栽培植物野生近缘种的保护与利用

栽培植物是人类赖以生存和发展的重要物质基础。全球人口与人均需求量的持续增长导致对植物资源的需求与日俱增。栽培植物较低的遗传多样性是限制其产量增长和质量提高的主要因素。栽培植物野生近缘种在自然环境中积累了丰富的遗传变异, 并在应对环境变化的过程中产生了很多新的适应性状, 是栽培植物种质创新和品种改良的重要遗传资源。然而, 栽培植物野生近缘种的存续和自然进化因生境破坏以及全球气候变化等正面临严重威胁, 需要采取有效的措施进行保护。本文总结了国内外对栽培植物野生近缘种进行原生境保护与迁地保护所取得的进展, 并基于我国实际情况提出了栽培植物野生近缘种的保护建议。此外, 本文还对栽培植物野生近缘种利用技术进行了梳理, 探讨了栽培植物野生近缘种遗传资源可持续利用的新思路。最后, 我们以长江流域几种代表性栽培植物为例, 对主要作物类型的保护与利用情况进行了讨论。     

Insights on the evolution of a vegetatively propagated crop species

The opportunity for gene flow between a vegetatively propagated crop and its wild relatives is expected to be much lower than for seed-propagated crops, since sexual reproduction in the crop occurs only infrequently. A study by Duputié and colleagues now demonstrates evidence of sexual reproduction between a vegetatively propagated crop and a closely related wild congener. Working in French Guiana, these workers have documented a hybrid zone arising from introgression between cassava (Manihot esculenta ssp. esculenta, Euphorbiaceae), which is propagated by stem cuttings, and wild Manihot populations growing in close proximity. Patterns of heterozygosity suggest that there are little-to-no barriers to reproduction between the crop and these wild populations. Previous work by these researchers has documented the importance of occasional sexual reproduction for the development of cassava varieties in traditional Amerindian farming systems. Taken together with their previous work, these new findings suggest that gene flow between wild Manihot populations and cassava plants could potentially play a much greater role in the crop's evolution than previously thought.     

Microsatellite variation in cassava (Manihot esculenta, Euphorbiaceae) and its wild relatives: further evidence for a southern Amazonian origin of domestication

Genetic variation at five microsatellite loci was used to investigate the evolutionary and geographical origins of cassava (Manihot esculenta subsp. esculenta) and the population structure of cassava's wild relatives. Two hundred and twelve individuals were sampled, representing 20 crop accessions, 27 populations of cassava's closest wild relative (M. esculenta subsp. flabellifolia), and six populations of a potentially hybridizing species (M. pruinosa). Seventy-three alleles were observed across all loci and populations. These data indicate the following on cassava's origin: (1) genetic variation in the crop is a subset of that found in the wild M. esculenta subspecies, suggesting that cassava is derived solely from its conspecific wild relative. (2) Phenetic analyses group cassava with wild populations from the southern border of the Amazon basin, indicating this region as the likely site of domestication. (3) Manihot pruinosa, while closely related to M. esculenta (and possibly hybridizing with it where sympatric), is probably not a progenitor of the crop. Genetic differentiation among the wild populations is moderately high (F:(ST) = 0.42, rho(ST) = 0.54). This differentiation has probably arisen primarily through random genetic drift (rather than mutation) following recent population divergence.     

Transgene introgression in crop relatives: molecular evidence and mitigation strategies

Incorporation of crop genes into wild and weedy relative populations (i.e. introgression) has long been of interest to ecologists and weed scientists. Potential negative outcomes that result from crop transgene introgression (e.g. extinction of native wild relative populations; invasive spread by wild or weedy hosts) have not been documented, and few examples of transgene introgression exist. However, molecular evidence of introgression from non-transgenic crops to their relatives continues to emerge, even for crops deemed low-risk candidates for transgene introgression. We posit that transgene introgression monitoring and mitigation strategies are warranted in cases in which transgenes are predicted to confer selective advantages and disadvantages to recipient hosts. The utility and consequences of such strategies are examined, and future directions provided.     

中国粮食作物的野生近缘植物及其保存概况

中国的主要粮食作物约有20种,它们的多数都有野生近缘植物.目前,中国保存的粮食作物野生近缘植物资源约1.5万份,分别保存在国家作物种质资源库和种质圃内.     

