Fertility variation, seed collection and gene diversity in natural stands of Taurus cedar (Cedrus libani)

  • Isparta University of Applied Sciences
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Background Seed stand is one of the important seed sources that is essential for global seed production programs. The primary objective of seed stands is to produce seeds as fast as possible. Characteristics of seed stand seeds depend mainly on stand quality, fertility variation and mating system. Individual fertility is an ability to produce progeny to next generation. Prediction of fertility variation is useful for seed production, genetic resources management and gene conservation. In this study, we report how to estimate fertility variation and gene diversity, and discuss its effect on the management of natural stands of Taurus cedar. Results Fertility variation and gene diversity were estimated based on the differences of strobilus production in female and male parents from three seed stands of Taurus cedar. A total of 50 trees were randomly chosen from each seed stand, and the female and male strobili were counted for three consecutive years. The coefficients of variation for female and male strobilus production were subjected to estimation female and male fertility variation. The total fertility variation (Ψ) was then estimated from the female and male fertility variation. The effective number of parents ( Np ) was calculated based on the Ψ. The mean of female strobili ranged from 31 to 150, and that of male strobili ranged between 77 and 828. The Ψ in a good crop year was smaller than in a poor year and the Np varied from 34.7 to 44.2. The Ψ was improved and the Np was increased when strobilus productions were pooled across three years or populations. The equal cone harvest could mitigate the fertility variation among individuals but caused loss of seed production. Conclusions The effective number of parents could estimate gene diversity of seeds from natural stands, which was based on the function of correlated fertility variation between female and male parents. Mixing seeds from different years could improve the fertility variation among individuals and increase the gene diversity of seeds. However, a balancing between the effective number of parents and the number of mixed years or populations should be carefully considered for maintaining the gene diversity.

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There are many environmental and biological factors on forestry practices as known. Aspect called as slope faces is one of the most important environmental factors in these practices because of its easy application for managers. Fertility variation defined as an individual ability to give progeny and gene diversity estimated based on effective number of parents were investigated as the proportion of numbers of cones counted from individuals in natural stands sampled aspectual of Taurus cedar ( Cedrus libani A. Rich.) for three consecutive years. The averages of cone number were 19.4, 47.2, and 75.5 for the years. It was the highest in flat (23.5) for 2013, in south (92.1) for 2014, and in flat (95.7) for 2015, while it was lowest in south (16.3), in east (18.2), and in north (39.4) for the years, respectively. Significant correlations (p≤0.01) were estimated among years for cone production in polled aspect. Estimated fertility variations changed for the years and stands. It could be generally acceptable level for typical natural stands except of west of 2014. Fertility variations were 1.55, 3.05, and 1.64 in polled stands for the years. Gene diversity was 0.99 for the years in polled stands. North aspect could be taken into consideration in establishment and selection of seed sources and gene conservation areas based on fertility variation and gene diversity.
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The numbers of female and male strobili were counted in clonal seed orchards with 99 clones of Pinus densiflora and 60 clones of P. thunbergii and in an archive consisting of 180 clones of P. koraiensis, respectively. The observation data show-ed a great variation in both female and male strobili among clones in the three populations. It was possible to express the expected contribution of genotypes to seed crop as an inverse of cumulative function of type, x = F(x) 1/a , where x is the expected contribution of seed orchard genotypes and F(x) is the ranked relative contribution of flowering production. Parameter a is a parameter which describes flowering variation. Status number and variance effective population size could be related to the square sum of contribution. The status numbers were calculated to be 69.2 (70 % of the initial census number), 54.6 (91%) and 38.8 (22 %) in the expected crops of clonal seed orchards of P. densiflora, P. thun-bergii and P. koraiensis, respectively. The variance effective population sizes connecting these orchards with their expected crops were estimated to be 230.3, 610.3 and 49.4, respectively. Despite the large differences in status numbers and variance effective population sizes, the group coancestry remained at a low value in all expected seed orchard crops. Relative gene diversity compared to the reference population from which plus trees were selected was quite high in all populations.
