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1.
Many crop wild relatives are usually widely distributed species, and in this relation a question arises about selecting populations of special importance for conservation. Using Rubus idaeus as an example, we propose a compound selection of wild populations for in situ conservation. Twelve raspberry populations in the Leningrad region have been evaluated from the point of view of their significance for in situ conservation. To exclude the run-wild forms from the evaluation process, we tried to identify them applying a mathematical model developed by statusmetry method. The constructed model is based on morphological features of leaves of primocanes and helps to distinguish the wild forms from the cultivated and run-wild ones. The wild raspberry populations were screened for plants with features useful for cultivated raspberry improvement such as waxy cover presence, yellow fruiting plants, spinelessness, fruiting primocanes and others. The diversity of wild raspberry populations was assessed by variation of morphological features, presence of botanical varieties and polymorphism of seed storage proteins. The results of viability status assessment for the chosen populations reflect the perspectives of their development and permit to determine the strategy and measures for optimal conservation.  相似文献   

2.
There is considerable wealth of genetical and morphological variation in tetraploid wheat collected from Ethiopia by past expeditions. Several authors have speculated on the reasons for this concentration of diversity so far removed from the centre of origin of wheats in West Asia. The present study reports results of evaluation carried out on material collected in the early 1970's from Ethiopia. The landraces from the two provinces Shewa and Tigray were found to be distinctly different. This divergence was attributed to the differences in environmental conditions between them. Wide differentiation among landraces within each province was also present. The Ethiopian farmer's practice of growing composite cultivars in the field has resulted in bulk samples of Ethiopian landraces containing several agrotypes. The proportion of total variance due to differences among agrotypes within landraces was by far the greatest found in this study, followed in most cases by the variation among landrace populations within provinces which exceeded, in turn, the variation between province gene pools. The optimal strategy for further germplasm collections and implications for improvement and conservation in locally-based community gene banks are discussed.  相似文献   

3.
Manilkara hexandra (Roxb.) Dubard (Khirni) is a socio-economically important fruit and nut species of tribal population of tropical deciduous forests of western and central India. Survey and collection missions were undertaken to study the extent of variability and socio-economic importance of Khirni germplasm in diversity rich areas of Rajasthan, Gujarat, Madhya Pradesh and Maharashtra. A total of 99 accessions of this important tree species were collected from surveyed regions, of which 47 diverse accessions were selected for morphological characterization showing wide range of variation in agro-morphological traits. During the survey, sizable variability in morphological characters and high socio-economic potential of Khirni was recorded. Bark, fresh fruits and extracted seeds have high nutritional and medicinal value. Tree provides substantial livelihood support to local inhabitants as collected fresh fruits from natural populations fetch good price in local markets. Besides livelihood support species, M. hexandra contributes in the nutritional security of the women and children of this area by fulfilling the need of micronutrients and vitamin A. Due to the high market demand of fresh fruits and seeds and without any organized cultivation, pressure on natural wild populations is severely building up since last several decades and therefore, the genetic variability of this species is now facing a great threat and need immediate complementary conservation efforts. Based on higher diversity index and natural population size of this species six in situ conservation sites have been suggested for dynamic conservation in western and central Indian states and 60 accessions have been successfully cryostored.  相似文献   

4.
The preservation of seed in cold stores provides a convenient and effective method of conserving many species of plants. The ease with which collections of some species may be kept in this way poses the danger that it may be applied uncritically to populations or taxa to which it is less suited. The paper briefly reviews the major factors which contribute to the success of collections for a seed bank and derives criteria from them which may be used as a means of evaluating proposals for seed conservation by this means. The method can also be used to identify possible problems or to estimate relative expenditures of time and other resources which would be involved in making collections or looking after banked seed.  相似文献   

5.
Aloe peglerae Schönland, an Endangered species endemic to South Africa, is threatened mainly by illegal collection. Lower densities of plants in areas easily accessible to the public led to questions concerning the sensitivity of this species to collection. Demographic monitoring data collected between 1976 and 1995 were used to build a stochastic population model, where parameters were allowed to vary randomly between observed minimum and maximum values. The model indicated that A. peglerae is highly sensitive to harvest of adult plants, with use sustainable at only very low levels of not more than 0.12%. Harvesting one plant annually is only sustainable in large populations of more than 1000 individuals; populations of this size, however, are rare. A maximum of fifteen percent of the annual seed output can be harvested sustainably. This long-term evaluation demonstrates that current collection of this species from the wild is unsustainable. Ex situ cultivation is therefore vital.  相似文献   

