首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Bactris gasipaes Kunth (peach palm or Pejibaye) is the only domesticated palm of the Neotropics. The genetic relationships between the crop and its wild relatives are still unclear. We undertook field and laboratory work in order to describe differentiation and relationships between the wild and cultivated populations of the species in Western Ecuador, and their possible interactions. A volumetric study was undertaken on the fruits of both populations, as well as a population genetic analysis in order to clarify these relationships. Fruits from cultivated plants collected in the region of sympatry of wild and cultivated plants in North-West Ecuador showed intermediate volumes between those of reference samples for the wild and cultivated plants in allopatry. Using 8 microsatellite loci, we assessed 83 wild and cultivated individuals from Western Ecuador and cultivated plants from Amazonia and Central America as a reference for the cultivated form. We detected high polymorphism in the wild and cultivated samples and low, but significant level of genetic differentiation between wild and cultivated populations. The cultivated population in North-Western Ecuador showed close genetic proximity with the sympatric wild population, consistent with the volumetric study. These results have implications for hypotheses on evolution of this crop and for strategies of genetic conservation of the wild forms.  相似文献   

2.
Weedy rice (Oryza sativa f. spontanea Baker) is one of the most serious weeds in direct-seeded rice production; adversely affecting rice areas and yield in Thailand. The objectives of this study were to evaluate the level of morphological and agronomical variation and the level and pattern of genetic diversity and population structure of weedy rice populations in Thailand. Sixty-three weedy rice populations collected from three rice production areas of Thailand were sampled over four rice cultivation seasons to study phenotypic characteristics, genetic diversity and population structure. All analysis included comparison with seven cultivated rice varieties and seven local common wild rice populations. The results demonstrated considerable genetic and morphological variation, population structure, and changing dynamics of Thai weedy rice populations, both within and between regions and growing seasons. Phenotypic and genotypic variations and population structure of weedy rice populations changed temporally, with a trend over five years toward greater similarity to companion crop rice varieties. The ongoing gene flow, combined with ecological conditions created by farmers’ selection and agronomic practices, may enhance fitness and adaptability of weedy rice populations and stimulate the evolution of invasiveness in weedy rice plants. The adaptive evolution of weedy rice tended to parallel cultivated rice for high adaptation to the agronomic practices, possibly including selection for crop mimicry, which has led to the convergence of weedy populations phenotypically and genetically with the companion crop rice.  相似文献   

3.
Climate change and other anthropogenic disturbances can lead to the loss of genetic variation and thereby affect evolutionary potential and survival of plant populations in the wild. We examined these predictions in the primary wild relative of barley, Hordeum vulgare L. subsp. spontaneum (K. Koch) Thell., within its center of diversity, in Jordan. Changes in genotypic and phenotypic diversity were assessed using seed samples collected in 1981 and 2012 from the same 18 sites across Jordan. The overall population structure was conserved, but we observed an increase of within population genetic diversity and a reduction in population differentiation. Phenotypic variation differed among years and sites but the magnitude and direction of change variated among sites. While the sampled region became significantly hotter and drier during this period, simple correlation models did not support association between measures of climate change and the observed genetic and phenotypic changes. Agricultural activities that promote disturbance and demographic fluctuations may affect crop wild relatives that grow in agricultural landscapes, in unexpected ways. The observed increase in genetic diversity within populations might be explained by increased migration or by an advantage of increased genetic variation in the face of variable environmental conditions. This study provides a new perspective on the range of possible responses of crop wild relatives to environmental pressures.  相似文献   