Evaluating genetic containment strategies for transgenic plants

One of the primary concerns about genetically engineered crop plants is that they will hybridize with wild relatives, permitting the transgene to escape into the environment. The likelihood that a transgene will spread in the environment depends on its potential fitness impact. The fitness conferred by various transgenes to crop and/or wild-type hybrids has been evaluated in several species. Different strategies have been developed for reducing the probability and impact of gene flow, including physical separation from wild relatives and genetic engineering. Mathematical models and empirical experimental evidence suggest that genetic approaches have the potential to effectively prevent transgenes from incorporating into wild relatives and becoming established in wild populations that are not reproductively isolated from genetically engineered crops.     

CWRML: representing crop wild relative conservation and use data in XML

Background  

Crop wild relatives are wild species that are closely related to crops. They are valuable as potential gene donors for crop improvement and may help to ensure food security for the future. However, they are becoming increasingly threatened in the wild and are inadequately conserved, both in situ and ex situ. Information about the conservation status and utilisation potential of crop wild relatives is diverse and dispersed, and no single agreed standard exists for representing such information; yet, this information is vital to ensure these species are effectively conserved and utilised. The European Community-funded project, European Crop Wild Relative Diversity Assessment and Conservation Forum, determined the minimum information requirements for the conservation and utilisation of crop wild relatives and created the Crop Wild Relative Information System, incorporating an eXtensible Markup Language (XML) schema to aid data sharing and exchange.     

In situ conservation of crop wild relatives: status and trends

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.     

Population structure and phylogeography of Solanum pimpinellifolium inferred from a nuclear gene

Phylogeographical studies are emerging as a powerful tool for understanding the population structure and evolution of wild relatives of crop species. Because of their value as genetic resources, there is great interest in exploring the distribution of variation in wild relatives of cultivated plants. In this study, we use sequence variation from the nuclear gene, fruit vacuolar invertase (Vac), to investigate the population history of Solanum pimpinellifolium. Solanum pimpinellifolium is a close relative of the cultivated tomato and has repeatedly served as a source of valuable traits for crop improvement. We sequenced the second intron of the Vac gene in 129 individuals, representing 16 populations from the northern half of Peru. Patterns of haplotype sharing among populations indicate that there is isolation by distance. However, there is no congruence between the geographical distribution of haplotypes and their genealogical relationships. Levels of outcrossing decrease towards the southernmost populations, as previously observed in an allozyme study. The geographical pattern of Vac variation supports a centre of origin in northern Peru for S. pimpinellifolium and a gradual colonization along the Pacific coast. This implies that inbreeding populations are derived from outcrossing ones and that variation present at the Vac locus predates the spread of S. pimpinellifolium. The expansion of cities and human agricultural activity in the habitat of S. pimpinellifolium currently pose a threat to the species.     

Ex Situ Conservation Priorities for the Wild Relatives of Potato (Solanum L. Section Petota)

Crop wild relatives have a long history of use in potato breeding, particularly for pest and disease resistance, and are expected to be increasingly used in the search for tolerance to biotic and abiotic stresses. Their current and future use in crop improvement depends on their availability in ex situ germplasm collections. As these plants are impacted in the wild by habitat destruction and climate change, actions to ensure their conservation ex situ become ever more urgent. We analyzed the state of ex situ conservation of 73 of the closest wild relatives of potato (Solanum section Petota) with the aim of establishing priorities for further collecting to fill important gaps in germplasm collections. A total of 32 species (43.8%), were assigned high priority for further collecting due to severe gaps in their ex situ collections. Such gaps are most pronounced in the geographic center of diversity of the wild relatives in Peru. A total of 20 and 18 species were assessed as medium and low priority for further collecting, respectively, with only three species determined to be sufficiently represented currently. Priorities for further collecting include: (i) species completely lacking representation in germplasm collections; (ii) other high priority taxa, with geographic emphasis on the center of species diversity; (iii) medium priority species. Such collecting efforts combined with further emphasis on improving ex situ conservation technologies and methods, performing genotypic and phenotypic characterization of wild relative diversity, monitoring wild populations in situ, and making conserved wild relatives and their associated data accessible to the global research community, represent key steps in ensuring the long-term availability of the wild genetic resources of this important crop.     

Comparing species and evolutionary diversity metrics to inform conservation

Phylogenetic diversity (PD) is an important measure for identifying areas of conservation. Phylogenetic diversity is a robust biodiversity metric because it accounts for the relationships among species, and not just the number of species. For this reason, it is an essential element for conservation planning. Unfortunately, PD metrics are not used by many for conservation planning. In the case of Colombia, which is rich in crop and wild plant biodiversity, lacks information on genetic resources of Crop Wild Relatives (CWR). Due to deforestation and agriculture expansion, the habitat, where these crop wild relatives grow, is being reduced at an alarming rate and could be destroyed altogether. This study focuses on crop wild relatives in Colombia, comparing species diversity versus PD-based metrics to show the advantages of using evolutionary information for conservation planning. We identified new areas with high PD and endemism among CWR diversity which are important to establishing comprehensive conservation strategies.     

