The genetic diversity and evolution of field pea (<Emphasis Type="Italic">Pisum</Emphasis>) studied by high throughput retrotransposon based insertion polymorphism (RBIP) marker analysis

Background  

The genetic diversity of crop species is the result of natural selection on the wild progenitor and human intervention by ancient and modern farmers and breeders. The genomes of modern cultivars, old cultivated landraces, ecotypes and wild relatives reflect the effects of these forces and provide insights into germplasm structural diversity, the geographical dimension to species diversity and the process of domestication of wild organisms. This issue is also of great practical importance for crop improvement because wild germplasm represents a rich potential source of useful under-exploited alleles or allele combinations. The aim of the present study was to analyse a major Pisum germplasm collection to gain a broad understanding of the diversity and evolution of Pisum and provide a new rational framework for designing germplasm core collections of the genus.     

Genetic diversity assessment and ex situ conservation strategy of the endangered Dendrobium officinale (Orchidaceae) using new trinucleotide microsatellite markers

Dendrobium officinale (Orchidaceae) is an endangered plant species with important medicinal value. To evaluate the effectiveness of ex situ collection of D. officinale genetic diversity, we developed 15 polymorphic trinucleotide microsatellite loci of D. officinale to examine the genetic diversity and structure of three D. officinale germplasm collections comprising 120 individuals from its germplasm collection base and their respective wild populations consisting of 62 individuals from three provinces in China. The three germplasm collections showed reductions in gene diversity and average number of alleles per locus, but an increase in average number of rare alleles (frequency?≤?0.05) per locus in comparison to their wild populations. However, the differences in gene diversity between the germplasm collections and wild populations were not statistically significant. The analysis using STRUCTURE revealed evident differences in genetic composition between each germplasm collection and its wild population, probably because the D. officinale individuals with distinct genotypes in each wild population were unevenly selected for establishing its germplasm collection. For conservation management plans, we propose that D. officinale individuals with rare alleles need to be conserved with top priority, and those individuals with the most common alleles also should be concerned. The 15 new microsatellite loci may be used as a powerful tool for further evaluation and conservation of the genetic diversity of D. officinale germplasm resources.     

Genetic diversity and population structure in cultivated sunflower and a comparison to its wild progenitor, <Emphasis Type="Italic">Helianthus annuus</Emphasis> L

Crop germplasm collections are valuable resources for ongoing plant breeding efforts. To fully utilize such collections, however, researchers need detailed information about the amount and distribution of genetic diversity present within collections. Here, we report the results of a population genetic analysis of the primary gene pool of sunflower (Helianthus annuus L.) based on a broad sampling of 433 cultivated accessions from North America and Europe, as well as a range-wide collection of 24 wild sunflower populations. Gene diversity across the cultivars was 0.47, as compared with 0.70 in the wilds, indicating that cultivated sunflower harbors roughly two-thirds of the total genetic diversity present in wild sunflower. Population structure analyses revealed that wild sunflower can be subdivided into four genetically distinct population clusters throughout its North American range, whereas the cultivated sunflower gene pool could be split into two main clusters separating restorer lines from the balance of the gene pool. Use of a maximum likelihood method to estimate the contribution of the wild gene pool to the cultivated sunflower germplasm revealed that the bulk of the cultivar diversity is derived from two wild sunflower population genetic clusters that are primarily composed of individuals from the east-central United States, the same general region in which sunflower domestication is believed to have occurred. We also identified a nested subset of accessions that capture as much of the allelic diversity present within the sampled cultivated sunflower germplasm collection as possible. At the high end, a core set of 288 captured nearly 90% of the alleles present in the full set of 433, whereas a core set of just 12 accessions was sufficient to capture nearly 50% of the total allelic diversity present within this sample of cultivated sunflower.     