6.
Summary The first explorations for the collection of genetic resources of crop plants took place in areas designated as centers of origin. Later, important characters were found to be present in areas other than those indicated by Vavilov. Hence collection missions were extended to cover other areas in addition to the centers of diversity with different ecogeography and agromorphological features. Collecting activities were aimed not only at providing germplasm for immediate use in breeding but also at conserving genetic variation for future contingencies. The analysis of the collected material has revealed the complex nature, amount and distribution of genetic variation present in natural populations as well as in landraces, old varieties and primitive forms. The study of variation for characters from different regions indicated that it is possible to select certain characters for detecting variability in the populations and establishing the minimum number of genotypes to be sampled. A minimum number of 20–130 plants per sample, depending on the crop, is recommended in order to capture 95% of the total variation in the field. However, it has been emphasized that the number of different populations sampled rather than the sample size per population determines the overall efficiency of a collection. The findings reported allow better utilization of the collected material and formulation of optimal and cost-effective sampling strategies for the future.  相似文献   

7.
Four methods of obtaining seeds of wild species of plants for long-term conservation in Gene Banks were compared. (a) From collections growing within botanic gardens; (b) by making sample collections from wild populations and bulking up stocks by regeneration under cultivation; (c) by making arrangements with external collectors; (d) by organising plant collecting expeditions.Collections from plants in botanic gardens were unsatisfactory material on which to base collections. Regeneration under cultivation depends on expertise and knowledge of the plant's cultural requirements which were frequently not available, leading to unacceptably heavy losses of individuals and selection of populations, during cultivation. Collecting seeds directly from populations of wild plants was, scientifically, the most successful method and costings showed it also to be economically the least demanding of resources.The results suggest that, except in special cases—perhaps with rare plants where natural populations are small—every effort should be made to obtain initial collections of seed which are large enough to fulfil all the purposes intended by long-term conservation. Collections of small numbers of seeds which require bulking up before they can be used should be avoided, as a waste of effort, time and plant resources.  相似文献   

8.
An understanding of the genetic structure of populations is vital for the formation of optimum collection, conservation and utilization strategies for plant genetic resources. This is of particular importance in the case of in-situ conservation, a strategy gaining in popularity. The population genetic structures of five wild lentil taxa, Lens culinaris subsp. orientalis, L. odemensis, L. ervoides, L. nigricans and L. lamottei were investigated using isozyme electrophoresis and random amplified polymorphic DNA (RAPD). Approximately 20 plants from each of 5 populations per taxon were screened for variation at 11 isozyme loci and using three RAPD primers. Levels of variation were generally low, although considerable variation existed in the levels of diversity found within populations of L. culinaris subsp. orientalis and L. lamottei. Comparison of the results obtained in this study with the results obtained in a previous study indicate that this is a trend occurring across all species. It implies that levels of diversity within populations must be measured and considered prior to targeting of specific populations for in-situ conservation. Analysis of molecular variance of both isozyme and RAPD data revealed that between 78% and 99% of the variation was attributable to between-population differences. Isozyme results from L. lamottei populations were, however, contradictory. Possible explanations for this difference are discussed.  相似文献   

9.
Integrating demographic and genetic approaches in plant conservation   总被引：1，自引：0，他引：1  
We summarize the problems that populations of formerly common plants may encounter when habitat fragmentation isolates them and reduces population size. Genetic erosion, inbreeding depression, Allee-effects on reproductive success, catastrophes and environmental stochasticity are illustrated with studies on species that have recently become rare in The Netherlands due to habitat fragmentation. These clearly indicate that population viability is negatively affected. We also show that in the recent literature (since 1980), most studies on the conservation of rare plants have addressed population genetic structure and relationships between genetic variation and population size. Though important, these studies are not suitable for assessing the importance of genetics for population viability. In turn, demographic studies can detect changes in vital rates in small populations, but cannot reveal underlying genetic causes. Fitness and demographic studies are also well-represented in the literature, but remarkably few studies have attempted to integrate empirical demographic and genetic studies. We discuss two approaches to fill this very important lacuna in our knowledge. One of these constructs matrix-projection models on the basis of demographic censuses of—if possible—large and viable populations, and combines these with the results of experiments to determine inbreeding effects on demographic transitions and, subsequently, population growth and extinction. The other approach is to demographically monitor experimentally created small and large populations with low and high genetic variation and measure their actual growth rates and probabilities of extinction. We conclude that demography and demographic-genetic experiments should play a central role in plant conservation genetics.  相似文献   

