Male Strobilus Production Research Articles

Topgrafting as a tool in operational Scots pine breeding

Effective breeding requires multiplying desired genotypes, keeping them at a convenient location to perform crosses more efficiently, and building orchards to generate material for reforestation. While some of these aims can be achieved by conventional grafting involving only rootstock and scion, topgrafting is known to deliver all in a shorter time span. In this study, Scots pine scions were grafted onto the upper and lower tree crowns in two clonal archives with the aim of inducing early female and male strobili production, respectively. Their survival rates and strobili production were analyzed with generalized linear mixed models. Survival was low (14%) to moderate (41%), and mainly affected by the topgraft genotype, interstock genotype, crown position and weather conditions in connection with the grafting procedure. Survival was not affected by the cardinal position in the crown (south or north). Male flowering was ample three years after grafting and reached 56% in the first year among live scions, increasing to 62 and 59% in consecutive years. Female flowering was scarce and was 9% at first, later increasing to 26 and 20% of living scions but was strongly affected by the topgraft genotype. In one subset of scions, female flowering was observed 1 year after grafting. Overall, flowering success was mainly affected by the topgraft and interstock genotypes, and secondary growth of scions. This is one of few reports on topgrafting in functional Scots pine clonal archives.

Flowering variation and its effect on the gene diversity of seed crops in a clonal seed orchard of Pinus koraiensis Siebold et Zucc.

ABSTRACT Pinus koraiensis, an economically and ecologically vital five-needle pine species, was surveyed for female and male strobilus production variation among 52 clones over five years in a seed orchard in Gangwon province of South Korea. We estimated heritability, effective population size and gene diversity, calculated maleness index, and drew parental balance curves for the strobilus production annually. Results demonstrated marked variation in female and male strobilus production among clones and years, particularly in male strobilus production. The maleness indices indicated a considerable deviation from sexual balance. Parental balance curves revealed that the top 20% of the most fertile clones contributed significantly to the total strobilus production. High heritability values underscored the substantial genetic influence on strobilus production. The gene diversity of orchard parents (GDp ) was set as one (GDp = 1) considering panmictic situations, and then loss of gene diversity in the female gametes (GDf ) was relatively estimated to be ranged from 0.096 (loss = 1 − GDf = 1 − 0.904, 9.6% in 2017) to 0.017 ( = 1 − 0.983, 1.7% in 2020). We emphasize the importance of the effective number of parents as a crucial parameter for informing seed orchard management decisions.

Clonal fertility and heritability in strobilus production, and gene diversity of seed crops in a second-generation seed orchard of Pinus thunbergii

Abstract Variation of female and male strobilus production among clones over 4 consecutive years was estimated, and genetic variance, heritability, and genetic correlation in strobilus production were investigated in the second-generation seed orchard of Pinus thunbergii. This seed orchard was created with grafts selected according to the volume growth of their offspring. The production of female strobili continued to increase, whereas the production of male strobili fluctuated throughout the investigated period. The number of female strobili was highest in rich cone years, but the production of male strobili was not the same in rich or poor years. The maleness index showed a balance between female and male parents that occurred when male strobilus production was in rich or poor years. The parental balance curve for female strobilus production was closer to the expectation (i.e., more equal contribution) than that for male strobilus production in all years. The analysis of variance revealed significant differences among clones in female and male strobilus production over the four-year period. The narrow-sense heritability was higher in male strobilus production than female strobilus, implying that male strobilus production was under genetic control. The Pearson’s correlation was positive and mostly significant, indicating that female strobilus production was reflected in male strobilus production. The effective parent number was lowest in moderate and good years for cone production. The loss of gene diversity in seed crops was lower than expected based on clonal fertility variation.

Gender, reproductive output covariation and their role on gene diversity of Pinus koraiensis seed orchard crops

