurit Katzir. Biocomplexity and Selective modulation of whitefly symbiotic composition. United States Department of Agriculture, June 2006. http://dx.doi.org/10.32747/2006.7591733.bard.

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Whiteflies are sap-sucking insects that harbor obligatory symbiotic bacteria to fulfill their dietary needs, as well as a facultative microbial community with diverse bacterial species. The sweetpotato whitefly Bemisia tabaci (Gennadius) is a severe agricultural pest in many parts of the world. This speciesconsists of several biotypes that have been distinguished largely on the basis of biochemical or molecular diagnostics, but whose biological significance is still unclear. The original objectives of the project were (i) to identify the specific complement of prokaryotic endosymbionts associated with select, well-studied, biologically and phylogeographically representative biotypes of B. tabaci, and (ii) to attempt to 'cure’ select biotypes of certain symbionts to permit assessment of the affect of curing on whitefly fitness, gene flow, host plant preference, and virus transmission competency.To identify the diversity of bacterial community associated with a suite of phylogeographically-diverseB. tabaci, a total of 107 populations were screened using general Bacteria primers for the 16S rRNA encoding gene in a PCR. Sequence comparisons with the available databases revealed the presence of bacteria classified in the: Proteobacteria (66%), Firmicutes (25.70%), Actinobacteria (3.7%), Chlamydiae (2.75%) and Bacteroidetes (<1%). Among previously identified bacteria, such as the primary symbiont Portiera aleyrodidarum, and the secondary symbionts Hamiltonella, Cardinium and Wolbachia, a Rickettsia sp. was detected for the first time in this insect family. The distribution, transmission, and localization of the Rickettsia were studied using PCR and fluorescence in situ hybridization (FISH). Rickettsia was found in all 20 Israeli B. tabaci populations screened as well as some populations screened in the Arizona laboratory, but not in all individuals within each population. FISH analysis of B. tabaci eggs, nymphs and adults, revealed a unique concentration of Rickettsia around the gut and follicle cells as well as its random distribution in the haemolymph, but absence from the primary symbiont housing cells, the bacteriocytes. Rickettsia vertical transmission on the one hand and its partial within-population infection on the other suggest a phenotype that is advantageous under certain conditions but may be deleterious enough to prevent fixation under others.To test for the possible involvement of Wolbachia and Cardiniumin the reproductive isolation of different B. tabacibiotypes, reciprocal crosses were preformed among populations of the Cardinium-infected, Wolbachia-infected and uninfected populations. The crosses results demonstrated that phylogeographically divergent B. tabaci are reproductively competent and that cytoplasmic incompatibility inducer-bacteria (Wolbachia and Cardinium) both interfered with, and/or rescued CI induced by one another, effectively facilitating bidirectional female offspring production in the latter scenario.This knowledge has implications to multitrophic interactions, gene flow, speciation, fitness, natural enemy interactions, and possibly, host preference and virus transmission. Although extensive and creative attempts undertaken in both laboratories to cure whiteflies of non-primary symbionts have failed, our finding of naturally uninfected individuals have permitted the establishment of Rickettsia-, Wolbachia- and Cardinium-freeB. tabaci lines, which are been employed to address various biological questions, including determining the role of these bacteria in whitefly host biology.
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8

Wisniewski, Michael E., Samir Droby, John L. Norelli, Noa Sela, and Elena Levin. Genetic and transcriptomic analysis of postharvest decay resistance in Malus sieversii and the characterization of pathogenicity effectors in Penicillium expansum. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7600013.bard.

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Blue mold of apple caused by Penicilliumexpansumis a major postharvest disease. Selection for postharvest disease resistance in breeding programs has been ignored in favor of fruit quality traits such as size, color, taste, etc. The identification of postharvest disease resistance as a heritable trait would represent a significant accomplishment and has not been attempted in apple. Furthermore, insight into the biology of the pathogenicity of P. expansumin apple could provide new approaches to postharvest decay management. Hypothesis: Postharvest resistance of apple to P. expansumcan be mapped to specific genetic loci and significant quantitative-trait-loci (QTLs) can be identified that account for a major portion of the population variance. Susceptibility of apple fruit to P. expansumis dependent on the ability of the pathogen to produce LysM effectors that actively suppress primary and/or secondary resistance mechanisms in the fruit. Objectives: 1) Identify QTL(s) and molecular markers for blue mold resistance in GMAL4593 mapping population (‘Royal Gala’ X MalussieversiiPI613981), 2) Characterize the transcriptome of the host and pathogen (P. expansum) during the infection process 3) Determine the function of LysM genes in pathogenicity of P. expansum. Methods: A phenotypic evaluation of blue mold resistance in the GMAL4593 mapping population, conducted in several different years, will be used for QTL analysis (using MapQTL 6.0) to identify loci associated with blue mold resistance. Molecular markers will be developed for the resistance loci. Transcriptomic analysis by RNA-seq will be used to conduct a time course study of gene expression in resistant and susceptible apple GMAL4593 genotypes in response to P. expansum, as well as fungal responses to both genotypes. Candidate resistance genes identified in the transcriptomic study and or bioinformatic analysis will be positioned in the ‘Golden Delicious’ genome to identify markers that co-locate with the identified QTL(s). A functional analysis of LysM genes on pathogenicity will be conducted by eliminating or reducing the expression of individual effectors by heterologous recombination and silencing technologies. LysMeffector genes will also be expressed in a yeast expression system to study protein function. Expected Results: Identification of postharvest disease resistance QTLs and tightly-linked genetic markers. Increased knowledge of the role of effectors in blue mold pathogenic
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9