10.
Different conservation measures including domestication approaches are needed to preserve rare and extensively used plant species and to satisfy future market demands. Snow lotus (a common name used for a number of high altitude species in central Asia) species in Mongolia are important medicinal plants, mostly endangered at the regional level due to the extensive use for medicinal purposes and naturally limited distribution ranges. In order to develop effective conservation and cultivation approaches we studied the morphological and genetic diversity as well as the seed germination behavior of three populations of Saussurea involucrata in the Altay Mountains of Western Mongolia. Plant height and leaf length were measured on 41–53 randomly selected individuals in each population. Enhancement of seed germination was studied using either mechanical or chemical scarification with potassium nitrate and gibberellic acid. Genetic diversity within and among three populations of the species was analyzed using Amplified Fragment Length Polymorphisms. Plants in three populations differed in height and leaf length (P < 0.001). Plant size tended to be negatively correlated with habitat altitude. Seed germination rate was low and increased with seed soaking in gibberellic acid. However, the response of seeds to different treatments was rather population-specific. Most treatments did not significantly affect mean days to germination and the ratio of shoot to root dry weight of 2-weeks old seedlings. The level of genetic diversity in the studied populations was lower than the average value for other long-lived perennial herbs. Analysis of molecular variance revealed a high differentiation within populations (92 % of total variation) indicating sufficient gene flow among populations.  相似文献   

11.
Although conservation and restoration practitioners have focused on maximizing aboveground population size and seed set of rare plants, a clear understanding of seed bank dynamics is crucial to managing these species. Santa Cruz tarplant (Holocarpha macradenia) is a threatened annual forb restricted to coastal prairie habitats in central California. Holocarpha produces disk achenes germinating within a year of production and ray achenes forming a persistent seed bank. We constructed both deterministic and stochastic demographic models for a restored Holocarpha population, using demographic rates measured separately for unmanipulated plants and plants growing in plots where vegetation was clipped. The deterministic models indicated that regardless of germination from the seed bank, the population would decline without clipping or similar treatments that enhance survival and reproductive output. Deterministic models showed only a slight positive effect of increased ray seed germination rates on population growth, which would need to be balanced against a potential loss of buffering against environmental variation as the dormant seed bank was reduced. Our stochastic simulations suggested that extinction risk for Holocarpha populations would be minimized by intermediate levels of ray seed germination. Thus, managers should focus on improving the performance of aboveground plants before considering actions to stimulate germination, since the former will yield a greater increase in deterministic population growth and not sacrifice any buffering effect of the seed bank. This case study emphasizes the importance of considering dormant seeds and seed banks in designing successful restoration and management strategies for plant species at risk of extinction.  相似文献   

12.
A recent approach to restoration of degraded mountain landscapes (e.g. ski slopes) recommend to sow seed mixtures including ‘site-specific’ species, i.e. native germplasm adapted to the prevailing conditions and ecologically compatible with the area of intervention. To better exploit the potential of these species and enhance their spread in revegetation projects, deeper knowledge is needed, however, on the existing variation in their germplasm, particularly for economically useful traits such as seed yield. Snow clover is one of the recommended ‘site-specific’ legumes. This study evaluated 12 populations of snow clover, collected in three valleys of the Rhaetian Alps, Italy, to assess their variation and highlight any promising material. The evaluation encompassed a mountain and a lowland site, to verify the behaviour of the germplasm also in one environment markedly different from that of origin. Differences among valleys were observed for flower colour, growth habit and type, flowering time and susceptibility to mildew, although the overall pattern of phenotypic diversity was similar among valleys. Some effect of the evaluation site on the expression of morphological and seed production traits, and on the overall diversity, was also evident. Furthermore, the lowland site experienced very high plant mortality towards the end of the first growing season. Individual populations proved a valuable source of variation for seed production. Some populations, in particular, were worth of attention for a possible selection of high-seed-yielding snow clover cultivars. An assessment of the mating system suggested a lack of self-tripping or an almost absolute self-incompatibility in snow clover.  相似文献   

