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1.
The widespread European forest tree Fagus sylvatica L. is of great importance for forest management. However, information about seed dispersal is still very rare, though important for harvesting strategies and later on seed source identification. We refined a DNA fingerprinting method for beech nut shells in order to directly assign dispersed seeds to their mother trees. A pilot study was conducted in two beech stands in Germany where leaves of the adult trees and the exocarp of dispersed seeds were fingerprinted at six nSSR loci. While one stand was randomly analysed for adults and dispersed seeds the other was systematically investigated following common harvesting procedures. Imitating the typical net harvesting strategy, seeds were collected beneath 19 adult trees. Exocarp genotyping revealed that on average three different mother trees contributed to a sample of five or six seeds collected beneath a single adult tree. Of the identified mother trees most were located within a radius of 15 m from the sampling point. The repeated pattern of seed dispersal within a short distance constitutes the basis for a straightforward strategy for the assignment of seed lots to a seed source stand. This strategy is based on the matching of individual genotypes without the necessity for a full inventory of the putative source stand. Additionally, we provide allelic ladders of five nSSR loci for standardization among laboratories.  相似文献   

2.
Supplemental mass pollination (SMP) success in a grafted lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed orchard in southern British Columbia was studied by employing four chloroplast DNA (cpDNA) markers to determine fertilization success of 10 pollen parents. SMP was conducted operationally with a bulked pollen mix twice during peak receptivity in the seed orchard. Fertilization success of the 10 SMP parents averaged 16% greater than for wind-pollinated controls in a different section of the orchard. SMP also increased the uniformity of the male contribution in treated seeds.  相似文献   

3.
1988～1989年在卢氏油松无性系种子园和人工油松林内外设立花粉采样点,观测花粉在不同山地类型的传播特点及对下风方向种子园侵染的危险性。结果表明:油松花粉传播受地形、散粉日期、风速、大气湿度等因素的影响。风速大、空气干燥,天气晴朗的日子,散粉速度快,传粉距离远,在开阔地、抬升地、对坡地形中,距离花粉源数百米甚至数千米地点的花粉浓度常高于花粉源的花粉浓度,对坡地形尤为显著。因而,在营建山地种子园时,至少应保持1000 m的隔离距离。本文还结合实验结果,对山地种子园的建立和管理提出了一些看法。  相似文献   

4.
Short distance pollen dispersal shapes the local genetic structure of plant populations and determines the opportunity for genetic drift and local selection. In this paper we focus on short distance dispersal (SDD) of pollen in a low-density stand of a savannah oak, Quercus lobata Née. Specifically, we are interested in the proportional contributions of pollen donors, the pollen dispersal kernel that describes local matings, the extent to which wind influences mating success, and the extent to which pollen sources vary within the large canopy of these trees. Using maximum likelihood paternity analysis, we assigned sires for 474 outcrossed progeny of five seed trees, representing 120 of 160 potential mating pairs within a 250 m radius of each focal tree (ca. 20 ha plots). We first established that the effective number of pollen donors for progeny with sires within the plot was about 10 individuals, with average weighted pollination distances of 114.1 m. We estimated 18.5% pollen immigration into the 20 ha plots. We next established that the SDD portion of the dispersal kernel is best described by the exponential power, inverse power, and Weibull functions, all that capture high local dispersal with steep decay. Two of these models suggest that long distance dispersal is abundant, represented by a fat tail, while the Weibull indicates depauperate long distance dispersal, represented by a thin tail. The addition of a directional component corresponding to the predominant wind axis had no meaningful impact on these models. Finally, we established that different parts of an individual tree canopy of Q. lobata sample from the same homogeneous pollen pool showing no bias towards pollen sources near that part of the canopy. Overall findings suggest low-density Q. lobata populations show steep decay of SDD. Policies and ordinances governing the amount of allowable tree removal of savannah oak populations should recommend the preservation of local clusters of adults, as well as some connectivity among clusters.  相似文献   

