In this article, we expand the analytical and theoretical foundations of the study of knowledge commons in the context of more classical agrarian commons, such as seed commons. We show that it is ...possible to overcome a number of criticisms of earlier work by Ostrom (Governing the commons. The evolution of institutions for collective action, Cambridge University Press, Cambridge, 1990) on natural commons and its excludability/rivalry matrix in addressing the inclusive social practices of “commoning”, defined as a way of living and acting for the preservation of the commons. Our empirical analysis emphasizes, using the most recent advances in the IAD/SES framework, the distributed and collaborative knowledge governance in a French peasant seed network as a key driver for reintroducing cultivated agrobiodiversity and on-farm seed conservation of ancient and landrace varieties. These inclusive peasant seed groups developed alternative peer-to-peer models of collaborative peasant-led community-based breeding and grassroots innovations in the search for more resilient population varieties. Our results highlight the various models of collective action within the network and discuss the organizational tradeoffs of opting out of peasant seed activities and recreating a shared collective knowledge base on the benefits of restoring cultivated agrobiodiversity. It helps us better understand how modern peasant seed groups function as epistemic communities which contributes to envisioning alternative agricultural systems.
•We used a new integrative indicator to assess wheat genetic diversity in fields.•We studied the trend of wheat diversity in French landscapes in the 20th century.•Unlike the number of variety the ...index revealed increasing genetic homogenization.•The reasons are: landrace extinction, spatial homogenization, genetic similarity.•Genetic homogeneity might increase vulnerability and lower resilience of farming.
Changing and more volatile climate conditions are leading to higher vulnerability and lower resilience for crop production. Recent studies indicate that crop diversity in agricultural fields may ensure pest control and yield stability in the face of environmental changes. However, few studies have evaluated crop diversity in the field, especially at the within-species level. Applying a new indicator, HT*, which integrates both the spatial evenness of different varieties and molecular genetic data (within and between variety genetic diversity), we followed the evolution of bread wheat genetic diversity on French agricultural landscapes during the 20th century. To our knowledge, the monitoring of crop genetic diversity at such a large but detailed spatial and temporal scale has never before been conducted. In comparison to two frequently used but less integrative indicators (the number of varieties grown in the field and their allelic diversity as measured by the Nei index), the HT* indicator revealed increasing genetic homogenization overall. This trend was due to the disappearance of diversity within varieties (initial replacement of landraces by more homogeneous old lines and later by modern pure lines), to the spatial homogenization occurring in the last period of the 20th century with the different ‘départements’ (French administrative territories) progressively cultivating the same varieties and to their increasing genetic similarities. This result calls into question the effects of plant breeding, seed system organization and seed regulation on wheat genetic diversity, especially in the context of current environmental changes.
Mixed cropping has been suggested as a resource-efficient approach to meet high produce demands while maintaining biodiversity and minimizing environmental impact. Current breeding programs do not ...select for enhanced general mixing ability (GMA) and neglect biological interactions within species mixtures. Clear concepts and efficient experimental designs, adapted to breeding for mixed cropping and encoded into appropriate statistical models, are lacking. Thus, a model framework for GMA and SMA (specific mixing ability) was established. Results of a simulation study showed that an incomplete factorial design combines advantages of two commonly used full factorials, and enables to estimate GMA, SMA, and their variances in a resource-efficient way. This model was extended to the Producer (Pr) and Associate (As) concept to exploit additional information based on fraction yields. It was shown that the Pr/As concept allows to characterize genotypes for their contribution to total mixture yield, and, when relating to plant traits, allows to describe biological interaction functions (BIF) in a mixed crop. Incomplete factorial designs show the potential to drastically improve genetic gain by testing an increased number of genotypes using the same amount of resources. The Pr/As concept can further be employed to maximize GMA in an informed and efficient way. The BIF of a trait can be used to optimize species ratios at harvest as well as to extend our understanding of competitive and facilitative interactions in a mixed plant community. This study provides an integrative methodological framework to promote breeding for mixed cropping.
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.
Sustainable management of genetic resources is a crucial issue in the global context of food security. On-farm conservation is now widely acknowledged as a relevant strategy to reach this goal ...because it maintains evolutionary forces within and between the different components of the agricultural system. Seed exchanges between farmers play a key role in this process but are complicated to study over different agricultural contexts. This review begins by illustrating how interdisciplinary approaches combining ethnobotany and genetics helps provide a detailed analysis of the role of social and genetic dynamic interactions related to seed exchanges in traditional farming systems with farmer-led on-farm conservation. Secondly, the evolution of crop genetic diversity management is described in the context of industrialized farming systems. We follow the evolution of crop biodiversity perception by involved actors using a socio-historical perspective. After the agricultural shift from a traditional to a productivist model, recent social developments such as citizen science and participatory research movements are emerging and are strongly concerned by the question of biodiversity. These emerging trends which recognize and value seed exchanges between farmers show similarities to farmer-to-farmer seed exchanges in traditional farming systems. To what extent are these systems comparable? To fully benefit from studies in both traditional and industrialized contexts, it will be critical to develop an interdisciplinary framework to rigorously compare seed exchange systems and more generally farmer-led on-farm conservation strategies in diverse agricultural systems.
