RAPDs as an aid to evaluate the genetic integrity of somatic embryogenesis-derived populations of Picea mariana (Mill.) B.S.P

An assessment for in vitro propagation and genetic stability of Phoebe goalparensis Hutchinson, an endemic valuable timber tree of North East India

BACKGROUND

Phoebe goalparensis is an endemic forest species of North East India that belongs to Lauraceae family. P. goalparensis is used as timbers yielding plants for commercial importance in the local furniture markets of North East India. A rapid in vitro micropropagation protocol was established by using apical and axillary shoot tips on Murashige and Skoog medium with varied concentrations of plant growth regulators.

RESULTS

In this study, 5.0 mg/l BAP augmented medium was chosen as the best for shoot multiplication of the plant. However, IBA (2.0 mg/l) was the most responsive for root induction. Moreover, 70% of root induction was recorded during rooting experiment and 80-85% survivability was observed during the acclimatization of this species. Clonal fidelity of P. goalparensis was determined with ISSR marker and it was observed that in vitro raised plantlets were polymonomorphic.

CONCLUSION

Hence, an efficient protocol with high proliferation and rooting was established for P. Goalparensis that could aid in massive propagation in future.

Random Amplified Polymorphic DNA (RAPD) and Derived Techniques

Understanding biology and genetics at molecular level has become very important for dissection and manipulation of genome architecture for addressing evolutionary and taxonomic questions. Knowledge of genetic variation and genetic relationship among genotypes is an important consideration for classification, utilization of germplasm resources, and breeding. Molecular markers have contributed significantly in this respect and have been widely used in plant science in a number of ways, including genetic fingerprinting, diagnostics, identification of duplicates and selection of core collections, determination of genetic distances, genome analysis, development of molecular maps, and identification of markers associated with desirable breeding traits. The application of molecular markers largely depends on the type of markers employed, distribution of markers in the genome, type of loci they amplify, level of polymorphism, and reproducibility of products. Among many DNA markers available, random amplified polymorphic DNA (RAPD) is the simplest, is cost-effective, and can be performed in a moderate laboratory for most of its applications. In addition, RAPDs can touch much of the genome and has the advantage that no prior knowledge of the genome under research is necessary. The recent improvements in the RAPD technique like arbitrarily primed polymerase chain reaction (AP-PCR), sequence characterized amplified region (SCAR), DNA amplification fingerprinting (DAF), sequence-related amplified polymorphism (SRAP), cleaved amplified polymorphic sequences (CAPS), random amplified microsatellite polymorphism (RAMPO), and random amplified hybridization microsatellites (RAHM) can complement the shortcomings of RAPDs and have enhanced the utility of this simple technique for specific applications. Simple protocols for these techniques are presented along with the applications of RAPD in genetic diversity analysis, mapping, varietal identification, genetic fidelity testing, etc.

Development of a Traceability System Based on a SNP Array for Large-Scale Production of High-Value White Spruce (Picea glauca)

Biological material is at the forefront of research programs, as well as application fields such as breeding, aquaculture, and reforestation. While sophisticated techniques are used to produce this material, all too often, there is no strict monitoring during the "production" process to ensure that the specific varieties are the expected ones. Confidence rather than evidence is often applied when the time comes to start a new experiment or to deploy selected varieties in the field. During the last decade, genomics research has led to the development of important resources, which have created opportunities for easily developing tools to assess the conformity of the material along the production chains. In this study, we present a simple methodology that enables the development of a traceability system which, is in fact a by-product of previous genomic projects. The plant production system in white spruce (Picea glauca) is used to illustrate our purpose. In Quebec, one of the favored strategies to produce elite varieties is to use somatic embryogenesis (SE). In order to detect human errors both upstream and downstream of the white spruce production process, this project had two main objectives: (i) to develop methods that make it possible to trace the origin of plants produced, and (ii) to generate a unique genetic fingerprint that could be used to differentiate each embryogenic cell line and ensure its genetic monitoring. Such a system had to rely on a minimum number of low-cost DNA markers and be easy to use by non-specialists. An efficient marker selection process was operationalized by testing different classification methods on simulated datasets. These datasets were generated using in-house bioinformatics tools that simulated crosses involved in the breeding program for which genotypes from hundreds of SNP markers were already available. The rate of misidentification was estimated and various sources of mishandling or contamination were identified. The method can easily be applied to other production systems for which genomic resources are already available.