5.
Pollen flow and mating patterns are the most important factors influencing the genetic structure of insect-pollinated forest trees and are essential parts of genetic management in seed orchards. We investigated pollen flow, the mating system and the level of pollen contamination in a clonal seed orchard of Schima superba Gardn. et Champ. In total, 328 open-pollination progenies coming from 11 mother trees were identified using 13 polymorphic microsatellite loci. A total of 203 full-sib families were identified and were nested among the 11 studied seed donors. The male reproductive success rate from 0.49 to 7.77% for most male parents, with an average of 2.44%. More than 80% of the crosses were found within a distance of 60 m, and the most frequent pollination distance between female parent and male parents was approximately 20 m. Mating system analysis showed that the outcrossing level was very high (t m  = 1.000, outcrossing rate = 98.5%) in the seed orchard and that there was an average of 2.3 effective pollen donors (N ep ) per female parent. In addition, the mating success of individual males within neighborhoods was moderately influenced by their fecundity and the direction of their location relative to mother trees. The pollen contamination from outside the seed orchard was high (7.01%). Our findings are valuable for the assessment of seed orchards, and it may be worthwhile to use pollen management strategies to decrease pollen contamination and increase the genetic quality of the seeds produced.  相似文献   

6.
Spatial genetic structure and diversity of Cryptomeria japonica trees in old growth forest but selectively logged in approximately 300 years ago were analyzed using seven nuclear microsatellite markers and one chloroplast microsatellite marker. The individuals were sampled from a 4-ha natural forest plot (200 m × 200 m), which are consisted of three size classes including newly regenerated individuals such as regenerated individuals (REG class; stem diameter at breast height (DBH), 5–110 cm), remaining individuals (REM class; DBH ≥ 110 cm), and old stumps. Genetic diversity was similar between the three groups. These results suggest that genes from the old growth forest may have been passed on to the next generation (i.e., the current forest). DNA extraction and analysis from old stumps was partly successful and we could compare the genetic diversity between old stumps and living trees using four microsatellite loci. Patterns of spatial genetic structure detected by analyses of the nuclear and chloroplast markers differed substantially; all nuclear markers showed significant positive autocorrelation (P < 0.05) over short distances, but the chloroplast marker showed no significant autocorrelation over any distance. We concluded that Moran's I spatial autocorrelation pattern for the chloroplast microsatellite may have been influenced by the extensive pollen flow characteristic of this species, because chloroplast DNA of C. japonica is paternally inherited through pollen and is a wind-pollinated species that produces abundant pollen every few years. In contrast, Moran's I spatial autocorrelation pattern for nuclear microsatellites may reflect limited seed dispersal in gaps where the forest has regenerated and low levels of seed shadow overlap due to past logging. The average seed dispersal distance was 86.0 m at the study site and about 34.0% of the seeds were from the outside of the site, which revealed by parentage analysis. The individuals remaining after logging, and the extensive pollen flow from outside our study plot, may play important roles in maintaining the forests on this island. Gaps created by the selective logging activities appear to have been important for the regeneration of this species in the past but in the present time, natural disturbances such as typhoon and landslide are also important for gap creation.  相似文献   