4.
Spontaneous gene flow between wild and cultivated chicory, Cichorium intybus L., may have implications for the genetic structure and evolution of populations and varieties. One aspect of this crop-wild gene flow is the dispersal of transgenes from genetically modified varieties, e.g. gene flow from GM chicory to natural chicory could have unwanted consequences. With the purpose to identify and quantify crop-wild gene flow in chicory, we analysed introgression in 19 wild chicory populations and 16 accessions of chicory varieties and landraces distributed across Northern, Central and Mediterranean Europe. The analysis used 281 AFLP markers and 75 SSAP markers giving a total of 356 polymorphic markers. Results from model based assignments with the program STRUCTURE indicated many incidents of recent gene flow. Gene flow was observed both between cultivars and wild populations, between landraces and wild populations, between different wild populations as well as between cultivars. Population structure visualized by distance-based clustering showed a North–South geographical structuring of the wild populations, and a general grouping of the cultivars corresponding to known origin. The results indicated, however, that the structuring between the two groups of wild and cultivated types was weak. As crop and wild recipients are genetically close and genes are transferred between the two types rather frequently, focus on mitigating crop-wild gene flow should be increased, before transgenic varieties are cultivated openly.  相似文献   

5.
The gene pool of cultivated Asian rice consists of wild rice (Oryza rufipogon Griff.), cultivated rice (O. sativa L.) and a weedy form (O. sativa f. spontanea). All three components are widespread in Thailand, frequently co-occurring within fields and providing the opportunity for gene flow and introgression. The purpose to this study is to understand the on-going evolutionary processes that affect the gene pool of rice by analysis of microsatellite variation. Results indicate that O. rufipogon, the wild ancestor of rice, has high levels of genetic variation both within and among populations. Moreover, the variation is structured predominantly by annual and perennial life history. High levels of variation are detected among cultivars indicating Thai cultivated rice has a broad genetic base with only a 20 % reduction in diversity from its wild ancestor. The weedy rice populations reveal varying levels of genetic variation, from nearly as high as wild rice to near zero. Weedy rice is genetically structured into 2 groups. Some populations of invasive weedy rice are the result of hybridization and gene flow between local wild rice and local cultivated rice in the regions of co-occurrence. Other populations of weedy rice are genetically nearly identical to the local cultivated rice. The diversity analysis indicates that the rice gene pool in Thailand is a dynamic genetic system. Gene flow is ongoing among its three main components, first between cultivated and wild rice resulting in weedy rice. Weedy rice in turn crosses with both cultivated varieties and wild rice.  相似文献   

6.
Introgression from soybean cultivars to its wild progenitor species is an interesting antidromic recombination in natural ecosystem with many consequences, including the alteration of genetic diversity, the origin of semi-wild soybean, and implication for biosafety of the wild progenitor species with future release of the genetically modified varieties. Although such interspecific introgression is not suspected to be ubiquitous in the sympatric regions of wild and cultivated soybeans, the documentations published based on some molecular experimental analyses on the introgression have been little substantiated by the occurring process morphologically and remain deficient for unquestionable evidence, owing to the lack of actual insight into the population dynamics. Here, we found the phenomenon of gene escape and presented the evidence for occurrence of introgression from soybeans into the wild species and for how originates about the semi-wild type soybean based on morphological investigation of population dynamics. Our results suggest that more attention should be paid to the escape of genetically modified genotypes to safeguard the biosafety of wild soybean gene pool, if GM soybeans are released in China, the place of origin of cultivated soybeans.  相似文献   

7.
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   

8.
In situ population studies of wild relatives of crops are crucial for the conservation of plant genetic resources, especially in regions with high genetic diversity and a risk of local extinction. Ethiopia is the center of origin for sorghum, yet little is known about the genetic structure of extant wild populations. Using 9 Simple Sequence Repeat loci, we characterized 19 wild populations from five regions, 8 local cultivar populations from three regions, and 10 wild sorghum accessions from several African countries. To our knowledge, this is the most comprehensive study to date of in situ wild sorghum populations in Africa. Genetic diversity corrected for sample size was significantly greater in the wild populations in situ than in local cultivars or the accessions. Approximately 41 % of the genetic variation in the wild plants was partitioned among populations, indicating a high degree of differentiation and potential value for germplasm conservation, and the average number of migrants (Nm) per generation was 0.43. Cluster analyses showed that some wild populations were grouped by geographic region, whereas others were not, presumably due to long-distance seed movement. Four wild populations from disjunct regions formed a unique cluster with an Ethiopian accession of subsp. drummondii and probably represent a weedy race. STRUCTURE and other analyses detected evidence for crop-wild hybridization, consistent with previous molecular marker studies in Kenya, Mali, and Cameroon. In summary, in situ wild sorghum populations in Ethiopia harbor substantial genetic diversity and differentiation, despite their close proximity to conspecific cultivars in this crop/wild/weedy complex.  相似文献   