Micropropagation and Biomass Production of True-to-Type Stevia rebaudiana Bertoni

Here we describe an efficient micropropagation protocol for Stevia rebaudiana Bertoni. We present experiments carried out to optimize the suitable media for in vitro shoot multiplication and root induction and to study the effect of culture vessel on shoot multiplication. Among all different media tested for in vitro shoot multiplication, hormone-free liquid medium is most suitable. The highest number of nodes per shoot (5.4) and length of shoot (4.76 cm) at 4 weeks after subculturing are observed when single node explants are placed on modified MS medium supplemented with 1 % sucrose and 0.7 % agar. The highest response of multiplication rate (9.56) is observed on half strength of macroelement of MS with full strength of microelement of MS and 170 mg/l KH2PO4, and 185 mg/l MgSO4 in plastic growth container. Further, RAPD marker analysis of in vitro-raised plants maintained their clonal fidelity and true-to-type without showing any somaclonal variation.

Randomly amplified polymorphic DNA (RAPD) and derived techniques

Understanding biology and genetics at molecular level has become very important for dissection and manipulation of genome architecture for addressing evolutionary and taxonomic questions. Knowledge of genetic variation and genetic relationship among genotypes is an important consideration for classification, utilization of germplasm resources, and breeding. Molecular markers have contributed significantly in this respect and have been widely used in plant science in a number of ways, including genetic fingerprinting, diagnostics, identification of duplicates and selecting core collections, determination of genetic distances, genome analysis, developing molecular maps, and identification of markers associated with desirable breeding traits. The application of molecular markers largely depends on the type of markers employed, distribution of markers in the genome, type of loci they amplify, level of polymorphism, and reproducibility of products. Among many DNA markers available, random amplified polymorphic DNA (RAPD) is the simplest and cost-effective and can be performed in a moderate laboratory for most of its applications. In addition RAPDs can touch much of the genome and has the advantage that no prior knowledge of the genome under research is necessary. The recent improvements in the RAPD technique like AP-PCR, SCAR, DAF, SRAP, CAPS, RAMPO, and RAHM can complement the shortcomings of RAPDs and have enhanced the utility of this simple technique for specific applications. Simple protocols for these techniques are presented.

In vitro plant propagation of Catharanthus roseus and assessment of genetic fidelity of micropropagated plants by RAPD marker assay

An investigation was carried out to develop an efficient micropropagation protocol for Catharanthus roseus. Experiments were conducted to optimize suitable media for in vitro shoot multiplication and root induction. Out of the different media compared for in vitro shoot multiplication, Murashige and Skoog (MS) medium supplemented with 1 mg/l of 6-benzylaminopurine and 0.2 mg/l α-naphthaleneacetic acid showed better response in terms of the emergence of shoots from axillary buds as well as proliferation and multiplication of shoots. The shoots when placed on half strength of MS medium having 1 mg/l indole 3-butyric acid and 0.25 % charcoal showed cent percent root induction with maximum number of roots per shoot (4.2) as well as maximum root length (1.72 cm). Further, clonal fidelity of the in vitro-raised plants was carried out using randomly amplified polymorphic DNA marker and results indicated that all the tissue culture-derived plants are true-to-type and there were no somaclonal variations among these plants.