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Status number is a measure of effective population size that is based on current relatedness only. Formulae are developed for group coancestry (=average coancestry) and status number for seed orchard crops. The formulae consider (1) differences in reproductive success among orchard genotypes, (2) relatedness between pairs of orchard genotypes, (3) inbreeding of orchard genotypes, (4) influence of pollen contamination (considering its relatedness both to itself and to the genotypes in the orchard), and (5) gender differences and sexual asymmetries of orchard genotypes. Properties of status number and other measures of effective number are discussed. They may refer to rate or state, to the reference population or the development of an idealized population, and to different moments in the sexual cycle.
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Fertility (number of strobili) was investigated in six natural populations over three ranges of altitudes (215–960 m) in Brutian pine (Pinus brutia Ten.) for two consecutive years. The fertility and fertility variation varied among populations and years. The average of strobilus production varied between 173 and 269 in female, and between 533 and 1,060 in male, respectively. The fertility variation did not seem closely related to the altitude, and it was not consistently dependent on the richness of strobilus production. Positive significant correlations were found between female and male strobilus production for all populations and years. Coefficient of variation in strobilus production among individual trees varied between 0.638 and 0.838 for female; and between 0.603 and 0.809 for male when flowering assessments were combined. The clone fertility variations among trees were slightly different among all six stands (sibling coefficient ranged from 1.354 to 1.525) and it is unlikely that trees in typical stands vary extremely in reproductive success.
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Forecasts of the effects of tree breeding and conservation operations require information on fertility variation. In most cases, however, the information does not exist or is highly unreliable. In this paper, published studies on flowering abundance, fruit and seed production were used to estimate and review fertility variation in 99 stands and 36 seed orchards. Fertility variations were described by the coefficient of variation (CV) and the sibling coefficient (&PSgr;). Both measures express how parents differ in fertility; the former focuses on the variance of fertility among individuals while the later focuses on probabilistic aspects. As expected, fertility varied considerably within and among populations. Only ∼15 per cent in both stands and seed orchards indicated small variations in fertility. Fertility variation was higher in stands than in seed orchards. Differences in fertility were usually higher during poor flowering years and in young populations. In seed orchards, fertility differences were slightly larger on the male side than on the female side. For fertility predictions concerning objects that are neither juvenile nor characterized by poor flowering, we suggest, for seed orchards, a CV equal to 100 per cent with &PSgr; equal to 2 and, for stands, a CV equal to 140 per cent with &PSgr; equal to 3.
Douglas-fir (Pseudotsuga menziesii), native to western North America, was introduced to Europe about 150 years ago. Nowadays it represents the most frequent non-native forest tree species in Germany, covering about 2% of the forest area. While seeds were initially imported from its natural distribution range, the German seed market is now mainly supplied with seeds from local stands. In this study we examined four representative, different sized artificial Douglas-fir stands. We used microsatellite markers to characterise adults and offspring by analysing the genetic diversity and mating system. We detected a negative correlation of population size and genetic diversity. The loss of alleles with descending population sizes cannot be compensated by pollen from outside of the stand. The results showed an increased selfing rate (1-13%) correlated with increased inbreeding effects like a high percentage of empty seeds. Diversity parameters calculated as averages across the analysed loci should always be completed with the calculation of effective population sizes considering sibship structures based on multilocus genotypes. The combined approaches are an improved basis for drawing practical conclusions. We recommend that the current regulations for forest reproductive material should be adapted. For wind-pollinated stand-forming tree species a minimum number of 100 adult trees should be required to form approved seed stands in the category "Selected".