9.
Groundnut, an important crop of many countries of the world, is susceptible to a range of diseases and pests. High levels of resistances are not available in the cultivated gene pool as the crop is said to have a narrow genetic base. Narrow genetic base is attributed to the evolution of the crop which took place by the combination of A and B genome species, and later doubling their chromosome number, giving rise to tetraploid cultivated groundnut. Direct utilization of cross-compatible wild relatives, which are diploids, to broaden the genetic base and introduction of useful traits, is not a straight-forward process due to ploidy differences between the cultivated species and wild relatives. Hence amphiploids and autotetraploids were created by not only combining the putative genomes, but many other A and B genome species, thus producing a highly variable population of tetraploid groundnuts also called new sources of Arachis hypogaea. This study describes the development and characterization of newly generated tetraploid groundnuts and the level of molecular diversity as assessed by DArT markers.  相似文献   

10.
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   

11.
为科学评价茄子种质资源,选取有代表性的茄子种质材料135份,开展茄子表型性状鉴定和黄萎病抗性分析。结果表明,供试材料存在丰富的表型变异,21个表型性状变异系数变幅为15.71%~89.86%,平均为40.09%;遗传多样性指数变幅为0.322~2.135,平均为1.348。主成分分析将21个表型性状归结为6个主因子,即果形、色泽、果重、生长势、株型和果实商品性,6个主因子累计贡献率达72.84%。基于表型数据的聚类,在Pearson相关系数0.061处,将供试材料分为4组,即栽培茄+近缘野生茄、近缘野生茄、大果型栽培茄、紫色长条形栽培茄。黄萎病抗性试验鉴定出抗病(R)材料9份、中抗(MR)材料6份、耐病材料11份,占供试材料的19.26%;在抗性材料中,仅3份为栽培种,其余均为近缘野生茄。本研究结果为茄子优异种质的发掘和有效利用提供了理论参考。  相似文献   

12.
Introgression was detected within wild emmer wheat population in Jordan during the year 2000. Wild emmer wheat was found to occur in non-disturbed habitat, very close to cultivated durum wheat in northern parts of Jordan, and it was found in cultivated durum wheat in southern parts of Jordan. Random Amplified Polymorphic DNA (RAPD) test was constructed to assess natural introgression occurrence within wild emmer wheat population. Associated durum wheat land races from the vicinity of durum wheat fields were also collected. Shannon Diversity Index for wild emmer wheat populations was 0.46 and for durum wheat landraces was 0.45. The percentage of polymorphic loci for wild emmer wheat populations was 92.6. The close genetic distance between certain wild emmer wheat populations and durum wheat landraces provided proofs that massive introgression has occurred.  相似文献   

13.
This paper reviews the status of crop genetic resources in Yunnan province of China from 1978 to 1999. Results are presented of same research in the field of the diversity of cultivated and wild crop. Yunnan is one of the centre of origin or genetic diversity of more than 200 cultivated and wild crops. There are over 500 cultivated plants which account for over 80% of the total in China and more than 650 species of wild crops. In addition, there are more than 440 species of main wild flowers. According to our recently researches there are abundant species, subspecies and varieties of crop genetic resources in Yunnan Province. The Lancang River Valley is the richest genetic diversity centre of rice, maize, wheat, barley, buckwheat, legumes, ramie, sugarcane, vegetable, tea, actinidia and so on. For example, there are 59 varieties (including all varieties of Oryza sativa L. in China) in 5933 accession of Yunnan indigenous rice. The Lancang River Valley is one of the centre for genetic diversity of rice resources and a rich region for elite and rare rice resources of Yunnan, too. In order to protect the highly endangered crop genetic resources in the Lancang River Valley, it is necessary and very important to set up a collection, conservation, utilization and research system, enhancing their protection and utilization, in situ- and ex situ-conservation, farm management and sustainable production.  相似文献   