13.
Population clonal diversity and fine-scale genetic structure of Oryza officinalis Wall. ex Watt, an endangered species in China recently experiencing habitat degradation, was estimated using inter simple sequence repeat markers. We analyzed the genetic variations of 440 samples exhaustively collected from nine O. officinalis populations. Relatively rich clonal diversity and poor genetic variation were found in the extant populations. We found that the number of genets, the percentage of polymorphic loci, and gene diversity decreased with population decline, suggesting that habitat degradation will lead to further genetic depletion of O. officinalis populations. A pronounced spatial genetic structure occurs at both the ramet and genet levels in several larger populations, which is the result of clonal growth and concomitant inbreeding. The in situ conserved population PS holds much more genotypes than other populations with the similar population size, which might have more seedling recruitments from the soil seed bank due to habitat disturbance, suggesting a moderate disturbance combined with habitat degradation-avoiding measures are effective for in situ conservation of this species.  相似文献   

14.
Hemigenia exilis (Lamiaceae) is a rare plant endemic to serpentine soils of the Goldfields of Western Australia. The species was presumed extinct until 1995, when it was re-discovered on a nickel ore deposit. To delineate the origin and extent of seed collection for rehabilitation after mining, and to identify the impact of removing one population due to mining, we assessed level and partitioning of genetic variation and differentiation. Twelve populations were sampled for DNA fingerprinting using the random amplified polymorphic DNA (RAPD) technique. Ten primers produced 89 bands, 97% being polymorphic. Genetic diversity within populations ranged from 0.197 to 0.409, averaging 0.38 at the species level, which is high compared with most other endemic species. Heterozygosity within populations ranged from 0.355 to 0.431, averaging 0.27 over the species. AMOVA partitioned over 80% of the total variation within populations. Multidimensional scaling revealed weak but significant differentiation into a northern and southern provenance. Despite selective sampling, the genetic data provided useful information for the management of Hemigenia exilis. For restoration, seed should be collected from a range of habitats of several populations, while keeping the two provenances separate. This strategy is likely to maintain high genetic diversity and locally adapted populations.  相似文献   

15.
Present study reported the variation in electrophoretic seed subfraction (albumins, globulin A, globulin B, glutelins) patterns in some Lathyrus species collected from their natural habitats different localities in Turkey. Electrophoretic data were documented by using a gel documentation system (Bio-Rad, USA) and analysed by using Quantity 1-D analysis software and also the dendograms were formed with 4.0% tolerance in UPGAMA (Unweighed Pair-Group Arithmetic Mean). The differences among species were observed and all seven species were clearly identifiable from the protein patterns. The dendograms obtained from cluster analysis of seed storage proteins data showed examined species have displayed a number of distinct relationships. According to our results, it seems justified to recommend a wider use of electrophoretic analysis of seed storage proteins in taxonomic investigations of leguminous plants.  相似文献   

16.
Previously, there has not been any in situ conservation sites for crop germplasm within the United States Department of Agriculture (USDA), Agricultural Research Service (ARS), National Plant Germplasm System (NPGS). Using morphologic and molecular (SSR markers) techniques, we assessed the genetic variation present in populations of rock grape (Vitis rupestris Scheele), a native American grape species, throughout its range. We identified seven in situ conservation sites for rock grape using a strategy based on morphologic and molecular data, taxonomic information, population size and integrity, and landholder commitment. In collaboration with federal and state landholding agencies, we have established the first NPGS in situ conservation sites for American wild relatives of a crop.  相似文献   