7.
Pollen flow from external sources is important for the conservation of tree species in fragmented forests or small populations, because it can be sufficient to prevent differentiation among them, and appears to be able to prevent the loss of their genetic diversity through genetic drift. In this study, we examined the genetic heterogeneity of pollen pools accepted by each Quercus semiserrata seed parent at the Khun Wang Royal Agriculture Research Center, Thailand, both within and among two mast fruiting years (2005 and 2007), using paternity analysis and analysis of molecular variance (AMOVA). The mating systems of the trees were also examined using the multilocus mating system model (MLTR), after determining the genotypes at eight microsatellite loci of 26 seed-trees and 435 seeds from 8 seed-trees in the 2 mast fruiting years. The average distance of effective pollen flow within the plot was estimated to be 52.4 m, and 95% of effective pollen was dispersed within 200 m, indicating that effective pollen flow is highly localized and that most effective pollen is contributed by near-neighbor trees. The proportion of effective pollen that immigrated from external sources was estimated to be 26.2%. The AMOVA analysis based on the pollen haplotypes showed that the pollen pools, both total and for each reproductive year, significantly genetically differed among the seed parents. Using a mixed mating model, the estimate of biparental inbreeding for the total population (tm − ts) was 0.013, indicating that a low proportion of mating occurred among close relatives. The effective number of pollen donors (Nep) was estimated to be 9.987 using the TwoGener model, or 10.989 using the mixed mating model. The effective number of pollen donors of seeds was higher in the mast fruiting year 2005 than in the other examined year, 2007. Consequently the allelic richness and genetic diversity of seeds produced in 2005 were higher than those produced in 2007. Overall, the results show that high outcrossing rates, high levels of gene flow from other populations and heterogeneity in the pollen received by an individual may enhance the ability of populations to maintain effective population sizes. Therefore, these processes may be sufficient to prevent loss of genetic diversity through genetic drift of Q. semiserrata at this study site.  相似文献   

8.
The effects of top pruning on subsequent seed and pollen cone production in lodgepole pine (Pinus contorta Dougl.) grafted clones in two seed orchards were evaluated. In the older orchard (14 years old), three pruning regimes were applied: an untreated control, a moderate pruning where 25% of the crown was removed and a severe pruning where 40% of the crown was removed. In the younger orchard (ten years old), only a control pruning and a severe pruning (50% of crown removed) were applied. Five-year seed cone production was lower in treated ramets compared to controls in both orchards. However, when cumulative seed cone yields were adjusted for reduced tree heights after pruning, differences were no longer significant in the older orchard. Strong clonal variation was observed in seed cone yields in both orchards. Pollen cone development was less variable among treatments in the older orchard. In the younger orchard, controls consistently produced heavier pollen crops. Pruning recommendations for similar orchards are made and results discussed for reducing the impacts of losses in seed cone yields.Deceased  相似文献   

9.
In this study, six highly polymorphic microsatellite loci and a categorical paternity analysis approach were used to investigate the contemporary pollen gene flow in the neotropical tree species Symphonia globulifera. Data for this study were taken from a 500 ha experimental plot in a dense terra firme forest in the Eastern Brazilian Amazon and included the mapping and genotyping of 161 reproductive trees, representing more than 90% of all adult trees, and the collection of 748 open-pollinated seeds from 56 seed-trees over two field seasons (2002 and 2003). High levels of pollen immigration from outside of the study plot were detected in both sampled seed-years (≥49%) suggesting long distance pollen gene flow. Low levels of self-fertilization were also detected (≤2%). The analysis showed long distance pollen dispersal occurred within the study area in both 2002 (δ = 907 ± 652 m SD) and 2003 (δ = 963 ± 542 m SD). Patterns of pollen dispersal distance within the plot were also found to be shorter than the distances between potential male parents and seed-trees. This result indicates that the distance between trees does not explain the identified pollen dispersal pattern. Our results support the hypothesis that animal pollinated species occurring in low-density populations can disperse pollen in long distances, despite the very dense nature of the forest.  相似文献   

10.
Mating system parameters and pollen contamination were estimated in an 11-year-old Pinus brutia Ten. clonal seed orchard, located in Antalya, Turkey, with the aid of isozymes. Isozyme analysis was performed on both maternal (megagametophyte) and embryo tissues of seeds collected from the seed orchard and the surrounding natural stand. Fourteen loci encoding nine enzyme systems were assayed. Based on a multilocus estimator, the proportion of viable seeds originating from outcrossing (tˆm) in the seed orchard was found to be 0.947; the remainder (0.053) was due to selfing. We estimated that 85.7% of the orchard seed resulted from pollen contamination by trees in surrounding stands. This may be related to the young age and subsequent low pollen production of the orchard. Only 9% [i.e., 1.0−0.857 (contamination)−0.053 (selfing) = 0.090] of the orchard offspring was due to cross-pollination among clones within the orchard. Due to the high level of pollen contamination, it is estimated that genetic gain in this seed crop is less than 57% of that expected if all offspring resulted from random mating among orchard clones (i.e., no contamination).  相似文献   