Consequences of recurrent gene flow from crops to wild relatives

Concern about gene flow from crops to wild relatives has become widespread with the increasing cultivation of transgenic crops. Possible consequences of such gene flow include genetic assimilation, wherein crop genes replace wild ones, and demographic swamping, wherein hybrids are less fertile than their wild parents, and wild populations shrink. Using mathematical models of a wild population recurrently receiving pollen from a genetically fixed crop, we find that the conditions for genetic assimilation are not stringent, and progress towards replacement can be fast, even for disfavoured crop genes. Demographic swamping and genetic drift relax the conditions for genetic assimilation and speed progress towards replacement. Genetic assimilation can involve thresholds and hysteresis, such that a small increase in immigration can lead to fixation of a disfavoured crop gene that had been maintained at a moderate frequency, even if the increase in immigration is cancelled before the gene fixes. Demographic swamping can give rise to 'migrational meltdown', such that a small increase in immigration can lead to not only fixation of a disfavoured crop gene but also drastic shrinkage of the wild population. These findings suggest that the spread of crop genes in wild populations should be monitored more closely.     

Stress and domestication traits increase the relative fitness of crop-wild hybrids in sunflower

After a decade of transgenic crop production, the dynamics of gene introgression into wild relatives remain unclear. Taking an ecological genetics approach to investigating fitness in crop-wild hybrid zones, we uncovered both conditions and characteristics that may promote introgression. We compared diverse crop-wild hybrid genotypes relative to wild Helianthus annuus under one benign and three stressful agricultural environments. Whereas relative fitness of crop-wild hybrids averaged 0.25 under benign conditions, with herbicide application or competition it reached 0.45 and was more variable. In some instances, hybrid fitness matched wild fitness (approximately 1). Thus, wild populations under agronomic stress may be more susceptible to introgression. Although 'domestication' traits are typically considered unlikely to persist in wild populations, we found some (e.g. rapid growth and early flowering) that may enhance hybrid fitness, especially in stressful environments. Rigorous assessment of how particular genotypes, phenotypes, and environments affect introgression will improve risk assessment for transgenic crops.     

The Evolutionary History of Wild,Domesticated, and Feral Brassica oleracea (Brassicaceae)

Understanding the evolutionary history of crops, including identifying wild relatives, helps to provide insight for conservation and crop breeding efforts. Cultivated Brassica oleracea has intrigued researchers for centuries due to its wide diversity in forms, which include cabbage, broccoli, cauliflower, kale, kohlrabi, and Brussels sprouts. Yet, the evolutionary history of this species remains understudied. With such different vegetables produced from a single species, B. oleracea is a model organism for understanding the power of artificial selection. Persistent challenges in the study of B. oleracea include conflicting hypotheses regarding domestication and the identity of the closest living wild relative. Using newly generated RNA-seq data for a diversity panel of 224 accessions, which represents 14 different B. oleracea crop types and nine potential wild progenitor species, we integrate phylogenetic and population genetic techniques with ecological niche modeling, archaeological, and literary evidence to examine relationships among cultivars and wild relatives to clarify the origin of this horticulturally important species. Our analyses point to the Aegean endemic B. cretica as the closest living relative of cultivated B. oleracea, supporting an origin of cultivation in the Eastern Mediterranean region. Additionally, we identify several feral lineages, suggesting that cultivated plants of this species can revert to a wild-like state with relative ease. By expanding our understanding of the evolutionary history in B. oleracea, these results contribute to a growing body of knowledge on crop domestication that will facilitate continued breeding efforts including adaptation to changing environmental conditions.     

