Paternal Trees Research Articles

Pollination success of Fraxinus excelsior L. in the context of ash dieback

Key messagePaternity analyses show that effective pollination of ash (Fraxinus excelsior L.) in a seed orchard and a floodplain forest affected by ash dieback is more likely to be facilitated by healthier males. Thereby, natural selection can have a positive effect on the health of future generations.ContextOngoing ash dieback and increasing fragmentation of ash populations may result in reduced pollen flow, which can reduce pollination success of future generations of ash trees. Therefore, it is essential to further improve our understanding of gene flow patterns, especially with respect to ash dieback.AimsIn this study, paternity analyses were conducted in a seed orchard and a floodplain forest in Germany in 2018 to explain the relationship between pollination success and the health status of ash trees and distances of effective pollen transport.MethodsCambium samples (i.e., from twigs and stumps) were collected from 251 ash trees (putative father and mother trees) for genotyping, and the health status of each tree was documented using a scoring system to evaluate vitality. Additionally, seeds were harvested from 12 mother trees per site. Genetic analyses using nuclear microsatellites were performed to determine paternal trees. Paternities were assigned based on the likelihood model implemented in the Cervus 3.0.7 software.ResultsOur results showed that the average pollination distance was 76 m in the seed orchard and 166 m in the floodplain forest. In general, pollination success decreased substantially with increasing distance to the mother tree. Despite the dense tree cover in the floodplain forest, pollen were transported over long distances (greater than 550 m), suggesting that non-local sources also play a role in pollination. This is supported by the foreign pollen input identified in the seed orchard (66.5%). Self-pollination was detected only to a very small extent, and thus had no major influence on reproduction. In addition, both healthy and slightly diseased father trees showed similar mating success. However, this was not the case for the severely diseased ash trees (more than 50% of crown damage) because only a few offspring could be assigned to them. Nevertheless, in contrast to the floodplain forest, there was no significant correlation between damage classes and pollination success in the seed orchard.ConclusionLong-distance pollen transport contributes to the connectivity of ash trees in the landscape. Additionally, both healthy and slightly diseased fathers have a greater contribution to pollination, thus potentially improving the health of the next generation of ash trees. Moreover, gene flow between stepping stone populations is necessary to ensure the positive impact on the genetic diversity of ash populations in the future.

Crossability of Putative Hybrids of <i>Pinus sylvestris</i> and <i>Pinus mugo</i> with Their Parents

Artificial hybridization experiment with the Pinus sylvestris and Pinus mugo putative hybrid individuals and their parents revealed a selective nature of their crossability conditioned by the identical chloroplast DNA (cpDNA) haplotypes of the crossed individuals. Efficiency of hybridization between hybrid individual H1 of P. sylvestris haplotype and P. sylvestris paternal tree was relatively high, as evidenced by 78.03% of filled seeds. On the contrary, the crossing of H1 individual with P. mugo was unsuccessful. Likewise, the crossability of the H2 individual of P. mugo haplotype with the paternal tree P. mugo resulted in 31.15% of filled seeds. A relatively high crossability was characteristic also for the H1 and H2 hybrid trees of different cpDNA haplotypes. A conclusion has been drawn postulating weakened reproduction barrier between hybrid swarm individuals and the paternal species P. sylvestris and P. mugo. Differentiation of the putatively hybrid individuals from the parental species is accompanied by the variation in cpDNA inheritance.

Characterizing offspring of Dutch elm disease-resistant trees (Ulmus minor Mill.)

Abstract Populations of Ulmus minor in Europe were severely damaged by Dutch elm disease (DED) pandemics. However, elm breeding programmes have permitted selection of resistant elm varieties currently used for reforestation. In restored elm forests, resistant (R) and susceptible (S) trees interbreed, but little is known about resistance in their offspring. In this work, growth, DED resistance and xylem anatomy in the offspring of two resistant U. minor trees (R1 and R2) were studied. To verify whether transmission of traits in offspring is determined by maternal or paternal trees, a complete randomized plot was established with clonal material from controlled crosses (R1 × S and R2 × S) and parent trees (R1, R2 and S). Trees were inoculated with O. novo-ulmi firstly at age 4 years and again at 5 years. Growth, susceptibility to DED and vessel size in offspring were closer to the traits of maternal than of paternal trees. This association disappeared after the second inoculation when symptoms increased. The more resistant trees in R1 × S and R2 × S had wide and narrow earlywood vessels, respectively, suggesting that water-conducting strategies and resistance mechanisms vary in offspring. Tylosis formation was related to resistance only in R2 × S offspring, possibly due to the narrow earlywood vessles of trees. Latewood vessels were normally narrower in the more resistant trees. This study sheds light on anatomical resistance mechanisms of elms against DED: (1) offspring exhibit high variability in responses among individuals, (2) narrow earlywood vessels are not a prerequisite for DED resistance and (3) barrier zones are not fully associated with tree resistance in offspring.