Regeneration and assessment of genetic fidelity of the endangered tree Moringa peregrina (Forsk.) Fiori using Inter Simple Sequence Repeat (ISSR)

Moringa peregrinais an endangered species of Moringaceae.M. peregrinais a multipurpose tree with a wide variety of potential uses including its medicinal activity. In our study, a rapid and efficient micropropagation protocol for M. peregrina has been established. In vitro germinated seedlings were cultured on Murashige and Skoog (MS) medium supplemented with different levels of either 6-benzyladenine (BA) or kinetin (Kin). The maximum shoot proliferation of 6.5 shoots per explant with 100 % shoot proliferation rate was observed on MS medium supplemented with 1.0 mg/l BA. On the other hand, MS medium supplemented with 1 mg/l indole-3-butyric acid (IBA) resulted in the maximum number of roots. Micropropagated plants were successfully acclimatized. Genetic stability of micropropagated plants was assessed using Inter-Simple Sequence Repeat (ISSR). The amplification products were monomorphic in all in vitro grown plants. No polymorphism was detected indicating the genetic integrity of in vitro propagated plants. This micropropagation protocol could be useful for raising genetically uniform plants for plant propagation and commercial cultivation.

Plastid DNA variation in highly fragmented populations of Microbiota decussata Kom. (Cupressaceae), an endemic to Sikhote Alin Mountains

Microbiota decussata Kom. (Cupressaceae) is a subalpine species endemic to the Sikhote Alin Mountains with populations scattered throughout the range. We used sequence data for four noncoding regions of chloroplast DNA to characterize the genetic diversity in populations sampled from different parts of M. decussata natural range. No variation was observed in the trnT-trnF region, whereas the trnH-psbA, trnS-trnfM, and trnS-trnG regions showed polymorphisms. At the species level, we found a low nucleotide diversity (pi = 0.0009) and high haplotype diversity (h = 0.981) as well as high differentiation (Phi(ST) = 0.420). N(ST) and G(ST) values suggested the existence of a phylogeographic structure in M. decussata. The observed patterns of diversity could be explained in part by ecological features of the species and its long-term persistence throughout the range with population expansion, successive fragmentation and isolation.

Analysis of genetic stability at SSR loci during somatic embryogenesis in maritime pine (Pinus pinaster)

Somatic embryogenesis (SE) is a propagation tool of particular interest for accelerating the deployment of new high-performance planting stock in multivarietal forestry. However, genetic conformity in in vitro propagated plants should be assessed as early as possible, especially in long-living trees such as conifers. The main objective of this work was to study such conformity based on genetic stability at simple sequence repeat (SSR) loci during somatic embryogenesis in maritime pine (Pinus pinaster Ait.). Embryogenic cell lines (ECLs) subjected to tissue proliferation during 6, 14 or 22 months, as well as emblings regenerated from several ECLs, were analyzed. Genetic variation at seven SSR loci was detected in ECLs under proliferation conditions for all time points, and in 5 out of 52 emblings recovered from somatic embryos. Three of these five emblings showed an abnormal phenotype consisting mainly of plagiotropism and loss of apical dominance. Despite the variation found in somatic embryogenesis-derived plant material, no correlation was established between genetic stability at the analyzed loci and abnormal embling phenotype, present in 64% of the emblings. The use of microsatellites in this work was efficient for monitoring mutation events during the somatic embryogenesis in P. pinaster. These molecular markers should be useful in the implementation of new breeding and deployment strategies for improved trees using SE.

Detection of somaclonal variation of cotton (Gossypium hirsutum) using cytogenetics, flow cytometry and molecular markers

Two protocols of plant regeneration for cotton were adopted in this study, namely, 2, 4-D and kinetin hormone combination and IBA and kinetin hormone combination. Twenty-eight embryogenic cell lines via somatic embryogenesis and 67 regenerated plants from these embryogenic calli were selected and used for random amplified polymorphic DNA (RAPD), simple sequence repeat (SSR), chromosomal number counting, and flow cytometric analysis. The roles of RAPD and SSR markers in detecting somaclonal variation of cotton (Gossypium hirsutum L.) were evaluated. Two cluster analyses were performed to express, in the form of dendrograms, the relationships among the hormone combinations and the genetic variability. Both DNA-based techniques were able to amplify all of the cell clones and regenerated plantlets genomes and relative higher genetic variation could be detected in the culture type with 2, 4-D and kinetin hormone combination. The result suggested that 2, 4-D and kinetin hormone combination could induce relative high somaclonal variation and RAPD and SSR markers are useful in detecting somaclonal variation of regenerated cotton plants via somatic embryogenesis. Chromosome number counting and flow cytometry analysis revealed that the number of chromosomes and ploidy levels were nearly stable in all regenerated plants except two regenerated plantlets (lost 4 and 5 chromosomes, respectively) which meant that cytological changes were not correlated with the frequency of RAPD and SSR polymorphisms. This result also might mean that the cell lines with variation of chromosome numbers were difficult to regenerate plants.