A Multiplex Microsatellite Marker Kit for Diversity Assessment of Large Cassava (<Emphasis Type="Italic">Manihot esculenta</Emphasis> Crantz) Germplasm Collections

Current methods for molecular fingerprinting of cassava (Manihot esculenta Crantz) have limited throughput or are costly, thus preventing the characterization of large germplasm collections such as those held by the International Agricultural Research Centers or National Research Institutions, which comprise hundreds to thousands of accessions. Here, we report the development of a fluorescence-based multiplex simple sequence repeat (SSR) marker kit that enables accurate and cost-effective cassava fingerprinting. The kit comprises 16 SSR markers assembled into five multiplex panels and was tested on 21 cassava cultivars alongside one accession of Manihot epruinosa, a wild relative. A total of 68 alleles were detected with, on average, 4.25 alleles per locus and a polymorphism information content of 0.53. The marker kit reported here is comparable to previously published amplified fragment length polymorphism and SSR marker systems in terms of discriminating power and informativeness while offering significant advantages in speed and cost of marker analysis. Previous molecular genetic diversity studies have suggested that cassava germplasm collections contain duplicate entries based on the occurrence of identical genetic profiles. Using the newly developed microsatellite kit, three out of six putative duplicate accessions could be readily differentiated, showing that these are distinct genotypes. The relevance of these findings with respect to the characterization and management of large cassava germplasm collections is discussed.     

High‐throughput genotyping for species identification and diversity assessment in germplasm collections

Germplasm collections provide an extremely valuable resource for breeders and researchers. However, misclassification of accessions by species often hinders the effective use of these collections. We propose that use of high‐throughput genotyping tools can provide a fast, efficient and cost‐effective way of confirming species in germplasm collections, as well as providing valuable genetic diversity data. We genotyped 180 Brassicaceae samples sourced from the Australian Grains Genebank across the recently released Illumina Infinium Brassica 60K SNP array. Of these, 76 were provided on the basis of suspected misclassification and another 104 were sourced independently from the germplasm collection. Presence of the A‐ and C‐genomes combined with principle components analysis clearly separated Brassica rapa, B. oleracea, B. napus, B. carinata and B. juncea samples into distinct species groups. Several lines were further validated using chromosome counts. Overall, 18% of samples (32/180) were misclassified on the basis of species. Within these 180 samples, 23/76 (30%) supplied on the basis of suspected misclassification were misclassified, and 9/105 (9%) of the samples randomly sourced from the Australian Grains Genebank were misclassified. Surprisingly, several individuals were also found to be the product of interspecific hybridization events. The SNP (single nucleotide polymorphism) array proved effective at confirming species, and provided useful information related to genetic diversity. As similar genomic resources become available for different crops, high‐throughput molecular genotyping will offer an efficient and cost‐effective method to screen germplasm collections worldwide, facilitating more effective use of these valuable resources by breeders and researchers.     

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.     

Cryopreservation of grapevine (<Emphasis Type="Italic">Vitis</Emphasis> spp.)—a review

Grapevine (Vitis genus) is one of the economically most important fruits worldwide. Some species and cultivars are rare and have only a few vines, but represent national heritages with a strong need for preservation. Field collections are labor intensive, and expensive to maintain, and are exposed to natural disasters. In addition, infection with pathogens, especially viruses, is common in grapevine because of vegetative propagation, which is conventionally used for this genus. Cryopreservation provides an alternative and ideal means for the long-term preservation of Vitis germplasm, which can be used as a backup to field collections for important autochthonous cultivars or only as cryo-banks for rare, native cultivars that are worthy of preservation. Cryotherapy, based on cryopreservation protocols, provides an efficient method for the eradication of grapevine viruses. This review provides comprehensive and updated information on cryopreservation for long-term preservation of genetic resources and cryotherapy for virus eradication in Vitis. Additional research in grapevine cryopreservation and cryotherapy is needed.     

Mulberry biodiversity conservation through cryopreservation

A 238 mulberry germplasm accession collection from diverse regions maintained under tropical conditions was identified from an ex situ field gene bank. The purpose was to prioritize the in vitro conservation and cryopreservation to develop long-term biodiversity conservation for ensuring sustainable utilization of these valuable resources. Reliable cryo techniques using desiccation and slow freezing of winter-dormant buds were used. Storage potential of bud grafts of different Morus species at −1.5°C for 90 d indicated species-specific variation, and most of the wild species were found sensitive. In vitro regeneration and cryopreservation (−196°C) protocols using differentiated bud meristems, like axillary winter-dormant buds, were worked out for a wide range of landraces, wild, and cultivated varieties of Morus. Buds maintained under subtropical location are also amenable for cryopreservation. Successful cryopreservation of winter-dormant buds belonging to Morus indica, Morus alba, Morus latifolia, Morus cathayana, Morus laevigata, Morus nigra, Morus australis, Morus bombycis, Morus sinensis, Morus multicaulis, and Morus rotundiloba was achieved. Among wild species, Morus tiliaefolia and Morus serrata showed moderate recovery after cryopreservation. Survival rates did not alter after 3 yr of cryopreservation. Inter-simple sequence repeat markers were used to ascertain the genetic stability of cryopreserved mulberry germplasm accessions, which showed no difference detected among the plantlets regenerated from frozen apices in comparison to the nonfrozen material.     