14.
Ramie (Boehmeria nivea) was domesticated in China. However, the geographic region of domestication is not exactly known. Genetic diversity and population structure of ramie and their wild relatives were assessed using microsatellite markers. The 8 microsatellite primers revealed 96 alleles in 50 ramie populations, with an average of 10.25 alleles per locus. Cultivated ramie gene pool harbors approximately 82.9 % of the SSR diversity presented in wild B. nivea var. nivea. It is suggested that ramie has experienced a relatively moderate domestication bottleneck. The distribution of genetic diversity shows that genetic diversity is relatively high in populations along the Yangtze River compared to the peripheral ones. The scatter plots of principal coordinates analysis indicated that there are three well-supported varieties in B. nivea. The NJ tree and the distribution of genetic diversity showed that ramie has been domesticated in the middle and lower regions of the Yangtze valley, and populations in Sichuan province have been introduced from this region, forming naturalized populations.  相似文献   

15.
The diversity, genetic structure, and genetic flow of wild populations of Phaseolus vulgaris L. within its Mesoamerican area of domestication, were analyzed by means of morphological and inter-simple sequence repeat molecular markers. Overall, 89% of the loci studied were polymorphic, 35% in the least diverse population and 65% in the most diverse. Genetic diversity in the populations was high, between h = 0.14 and 0.29, as was the maximum distance between populations (D = 0.3). Between 40% and 45% of the diversity was explained by the differences among populations, indicating that a large number of populations is necessary to represent the wild gene pool in the germplasm collections. We found uniformity in allele frequencies among the populations, suggesting presence of outcrossing. We did not find correlation between genetic and geographic distances, but the dendrogram topology suggests geographical isolation due to the mountainous topography. Negative correlations were observed between the coefficient of variation of seed size and the distance between wild populations and fields . We obtained a highly negative correlation between percentage of polymorphic loci and distance to the nearest crop field, which also suggests gene flow from the domesticated populations. These observations suggest that genetic flow is taking place from domesticated toward wild populations and that the farmer, through his agricultural activities, could be influencing the magnitude and the characteristics of the gene flow, and along with this, the differentiation of wild populations. New approaches should be established for conservation in situ and maintaining bio-safety, given the risk of introducing genotypes from the Andes and transgenic varieties and causing genetic assimilation.  相似文献   

16.
American ginseng (Panax quinquefolius) is a native North American medicinal plant that is becoming increasingly vulnerable despite government harvest restrictions. To better understand the genetic diversity and gene flow of American ginseng, we studied RAPD variation in cultivated and wild populations. Classical and Bayesian analogues of genetic diversity statistics were estimated in seven wild and two cultivated populations. The wild populations were more highly structured (G stβ  = 0.41) than the cultivated populations (G stβ  = 0.24). The genetic diversity within populations ranged from H eβ  = 0.05 to 0.38. Based on genetic pairwise distances, six of the wild populations clustered with the locally-derived cultivated population, while one wild population was more similar to the non-local cultivated population than the local populations. This wild population was highly diverse (P = 1.0; U = 1.0) suggesting that it was supplemented from exotic seed. A set of eight RAPD markers was identified that differentiated plants of local and non-local origin. As a conservation strategy, we recommend that regional gene banks be established based on molecular and geographic diversity to preserve the locally adapted germplasm. These regional gene banks would serve as a conservation tool and also provide a source of genes for genetic improvement of cultivated ginseng.  相似文献   

17.
The small island of Ustica north of Sicily has been investigated for its plant genetic resources in 1997. A checklist of the agri- and horticultural crop plants comprises more than 110 species. Some of the species show still a large infraspecific variation but genetic erosion could be also found. Rare material has been collected for the conservation in genebanks.The considerable agrobiodiversity and the ongoing evolution as evidenced by introgression from wild relatives to several cultivated species and vice versa suggest the development of an on-farm conservation for the island. Nature protection and traditional farm management should develop an integrated approach.  相似文献   