Radiation induced alterations in Vigna radiata during in vitro somatic embryogenesis

PURPOSE

Tissue culture has been exploited to understand molecular aspects of regeneration potential of the plants in normal and in stressed conditions. The present study describes ionizing radiation from (60)Co source as the stress stimulator to assess in vitro development of somatic embryo of Vigna radiata, a protein-rich pulse.

MATERIALS AND METHODS

Callus culture was established, using leaves of V. radiata. Somatic embryogenesis was induced by manipulating plant hormones. Calli were exposed to gamma rays. Genomic DNA isolated from gamma-irradiated callus samples were subjected to random amplified polymorphic DNA analysis. A band of molecular weight 1440 bp was used as a probe and Southern hybridization was carried out. To determine alterations in DNA following irradiation, RAPD bands were cloned and sequenced from control and irradiated samples. Embryogenic calli were exposed to gamma irradiation and the effects were assessed immediately and after seven days of exposure. Phenotypic alterations were observed using scanning electron microscopy.

RESULTS

Exposed calli revealed altered frequency of somatic embryo formation. Results showed that the 1440 bp molecular weight probe hybridized with bands of low molecular weight. DNA sequences from irradiated samples showed recombination when compared to control. Scanning electron micrography illustrated presence of transient pores on the exposed embryos. BLAST search of the DNA sequences showed partial homology with some sequences from Arabidopsis thaliana.

CONCLUSION

The present report might help in designing a breeding program, where both radiation coupled with somatic embryogenesis could be employed to build up the desired variants.

In vitro regeneration of wild pear (Pyrus pyraster Burgsd) clones tolerant to Fe-chlorosis and somaclonal variation analysis by RAPD markers

An in vitro adventitious regeneration system under selective pressure was established in Pyrus pyraster Burgsd to obtain somaclones with higher adaptability to calcareous soils. P. pyraster is important species, both for its relative closeness to cultivated pear and for reforestation of marginal farmland and for the production of timber. Shoot regeneration was induced from leaves and vegetative apices of in vitro-grown shoots on a modified LP medium supplemented with naphtaleneacetic acid (1.07 microM) and benziladenine (BA, 8.9 microM). After 30 days, explants were transferred to an expression medium consisting of the same basal medium with only BA present. Selective treatments utilized MS medium with Fe-EDTA replaced by equimolar amount of FeSO4 with either KHCO(3) or NaHCO(3). Through the selection process 11 putatively tolerant lines were obtained from vegetative shoot apices. RAPD analysis was performed on these lines to allow comparison to the mother clone. A total of seven 10-mer primers were used to amplify all the genotypes and 74 scorable fragments were produced. These were analysed using the Dice similarity index, showing genetic variability among the 11 regenerated clones and between them and the mother clone.

Rapid plant regeneration and analysis of genetic fidelity of in vitro derived plants of Chlorophytum arundinaceum Baker--an endangered medicinal herb