Seleksi Pendonor Serbuk Sari Sifat Kuantitas Endosperma Skor Tinggi pada Kelapa dalam Kopyor

Endosperm quantity in kopyor coconut determines the quality of kopyor coconut. However, data of the best parental based on their progeny test is unavailable yet. In this study, we employed polycross approach and SSR molecular marker to estimate general combining ability of the best pollen contributor for the breeding purpose of this trait. Totally 151 kopyor coconuts were collected from the naturally open-pollinated population of kopyor Tall coconut Agom Lampung. The harvested nuts were rated for their endosperm quantity (scored 1-9). The analysis identified 31 paternal trees of the 53 progenies. The TJ-185 with the highest GCA has been considered as a promising paternal tree for development of high endosperm quantity of kopyor coconut.Keywords: combining ability, molecular marker, paternal trees, polycross, tall coconut

Screening for resistance of progenies derived from Castanea sativa × C. crenata and C. crenata to Cryphonectria parasitica

SummaryThe possibility of screening young seedlings of Castanea for chestnut blight resistance was examined to try to shorten time needed for a breeding programme. Two‐year‐old chestnut seedlings of eight progenies, derived from open and controlled pollination of three hybrids (Castanea sativa × C. crenata and a C. crenata tree by paternal tree of C. sativa) were screened for resistance to chestnut blight. One hybrid and a C. crenata were partially susceptible, and two hybrids were partially resistant to chestnut blight. A total of 179 seedlings were inoculated with two virulent and one hypovirulent strain of Cryphonectria parasitica at two dates (early June and early September). Stromata production was higher and canker size larger when seedlings were inoculated in early June. Differences in canker size among seedlings derived from different parental trees were observed only after September inoculation. However, differences in canker size among seedlings inoculated with the virulent strains were observed only after June inoculation. The only significant effect on seedling survival was based on fungal strains used for inoculation. Ratio of seedlings, which died after inoculation with the hypovirulent strain, was significantly lower (36.8%) than those that died after inoculation with virulent strains (88.4 and 95.1%). Survival of seedlings was affected only by fungal strains used in inoculation, and not influenced by parental trees. The risk of seedling dieback increased with increasing canker size and with decreasing stem diameter of seedlings.

Pollen mediated gene flow in a small experimental population of Moringa oleifera Lam. (Moringaceae)

Large-scale plantations of Moringa oleifera Lam. are carrying out in the dry-hot valley of Red River in Yunnan Province to make it the core cultivation area in China. Nevertheless, there is a deficient understanding of detailed pollen flow patterns, which leads to uncertainty in designing and managing seed orchards of M. oleifera to fit the breeding demand. In order to facilitate the design of breeding strategies for inbreeding lines, paternity analysis by SSR (Simple Sequence Repeat) was used to estimate the outcrossing rate and pollen mediated gene flow of M. oleifera. The analysis was carried out in an experimental population domesticated in the dry-hot valley area of Red River with two germplasms (India and Myanmar) of 60 trees, including 12 maternal trees and 60 pollen donors (bisexual flowers, maternal trees were also possible paternal trees in case of selfing). One hundred fifteen seeds out of 288 were confirmed pollen donors by 8 microsatellite loci at 95% strict confidence level. The multilocus outcrossing rate is tm = 0.797 ± 0.096, and single-locus outcrossing rate is ts = 0.742 ± 0.058. Pollen dispersal distance varied from 0 m (self-pollination) to 24.7 m, with an average of 11.9 m, and 95% of effective pollen was dispersed within 20 m, indicating that the effective pollen mediated gene flow is restricted to a limited distance. 50.3% of effective pollen was donated by 9 trees. Moreover, there was no apparent correlation between pollen dispersal distance and pollen contribution rate, as well as between germplasm and reproducibility. The maximum pollen dispersal distance between two trees estimated in this experimental stand is highly localized at current 3 × 3 m planting density, indicating that M. oleifera seed orchards and clones could be planted nearer to each other than previously thought (as far as kilometers).