Fridman, Eyal, Jianming Yu, and Rivka Elbaum. Combining diversity within Sorghum bicolor for genomic and fine mapping of intra-allelic interactions underlying heterosis. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7597925.bard.

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Heterosis, the enigmatic phenomenon in which whole genome heterozygous hybrids demonstrate superior fitness compared to their homozygous parents, is the main cornerstone of modern crop plant breeding. One explanation for this non-additive inheritance of hybrids is interaction of alleles within the same locus. This proposal aims at screening, identifying and investigating heterosis trait loci (HTL) for different yield traits by implementing a novel integrated mapping approach in Sorghum bicolor as a model for other crop plants. Originally, the general goal of this research was to perform a genetic dissection of heterosis in a diallel built from a set of Sorghum bicolor inbred lines. This was conducted by implementing a novel computational algorithm which aims at associating between specific heterozygosity found among hybrids with heterotic variation for different agronomic traits. The initial goals of the research are: (i) Perform genotype by sequencing (GBS) of the founder lines (ii) To evaluate the heterotic variation found in the diallel by performing field trails and measurements in the field (iii) To perform QTL analysis for identifying heterotic trait loci (HTL) (iv) to validate candidate HTL by testing the quantitative mode of inheritance in F2 populations, and (v) To identify candidate HTL in NAM founder lines and fine map these loci by test-cross selected RIL derived from these founders. The genetic mapping was initially achieved with app. 100 SSR markers, and later the founder lines were genotyped by sequencing. In addition to the original proposed research we have added two additional populations that were utilized to further develop the HTL mapping approach; (1) A diallel of budding yeast (Saccharomyces cerevisiae) that was tested for heterosis of doubling time, and (2) a recombinant inbred line population of Sorghum bicolor that allowed testing in the field and in more depth the contribution of heterosis to plant height, as well as to achieve novel simulation for predicting dominant and additive effects in tightly linked loci on pseudooverdominance. There are several conclusions relevant to crop plants in general and to sorghum breeding and biology in particular: (i) heterosis for reproductive (1), vegetative (2) and metabolic phenotypes is predominantly achieved via dominance complementation. (ii) most loci that seems to be inherited as overdominant are in fact achieving superior phenotype of the heterozygous due to linkage in repulsion, namely by pseudooverdominant mechanism. Our computer simulations show that such repulsion linkage could influence QTL detection and estimation of effect in segregating populations. (iii) A new height QTL (qHT7.1) was identified near the genomic region harboring the known auxin transporter Dw3 in sorghum, and its genetic dissection in RIL population demonstrated that it affects both the upper and lower parts of the plant, whereas Dw3 affects only the part below the flag leaf. (iv) HTL mapping for grain nitrogen content in sorghum grains has identified several candidate genes that regulate this trait, including several putative nitrate transporters and a transcription factor belonging to the no-apical meristem (NAC)-like large gene family. This activity was combined with another BARD-funded project in which several de-novo mutants in this gene were identified for functional analysis.
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10

Dawson, William O., Moshe Bar-Joseph, Charles L. Niblett, Ron Gafny, Richard F. Lee, and Munir Mawassi. Citrus Tristeza Virus: Molecular Approaches to Cross Protection. United States Department of Agriculture, January 1994. http://dx.doi.org/10.32747/1994.7570551.bard.

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Citrus tristeza virus (CTV) has the largest genomes among RNA viruses of plants. The 19,296-nt CTV genome codes for eleven open reading frames (ORFs) and can produce at least 19 protein products ranging in size from 6 to 401 kDa. The complex biology of CTV results in an unusual composition of CTV-specific RNAs in infected plants which includes multiple defective RNAs and mixed infections. The complex structure of CTV populations poses special problems for diagnosis, strain differentiation, and studies of pathogenesis. A manipulatable genetic system with the full-length cDNA copy of the CTV genome has been created which allows direct studies of various aspects of the CTV biology and pathology. This genetic system is being used to identify determinants of the decline and stem-pitting disease syndromes, as well as determinants responsible for aphid transmission.
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