Search

International audience; By the year 2050, agriculture will have to provide the food and nutrition requirements of some 9 billion people. Moreover, to maintain that level of productivity indefinitely it must do so using environmentally sustainable production systems. This task will be profoundly complicated by the effects of climate change, increasing competition for water resources and loss of productive lands. Agricultural production methods will also need to recognize and accommodate ongoing rural to urban migration and address a host of economic, ecological and social concerns about the ‘high inputs/high outputs’ model of present-day industrial agriculture. At the same time, there is a need to confront the unacceptable levels of continuing food and nutrition insecurity, greatest in the emerging economy countries of Africa and Asia where poverty, rapid population growth and climate change present additional challenges and where agriculture is practiced primarily by small-scale farmers. Within this context, we here review science-based evidence arguing that diversification with greater use of highly valuable but presently under-valorised crops and species should be an essential element of any model for sustainable smallholder agriculture. The major points of these development opportunity crops are presented in four sections: agricultural farming systems, health and nutrition, environmental sustainability and prosperity of the populations. For each section, these crops and their associated indigenous knowledge are reported to bring benefits and services when integrated with food systems. In this paper, we conclude that not only a change in policy is needed to influence behaviours and practices but also strong leadership able to synergize the various initiatives and implement an action plan.

This paper introduces the contents of a special issue of Agriculture, Ecosystems and Environment dedicated to “Agrobiodiversity & Africa”. Placed within the context of the scientific literature on agricultural biodiversity, its contribution to sustainable production and its importance in Africa, this special issue starts off with background articles which reviewed major agroecosystems in Africa, descriptions of their biodiversity resources, management, limitations and concerns. The follow-up scientific papers covered major components of biodiversity for agriculture namely soil biota, species diversity and germplasm diversity. The soil biota papers report research and findings on arbuscular mycorrhizal fungi in the rhizosphere, termite and bacterial communities and evidence on the influence of their diversity on crop production. The crop species diversity papers provide evidence on the role of the diversity in influencing soil microbial properties as well as managing pest and diseases in crop production. Scientific evidence on the role and interactions of germplasm diversity and provenance with the environment are also presented.

Over the next decades, agricultural production practices will change significantly and become more sustainable while they also respond to the need to contribute to reducing malnutrition and hunger and meeting the challenges of climate change. The enhanced use of agricultural biodiversity will play an essential role in this process, providing improved adaptability and resilience in agro-ecosystems. Plant genetic resources, a major component of agricultural biodiversity, play a key role in improving agricultural production and productivity. They are also essential to coping with climate change. As a result of climate change, increased efforts will be needed to conserve the diversity of crops and their wild relatives, and both in situ and ex situ conservation strategies will have to be adapted to meet changing environmental conditions and the need to secure biodiversity threatened by changing climate and altered production practices. Improved use of plant genetic resources will be essential, and this is like...

Agricultural biodiversity has hitherto been valued almost exclusively as a source of traits that can be used in scientific breeding programs to improve the productivity of crop varieties and livestock breeds. We argue that it can make a far greater contribution to increased productivity. In particular, a wider deployment of agricultural biodiversity is an essential component in the sustainable delivery of a more secure food supply. Diversity of kingdoms, species and genepools can increase the productivity of farming systems in a range of growing conditions, and more diverse farming systems are also generally more resilient in the face of perturbations, thus enhancing food security. Diversity can maintain and increase soil fertility and mitigate the impact of pests and diseases. Diversity of diet, founded on diverse farming systems, delivers better nutrition and greater health, with additional benefits for human productivity and livelihoods. Agricultural biodiversity will also be absolutely essential to cope with the predicted impacts of climate change, not simply as a source of traits but as the underpinnings of more resilient farm ecosystems. Many of the benefits of agricultural biodiversity are manifested at different ecological and human scales, and cut across political divisions, requiring a cross-sectoral approach to reassess the role of agricultural biodiversity in sustainable and secure food production.

This paper reviews and discusses how studies on (i) on-farm diversity assessment, (ii) access to diversity and information, (iii) extent of use of available materials and information, and (iv) benefits obtained by the farmer or farming community from their use of local crop diversity, are necessary to identify the different ways of supporting farmers and farming communities in the maintenance of traditional varieties and crop genetic diversity within their production systems. Throughout this paper two key themes are emphasized. First, any description or analysis within the four main areas (assessment, access, use and benefit) can, and most probably will, lead to a number of different actions. Second, the decision to implement a particular action, and therefore its success, will depend on farmers and the farming community having the knowledge and leadership capacity to evaluate the benefits that this action will have for them. This in turn emphasizes the importance of activities (whether by local, national...