Current status and conservation of Pistacia germplasm

The genetic erosion of Pistacia germplasm has been highlighted in many reports. In order to emphasize this and to focus more attention on this subject, national and international (especially IPGRI and IFAR) institutions have initiated projects proposing to characterize, collect and conserve Pistacia germplasm. Therefore, this paper reviews recent research concerning conventional (in situ and ex situ) and unconventional biotechnological conservation strategies applied to the preservation of Pistacia germplasm. As regards conventional conservation, the majority of germplasm collections of Pistacia species are preserved on farms (in situ) and in seed and field genebanks (ex situ), as well as in the wild, where they are vulnerable to unexpected weather conditions and/or diseases. Hence, complementary successful unconventional in vitro methods (organogenesis, somatic embryogenesis and micrografting) and slow-growth storage conditions for medium-term preservation of Pistacia are presented together with the morphological and molecular studies carried out for the characterization of its species in this review. Moreover, special attention is additionally focused on cryopreservation (dehydration- and vitrification-based one-step freezing techniques) for the long-term preservation of Pistacia species. Possible basic principles concerning the establishment of a cryobank for the successful conservation of Pistacia germplasm are also discussed.     

Droplet-vitrification and morphohistological studies of cryopreserved shoot tips of cultivated and wild pineapple genotypes

Germplasm conservation of pineapple [Ananas comosus (L.) Mer.] is crucial to preserve the genus’ genetic diversity, to secure material for genetic improvement and to support innovative and new research. Long-term conservation is accomplished through cryopreservation, that is done by storing cells or tissues at ultra-low temperature in liquid nitrogen (−196 °C). Droplet-vitrification, a combination of droplet freezing and solution-based vitrification, was used to establish a protocol for cryopreservation of pineapple genetic resources. This protocol was tested on cultivated and wild pineapple genotypes to establish a long-term germplasm security duplicate as well as to investigate cryo-injuries in the tissues by means of histological techniques. Excised shoot tips (0.5–1 mm with one primordial leaf) of different pineapple genotypes were precultured for 48 h on solid MS medium containing 0.3 M of sucrose. Three PVS2 exposure times (30, 45 and 60 min) were tested. The results showed high post cryopreservation survival for all genotypes evaluated. The best PVS2 exposure time varied according to genotype, although 45 min gave the best survival for the majority of genotypes. The technique was highly efficient in cryopreserving meristem shoot tips of different pineapple genotypes, and was also less laborious than techniques previously reported. This is a first report on application of the droplet-vitrification technique to diverse genotypes of cultivated and wild pineapples and the first report on histological changes occurring in cryopreserved Ananas tissue.

     

<Emphasis Type="Italic">In Vitro</Emphasis> Preservation of Spanish Biodiversity

Spanish territories contain many of the hot spots of plant biodiversity among European countries. Most of the Spanish territory is found in the Mediterranean basin and in the Canary Islands, a region of great floral singularity and diversity (Macaronesian bioregion). Therefore, an important effort must be made to contribute to its conservation. Several strategies can be considered, but seed conservation under standard conditions is the most resource-efficient method. However, the application of this methodology is not always possible for recalcitrant seeds or species for which vegetative propagation is necessary or convenient under some circumstances. Micropropagation is one of the measures suggested for preserving endangered species. During the 1990s, several in vitro culture protocols for Spanish endemics were established. The main purpose of this strategy was to obtain a considerable number of individuals to reduce the loss of natural populations. Likewise, diverse slow growth protocols were developed for this material. However, these efforts usually did not lead to the establishment of in vitro collections. The advantages and disadvantages of the in vitro conservation strategy will be reviewed for some cases. The establishment of the in vitro protocols together with the development of cryopreservation techniques created the ideal conditions to generate cryogenic collections. In this paper, we review the knowledge and experience accumulated during the last decades in micropropagation, slow growth, and cryopreservation for Spanish plant wild species. Their application in the development ex situ collections and their contribution toward an integrated system to conserve threatened species will be discussed.     