11.
Reproductive phenology was observed over three years in a Eucalyptus grandis seed orchard in Madagascar to determine the impact of geographic differences of parental selections on the expected genetic composition of seed crops. Pollen flow (observed pollen cloud) was deduced from a paternity assignment based on sampling from one year’s seed production. The two approaches were used to verify whether knowledge of phenology is sufficient to predict the genetic quality of the seeds collected. Despite the high flowering level, with a constant cycle over three years, the results demonstrated wide reproductive phenological differences associated with the parents’ origin, suggesting putative pollination disequilibrium. From both observed and expected pollen clouds, the results showed preferential mating among different provenances, which has consequences for seed crop composition. Phenological observations, which can be made inexpensively, can be used to promote methods of effective seed orchard management in order to improve the genetic quality of seeds.  相似文献   

12.
Gene dispersion within a population was studied in a 2‐hectare stand of 74 seed trees and 1100 seedlings. Isozyme markers were used to determine the genetic relationships among parental trees, embryos and seedling progenies. Paternity exclusion analyses were used to study multilocus progeny genotypes from certain parents. Results demonstrate large variation between trees in their capacity to contribute their genes through natural regeneration. The proportion of all genes dispersed into a specific distance interval from the source was estimated. The estimation procedure took into account the background of seedlings where parenthood was not excluded, but where the seedlings turned out to be unrelated. We found little evidence for clusters of progeny seedlings surrounding their parental tree. Within 15 m from a tree, approximately 5 % of the genes originated from that tree and 95 % originated from other trees. We found no evidence for an increase in levels of inbreeding, or genetic substructuring in the seedling progeny stand relative to the parental seed trees. A mathematical model for pollen distribution was developed. According to this model, 90% of pollen was distributed more than 15 m from the source. It is concluded that the marker seed trees had a surprisingly low detectable genetic contribution to the regeneration. It seems likely that a considerable part of the new seedlings have parents among felled trees or from surrounding stands.  相似文献   

13.
At age 5–6 years, rooted cuttings in a western hemlock (Tsuga heterophylla) clonal seed orchard received either a severe (ST) or moderate (MT) top pruning (upper 50 and 25% of live crown removed, respectively), or were left untopped (UT). Over the following 6 years, UT trees increased in height from 1.5 to 3.9 m, whereas through annual and biennial top and side pruning, MT trees grew to 2.2 m and ST trees were maintained at 2.0 m. Crown pruning had no effect on the subsequent annual production of seed or pollen cones. Spray applications of gibberellin A4/7 in years 2 and 4 of the study increased 5-fold and 2-fold the percentage of trees producing a medium and greater crop, respectively, of seed and pollen cones in each year 3 and 5.  相似文献   

14.
Genetic variation in seed/cone production among clones was studied in a hinoki (Chamaecyparis obtusa Endl.) seed orchard containing 25 plus-trees by analyzing the number of cones, the yield of cones and seeds of individual ramets for 5 successive years (1982 to 1986). There was significant variation among clones each year and parental contribution in the seed orchard. Specifically, in the years 1982, 1983, 1984, 1985, and 1986, 20% of the clones produced 37.2, 60.6, 36.0, 44.3, and 44.8% of the total cones, respectively. The size of the crop greatly influenced the parental balance in the resulting seed/cone crops. The product moment correlation coefficients and Spearman’s coefficients of rank correlation were small and insignificant between consecutive years, but large and highly significant between alternate years, suggesting the presence of carry-over effects in seed/cone production. The broad-sense heritability on a clone mean basis was 0.74 ± 0.15 for the number of cones, 0.72 ± 0.14 for the yield of cones, and 0.68 ± 0.13 for the yield of seeds. The corresponding heritabilities from analyses combined over all years were 0.24, 0.558, and 0.724, respectively. These results indicate that seed/cone production in hinoki is under strong genetic control. Several managerial measures are discussed that maintain the genetic diversity in seedlots used for reforestation, by reducing the variation in seed/cone production among clones and producing seed crops with equal contributions from all parents.  相似文献   