In light of the growing concern over the potentially devastating impacts on biodiversity and food security of climate change and the massively growing world population, taking action to conserve crop wild relatives (CWR), is no longer an option — it is a priority. Crop wild relatives are species closely related to crops, including their progenitors, many of which have the potential to contribute beneficial traits to crops, such as pest or disease resistance, yield improvement or stability. They are a critical component of plant genetic resources for food and agriculture (PGRFA), have already made major contributions to crop production and are vital for future food security; their systematic conservation in ways that ensure their continuing availability for use is therefore imperative. This is a complex, interdisciplinary, global issue that has been addressed by various national and international initiatives. Drawing on the lessons learnt from these initiatives we can now propose a global approach to CWR conservation, the key elements of which are: (1) estimating global CWR numbers, (2) assessment of the global importance of CWR diversity, (3) current conservation status, (4) threats to CWR diversity, (5) systematic approaches to CWR conservation, (6) CWR informatics, and (7) enhancing the use of CWR diversity.

В данной обзорной статье представлена информация о генах диких видов растений, которые были перенесены в сельскохозяйственные культуры в ходе селекционного процесса за последние 20 лет. За эти годы наблюдалось стабильное увеличение количества новых сортов, содержащих генетический материал диких видов, а также расширился диапазон характеристик тех генов, которые вводятся в культурные сорта. Те сельскохозяйственные культуры (пшеница, томат), чьи дикорастущие сородичи традиционно использовались как источники ценных признаков, по-прежнему остаются приоритетными для переноса новых генов от их диких видов. Несмотря на то, что постоянно улучшаются технологии межвидового скрещивания, вводятся в селекционную практику молекулярные методы, пополняются коллекции в генбанках и все больше публикуется работ с описанием наиболее значимых признаков дикорастущих видов, тем не менее, вклад дикорастущих сородичей культурных растений в усовершенствование новых сортов остается меньше, чем это можно было бы ожидать.

Over the last decade, Bioversity International has worked with national, regional and local partners in eight countries (Burkina Faso, Ethiopia, Hungary, Mexico, Morocco, Nepal, Peru, and Vietnam) on the maintenance and use of crop genetic diversity on farm, particularly that found in traditional varieties (or landraces). The work has involved investigating the extent and distribution of diversity in over 27 crops and exploring with farmers and rural communities the management practices used to maintain traditional varieties. The results of this collaboration have (i) provided tools to assess the amount and distribution of crop genetic diversity in production systems (ii) increased our understanding of when, where and how this diversity will be maintained, (iii) identified practices, communities and institutions that support maintenance and evolution of crop genetic diversity in production systems, and (iv) provided possible mechanisms for ensuring that the custodians of these systems and genetic...

The use of crop wild relatives (CWR) genes to improve crop performance is well established with important examples dating back more than 60 years. In this paper, we review available information on the presence of genes from CWR in released cultivars of 16 mandate crops of the CGIAR institutes, and some selected additional crops, focusing on the past 20 years—the period since a comprehensive review by Robert and Christine Prescott-Allen in 1986. It appears that there has been a steady increase in the rate of release of cultivars containing genes from CWR. While there continues to be a strong emphasis on using pest and disease resistance genes, a wider range of characteristics are being introduced than in the past. Those crops whose wild relatives have traditionally been used as sources of useful traits (e.g., wheat, tomato) continue to be most likely to include new genes from their wild relatives. CWR are continually gaining in importance and prevalence, but, we argue, their contributions to the development of new cultivars remain less than might have been expected given improved procedures for intercrossing species from different gene pools, advances in molecular methods for managing backcrossing programes, increased numbers of wild species accessions in gene banks, and the substantial literature on beneficial traits associated with wild relatives.

▪ Abstract Plant genetic resources provide the biological underpinning for agriculture and food production. No nation is independent in terms of these resources. Interdependence levels are high among countries. Policy impediments to access may subside, increasing already substantial germplasm flows. Serious questions exist, however, about the health and availability of the actual resources. Genebank collections contain many unintended duplicates, making aggregate numbers seem larger than they really are. Information about individual accessions, particularly those found in situ, is often poor, reducing frequency and efficiency of use and ultimate benefits. Although not firmly established today, the link between conservation and use must be strengthened.

Recognized as a priority three decades ago, in situ conservation of crop wild relatives has developed theoretical and methodological focus and achieved significant on-the-ground progress in the last 10 years, most notably under the impetus of the plant genetic resources community. Literature and Internet searches and interviews with experts were undertaken as a basis for reviewing the current status and trends of this effort worldwide. Country-by-country summaries on in situ crop wild relatives conservation activities are presented, and recommendations are made for future action. Principal recommendations include ‘flagging’ of appropriate taxa as crop wild relatives in botanical and conservation databases, undertaking gap analyses to locate crop wild relatives hotspots, and enhancing cooperation between the plant genetic resources and plant conservation communities.