The role of domestication and maternal effects on seed traits of crop–wild sunflower hybrids (Helianthus annuus)

Hybridisation between crops and their wild relatives may promote the evolution of weeds. Seed germination and dormancy are the earliest life‐history traits and are highly influenced by the maternal parent. However, the ecological role of the maternal effect on seed traits in the evolution of crop–wild hybrids has received little attention. In this study, we test the relative importance of maternal and hybridisation effects on seed traits of the first generation of crop–wild sunflower hybrids (Helianthus annuus). Seed germination was tested in two wild populations with contrasting dormancy, two cultivated materials and their reciprocal crosses at four different times after harvest and three different temperatures. Seed germination at each of the four times, after ripening response and secondary dormancy were recorded along with four morphological traits. Additionally, the pericarp anatomy was analysed with light and scanning electron microscopy. We observed strong maternal effects on all seed traits. Seed germination, morphology and pericarp anatomy differed largely between the crop and wild seeds and these traits in the crop–wild hybrids resembled their female parent. Slight but significant hybridisation effects were observed in germination, mainly in seeds produced on wild plants. Crop hybridisation changed seed germination, the after ripening response and secondary dormancy in the crop direction. Morphological and anatomical traits associated with domestication strongly correlated with the observed differences in seed germination and dormancy in crop–wild sunflower hybrids. The large maternal effects along with the evolutionary divergence in seed traits were responsible for the large phenotypic differences observed in crop–wild hybrids with the same genetic composition. Wild‐like seed traits of hybrids suggest that there are no barriers to crop gene introgression at the seed level whereas crop‐like seed traits could be strongly selected against, conditioning the selection of traits expressed later in the life cycle and in the next generations.     

转基因植物对农业生物多样性的影响

论述了近年来转基因植物对农业生态系统生物多样性影响的研究进展．主要在遗传多样性、物种多样性和生态系统多样性3个层次上予以评述．包括转基因植物对作物遗传多样性的影响;转基因植物的外源基因向杂草和近缘野生种转移;转基因抗虫植物对目标害虫的影响。抗除草剂转基因植物对作物和杂草的影响,抗病毒转基因植物对病毒的影响;转基因植物对非目标生物的影响,对土壤生态系统的影响等．     

中国作物野生近缘植物资源

中国地域辽阔,气候多样,地形复杂,土壤类型繁多,加之农业历史悠久,不仅作物种类众多,而且很多作物都有其野生近缘种,从而使得中国成为世界作物的重要起源中心之一。本文在介绍中国作物种类的同时,列出了各类作物的野生近缘植物资源,为进一步深入研究和开发利用这些资源,以及国家制定野生植物保护有关政策提供基础数据和信息。     

First use of microsatellite markers in a large collection of cultivated and wild accessions of tepary bean (Phaseolus acutifolius A. Gray)

Tepary bean (Phaseolus acutifolius A. Gray) is a dry-land crop species that originated in the deserts of Mexico and the south-western United States and therefore is proposed as a source of drought and salt tolerance for related species and for production in marginal rainfall areas. Few genetic tools have been developed or tested for tepary bean but microsatellites from common bean are an obvious choice for diversity analysis in the crop. The first goal of this study was to validate a set of gene-derived and non-gene simple sequence repeat or microsatellite markers from common bean in tepary bean cultivars and wild relative accessions. The second and more extensive objective of this study was to evaluate the genetic diversity and population structure of the tepary bean accessions to determine if leaf-morphology variants are valid as separate sub-groups of wild tepary beans; if P. parvifolius exist as a separate variants or species; and if cultivated tepary beans originated from one domestication event or several events. Our analysis of 140 tepary bean genotypes showed that a single domestication was likely as the cultivars were most closely related to accessions from Sinaloa and northern Mexico and that diversity was much higher in the wild genotypes compared to the cultivated ones. Other results were that P. parvifolius was classified as a separate species by population structure analysis while the variants P. acutifolius var. acutifolius and var. tenuifolius were admixed and inter-crossed. P. latifolius is not a valid species or variant of P. acutifolius but represents a group of cultivars within tepary bean. This is the first analysis of microsatellite diversity in tepary beans and has implications for breeding and conservation of this crop and its wild relatives.     

Metabolite analysis for the comparison of irrigated and non-irrigated field grown tomato of varying genotype

Every year the consequences of water deficit on crop yield and quality are profound. The observation that many wild species relatives of cultivated crops display a greater stress tolerance and the fact that the cultivated species generally display only a fraction of the allelic diversity available within the tomato clade suggest that crossing of wild species with elite cultivars could improve the stress physiology of modern crops. To assess this from the basis of chemical composition we applied an established GC-MS based metabolite profiling method to fruits from irrigated and non-irrigated tomato plants either of the cultivated tomato (Solanum lycopersicum) or of its hybrid with its wild species relative (Solanum pennellii). Results are discussed in terms of both the metabolic response to drought stress and the potential of utilizing exotic germplasm as a means to improve agronomically important characteristics of crop species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.