Earliness is very important for the adaptation of wheat to environmental conditions and the achievement of high grain yield. A detailed knowledge of key genetic components of the life cycle would ...enable an easier control by the breeders. The objective of the study was to investigate the effect of candidate genes on flowering time. Using a collection of hexaploid wheat composed of 235 lines from diverse geographical origins, we conducted an association study for six candidate genes for flowering time and its components (vernalization sensitivity and earliness per se). The effect on the variation of earliness components of polymorphisms within the copies of each gene was tested in ANOVA models accounting for the underlying genetic structure. The collection was structured in five groups that minimized the residual covariance. Vernalization requirement and lateness tend to increase according to the mean latitude of each group. Heading date for an autumnal sowing was mainly determined by the earliness per se. Except for the
Constans
(
CO
) gene orthologous of the barley
HvCO3
, all gene polymorphisms had a significant impact on earliness components. The three traits used to quantify vernalization requirement were primarily associated with polymorphisms at
Vrn
-
1
and then at
Vrn
-
3
and
Luminidependens
(
LD
) genes. We found a good correspondence between spring/winter types and genotypes at the three homeologous copies of
Vrn
-
1.
Earliness per se was mainly explained by polymorphisms at
Vrn
-
3
and to a lesser extent at
Vrn
-
1
,
Hd
-
1
and
Gigantea
(
GI
) genes. Vernalization requirement and earliness as a function of geographical origin, as well as the possible role of the breeding practices in the geographical distribution of the alleles and the hypothetical adaptive value of the candidate genes, are discussed.
The transition from vegetative to floral meristems in higher plants is determined by the coincidence of internal and environmental signals. Contrary to the photoperiod pathway, convergent evolution ...of the cold-dependent pathway has implicated different genes between dicots and monocots. Whereas no association between natural variation in vernalization requirement and Flowering time locus T (FT) gene polymorphism has been described in Arabidopsis, recent studies in Triticeae suggest implication of orthologous copies of FT in the cold response. In our study, we show that nucleotide polymorphisms on A and D copies of the wheat FT gene were associated with variations for heading date in a collection of 239 lines representing diverse geographical origins and status (landraces, old or recent cultivars). Interestingly, polymorphisms in the non-coding intronic region were strongly associated to flowering variation observed on plants grown without vernalization. But differently from VRN1, no epistatic interaction between FT homeologous copies was revealed. In agreement with the results of association study, the A and D copies of FT were mapped in regions including major QTLs for earliness traits in hexaploid wheat. This work, by identifying additional homeoalleles involved in wheat vernalization pathway, will contribute to a better understanding of the control of flowering, hence providing tools for the breeding of varieties with enhanced adaptation to changing environments.
In agricultural systems, biodiversity includes diversity within species and among species and provides many benefits for production, resilience and conservation. This article addresses the effects of ...a strategy of in situ conservation called dynamic management (DM) on population evolution, adaptation and diversity. Two French DM initiatives are considered, the first one corresponding to an experimental context, the second to an on-farm management. Results from a study over 26 years of experimental DM of bread wheat (Triticum aestivum L.) are first presented, including the evolution of agronomic traits and genetic diversity at neutral and fitness related loci. While this experiment greatly increased scientific knowledge of the effects of natural selection on cultivated populations, it also showed that population conservation cannot rely only on a network of experimental stations. In collaboration with a farmers’ network in France, researchers have begun studying the effects of on-farm DM (conservation and selection) on diversity and adaptation. Results from these studies show that on-farm DM is a key element for the long-term conservation and use of agricultural biodiversity. This method of in situ conservation deserves more attention in industrialised countries.
Certain temperate species require prolonged exposure to low temperature to initiate transition from vegetative growth to flowering, a process known as vernalization. In wheat, winter cultivars ...require vernalization to initiate flowering, making vernalization requirement a trait of key importance in wheat agronomy. The genetic bases of vernalization response have been largely studied in wheat, leading to the characterization of a regulation pathway that involves the key gene VERNALIZATION1 (VRN1). While previous studies in wheat and barley have revealed the functional role of histone modification in setting VRN1 expression, other mechanisms might also be involved. Here, we were interested in determining whether the cold-induced expression of the wheat VRN-A1 gene is associated with a change in DNA methylation.
We provide the first DNA methylation analysis of the VRN-A1 gene, and describe the existence of methylation at CG but also at non CG sites. While CG sites show a bell-shape profile typical of gene-body methylation, non CG methylation is restricted to the large (8.5 kb) intron 1, in a region harboring fragments of transposable elements (TEs). Interestingly, cold induces a site-specific hypermethylation at these non CG sites. This increase in DNA methylation is transmitted through mitosis, and is reset to its original level after sexual reproduction.
These results demonstrate that VRN-A1 has a particular DNA methylation pattern, exhibiting rapid shift within the life cycle of a winter wheat plant following exposure to particular environmental conditions. The finding that this shift occurs at non CG sites in a TE-rich region opens interesting questions onto the possible consequences of this type of methylation in gene expression.
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