Plant genetic resources are conserved so that they can be used to improve crop plant pro- duction and in other ways. However, it is often asserted that use ofex situconserved germplasm is inadequate and that genetic diversity maintained in genebanks is underutilized. In part, this reflects an incomplete recognition of what constitutes use of plant genetic resources, and of the many different ways in which material from genebanks contributes to improved agricultural production. Based on recent information from surveys of distribution of germplasm from genebanks, and from surveys of users, we suggest that the evidence indicates that there is substantial use ofex situconserved materials for a wide range of different uses. We suggest that barriers to use ofex situconserved germplasm may often result from a lack in numbers of users, and from limitations in capacity to effectively utilize the genetic diversity present in genebanks to reduce genetic vulnerability and increase sustainability in modern production systems.

This chapter surveys the conceptual basis of indicators of genetic diversity, genetic erosion, and genetic vulnerability. These are summary measures of genetic diversity in cultivated plants and their wild relatives that guide decisions, monitor progress, and warn of emerging issues of genetic resources for resilient agricultural production. Such indicators measure the genetic diversity currently present in agricultural populations on farm and held in germplasm collections, and aim to detect genetic erosion, or serious loss of diversity in time, and to warn of vulnerability due to adverse deployment of genetic diversity in space. While diversity itself encompasses many concepts, richness diversity—the number of different kinds of individuals regardless of their frequencies—is the most important theme, followed by evenness diversity—how similar the frequencies of the different variants are. Many variables are plausible as indicators of diversity. The more practical are based on number of individuals or area occupied in situ and on the number of accessions and the number of genebanks ex situ. Genetic erosion is measurable as the proportion of richness of genetic diversity no longer existing in current populations, when compared with the crop a decade previously or predicted to be lost in the next decade without remedial action. Genetic vulnerability is inversely related to richness diversity that is present locally, particularly if it is known to possess adaptation to exotic or new mutant pathotypes or insect strains or environments. Census information forms the primary data. For cultivated species, these data are based on the farmer’s unit of diversity management, most often their named varieties, their number, relative frequencies and divergence over various units of spatial and temporal scale. For wild species, the analogous units of diversity are the lowest recognized (e.g. subspecies, morphological types, ecotypes). Census data should be supplemented and validated using more direct assays at the DNA level with molecular techniques in carefully constructed samples.

Biodiversity refers to variation within the living world, while genetic diversity represents the heritable variation within and between populations of organisms, and in the context of this paper, among plant species. This pool of genetic variation within an inter-mating population is the basis for selection as well as for plant improvement. Thus, conservation of this plant genetic diversity is essential for present and future human well-being. During recent years, there has been increasing awareness of the importance of adopting a holistic view of biodiversity, including agricultural biodiversity, conservation for sustainable utilization and development. These principles have been enshrined in the Convention on Biological Diversity and the Global Plan of Action of the Food and Agriculture Organization of the United Nations. The emphasis is now to understand the distribution and extent of genetic diversity available to humans in plant species, so that the genetic diversity can be safely conserved and efficiently used. It is generally recognized that plant genetic diversity changes in time and space. The extent and distribution of genetic diversity in a plant species depends on its evolution and breeding system, ecological and geographical factors, past bottlenecks, and often by many human factors. Much of the large amount of diversity of a species may be found within individual populations, or partitioned among a number of different populations. A better understanding of genetic diversity and its distribution is essential for its conservation and use. It will help us in determining what to conserve as well as where to conserve, and will improve our understanding of the taxonomy and origin and evolution of plant species of interest. Knowledge of both these topics is essential for collecting and use of any plant species and its wild relatives. In order to mange conserved germplasm better, there is also a need to understand the genetic diversity that is present in collections. This will help us to rationalize collections and develop and adopt better protocols for regeneration of germplasm seed. Through improved characterization and development of core collections based on genetic diversity information, it will be possible to exploit the available resources in more valuable ways.

A sesame core collection containing 453 accessions was established by assessing genetic diversity of 4251 accessions collected in China. The accessions in the whole collection were grouped based on their origin, varietal and agro-ecological type. A computer program was used to cluster the data of 14 traits from the random small sample. Ward's method was chosen as the desirable method for clustering sesame germplasm resources. A set of technical methods for establishing core collection has been developed through determining the number of selected accessions based on the diversity distribution. The agronomic traits of the pre-selected core collection were investigated and tested in three ecological locations in China for two years. Among six qualitative traits, including plant type and flower color in a total of 5304 accessions, 97.85% was completely the same as the original data, and three quantitative traits, including growth period and plant height, were significantly and positively related with the original data. The representativeness assessment of the final core collection indicated that 35 phenotypes of 10 qualitative traits in the core collection were basically similar to those of the pre-selected core collection. Six feature values such as mean, standard deviation etc. of four quantitative traits including oil content and 1000-seed weight were close to those of the pre-selected core collection. The final core collection possessed a fair representativeness of the pre-selected core collection.