Aspen hybridization: Parents’ compatibility and seedlings’ growth

Abstract First results of new trembling aspen (Populus tremula L.) special factorial crosses are presented. At first, productive parent trees were selected: five maternal and five paternal trees without symptoms of heart rot and one tree with fruiting bodies of this fungal attack. The results of phenotypic and genotypic analyses of parent trees, their compatibility, and growth performance are presented. The analysis of the hybrid seedlings’ survival and their growth performance on open ground are shown. Estimates of general and specific combining abilities of the parent trees were carried out and potentially best hybrid families and seedlings were selected.

Breeding system and spatial isolation from congeners strongly constrain seed set in an insect-pollinated apomictic tree: Sorbus subcuneata (Rosaceae)

In plants, apomixis results in the production of clonal offspring via seed and can provide reproductive assurance for isolated individuals. However, many apomicts require pollination to develop functional endosperm for successful seed set (pseudogamy) and therefore risk pollination-limitation, particularly in self-incompatible species that require heterospecific pollen. We used microsatellite paternity analysis and hand pollinations to investigate pollen-limitation in Sorbus subcuneata, a threatened endemic tree that co-occurs with its congener, S. admonitor. We confirmed that S. subcuneata is an obligate pseudogamous apomict, but open-pollinated flowers rarely produced seed (flower-to-seed conversion < 1%) even though they rapidly accumulated pollen on their stigmas. Manual heterospecific pollination by S. admonitor resulted in a high flower-to-seed conversion rate (65%), however, we estimate that the ratio of self: heterospecific pollination in open-pollinated flowers was at least 22:1. Despite the efficacy of heterospecific pollination, the contribution of S. admonitor trees to paternity in seed from open-pollinated flowers of S. subcuneata decreased rapidly with the spatial separation between paternal and maternal trees. Conservation efforts aimed at maintaining species with this breeding system must therefore manage the congeners in tandem which will also maintain the potential for rare heterospecific fertilisation that typically cause rapid diversification in these lineages.

What is long‐distance dispersal? And a taxonomy of dispersal events

Summary Dispersal is a key individual‐based process influencing many life‐history attributes and scaling up to population‐level properties (e.g. metapopulation connectivity). A persistent challenge in dispersal ecology has been the robust characterization of dispersal functions (kernels), a fundamental tool to predict how dispersal processes respond under global change scenarios. Particularly, the rightmost tail of these functions, that is the long‐distance dispersal (LDD) events, are difficult to characterize empirically and to model in realistic ways. But, when is it a LDD event? In the specific case of plants, dispersal has three basic components: (i) a distinct (sessile) source, the maternal plant producing the fruits or the paternal tree acting as a source of pollen; (ii) a distance component between source and target locations; and (iii) a vector actually performing the movement entailing the dispersal event. Here, I discuss operative definitions of LDD based on their intrinsic properties: (i) events crossing geographic boundaries among stands; and (ii) events contributing to effective gene flow and propagule migration. Strict‐sense long‐distance dispersal involves movement both outside the stand geographic limits and outside the genetic neighbourhood area of individuals. Combinations of propagule movements within/outside these two spatial reference frames result in four distinct modes of LDD. Synthesis. I expect truncation of seed dispersal kernels to have multiple consequences on demography and genetics, following to the loss of key dispersal services in natural populations. Irrespective of neighbourhood sizes, loss of LDD events may result in more structured and less cohesive genetic pools, with increased isolation by distance extending over broader areas. Proper characterization of the LDD events helps to assess, for example, how the ongoing defaunation of large‐bodied frugivores pervasively entails the loss of crucial LDD functions.

Parent Identification in a Multi Location Trial Seed Orchard of Acacia Mangium Using Microsatellite Markers

Variation of parent gametes' contribution might affect the growth patterns among offspring produced from seed orchards. This paper studies the mating system statuses and to identify parent trees that produce good growth performance of offspring in seedling seed orchard of A. mangium . The study was conducted in two seed orchards, i.e. a first generation seedling seed orchard (F1 SSO) of A. mangium, used as the parent population hereafter and a multi location trial (MLT) as an offspring population. Based on 10 microsatellite markers, mating system in the F1 SSO was under panmictic equilibrium condition. The good growth trees in the MLT originated from various parent genes contribution in the F1 SSO. Several behaviors were observed: a). the best trees in MLT dominantly originated from singlepair trees, between maternal and paternal trees, in F1 SSO; b). a maternal tree was pollinated by two paternal trees; c). a paternal tree pollinated several maternal trees. Flowering synchronization and genetic compatibility among trees might be responsible for these mating system patterns. In order to maximize seeds production, studies on male and female flowers characteristic should be employed to assess flowering synchronization among individual trees in the seed orchard.