The genetic gain and gene diversity of seed crops from a 1.5-generation clonal seed orchard of Pinus koraiensis Siebold & Zucc. were estimated under consideration of parental genetic values and fecundity variation. Fecundity variation among clones was estimated for 5 consecutive years (2010–2014) as the sibling coefficient, which was drawn from clonal contribution to the total production of seed conelet. To monitor gene diversity, status number was estimated by the integration of fecundity variation and group coancestry. Group coancestry was calculated as the average of genetic relatedness (coancestry) among orchard clones. The averages of conelet production were high in 2010 and 2011, moderate in 2013 and 2014, and poor in 2012 with a grand mean of 13.7. Correlation analysis showed that good conelet producers consistently gave good production. Cumulative distribution of clonal conelet production was presented as a function of the total conelet yield, and this distribution indicated deviation from the expected clonal equal production. Group coancesrtry was 0.0096, indicating minimal loss of gene diversity. Status number and genetic gain were higher in good than in poor conelet production years, highlighting the importance of fecundity variation in determining the genetic gain and gene diversity of seed orchard crops.
Growth and reproductive traits were assessed in seed stands of two native Indian tree species Tamarindus indica and Azadirachta indica. Positive correlation between growth (height and GBH) and reproductive traits (male and female contribution) were found in both species. Fertility was estimated from the flower and fruit production of individuals. Based on the fertility variation among individuals, parental balance, femaleness index and status number (Ns) were determined. The option of equal seed collection among individuals was also considered for estimating Ns. The percentage of fertile trees was higher in the high flowering year in both species. The best male contributing individuals also showed high female contribution (fruit production). The parental contribution in seed stands showed high deviation from expectation; 20% individuals contributed about 70% of male and female gametes in both species. Femaleness index showed that female and male contribution of individual tree was more balanced in the good flowering year, compared to the poor year. Coefficient of variation in male and female fertility was higher in the low flowering year resulting in high fertility variation among individuals and low status number. In T. indica, the female contribution was less variable compared to that of male fertility whereas in A. indica the female fertility variation was higher than that of male fertility. The relative status number (Nr = Ns/N) of the stands was lower for male and female fertility compared to the combined (male and female) fertility of individual trees.
Number of fruits (female fertility), stamens (male fertility) and filled seeds were assessed in wild rose (Rosa canina L.) populations sampled from Beysehir watershed divided into two main (A & B) and six sub-habitats classes based on ecological characters. Fertility variation, effective number and coancestry were estimated based on fecundity assessment in the populations. Beside, the habitats were compared by multiple analyses of variance. Results showed that main habitats (A & B) had similar mean and coefficients of variation for the assessments. The mean values among sub-habitats within the main habitat 'A' varied considerably unlike the main habitat 'B' which was more homogenous. Coefficient of variation of fecundity estimates among individuals was more than 60% in main habitats and most of the sub-habitats. Variation was the lowest for seed number in main and sub-habitats and the highest for female flower production in main and sub-habitats (with the exception of one sub-habitat). Coancestry computed with total gene pool of flowers was higher than that for number of filled seeds in both main and sub habitats. Statistically significant (p≤ 0.05) differences were found among habitat classes for flower and filled seed productions. Results emphasized that habitat class was more effective on production of studied characters than that of fertility variation.
Sexual allocation theory assumes trade-offs and negative genetic correlations between male and female allocation in hermaphrodite plants. We tested this assumption by studying variation in male and female fertility in two experimental populations of Pinus sylvestris. In these populations, the genotypes have been vegetatively replicated, which allowed separation of the genctic and environmental components of variation. The genetic components of variation accounted for 36% of the total variation in pollen production in the two populations, and for 54% of cone production. As assumed by sexual allocation theory the genetic correlation of pollen and cone production was negative in both populations (-0.59 and -0.15). However, positive environmental correlations between these traits (0.43 and 0.45) resulted in no phenotypic correlation in one population and a positive phenotypic correlation in the other.
Lebanon cedar (Cedrus libani A. Rich.) is significant from the historical, cultural, aesthetic, scientific and economic perspectives. It is presently found primarily in the Taurus Mountains of Turkey with extensive and magnificent forests. Historical records also indicate extensive and splendid forests of it in Syria and Lebanon. However, heavy cutting, burning and goat grazing for the past 5000 years have left only small populations in these countries. Although the same disturbances have continued in Anatolia (Asia Minor), the almost inaccessible topography of the Taurus Mountains has prevented Lebanon cedar from being extirpated.