Comparative analysis of genetic diversity in sacred lotus (<Emphasis Type="Italic">Nelumbo nucifera</Emphasis> Gaertn.) using AFLP and SSR markers

The sacred lotus (Nelumbo nucifera Gaertn.) is an aquatic plant of economic and ornamental importance in China. In this study, we developed twenty novel sacred lotus SSR markers, and used AFLP and SSR markers to investigate the genetic diversity and genetic relationships among 58 accessions of N. nucifera including 15 seed lotus, 12 rhizome lotus, 24 flower lotus and 7 wild lotus. Our results showed that sacred lotus exhibited a low level of genetic diversity, which may attribute to asexual reproduction and long-term artificial selection. A dendrogram based on both AFLP and SSR clustering data showed that: (1) the seed lotus accessions and rhizome lotus accessions were distinctly clustered into different groups, which indicated the significant genetic differentiation between them. This may be attributed to the two modes of reproduction and lack of genetic exchange; (2) the accessions of Thailand wild lotus were separated from other wild lotus accessions. This implied that the Thailand lotus might be genetically differentiated from other wild lotuses. In addition, Mantel test conducted gave highly significant correlation between AFLP-SSR data and each of the AFLP and SSR ones, with the values of r = 0.941 and r = 0.879, respectively, indicating the higher efficiency of the combination of these techniques (AFLP and SSR) in estimation and validation of the genetic diversity among the accession of sacred lotus. This knowledge of the genetic diversity and genetic relatedness of N. nucifera is potentially useful to improve the current strategies in breeding and germplasm conservation to enhance the ornamental and economic value of sacred lotus.     

Genetic differentiation between collections of hatchery and wild masu salmon (<Emphasis Type="Italic">Oncorhynchus masou</Emphasis>) inferred from mitochondrial and microsatellite DNA analyses

There has been very little effort to understand genetic divergence between wild and hatchery populations of masu salmon (Oncorhynchus masou). In this study, we used mitochondrial (mt) NADH dehydrogenase subunit 5 gene (ND5) and six polymorphic nuclear microsatellite DNA loci to compare the genetic variability in three hatchery broodstocks of masu salmon with the variability in eight putative wild masu populations sampled in five rivers including one known source river for the hatchery broodstocks. Both ND5 and microsatellites showed no significant genetic divergence (based on F_ST estimates) between four annual collections from the source river population, suggesting no change in genetic diversity over this time period. The F_ST estimates, an analysis of molecular variance (AMOVA), and a neighbor-joining tree using both DNA markers suggested significant differentiation between the three hatchery and all eight putative wild populations. We conclude that genetic diversity of hatchery populations are low relative to putative wild populations of masu salmon, and we discuss the implications for conservation and fisheries management in Hokkaido.     

Characterization of genetic diversity and population structure in wheat using array based SNP markers

Genetic diversity is crucial for successful adaptation and sustained improvement in crops. India is bestowed with diverse agro-climatic conditions which makes it rich in wheat germplasm adapted to various niches. Germplasm repository consists of local landraces, trait specific genetic stocks including introgressions from wild relatives, exotic collections, released varieties, and improved germplasm. Characterization of genetic diversity is done using morpho-physiological characters as well as by analyzing variations at DNA level. However, there are not many reports on array based high throughput SNP markers having characteristics of genome wide coverage employed in Indian spring wheat germplasm. Amongst wheat SNP arrays, 35K Axiom Wheat Breeder’s Array has the highest SNP polymorphism efficiency suitable for genetic mapping and genetic diversity characterization. Therefore, genotyping was done using 35K in 483 wheat genotypes resulting in 14,650 quality filtered SNPs, that were distributed across the B (~?50%), A (~?39%), and D (~?10%) genomes. The total genetic distance coverage was 4477.85 cM with 3.27 SNP/cM and 0.49 cM/SNP as average marker density and average inter-marker distance, respectively. The PIC ranged from 0.09 to 0.38 with an average of 0.29 across genomes. Population structure and Principal Coordinate Analysis resulted in two subpopulations (SP1 and SP2). The analysis of molecular variance revealed the genetic variation of 2% among and 98% within subpopulations indicating high gene flow between SP1 and SP2. The subpopulation SP2 showed high level of genetic diversity based on genetic diversity indices viz. Shannon’s information index (I)?=?0.648, expected heterozygosity (He)?=?0.456 and unbiased expected heterozygosity (uHe)?=?0.456. To the best of our knowledge, this study is the first to include the largest set of Indian wheat genotypes studied exclusively for genetic diversity. These findings may serve as a potential source for the identification of uncharacterized QTL/gene using genome wide association studies and marker assisted selection in wheat breeding programs.