Selection occurs within linear fruit and during the early stages of reproduction in Robinia pseudoacacia.

BackgroundPollen donor compositions differ during the early stages of reproduction due to various selection mechanisms. In addition, ovules linearly ordered within a fruit have different probabilities of reaching maturity. Few attempts, however, have been made to directly examine the magnitude and timing of selection, as well as the mechanisms during early life stages and within fruit. Robinia pseudoacacia, which contains linear fruit and non-random ovule maturation and abortion patterns, has been used to study the viability of selection within fruit and during the early stages of reproduction. To examine changes in the pollen donor composition during the early stages of reproduction and of progeny originating from different positions within fruit, paternity analyses were performed for three early life stages (aborted seeds, mature seeds and seedlings) in the insect-pollinated tree R. pseudoacacia.ResultsSelection resulted in an overall decrease in the level of surviving selfed progeny at each life stage. The greatest change was observed between the aborted seed stage and mature seed stage, indicative of inbreeding depression (the reduced fitness of a given population that occurs when related individual breeding was responsible for early selection). A selective advantage was detected among paternal trees. Within fruits, the distal ends showed higher outcrossing rates than the basal ends, indicative of selection based on the order of seeds within the fruit.ConclusionsOur results suggest that selection exists both within linear fruit and during the early stages of reproduction, and that this selection can affect male reproductive success during the early life stages. This indicates that tree species with mixed-mating systems may have evolved pollen selection mechanisms to increase the fitness of progeny and adjust the population genetic composition. The early selection that we detected suggests that inbreeding depression caused the high abortion rate and low seed set in R. pseudoacacia.

Terpenoid Variations within and among Half-Sibling Avocado Trees, Persea americana Mill. (Lauraceae)

Chemical analyses were conducted to determine the qualitative and quantitative differences in monoterpenes and sesquiterpenes in plant material from avocado trees, Persea americana Mill. (Lauraceae). The initial study analyzed plant material sampled from the trunk to the leaves through different branch diameters to quantify proximo-distal spatial differences within a tree. All trees were seedlings initiated from a single maternal tree. Two-way analysis of variance was conducted on 34 chemicals that comprised at least 3% of the total chemical content of at least one tree and/or location within a tree. There were significant interactions between genotype and location sampled for most chemicals. Parentage analysis using microsatellite molecular markers (SSR's) determined that the four trees had three fathers and that they represented two full-siblings and two half-sibling trees. Descriptive discriminant analysis found that both genotype and location within a tree could be separated based on chemical content, and that the chemical content from full-siblings tended to be more similar than chemical content from half-siblings. To further explore the relationship between genetic background and chemical content, samples were analyzed from leaf material from 20 trees that included two sets of full-sibling seedling trees, the maternal tree and the surviving paternal tree. Descriptive discriminant analysis found good separation between the two full-sibling groups, and that the separation was associated with chemistry of the parental trees. Six groups of chemicals were identified that explained the variation among the trees. We discuss the results in relation to the discrimination process used by wood-boring insects for site-selection on host trees, for tree selection among potential host trees, and the potential use of terpenoid chemical content in chemotaxonomy of avocado trees.

Using Simple Sequence Repeats (SSRs) to Measure Pollen Flow in a Flowering Dogwood Orchard

Abstract Dispersal of flowering dogwood pollen in an orchard was evaluated by performing parentage analyses on open pollinated seedlings collected from a single maternal tree. Pollen sources for 45 seedling trees were established using three polymorphic simple sequence repeat (SSR) loci. Previous data suggest that Cornus florida pollen is typically limited to travel between closely situated trees. If this is true, breeding may be simplified by crossing trees through open pollination rather than more laborious current methods involving pollination cages. However, the expected leptokurtic distribution, in which the likelihood that pollen transfer will occur between trees decreases quickly as distance increases, was not seen. Although the majority of paternal trees were located within the 12 m (39.4 ft) radius of the study area, the trees most likely to have donated pollen were some of those located the greatest distance from the mother tree. Unusual pollen movement may be explained, in part, by asynchronous flowering times of trees within the study or by genetic similarities exhibited between the mother tree and potential pollen donors in the area. Additionally, andrenid and halictid bees, which were the predominant pollinators observed at this site, may have moved pollen farther than expected.