An efficient in vitro multiplication system via multiple shoot bud induction and regeneration has been developed in Chlorophytum arundinaceum using shoot crown explants. Optimum regeneration frequency (87%) and desirable organogenetic response in the form of de novo organized multiple shoot buds without an intervening callus phase was obtained on Murashige and Skoog's (MS) minimal organics medium containing 3% sucrose (w/v) supplemented with 4 x 10(-6) M Kn and 2 x 10(-6) MIBA. Axenic secondary explants with multiple shoot buds on subculturing elicited best response with 1 x 10(-5) M Kinetin (Kn) and 5 x 10(-6) M indole-3-butyric acid (IBA) giving rise to an average of 18.74 shoots per culture with mean shoot length of 7.6 cm +/- 1.73. Varying molar ratios of either Kn/IBA or Kn/NAA revealed statistically significant differences in the regeneration frequencies among the phytohormone treatments. It was observed that the shoot bud differentiation and regeneration was influenced by the molar ratios of cytokinins/auxin rather than their relative concentrations. Healthy regenerated shoots were rooted in half strength MS basal medium containing 3% sucrose (w/v) supplemented with 5 x 10(-6) M IBA. Following simple hardening procedures, rooted plantlets, were transferred to soil-sand (1:1; v/v) with more than 90% success. Genetic fidelity was assessed using random amplified polymorphic DNA (RAPD), karyotype analysis and meiotic behaviour of in vitro and in vivo plants. Five arbitrary decamers displayed same banding profile within all the micropropagated plants and in vivo explant donor. The cytological and molecular analysis complemented and compared well and showed no genomic alterations in the plants regenerated through shoot bud differentiation. High multiplication frequency, molecular, cytological and phenotypic stability ensures the efficacy of the protocol developed for the production and conservation of this important endangered medicinal herb.

Efficient callus induction and plant regeneration from anther of Chinese narcissus (Narcissus tazetta L. var. chinensis Roem)

Callus culture has, to date, been reported only in a few species of Narcissus. We used anthers of Chinese narcissus (Narcissus tazetta L. var. chinensis Roem) as explants for callus induction and plant regeneration. A high percentage of anthers at the early- to mid-uninucleate microspore stage were responsive on the basal MS medium supplemented with 0.5-1 mg l(-1) 2,4-dichlorophenoxyacetic acid and 0.5-2 mg l(-1) 6-benzyladenine under dark conditions. Calli were initiated from anther connective tissue or anther wall tissue, and no division of microspores occurred during callus formation, as determined by histological observation. Using 20 random amplified polymorphic DNA primers, we verified the genetic integrity of the anther-derived plants of Chinese narcissus with respect to the donor plants. These results suggest that anther culture in vitro can provide an efficient new micropropagation technique for Chinese narcissus as well as a new strategy for in vitro mass propagation of other daffodils.

Genetic stability of micropropagated almond plantlets, as assessed by RAPD and ISSR markers

Almond shoots produced by axillary branching from clone VII derived from a seedling of cultivar Boa Casta were evaluated for somaclonal variation using randomly amplified polymorphic DNA (RAPD) and inter-simple sequence repeats (ISSR) analysis. To verify genetic stability we compared RAPD and ISSR patterns of plantlets obtained after 4 and 6 years of in vitro multiplication. A total of 64 RAPD and 10 ISSR primers gave 326 distinct and reproducible band classes, monomorphic across all 22 plantlets analysed. Thus, a total of 7,172 bands were generated, exhibiting homogeneous RAPD and ISSR patterns for the plantlets tested. These results suggest that the culture conditions used for axillary branching proliferation are appropriate for clonal propagation of almond clone VII, as they do not seem to interfere with the integrity of the regenerated plantlets. These results allowed us to establish the use of axillary branching plantlets (mother-plants) as internal controls for the analysis of somaclonal variation of shoots regenerated from other in vitro culture processes performed with clone VII (adventitious regeneration, regeneration from meristem culture, virus sanitation programs and genetic engineering).

Induction of tolerance to fast desiccation in black spruce (Picea mariana) somatic embryos: relationship between partial water loss, sugars, and dehydrins

Events associated with the induction of tolerance to fast desiccation in black spruce (Picea mariana) somatic embryos were investigated. An experimental approach using an initial period of partial water loss was developed to induce either no, partial, or complete tolerance to fast desiccation. Tolerance to subsequent fast desiccation was not promoted by decreasing embryo water content from 1.5 to 1.1 g H2O g-1 DW (g g-1) throughout the first 24 h of slow desiccation. However, tolerance increased from 10 to 95% germination during the second 24-h period of slow desiccation after partial water loss from 1 to 0.55 g g-1. Emphasis was also placed on the relationship between observed tolerance, and sugar and dehydrin contents. Compared to controls, sucrose content in embryos doubled after 24 h of slow desiccation and more than tripled after 48 h. Conversely, starch content was decreased by one half after 24 h and by three quarters after 48 h. Sucrose abundance and raffinose occurrence after 48 h of slow desiccation were congruent with complete tolerance to fast desiccation. The period of slow desiccation between 24 and 48 h also increased the content of a 24-kDa dehydrin and the appearance of a 42-kDa dehydrin. The relationship between partial water loss, sugars and dehydrins is discussed with respect to tolerance to fast desiccation in black spruce somatic embryos.