18.
Thus far, there is little knowledge of the genetic diversity, structure and gene flow dynamics in rare wild and semi-wild soybean mixed populations, and such information is vital for understanding of the origin of semi-wild soybean (Glycine gracilis) and the biosafety protection of wild soybean from transgenic soybeans. Population eco-genetic data are necessary to provide a more coherent and comprehensive understanding of the genetic events that occurred in the natural habitats of wild soybean (Glycine soja). We tested genetic diversity and structure of 11 wild mixed populations of wild soybean (Glycine soja) and semi-wild soybean (G. gracilis), 1 wild soybean population, and 1 cultivated soybean variety population were studied using 20 nuclear microsatellite markers (SSRs). We found based on microsatellite polymorphisms that the mixed populations were characterized by higher mean heterozygosity (H o = 0.029) and outcrossing rate (t m = 6.35 %), and lower fixation index (F is = 0.891), and the semi-wild plants had distinctly higher heterozygosity (H o = 0.081) than that of the wild plants (H o = 0.007). The occurrence of semi-wild plants influenced population genetic structure but not geographical population differentiation. These mixed populations exhibited strong ecogeographical differentiation, which suggests that their original populations were colonized over a long phytogeographical history. The introgression occurred through pollen gene flow from the soybean fields into wild populations and created the semi-wild plants, with significant genetic differentiation from the typical wild ones. Introgressive genes could become established by two possible modes in wild soybean populations by both self-segregation and/or intrapopulation secondary hybridization. The latter deserves attention because of the possibility of rapid transgene escape.  相似文献   

19.
During a long evolutionary history across a range of environmental conditions in the Near East Fertile Crescent, wild emmer wheat (Triticum turgidum subsp. dicoccoides) has accumulated a wealth of genetic diversity and adaptations to multiple biotic and abiotic stress conditions. The joint effects of the domestication and subsequent selection in man-made agro-ecosystems have considerably reduced the genetic variation in cultivated crop species as compared to their wild progenitors. The wild emmer gene pool harbors a rich allelic repertoire for improving numerous agronomically important traits. A set of advanced wild emmer wheat introgression lines (ILs) was previously established on a bread wheat genetic background. It combines genetic diversity from the wild progenitor as well as the genetic background of the cultigen. Based on field evaluations, the set of ILs (divided hierarchically into different families based on the genetic background) has exhibited high phenotypic variance in agronomically important traits. Analyses of variance ?(ANOVA) have shown that the effect of the hierarchical genetic factors was significant in the vast majority of the traits. Similarly, characterizations by molecular markers of known traits have shown that the genetic profile differs between ILs from different genetic backgrounds. Multivariate principal component analysis has revealed interesting associations between vegetative and reproductive traits and illustrated the impact of some of these traits on ILs distribution in the PC1 and PC2. The exploitation of the wild emmer wheat ILs as a tool for reintroduction of alleles that were lost during domestication and possible implications for wheat breeding are discussed.  相似文献   

20.
The mountain rye Secale strictum is native to the Middle East and is the progenitor of the cultivated rye. Regarding lack of information about the genetic diversity of this species in Iran, this study was aimed to evaluate its genetic variation and to examine the patterns of diversity related to the varieties and geography. Fifteen wheat and rye derived microsatellite markers were used to achieve this aim. High levels of diversity, with an average number of 6.1 alleles per locus (ranging up to 11) and high level polymorphism with polymorphism rate averaging 0.624 (between populations) and 0.357 (within populations) were observed among 125 individuals from 19 populations collected from various regions of Iran. The Northwestern populations showed the highest and the Northern populations showed the lowest polymorphism and diversity. One population of the Northwest of the country was notably closer in its allele range to the S. cereale accessions used as outgroup. No taxon or geographic specific marker was detected, suggesting high gene flow between the populations, however some groupings which can be related to the geographic regions and varieties, were evident. The analysis of molecular variance attributed same portions of genetic diversity to the within and between populations with no significant variation among different geographic regions. The results of this study indicated that the Iranian genepool of Secale strictum is valuable to search for new useful alleles for crop improvement.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号