Effect of Eucalyptus pollen isolation methods on pollen viability, debris content, quantity isolated and pollen density per stigma

Success of interspecific hybridization in Eucalyptus depends on the availability of contamination free, clean and viable pollen from elite paternal trees. Unlike the natural process of open pollination, control pollination (CP) in Eucalyptus orchards, is a slow, tedious and labour-intensive procedure that involves high costs, but results in low seed yields. In order to overcome these short-comings, Eucalyptusbreeders use various methods of pollen isolation (PI) procedures and pollination techniques. Here, we report an efficient method of PI, named as wet-lyophylisation method (WL) and compared the same with the conventionally followed dry sieving (DS) method. Clean pollen isolated by WL method resulted in a reduced debris content, in which the percent pollen viability and quantity of pollen obtained/gram of stamen were not significantly different between WL and DS methods at P < 0.05. During wide-interspecific hybridization, the use of clean pollen isolated by WL method resulted in an enhanced pollen density per receptive stigma. When compared to the conventional dry sieving method, the new (WL) method of PI was efficient in reducing the debris content and enhanced the number of pollen deposited on the receptive stigmas. In addition, the amount of pollen obtained per gram of stamen and percent pollen viability are not significantly different between the two methods of pollen collection under study. Key words: Eucalyptus, hybridization, control pollination, wet-lyophylisation method, pollen viability.

Spontaneous Interspecific Hybridization and Patterns of Pollen Dispersal in Ex Situ Populations of a Tree Species (Sinojackia xylocarpa) that is Extinct in the Wild

For endangered plants interspecific hybridization occurring in ex situ collections may lead to failure of reintroduction actions. We used Sinojackia xylocarpa, a well documented Chinese endemic species that is extinct in the wild, as a model case to address this concern. We used paternity analyses to assess the spontaneous hybridization and patterns of pollen flow between S. xylocarpa and its congener species, S. rehderiana, in conserved populations in Wuhan Botanic Garden. Interspecific hybridization events were detected in seven out of eight maternal trees of S. xylocarpa, and an average of 32.7% seeds collected from maternal trees of S. xylocarpa were hybrids. The paternity of 93 out of 249 seedlings from S. xylocarpa assigned to S. rehderiana provided convincing evidence that spontaneous interspecific hybridization occurred extensively in the living garden collection we studied. Different patterns of pollen dispersal (predominantly short-distance vs. long-distance pollination) were observed between intra- and interspecific hybridization events in the garden. Pollen dispersal within the ex situ populations was not restricted by distance, as evidenced by a lack of significant correlations between the average effective pollen dispersal distance (delta) and the geographic distances (d1 and d2) between maternal and paternal trees. The interspecific pollen-dispersal distance ranged from 10 to 620.1 m (mean 294.4 m). Such extensive hybridization in ex situ collections could jeopardize the genetic integrity of endangered species and irrevocably contaminate the gene pool if such hybrids are used for reintroduction and restoration. We recommend strongly that measures be taken to minimize the genetic risks of this kind of hybridization, including establishing buffer zones in ex situ collections, manipulating flowering phenology, testing seed lots before use in reintroduction programs, and controlling pollination for seed purity.

Male Reproductive Success at Three Early Life Stages in the Tropical TreePlatypodium elegans

We conducted a paternity analysis within a population of the Neotropical tree Platypodium elegans using microsatellite markers to determine rates of gene flow and to investigate whether postpollination selection affects male reproductive success. Paternity was assigned for three early life stages (aborted fruit, mature seeds, and seedlings) of five adult trees. The rate of pollen immigration into the population was high (>40%). Significant heterogeneity in pollen allele frequencies was discovered among families but subsequently declined across life stages. Comparisons of parentage among the three life stages showed no significant differences in the number of progeny resulting from immigrant pollen, and, similarly, the average distance between mating pairs did not differ over time. Only self‐fertilized seeds exhibited a significant decline across life stages, indicating inbreeding depression due to self‐pollination. Estimates of total and effective numbers of pollen donors were high, and we did not detect a selective advantage among paternal trees. High initial levels of pollen heterogeneity and the lack of evidence for selection among outcrossed seeds of pollen parents suggest that differences in male fitness at early life stages other than self‐fertilization are due to initial pollination success rather than the differential survival of progeny among fathers.