The female and male flowering frequency were studied in a clone trial of Picea abies at Röskär nine kilometers north-east of Stockholm. During 1971 the extension in time of pollen shedding and female receptivity was recorded following daily examination of individual strobili. The data obtained revealed a great variation in female as well as male flowering between the clones. Only a part of this variation could be attributed to differences in height of the clones. Great yearly variations in flowering of individual grafts were noticed. Based on the flowering frequency as well as the pollen shedding and female receptivity during each day, the expected contribution of the different clones to the offspring was calculated. According to the calculations four of the clones contributed 55 per cent of the genes to the offspring. Many (66) of the 190 theoretically possible combinations among the 20 clones occurred in a lower frequency than 0.1 per cent. The consequences of the data obtained for the genetic composition of the seed orchard progeny were discussed.
The relationship between reproductive energy and reproductive success and its impact on parental balance were studied in a clonal Sitka spruce (Picea sitchensis (Bong) Carr) seed orchard over 2 crop-years. Parental reproductive output and effective female population number estimates gave a good indication of the parental imbalance in the orchard crops, however, they did not show the existing differences in reproductive energy and reproductive success among the studied clones. Parental balance estimates based on seed data were more accurate than those based on cone counts. The orchard's parental balance showed consistent improvement over time. Two management options, namely, supplemental-mass-pollination and harvesting the cone crop by subsets of cone production level, were proposed to alleviate parental imbalance. Estimation de la contribution clonale à la production de cones et de graines dans un verger à graines d'épicéa de Sitka. Cet article étudie les relations entre énergie reproductive (nombre de cones produits par un arbre) et succès reproductif (nombre de graines produites). L'impact de ces 2 facteurs sur la contribution de chaque clone à la production de graines d'un verger d'épicéa de Sitka durant 2 années successives est également abordé. Les estimations du nombre efficace d'arbres mères rendent bien compte de la contribution très inégale des différents clones à la production de graines. Cependant, elles ne mettent pas en évidence les différences clonales entre énergie reproductive et succès reproductif. La contribution relative de chaque parent basée sur la production de graines est plus précise que celle basée sur la production de cones. L'amplitude de variation de ces contributions clonales tend à diminuer avec l'âge du verger. Une alternative à la contribution très inégale est proposée : pollinisation complémentaire artificielle et récolte individualisée des cones par classe de production.
The correlation between 99 clone female and male fertilities in a first generation seed orchard of Pinus densiflora was studied over 6 years. The effective number of the parent (N p) and the variance effective population number [N e(v)] were used to assess the impact of total (ΨT), female (ψf) and male (ψm) fertility variation. A theoretical framework was developed to account for female and male fertility correlations as well as the impact of possible pollen contamination. Total fertility variation was described by the sibling coefficient (ΨT: the probability that two genes randomly chosen from the gamete gene pool originate from the same parent), which was further subdivided into ψf and ψm. These parameters were compared under various conditions including the total seed harvest, imposing on equal seed harvest among the orchard's clones and two contamination scenarios (M = 0 and 20%). Fertility variations among females, males and clones were observed within and among years. Sibling coefficients (ΨT) were lower, but the effective number of parent (N p) and variance effective population number (N e(v)) were higher in years with moderate female and good male strobilus production. N p for female and male reproductive outputs varied from 49 to 82 and from 57 to 93, respectively. N p was higher for males than females. When the crop of the 6 years was pooled, N p for female, male and the clone were 73, 87 and 85, respectively. The impact of female-male fertility correlation for conditions with no-, positive- and negative-correlations were assessed and their impact on ΨT, N p and N e(v) was also evaluated. It was demonstrated that the practice of equal seed harvesting from every clone, or the mixing of seeds from several years, would substantially improve the genetic diversity and the genetic representation of the seed orchard population when a positive correlation between gender fertilities was observed. The relevance of these results to supplemental-mass-pollination was discussed under two cases where equal- and un-equal amounts of pollen from clones were included in the pollen mixes.
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