RAPD analysis of somaclonal variants derived from embryo callus cultures of peach

Peach [Prunus persica (L.) Batsch] regenerants from cv 'Sunhigh' embryo no. 156, regenerants obtained from cv 'Redhaven' embryo no. 30, and two peach cultivars 'Sunhigh' and 'Redhaven', were screened for polymorphic RAPD (Random Amplified Polymorphic DNA) markers with up to 60 10-mer primers. Although 35 primers produced results with scoreable bands, only 10 of the primers revealed polymorphism for regenerants of embryo no. 156 and cv 'Sunhigh', and 1 revealed a low level of polymorphism for regenerants of embryo no. 30 and cv 'Redhaven'. This study demonstrates the feasibility of using RAPD markers to identify somaclonal variants of peach and provides evidence for the existence of genetic differences among these variants.

RAPD polymorphisms among variant and phenotypically normal rice (Oryza sativa var.indica) somaclonal progenies

RAPD analysis was performed among eight rice somaclonal families known to vary for specific characters and four somaclonal families which were phenotypically normal. The parental cultivar,indica rice cv. FR13A, was found to be homogeneous and homozygous at all but one of the 45 RAPD loci. Polymorphisms were found at 28 of the 45 bands among the somaclonal families, including both loss of parental bands, and the appearance of novel non-parental bands. Segregation data revealed both heterozygous and homozygous mutation events, with recessive mutations more prevalent than dominant. All somaclonal families differed significantly from the parental material, indicating that genomic alterations occurred in all families regardless of phenotype. None of the variant families could be regarded as isogenic lines of FR13A at the DNA level. However, some of the DNA level variation may be in highly repeated sequences with no phenotypic effects. The implications for somaclonal breeding and genetic engineering programs are discussed.

Genome flux in tomato cell clones cultured in vitro in different physiological equilibria. II. A RAPD analysis of variability

An analysis of the effect of changing physiological conditions on genome evolution in tomato cell populations has been carried out on long-term in vitro cultured clones grown on different auxin–cytokinin equilibria or selected for low–high competence for active defense against Fusarium oxysporum f.sp. lycopersici. RAPD analysis, confirmed through pattern rehybridization, was used as a random tool to measure the genetic variability. Through the use of a modified ANOVA, variation was shown to depend on both the initial genotype and the physiological conditions. Pattern correlation analysis through a mutual information algorithm suggested the fixation of RAPD patterns specific to physiological equilibria. The results are discussed in view of the possible relevance for evolution at hierarchical levels higher than cell populations. Key words : tomato clones, somaclonal variation, RAPD, coadaptation.

Analysis of genetic diversity in a sweetpotato (Ipomoea batatas) germplasm collection using DNA amplification fingerprinting

A DNA amplification fingerprinting (DAF) approach was employed to develop individual-specific profiles and analyze genetic relationships among 73 plant introductions of sweetpotato (Ipomoea batatas (L.) Lam.) including unadapted lines from around the world and a few selected U.S.A. cultivars. Reliable and informative fingerprint profiles were obtained employing single octamer primers and Stoffel fragment Taq polymerase in the polymerase chain reaction, polyacrylamide-based vinyl polymer for electrophoresis, and silver staining to visualize the DNA. Using seven highly informative octamer primers, individual-specific DAF profiles were obtained for all accessions tested. The degree of polymorphism in the sweetpotato collection was very large, indicating a high level of genetic variability. Several accessions clustered together based on their geographic source. Most U.S.A. cultivars formed a separate cluster in the phenogram, while accessions from Papua New Guinea exhibited the highest genetic diversity. The wild species I. triloba and tetraploid I. batatas formed a group distinct from the cultivated sweetpotato. DAF appears to be useful in sweetpotato germplasm characterization and may be employed to identify duplicate accessions or for creation of core subsets. DAF data may also be useful for facilitating the selection of parents for a breeding program to ensure a broad genetic base.