BackgroundGender and fertility variation have an impact on mating dynamics in a population because they affect the gene exchange among parental members and the genetic composition of the resultant seed crops. Fertility is the proportional gametic contribution of parents to their progeny. An effective number of parents, derivative of effective population size, is the probability that two alleles randomly chosen from the gamete gene pool originated from the same parent. The effective number of parents is directly related to the fertility variation among parents, which should be monitored for manipulating gene diversity of seed crops. We formulated a fundamental equation of estimating the effective number of parents and applied it to a seed production population.ResultsEffective number of parents (Np) was derived from fertility variation (Ψ) considering covariance (correlation coefficient, r) between maternal and paternal fertility. The Ψ was calculated from the coefficient of variation in reproductive outputs and divided into female (ψf) and male (ψm) fertility variation in the population under study. The Np was estimated from the parental Ψ estimated by the fertility variation of maternal (ψf) and paternal (ψm) parents. The gene diversity of seed crops was monitored by Ψ and Np. in a 1.5 generation Pinus koraiensis seed orchard as a case of monoecious species. A large variation of female and male strobili production was observed among the studied 52 parents over four consecutive years, showing statistically significant differences across all studied years. Parental balance curve showed greater distortion in paternal than maternal parents. The Ψ ranged from 1.879 to 4.035 with greater ψm than ψf, and the Np varied from 14.8 to 36.8. When pooled, the relative effective number of parents was improved as 80.0% of the census number.ConclusionsWe recommend the use of fertility variation (i.e., CV, Ψ), Person’s product-moment correlation (r), and effective number of parents (Np) as tools for gauging gene diversity of seed crops in production populations. For increasing Np and gene diversity, additional management options such as mixing seed-lots, equal cone harvest and application of supplemental-mass-pollination are recommended.

Survival and strobili production in topgrafted scions from young Pinus sylvestris seedlings

Reducing the generation turnover increases the genetic gain in a breeding programme. Topgrafting, new genetic material being grafted into the crown of ramets of reproductive mature trees, can deliver this aim since it is able to induce strobili production in young material of conifers. To this end, I studied the effect of scion age (seedlings of 4–6 years from seed) on topgraft vitality/survival, and female and male strobili production in Pinus sylvestris (L.) over 5 years. The seedlings' growing environment prior to topgrafting had a significant impact on topgraft vitality, with more vital topgrafts obtained from potted seedlings than from seedlings grown in raised nursery beds. However, the growth environment had no clear effect on female or male strobili production. In the second year, after grafting up to 76% of the topgrafted seedlings had female strobili. Vitality increased with age of the seedling from which the scions were collected, but differences in both female and male strobili production were only marginal. The position of the topgraft within the interstock crown influenced both vitality and strobili production, with higher vitality and greater male strobili production in low positions and greater female strobili production in high positions. Based on these results, breeders should perform topgrafting as soon as the seedlings have enough scions for planned crossing activities.

Fertility Variation and Status Number in Clonal Seed Orchards of Pinus sylvestris

The present study was carried out to evaluate fertility variation, status number and gene diversity based on strobili productions in two clonal seed orchards of Scots pine (Pinus sylvestris L.). There were large differences among clones for the female and male strobili productions in the orchards. Positive and significant (p< or =0.05) correlations were found between female and male strobili production (r = 0.76, 0.55). Female fertility variation (1.03, 1.07) was larger than male fertility variation (1.02, 1.03) in the orchards. The status numbers estimated based on the total fertility were very high (97 and 98% of census numbers). The large fertility variation could be balanced by different treatments such as mixing seed equally from clones or genetinc thinning.

Identification of QTLs associated with male strobilus abundance in Cryptomeria japonica

It has become increasingly important to understand the factors controlling the abundance of male strobili in Cryptomeria japonica since allergic reactions to the species’ pollen have become prevalent in Japan. There is considerable inter-annual variation in the abundance of male strobili, so it is important to investigate and validate quantitative trait loci (QTL) for strobili abundance across different years. Data on third generation families derived from an individual that produces abundant male strobili were studied using Kruskal–Wallis tests and Bayesian regression analysis, resulting in the detection of a single major QTL that was observed over multiple years. This QTL explained between 10.4 and 26.5 % of the phenotypic variation in male strobilus abundance. The consistency and significance of this QTL’s effects suggest that it has a major role in male strobilus production in C. japonica, although we also detected other QTLs, indicating that strobilus production is subject to complex and multifactorial regulation. These QTL may also affect precocity because we were unable to separate their effects from the genetic variability in male strobilus production. The major QTL that we detected occurs in a region homologous to a QTL detected in a previous study examining trees with a different genetic heritage following artificial induction of male strobilus production. This result further supports the importance of the QTL detected in the present study. Identifying the important genes in this QTL will therefore significantly increase our understanding of the genetic mechanisms of pollen production in C. japonica.