15.
To evaluate the practical application of an indoor seed orchard, we compared the seed production, final germination rates and mating patterns of potted Cryptomeria japonica D. Don clones in two miniature seed orchards: one in a glasshouse and the other outdoors. There was no statistically significant difference in total seed production between the orchards (P = 0.275, ANOVA). However, the final germination rate of seeds produced in the indoor orchard was significantly lower than that of seeds produced in the outdoor orchard (P < 0.01, Wilcoxon test). The average self-fertilization rate was higher in the indoor orchard (27.2%) than in the outdoor orchard (5.6%), and this parameter was strongly associated with the reduced final germination rates of the seeds harvested in the glasshouse. Pollen contamination was considerably lower in the indoor seed orchard (48.9% in the outdoor seed orchard and 4.4% in the indoor seed orchard). χ2 tests indicated that the paternal contributions of each constituent clone differed significantly in both orchards (P < 0.001 in both cases). The strong variations in paternal contributions among indoor orchard clones was significantly correlated with their respective pollen production capacities (Spearman ρ = 0.693, P < 0.001). To reduce the high self-fertilization rates, we recommend the use of orchard clones with similar pollen production capacity in indoor seed orchards.  相似文献   

16.
Genetic male sterility is a useful trait in plant breeding, especially in angiosperm crops such as corn, onion and carrot. We found a male sterile sugi (Cryptomeria japonica D. Don) tree in Toyama, Japan. Pollen of sugi is one of the major causes of pollinosis in Japan. We carried out this research in an attempt to make clear the characteristics and inheritance of this male sterility. Microsporogenesis of the male sterile tree proceeded meiosis, however, the microspores collapsed after they were separated from pollen tetrads in locules, resulting in complete male sterility. Most likely, ethylene evolution was responsible for male sterility expression. Full seed setting in the male sterile tree indicated normal macrosporogenesis. Seeds obtained from crossing between male sterile and normal lines showed relatively high level of germination and their seedlings grew vigorously. The somatic chromosome numbers of 241 germinated seeds, derived from the male sterile tree, were mostly 22, euploid. These results indicated that male sterile tree was different from other similar previously reported trees with low pollen fertility, resulting from triploid or trisomics. Probably, male sterility in sugi is either nuclear genetic male sterility or cytoplasmic male sterility. The study was partially supported by Program for Promotion of Basic Research Actives for Innovative Biosciences.  相似文献   

17.
Establishment of Polylepis forests endemic to the mountains of South America may be affected by seed dispersal, site characteristics and livestock density. Polylepis australis (“tabaquillo”) grows in the high mountains of central Argentina, where we set up 76 square study plots of 900 m2. To determine dispersal distance, we distributed 6 seed traps per plot in and around 20 plots. To determine the best site characteristics and livestock stoking rates, at two river basins differing in historic stocking rates, we analyzed the presence of seedlings in 56 plots and recorded topography, vegetation types and indicators of livestock activity. We also measured microsite characteristics in a sample of 32 comparable pairs of 1 m2 quadrats, with and without seedlings. Maximum recorded dispersal distance of P. australis seeds was 6 m, and seedlings were found no more than 10 m from seed trees. The numbers of seedlings and seed trees were 3.5 and 4 times higher, respectively, in the basin with less livestock. At the 900 m2 plot scale, a Poisson regression indicated a positive relationship between seedling number and P. australis canopy cover. At the quadrat scale (1 m2), seedlings were found in quadrats with significantly lower evidence of soil erosion than comparison quadrats without seedlings. We conclude that the main limitations to recruitment are short seed dispersal distances, lack of seed trees and extreme soil erosion. Management should therefore aim at preserving seed trees and reducing livestock density to prevent erosion.  相似文献   