High outcrossing and random pollen dispersal in a planted stand of Acacia saligna subsp. saligna revealed by paternity analysis using microsatellites

The mating system, patterns of pollen mediated gene flow and levels of genetic contamination were investigated in a planted stand of Acacia saligna subsp. saligna via paternity analysis using microsatellite markers. High levels of outcrossing were detected within the stand (tm = 0.98), and the average pollen dispersal distance was 37 m with the majority of progeny sired by paternal trees within a 50-m neighbourhood of the maternal tree. Genetic contamination from the natural background population of A. saligna subsp. lindleyi was detected in 14% of the progeny of A. saligna subsp. saligna and varied among maternal trees. Long distance inter-subspecific pollen dispersal was detected for distances of over 1,500 m. The results provide information for use in the breeding and domestication programme aimed at developing A. saligna as an agroforestry crop for the low rainfall areas of southern Australia.

Pollen-mediated gene flow in a small, fragmented natural population of Fagus crenata

Pollen-mediated gene flow was analyzed in a small, fragmented, natural population of Fagus crenata Blume by surveying five microsatellite markers in seedlings derived from open-pollinated crosses. Paternity of 162 seedlings derived from two maternal trees was assigned by the maximum-likelihood method using CERVUS 2.0, and pollen dispersal patterns within the study site were determined. Most of the trees within the site sired seeds, although we found evidence of limited pollen-mediated gene flow from outside the stand; 92% of the matings that generated the seedlings occurred between trees within the population, and 8% of the matings were mediated by pollen derived from trees located outside the study site. Although the pollen-mediated gene flow within the site was not strongly limited, mating frequencies of paternal trees were found to be weakly negatively correlated with their distance from the mother trees, positively correlated with their stem diameter at breast height, and uncorrelated with their relatedness to the mother trees.

Genetic Diversity and Gene Flow of Quercus crispula in a Semi-Fragmented Forest Together With Neighboring Forests

Abstract The genetic diversity and differentiation in Quercus crispula populations in the Chichibu Mountains, central Japan, were evaluated using six microsatellite markers. Gene flow into a 2500-m2 semi-fragment of a natural forest from the neighboring natural forest at a distance of more than 50m was also evaluated using parentage analysis. All five populations in the mountains had similar levels of genetic diversity (He = 0.752-0.792), and the level of population differentiation was low (FST = 0.016). The semi-fragmented stand showed similar genetic diversity with the neighboring unfragmented forests, and Hardy-Weinberg disequilibrium was not found (FIS = 0.083 in adults, 0.025 in seedlings). In the semifragment, 70 seedlings were examined; according to the parentage analysis, eight of the 70 seedlings (ca. 11%) had neither of the parent trees in this fragment. These seeds must have been transported from a distance of more than 50 m; therefore, there could be a possibility that the seeds were dispersed by birds. A similar trend of seed flow into the fragment was also confirmed by genotyping endocarps of hypogeal cotyledons, while more frequent seed flow was found in the neighboring unfragmented forest. Of the remaining 62 seedlings, the maternal trees (but not the paternal trees) of 29 seedlings and both parent trees of 33 seedlings were detected in the semi-fragment. These results indicate that the gene flow among the populations occurs frequently via pollen dispersal and occasionally via seed dispersal and that, at least the current levels of genetic diversity have been maintained in such fragmented forests.

GENETIC VARIATION IN WILD CHILEAN AND CULTIVATED BRITISH POPULATIONS OF PODOCARPUS SALIGNUS D. DON (PODOCARPACEAE)

The threatened Chilean conifer Podocarpus salignus D. Don is currently the focus of ex situ conservation eorts being undertaken by the Conifer Conservation Programme of the Royal Botanic Garden Edinburgh. To assess variation within in and ex situ populations of the species, leaf material collected from four wild populations was analysed by random amplified polymorphic DNA (RAPD). Amova of RAPD profiles indicated that 93% of the variation occurred within, rather than between, populations. Intraspecific genetic diversity, estimated using percentage polymorphic loci, Shannon's diversity index, and Nei's gene diversity, was relatively high (47%, 0.692 and 0.314, respectively). To assess genetic diversity in ex situ populations within the UK, RAPD analysis of parents and progeny at two Cornish arboreta was undertaken. The results provided evidence of novel hybridization with suspected paternal trees (P. hallii Kirk and P. totara G. Benn. ex D. Don) endemic to New Zealand. RAPD was found to be an effective tool for assessing the genetic structure of P. salignus, for providing a guide to future germplasm-sampling strategies, and for hybrid identification. Implications for genetic conservation of the species and the role of ex situ approaches are discussed.