Clone Fertility and Genetic Diversity in a Black Pine Seed Orchard

Abstract Clonal variation in the number of female and male strobili was studied for three consecutive years (2002-2004) in a clonal black pine seed orchard in Turkey. The data showed large differences in female and male fertility among clones in the three years. The correlation between female and male strobilus production was negative and statistically significant in 2004, a good-flowering year. Clonal fertility and fertility variation, expressed by the sibling coefficient and coefficient of variation in strobilus production among 30 clones, were reported. Fertility varied among clones and among years, producing three-year averages of 99.3 and 801.6 for female and male strobili per ramet, respectively. Male fertility variation was higher than was female fertility variation in the three years. The status number, a measure of genetic diversity, was calculated as 26.4 (2002), 23.9 (2003), and 24.0 (2004). On average, the relative status number, estimated based on total fertility, was 86% of the census number. Sexual asymmetry calculations showed that clonal contributions would be balanced between genders. Some management activities such as adjusting ramet number to balance clone contributions and mixing of seeds from consecutive years are suggested for the black pine seed orchard.

Further studies on sex expression in Taxus canadensis Marshall1

Sex expression was examined in two island populations of the monoecious Taxus canadensis at the Apostle Island National Lakeshore, USA. Long-term observations of tagged plants supported earlier published conclusions based on comparisons among populations of the effect of size and age on sex expression, measured as standardized phenotypic gender. As populations of plants increased in size and age, strobilus ratios became more male-biased and gender concordance increased. Male-biased plants remained male-biased and female-biased plants remained female-biased; gender switching was not a feature of either of these populations.The two Taxus canadensis populations were mapped to examine spatial dispersion of plants and plant attributes, such as size, strobilus production, and gender. Frequency distribution of gender in both populations was significantly bimodal supporting earlier studies; this conclusion held even when small (typically male) plants with unstable gender were excluded from the analysis. Distribution of T. canadensis in both populations was clumped. Plant attributes showed some spatial autocorrelation, although the results were not consistent across populations or at different lag distances. Size and male strobilus production tended toward spatial autocorrelation in both populations, female strobilus production showed significant spatial autocorrelation on Manitou Island only at a few lag distances, and gender showed no spatial autocorrelation at any lag distance in either island population. The implication of these results for genetic versus environmental determination of sex expression in T. canadensis are briefly discussed.

Variation in Clone Fertility and its Effect on the Gene Diversity of Seeds From a Seed Orchard of Chamaecyparis obtusa in Korea

Abstract Male and female strobilus production was assessed annually over a four-year period for a clonal seed orchard of hinoki (Chamaecyparis obtusa Endl.) in Korea. Clonal fertility and fertility variation, expressed by both sibling coefficient and coefficient of variation in strobilus production among 50 orchard clones, were reported. Fertility varied among clones and among years producing four-year averages per ramet of 510.2 and 1050.6 for female and male strobili, respectively. The correlation between female and male strobilus production was positive in each of the four years studied and, with the exception of one year, statistically significant. The clonal status number (Ns), a measure of gene diversity, was calculated based on the observed clonal fertility variation and varied from 28.0 (N = 50) in the poorest flowering year (2002) to 46.7 in the best year (2005). On average (pooled), the relative status number was 95% of the census number (N). Variation in female fertility was generally higher than that for male fertility, and this variation was reflected in the status numbers of female and male parents. The pooled Ns estimated from all four years was higher than that for any single year, implying that gene diversity would increase when seeds collected from different years are pooled. Sexual asymmetry calculations showed that clonal contributions would be balanced between genders.

Fertility Variation and Genetic Diversity in a Clonal Seed Orchard of Cryptomeria japonica

AbstractClonal differences in fertility (expressed as the number of female and male strobili) were determined for three consecutive years (2002-2004) in a clonal seed orchard of sugi (Cryptomeria japonica D. Don) in Korea. Fertility varied among clones and among years producing three-year averages of 196 and 652 for female and male strobili per ramet, respectively. Correlation between female and male strobilus production was positive over the three years and statistically significant in 2003, a good flowering year. Based on the observed fertility variation, the status numbers (Ns, measure of genetic diversity) were calculated and varied from 25.6 to 31.7 among the three studied years. On average (pooled), relative status number was 86% of the census number (N). Variation in female fertility was higher than that in male fertility, and this variation was reflected on female and male parents’ status numbers. Pooled Ns estimated from the three years was higher than that for any single year, implying that genetic diversity would increase when seeds collected from different years are pooled.

