The circulation of seed among farmers is central to agrobiodiversity conservation and dynamics. Agrobiodiversity, the diversity of agricultural systems from genes to varieties and crop species, from farming methods to landscape composition, is part of humanity's cultural heritage. Whereas agrobiodiversity conservation has received much attention from researchers and policy makers over the last decades, the methods available to study the role of seed exchange networks in preserving crop biodiversity have only recently begun to be considered. In this overview, we present key concepts, methods, and challenges to better understand seed exchange networks so as to improve the chances that traditional crop varieties (landraces) will be preserved and used sustainably around the world. The available literature suggests that there is insufficient knowledge about the social, cultural, and methodological dimensions of environmental change, including how seed exchange networks will cope with changes in climates, socio-economic factors, and family structures that have supported seed exchange systems to date. Methods available to study the role of seed exchange networks in the preservation and adaptation of crop specific and genetic diversity range from meta-analysis to modelling, from participatory approaches to the development of bio-indicators, from genetic to biogeographical studies, from anthropological and ethnographic research to the use of network theory. We advocate a diversity of approaches, so as to foster the creation of robust and policy-relevant knowledge. Open challenges in the study of the role of seed exchange networks in biodiversity conservation include the development of methods to (i) enhance farmers' participation to decision-making in agro-ecosystems, (ii) integrate ex situ and in situ approaches, (iii) achieve interdisciplinary research collaboration between social and natural scientists, and (iv) use network analysis as a conceptual framework to bridge boundaries among researchers, farmers and policy makers, as well as other stakeholders. (Résumé d'auteur

The importance of seed provisioning in food security and nutrition, agricultural development and rural livelihoods, and agrobiodiversity and germplasm conservation is well accepted by policy makers, practitioners and researchers. The role of farmer seed networks is less well understood and yet is central to debates on current issues ranging from seed sovereignty and rights for farmers to GMOs and the conservation of crop germplasm. In this paper we identify four common misconceptions regarding the nature and importance of farmer seed networks today. (1) Farmer seed networks are inefficient for seed dissemination. (2) Farmer seed networks are closed, conservative systems. (3) Farmer seed networks provide ready, egalitarian access to seed. (4) Farmer seed networks are destined to weaken and disappear. We challenge these misconceptions by drawing upon recent research findings and the authors' collective field experience in studying farmer seed systems in Africa, Europe, Latin America and Oceania. Priorities for future research are suggested that would advance our understanding of seed networks and better inform agricultural and food policy

Molecular recognition of duplex DNA by proteins plays a central role in biology. Although there are no clear and simple rules or codes to describe sequence-specific recognition, hydrogen bonds with the nucleic bases as well as with the phosphodiester backbone are of critical importance.[1] Efforts to mimic such recognition with smaller synthetic biopolymers have been described. [2] However, in all these cases, specific contacts with the DNA duplex are only provided by hydrogen bonds with the bases, and potential interactions with the DNA backbone are left unexploited. Here we report that 2'-aminoethoxy-modified oligonucleotides can interact simultaneously with the bases and the phosphodiester backbone at each base-pair step of the DNA target, which provides for a dramatic increase in the binding affinity as well as in the association rate constant.The sequence-specific recognition of duplex DNA by pyrimidine oligonucleotides involves the formation of triplehelical structures, which are stabilized by Hoogsteen hydrogen bonds between the bases on the DNA target and the pyrimidine third strand.[3] Examination of a molecular model of a triple helix with a RNA third strand indicates that the 2'-hydroxyl groups of the RNA and the phosphate groups of the DNA second strand are in close proximity.[4] Thus, it appeared conceivable that the attachment of a short amino alkyl group at the 2' position of the ribose of the third strand would allow the protonated amino group to form a specific intermolecular contact with a proximal phosphate group of the DNA duplex. Such charge ± charge interactions should strongly enhance the affinity of the modified oligonucleotide for double-strand DNA.To test this hypothesis, we first examined the properties of a 2'-aminoethoxy-modified oligonucleotide with regard to triplex formation. The synthesis of the 2'-aminoethyl-modified monomeric tymidine and C5-methylcytidine building blocks is summarized in Scheme 1. Alkylation of protected ribothymidine 1[5] with methyl bromoacetate followed by reduction of the ester group and tosylation gave the tosylate 2. Hydrogenolytic removal of the BOM group and subsequent replacement of the tosyloxy group by an azide substituent yielded the azidoethyl derivative 3, which was further transformed into the desired protected 2'-aminoethoxy-thymidine Scheme 1. Synthesis of protected 2'-aminoethoxy phosphoramidites thymidine (5) and C5-methylcytidine (8): a) BrCH 2 CO 2 Me (5 equiv), NaH (2.2 equiv), DMF, 1.5 h, À 5 8C, 98 %; b) LiBH 4 (4 equiv), MeOH/THF (2/ 8), 1.5 h, 5 8C, 84 %; c) TsCl (1.5 equiv), NEt 3 (1.6 equiv), DMAP (10 wt %), CH 2 Cl 2 , 8 h, 22 8C, 89 %; d) H 2 , Pd/C (20 wt %), HCl (0.02 equiv), THF/ MeOH (1/1), 7 h, 22 8C, 88 %; e) NaN 3 (3 equiv), DMF, 3 h, 65 8C, 92 %; f) SnCl 2 (3.5 equiv), MeOH, 1 d, 22 8C, 70 %; g) (CF 3 CO) 2 O (1.2 equiv), pyridine, 2 h, 22 8C, 57 %; h) TBAF (2.1 equiv), THF, 15 min, 22 8C, 100 %; i) DMTrCl (1.2 equiv), pyridine, 16 h, 22 8C, 85 %; j) (iPr 2 N) 2 -POCH 2 CH 2 CN (2.2 equiv), diisopropylammonium tetrazolide (...

How do people make decisions when they have to choose between unknown futures? Do they simply rely on anticipated costs and benefits or do they use some other criteria to assess their options? And what determines the criteria they use to make such decisions? This article explores the way voters take sides when they are faced with a fundamental political choice. Using data from a survey of voting intentions conducted prior to the 1995 referendum on sovereignty in Quebec, we find that attitude towards risk-taking influences political choice indirectly, as it affects the relative weights given to different decision criteria. Individuals who usually accept risk more readily tend to choose entirely on the basis of anticipated costs and benefits, but individuals who are more reluctant to take risks give almost as much weight to the perceived possibility of a ‘worst outcome’. Our analysis suggests that attitude towards risk-taking had a modest but significant impact on individual choice, and thus was a contributing factor in the outcome of the Quebec referendum.