     

Construction of nested genetic core collections to optimize the exploitation of natural diversity in <Emphasis Type="Italic">Vitis vinifera</Emphasis> L. subsp. <Emphasis Type="Italic">sativa</Emphasis>

Background  

The first high quality draft of the grape genome sequence has just been published. This is a critical step in accessing all the genes of this species and increases the chances of exploiting the natural genetic diversity through association genetics. However, our basic knowledge of the extent of allelic variation within the species is still not sufficient. Towards this goal, we constructed nested genetic core collections (G-cores) to capture the simple sequence repeat (SSR) diversity of the grape cultivated compartment (Vitis vinifera L. subsp. sativa) from the world's largest germplasm collection (Domaine de Vassal, INRA Hérault, France), containing 2262 unique genotypes.     

Geographical patterns of genetic variation in the world collections of wild annual Cicer characterized by amplified fragment length polymorphisms

Cicer reticulatum, C. echinospermum, C. bijugum, C. judaicum, C. pinnatifidum, C. cuneatum and C. yamashitae are wild annual Cicer species and potential donors of valuable traits to improve chickpea (C. arietinum). As part of a large project to characterize and evaluate wild annual Cicer collections held in the world gene banks, AFLP markers were used to study genetic variation in these species. The main aim of this study was to characterize geographical patterns of genetic variation in wild annual Cicer germplasm. Phylogenetic analysis of 146 wild annual Cicer accessions (including two accessions in the perennial C. anatolicum and six cultivars of chickpea) revealed four distinct groups corresponding well to primary, secondary and tertiary gene pools of chickpea. Some possible misidentified or mislabelled accessions were identified, and ILWC 242 is proposed as a hybrid between C. reticulatum and C. echinospermum. The extent of genetic diversity varied considerably and was unbalanced between species with greatest genetic diversity found in C. judaicum. For the first time geographic patterns of genetic variation in C. reticulatum, C. echinospermum, C. bijugum, C. judaicum and C. pinnatifidum were established using AFLP markers. Based on the current collections the maximum genetic diversity of C. reticulatum, C. echinospermum, C. bijugum and C. pinnatifidum was found in southeastern Turkey, while Palestine was the centre of maximum genetic variation for C. judaicum. This information provides a solid basis for the design of future collections and in situ conservation programs for wild annual Cicer.     

Microsatellite (SSR) markers reveal genetic identities, genetic diversity and relationships in a Malus×domestica borkh. core subset collection

 A collection of 66 Malus×domestica Borkh. accessions from the USDA-ARS Plant Genetic Resources Unit’s core collection was screened with a set of eight SSR (simple sequence repeat) primers developed at the PGRU in order to determine genetic identities, estimate genetic diversity, and to identify genetic relationships among these accessions. All eight primer pairs generated multiple fragments when used in amplification reactions with DNA from these accessions. High levels of variation were detected with a mean of 12.1 alleles per locus and a mean heterozygosity across all eight loci of 0.693. The eight primer pairs utilized in this study unambiguously differentiated all but seven pairs of accessions in this collection of 66 M.×domestica Borkh. genotypes. The probability of matching any two genotypes at all eight loci in this study was approximately 1 in 1 billion. The markers detected two misnamed accessions in the collection. Genetic-identity data produced a genetic-relatedness phenogram which was concordant with geographic origins and/or known pedigree information. These SSR markers show great promise as tools for managing Malus ex situ germplasm collections as well as for collection and preservation strategies concerning wild Malus populations in situ. Received: 28 March 1998 / Accepted: 29 April 1998     