18.
Fragmentation is a critical issue for tree populations because the creation of small patches can reduce local population size and increase isolation, both of which can promote inbreeding and its negative consequences, as well as loss of genetic diversity. To test the hypothesis that patch size and isolation influence mating patterns or seed production in forest trees, we utilize the spatial array of trees of an urban population of Chinese Pine (Pinus tabulaeformis Carr.) planted in patches around Beijing. Our design includes 28 urban patches, with patch size ranging from 1 to 2000 adult trees and isolation (edge distance index) ranging from 37.5 m to 245.8 m. We examined the average number of seeds per cone and percentage of viable seed per cone for each patch as measures of seed production. By utilizing seven paternally inherited chloroplast microsatellite loci, we estimated the mating pattern parameters for each patch, including the level of selfing, the amount of immigrant pollen and the effective number of pollen sources (Nep). Using a general linear model selection procedure based on AIC value, we found patch size was the best predictor of the selfing and immigration rate; smaller patches had a higher selfing and immigration rate. Small patches with one adult had relatively high Nep which indicates connectivity among urban patches. However, due to the reduced amount of immigrant pollen and limited diversity of local pollen, intermediate sized patches (with 5–10 adults) had the lowest Nep among the study patches. For patches with more than 10 adults, Nep was increased with patch size. The percentage of viable seeds per cone significantly decreased with patch size, indicating a possible negative consequence of inbreeding. The effect of patch size on mating patterns and seed production suggests that the patches of trees experience less connectivity than trees within continuous forest. These findings indicate that forest management practices should emphasize the maintenance of an optimal patch size because, despite the fact that tree species show the potential for long distance pollen movement, the number of local trees strongly influences the mating patterns.  相似文献   

19.
We attempted to evaluate the genetic diversity of long-distance transported pollen flowing over fragmented Pinus densiflora populations during a mating season. A P.?densiflora clonal seed orchard, which was located in a rural area where many fragmented populations exist, was selected for pollen capture. Immigrant pollen captured by three clones having different flowering times was regarded as the pollen flowing over fragmented populations during a mating season. The genetic diversity (H e) values of the immigrant pollen captured by the three clones were high (H e?>?0.894). The correlation of paternity (r p) values of the seeds having immigrant parent generated from the three clones were calculated to be negative. From these parameters, the pollen cloud is considered to have maintained high genetic diversity during the mating season. The genetic composition of the pollen cloud showed slight variation. The pollen captured by different trees (i.e., clonal ramets of the three clones) was significantly different based on analysis of molecular variance. Especially, the pollen pools captured by trees planted in the western side of the orchard were significantly different from the gene pool of the surrounding populations. Factors affecting this differentiation could be that the donors of the pollen transported to the orchard vary with time, as well as nonuniform dispersal of the pollen. From these results, the pollen flowing over fragmented P.?densiflora populations is considered to have high genetic diversity, compensating to some extent for fragmentation.  相似文献   

20.
The paper presents the results of a case study conducted to find out the influence of single row bund plantation of Acacia nilotica var. juquemontii on the growth and yield of associated wheat crop under irrigated conditions in Haryana, India. The indications are that the tree line does affect all crop parameters like height growth, shoot numbers, ear length, grain number and grain yield in the vicinity of trees upto 4 m distance from the tree line and establishes that as the distance from the tree line increases the growth and yield of wheat crop also improves. The effect on wheat crop was found more pronounced in the plots laid out towards the middle of the tree line as compared to plots towards the outer border.  相似文献   

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