Identification of chrysanthemum cultivars and stability of DNA fingerprint patterns

Several techniques of DNA analysis were applied to identify chrysanthemum cultivars. Unrelated cultivars could be distinguished by using RAPDs (random amplified polymorphic DNAs), inter-SSR (simple sequence repeat) PCR (polymerase chain reaction), hybridization-based DNA fingerprinting, as well as RFLPs (restriction fragment length polymorphisms). Cultivars with different flower colours and belonging to one family, i.e. vegetatively derived from 1 cultivar, appeared to have the same DNA fragment patterns, whichever technique was applied. The absence of polymorphisms between different accessions of the same cultivar indicated a high stability of the observed patterns.

Species-specific RAPD fingerprints for the closely related Picea mariana and P. rubens

Species-specific molecular markers were designed to assist in the identification of closely related black spruce (Picea mariana [B.S.P.] Mill.) and red spruce (P. rubens Sarg.) in northeastern North America. Trees from six provenances of black spruce and three provenances of red spruce were sampled from outside the sympatric zone. They were first classified using a composite index of five qualitative morphological traits. The species-specific genetic markers were developed using random amplified polymorphic DNAs (RAPD) and a combination of bulk sample and individual tree analyses. Each species bulk sample was constructed from DNAs obtained from 12 trees that were from outside the sympatric zone and showed a morphological composite index specific of each species. A total of 161 primers were screened with the bulk samples. From these, 52 primers showing segregating fingerprints were further screened with the individual trees. Most of the markers observed were shared by the two species, and there was less diversity in P. rubens. A small number of markers were found to be monomorphic or nearly monomorphic and specific to either P. mariana or P. rubens. These markers remained species-specific when F1 progenies derived from independent intraspecific crosses were screened, and they were subsequently found to co-segregate in hybrids derived from independent interspecific crosses here used as controls.

MAAP: a versatile and universal tool for genome analysis

Multiple arbitrary amplicon profiling (MAAP) uses one or more oligonucleotide primers (> or = 5 nt) of arbitrary sequence to initiate DNA amplification and generate characteristic fingerprints from anonymous genomes or DNA templates. MAAP markers can be used in general fingerprinting as well as in mapping applications, either directly or as sequence-characterized amplified regions (SCARs). MAAP profiles can be tailored in the number of monomorphic and/or polymorphic products. For example, multiple endonuclease digestion of template DNA or the use of mini-hairpin primers can enhance detection of polymorphic DNA. Comparison of the expected and actual number of amplification products produced with primers differing in length, sequence and GC content from templates of varying complexity reveal severe departures from theoretical formulations with interesting implications in primer-template interaction. Extensive primer-template mismatching can occur when using templates of low complexity or long primers. Primer annealing and extension appears directed by an 8 nt 3'-terminal primer domain, requires sites with perfect homology to the first 5-6 nt fom the 3' terminus, and involves direct physical interaction between amplicon annealing sites.

A genetic linkage map of Picea abies Karst., based on RAPD markers, as a tool in population genetics

Norway spruce (Picea abies Karst.) is a most important species among European forest trees for both economical and ecological reasons. However, this species has suffered from a lack of information on the genetic side due to the scarcity of linkage data. In this study we have used a population of 72 megagametophytes from a single tree in a natural Italian stand to produce a genetic linkage map by means of RAPD markers. Ninety-six random decamers used as primers yielded 185 polymorphic loci showing Mendelian inheritance. Analysis of the segregation by multipoint analysis allowed us to define 17 major linkage groups covering a total distance of 3584 cM, with an average spacing between markers of 22 cM. Possible uses of a genetic linkage map with respect to population ecology and genetics are discussed.