17.
Natural populations of wild rice, Oryza rufipogon Griff., are now threatened with the disturbance of their natural habitats by various human activities. To obtain basic information on genetic erosion or loss of genetic diversity in wild rice, we investigated how environmental changes of habitat affected the genetic structure of its natural population at a study site in the central plain of Thailand. During 10 years from 1985 to 1994, the wild-rice population at this site was seriously destroyed and fragmented. Using two sets of seed sample collected in 1985 and 1994 from the same population, allozyme variability at 17 loci of 11 enzymes were examined. Isozyme genotypes of mother plants of seed samples were estimated by the segregation in each progeny, and we calculated genetic parameters for the population. Gene diversity severely decreased in the 1994 sample compared with the 1985 sample. It is supposed that declining and fragmentation of the wild rice population, which happened during the 10 years, caused loss of genetic variability and forced the habitually outbreeding plants to inbreed, accelerating a reduction in gene variability. Pgi1-1 allele which was common in Indica rice cultivars of this region was found in the wild rice plants growing at the side of rice fields. Probably, introgression has occurred between wild and cultivated rice plants, and consequently the intrinsic nature of wild rice was gradually blurred by cultivar genes. We must realize that the genetic erosion of wild rice is rapidly proceeding and that an action for their conservation in natural environment, so called in situ conservation, is urgently needed.  相似文献   

18.
No single conservation technique can adequately conserve the full range of genetic diversity of a target species or genepool. To optimize the efficiency of germplasm conservation, a range of conservation techniques needs to be applied simultaneously. In this paper we review the progress made in the application of both in situ and ex situ complementary conservation strategies and techniques to the conservation of the genus Coffea and identify areas where more research work is required. Traditionally, Coffea species have been conserved ex situ as living plants in field genebanks due to their intermediate seed storage behaviour. However, progress made in the field of biotechnology in recent years have made it possible to envisage the use of in vitro, slow growth and cryopreservation for medium- and long-term conservation of Coffea germplasm, respectively. In situ conservation is also an important option for long-term conservation, but there are no genetic reserves specifically set up for conserving Coffea. Protected areas and managed reserves offer the best opportunities for conserving Coffea. A case study for Mascarene Coffea in Mauritius is presented and a strategy for their conservation is discussed.  相似文献   

19.
The greatest extent of genetic variation and outcrossing for Lycopersicon pimpinellifolium occurs in northern Peru. This is also the area most affected by EI Niño Southern Oscillation (ENSO). Using morphological and the molecular markers SSRs and AFLPs, we studied the genetic structure of L. pimpinellifolium populations collected after the ENSO event of 1997–1998. This was the most intense in the last century and caused a vast increase in the size of L. pimpinellifolium populations. Populations in the area surveyed were not regionally differentiated. We did not find any cline or eco-geographic association for genetic diversity, and positive correlations between genetic and geographic distances were found only at very short distances. Flooding and water streams caused by ENSO might have facilitated a periodical seed migration from distant areas. Gene flow between populations could then occur, facilitated by the increase in the population sizes of plants and pollinators and by the high levels of stigmatic exsertion. Results revealed a significant lack of heterozygotes in comparison with those expected in a panmictic population without consanguinity. A high degree of endogamy was found in all populations. In this context, endogamy can be explained by the occurrence of crosses between relatives rather than by autogamy. In an area intensely disturbed by ENSO, we found a population that had not been reported by earlier collectors in this region. This yellow-fruited population remained morphologically and molecularly differentiated from all L. pimpinellifolium and L. esculentum populations analyzed.  相似文献   

20.
Isatis tinctoria L. is a biennial species which was cultivated in Europe until the 18th century to produce indigo, a pigment used for dyestuffs. Today there is renewed interest in this ancient crop because of a market demand for natural dyes. Cultivation of the species appears to be particularly suitable for marginal areas. Information about the evolutionary and genetic patterns of I. tinctoria is needed if varieties or to be developed in future breeding programs. The aim of this study was to assess the genetic variation and similarity levels among and within natural populations of I. tinctoria from Europe and central Asia. Fifteen populations were used to carry out the genetic analyses with AFLP and SAMPL molecular markers. Data collected were analysed by the UPGMA method and were used to perform AMOVA. The results are consistent with the hypothesis that the crop originated in an eastern centre of origin and moved westward giving rise to a gene pool that is quite different from the original. The wide within-population variation revealed by this study suggests that effective breeding work to develop varieties suitable for marginal environments can be carried out easily.  相似文献   

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