Induction and cryopreservation of embryogenic cultures from nucelli and immature cotyledon cuts of mango (<Emphasis Type="Italic">Mangifera indica</Emphasis> L. <Emphasis Type="Italic">var Zihua</Emphasis>)

In this paper, we described the direct somatic embryogenesis from both immature cotyledon cuts and nucelli in the same mango cultivar (Mangifera indica L. var Zihua), studied the effect of growth conditions of embryogenic cultures (EMs) on cryopreservation and compared the cryopreservation response of EMs induced from these two different explants. Histological studies demonstrated that EMs derived from nucelli could be induced directly from epidermal cells of both sides of nucelli, whereas EMs derived from cotyledon cuts were induced only from epidermal cells of the adaxial side of the cotyledons. EMs from either nucelli or cotyledon cuts could be maintained in liquid medium or on solid medium and cryopreserved using a vitrification procedure. Success of cryopreservation of EMs depended on the dehydration treatment and the defined growth conditions during culture but not on their origins. When EMs were sampled during their exponential growth phase in liquid medium and dehydrated with PVS₃ solution for 5 min, survival of the EMs induced from cotyledon cuts and nucelli reached 77.7 and 80%, respectively, after cryopreservation in liquid nitrogen for 24 h. Furthermore, when dehydrated with PVS₃ solution for 30 min, all EMs induced from cotyledon cuts and 96.7% of EMs induced from nucelli could survive after cryopreservation. Cryopreservation did not affect the plant regeneration potential of EMs through somatic embryogenesis. The protocols of somatic embryogenesis and cryopreservation of mango EMs established in this study may offer potential ways to improve mango germplasm conservation and genetic improvement.     

Application of SSR and AFLP to the analysis of genetic diversity in <Emphasis Type="Italic">Gracilariopsis lemaneiformis</Emphasis> (Rhodophyta)

The agarophyte Gracilariopsis lemaneiformis is both important for biological research and of significant economic value. However, the genetic diversity of wild populations of the alga has not been studied. We used amplified fragment length polymorphism (AFLP) PCR and simple sequence repeat (SSR) analysis to investigate diversity in four field populations, three from the coast of Qingdao and one from Weihai, China. Forty G. lemaneiformis isolates collected from the four different geographical groups were analyzed using 16 pairs of SSR primers for PCR amplification. However, no polymorphisms were detected, indicative of a degree of genetic homogeneity. A total of 347 reproducible bands were then amplified using eight AFLP primer pairs, and genetic indices of diversity within and between populations were calculated. This analysis revealed only low levels of genetic diversity both within and between the four geographical groups of G. lemaneiformis. The Weihai population showed a higher within-population genetic diversity than any of the Qingdao populations. The data suggest that there is only limited gene flow between populations. An UPGMA dendrogram revealed two main clusters, and one of these included all the Qingdao isolates. The order of clustering was in accordance with their geographical distribution. These results suggest that the wild G. lemaneiformis populations are closely related and that there is little genetic diversity within wild germplasm in the regions sampled.     

Ex situ conservation of plant germplasm using biotechnology

Conservation of plant genetic resources attracts more and more public interest as the only way to guarantee adequate food supplies for future human generations. However, the conservation and subsequent use of such resources are complicated by cultural, economical, technical and political issues. Over the last 30 years, there have been significant increases in the number of plant collections and in accessions in ex situ storage centres throughout the World. The present review is of these ex situ collections and the contribution biotechnology has made and can make to conservation of plant germplasm. The applications and limitations of the new, molecular approaches to germplasm characterization are discussed. In vitro slow growth is used routinely for conserving germplasm of plants such as banana, plantain, cassava and potato. More recently, cryopreservation procedures have become more accessible for long-term storage. New cryopreservation techniques, such as encapsulation-dehydration, vitrification and desiccation, lengthen the list of plant species that can not only tolerate low temperatures but also give normal growth on recovery. Extensive research is still needed if these techniques are to be fully exploited.V.M. Villalobos is with the Food and Agriculture Organization of the United Nations, Viale delle Terme di Caracalia, 00100 Rome, Italy. F. Engelmann is with the International Plant Genetic Resources Institute (IPGRI), Via delle Sette Chiese 142, 00145 Rome, Italy.