Whether new combinations of genes that result from hybridization and introgression between wild and cultivated taxa are maintained, with the resultant development of populations with new characteristics, depends on natural selection, and in the case of crops, on human selection. While many cases of deliberate introgression of desirable traits into crop cultivars as part of breeding programmes are known, the extent and significance of natural or farmer-assisted introgression is uncertain. A range of techniques have been used to document natural hybridization and introgression of agricultural crops and their wild relatives in many crops including maize, wheat, barley, oats, pearl millet, foxtail millet, quinoa, hops, hemp, potato, cocona, casava, common bean, cowpea, pigeon pea, carrots, squash, tomato, radish, letuce, chilli, beets, sunflower, cabbage, and rasberries. However, the majority of these studies are based on morphological characters, and few have investigated the frequency with which such new types are produced and retained in natural and agroecosystems for farmer selection. Even more limited is information on the role of farmers in recognizing and selecting new genetic variation from the natural introgression of crops with their wild relatives, and the impact, once selected, of these new genetic combinations on the crop diversity. Molecular evaluation of natural introgression linked to investigations of farmer recognition and use of introgressed types provide ways of evaluating whether farmer selection for introgressed types is a significant process in increasing the genetic diversity of crop plants.

Cacao (Theobroma cacao L.) is indigenous to the Amazon basin, but is generally believed to have been domesticated in Mesoamerica for the production of chocolate beverage. However, cacao’s distribution of genetic diversity in South America is also likely to reflect pre-Columbian human influences that were superimposed on natural processes of genetic differentiation. Here we present the results of a spatial analysis of the intra-specific diversity of cacao in Latin America, drawing on a dataset of 939 cacao trees genotypically characterized by means of 96 SSR markers. To assess continental diversity patterns we performed grid-based calculations of allelic richness, Shannon diversity and Nei gene diversity, and distinguished different spatially coherent genetic groups by means of cluster analysis. The highest levels of genetic diversity were observed in the Upper Amazon areas from southern Peru to the Ecuadorian Amazon and the border areas between Colombia, Peru and Brazil. On the assumption that the last glaciation (22,000–13,000 BP) had the greatest pre-human impact on the current distribution and diversity of cacao, we modeled the species’ Pleistocene niche suitability and overlaid this with present-day diversity maps. The results suggest that cacao was already widely distributed in the Western Amazon before the onset of glaciation. During glaciations, cacao populations were likely to have been restricted to several refugia where they probably underwent genetic differentiation, resulting in a number of genetic clusters which are representative for, or closest related to, the original wild cacao populations. The analyses also suggested that genetic differentiation and geographical distribution of a number of other clusters seem to have been significantly affected by processes of human management and accompanying genetic bottlenecks. We discuss the implications of these results for future germplasm collection and in situ, on farm and ex situ conservation of cacao.

Varietal data from 27 crop species from five continents were drawn together to determine overall trends in crop varietal diversity on farm. Measurements of richness, evenness, and divergence showed that considerable crop genetic diversity continues to be maintained on farm, in the form of traditional crop varieties. Major staples had higher richness and evenness than nonstaples. Variety richness for clonal species was much higher than that of other breeding systems. A close linear relationship between traditional variety richness and evenness (both transformed), empirically derived from data spanning a wide range of crops and countries, was found both at household and community levels. Fitting a neutral “function” to traditional variety diversity relationships, comparable to a species abundance distribution of “neutral ecology,” provided a benchmark to assess the standing diversity on farm. In some cases, high dominance occurred, with much of the variety richness held at low frequencies. This suggested that diversity may be maintained as an insurance to meet future environmental changes or social and economic needs. In other cases, a more even frequency distribution of varieties was found, possibly implying that farmers are selecting varieties to service a diversity of current needs and purposes. Divergence estimates, measured as the proportion of community evenness displayed among farmers, underscore the importance of a large number of small farms adopting distinctly diverse varietal strategies as a major force that maintains crop genetic diversity on farm.

Summary - In recent years the possible use of wild relatives of crop species in plant breeding programs has been the subject of increased attention and this has stimulated the collection and ex situ maintenance of many wild plant species. These activities raise a number of questions concerning the number of wild species with which those interested in the conservation and utilization of plant genetic resources should be concerned, their relationships to crop species, the scale on which wild species' collection should be undertaken, the most suitable conservation methods for such material and the description of the genetic diversity available in these wider gene pools. Molecular genetic techniques have already provided useful information on such topics as the relationships between crop species and their wild relatives, the extent of genetic diversity in such species and genetic stability following ex situ storage. There remain significant opportunities for applying these techniques in studies of the distribution of genetic diversity in wild relatives of crop plants, and in the location, collection and maintenance of that diversity.