Fertility variation in six populations of Brutian pine (Pinus brutia Ten.) over altitudinal ranges

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.

Fertility Variation and Status Number Between a Base Population and a Seed Orchard of Pinus brutia

Abstract Female, male and total fertility variations were estimated in a base population and a seed orchard derived from the base population in Pinus brutia. Relative status number for gametes (female and male contribution) and zygotes (average of female and male contribution) were estimated based on the fertility variation. Average female and male strobilus production were 229.1 and 1003.3 in the base population, and 98.9 and 244.9 in the seed orchard for combined years, respectively. Positive and significant correlations were found between female and male strobilus production in both base population and seed orchard. The male fertility variation was higher than female fertility variation in the seed orchard, while female fertility variation was higher than male fertility variation in the base population. Coefficients of variations in female and male strobilus production were 0.721 and 0.696 in the base population, and 0.403 and 1.110 in the seed orchard for combined years, respectively. Total fertility variation was 1.41 in the base population and 1.40 in the seed orchard for combined years. The relative status numbers estimated based on the total fertility were 70% of census number in the base population, and 71% in the seed orchard for combined years.

Sexual Asymmetry based on Flowering Assessment in a Clonal Seed Orchard of Pinus densiflora

Abstract Two equations were formulated in order to estimate the degree of sexual asymmetry for monoecious species. The concepts of the equations were formulated on the basis of the effective population numbers of female and male parents [i.e, As (v)], and the differences of relative frequency between genders [i.e., As (x)]. These equations were applied to estimate the degree of sexual asymmetry based on the empirical data of flowering assessment in a clonal seed orchard of Pinus densiflora. The yearly variation in the production of female and male strobili was found. The effective population numbers at gamete levels (vf and vm) and clone level (vb) varied among 8 observation years. Both As (x) and As (v) were negatively correlated with effective numbers at gamete and clone levels. Averages of female and male strobilus production and estimates of sexual asymmetry were negatively correlated but the correlation was not significant. The correlations among effective number of clone (vb), arithmetic mean of female and male effective numbers (va) and estimate of sexual asymmetry [As (x)] were strong and significant. Relatively larger difference between vb and va were found when higher level of sexual asymmetry were observed.

Considerations of correlated fertility between genders on genetic diversity: the Pinus densiflora seed orchard as a model.

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 (Psi(T)), female (psi(f)) and male (psi(m)) 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 (Psi(T): the probability that two genes randomly chosen from the gamete gene pool originate from the same parent), which was further subdivided into psi(f) and psi(m). 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 (Psi(T)) 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 Psi(T), 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.

The effects of scion maturation on growth and reproduction of grafted slash pine

Establishment of the University of Florida Cooperative Forest Genetics Research Program's clone banks provided an opportunity to look at scion maturation effects on growth and reproduction of many grafted slash pine clones. In 1988 and 1989, clone banks were established in nine locations in the Southeastern United States. Over 460 scion clones varying from 5 to greater than 40 years old from time of seed germination (chronological age) were grafted into the clone banks. Comparisons of diameter growth, height growth, lateral branch number and female and male strobili production were made annually for six years after grafting. Within slash pine clone banks, there were significant effects due to scion chronological age. Chronologically older scions (backward selections) grew less, had fewer branches and produced only a few more female strobili than chronologically younger material (forward selections). Forward selections produced significantly more catkin clusters than backward selections. By year six, there was no significant difference in numbers of female strobili per tree between backward and forward scions, but forward selections produced about 2.5 times as many catkin clusters as the backward selections. Similar effects on growth and reproduction due to chronological age were also found among clones within the forward selections, with older selections growing more slowly and producing fewer catkin clusters. The size and breadth of this study lends strong support to the idea that these patterns of growth will occur for grafted slash pine in any location throughout its native range.

Interactions between Abert's Squirrel and Ponderosa Pine: The Relationship between Selective Herbivory and Host Plant Fitness

Abert's squirrels are highly specialized and selective herbivores and are ecologically dependent on their host species, ponderosa pine. Ponderosa pine trees defoliated as a result of inner bark feeding by Abert's squirrels (target trees) suffered significant reductions in several fitness components including incremental growth, male strobilus production, female cone production, and seed quality. Reproductive output was also depressed in trees defoliated experimentally to mimic squirrel herbivory. In previous work, I have shown that target tree selection is mediated by a suite of host characteristics, some of which are under genetic control. Abert's squirrels may be important agents of natural selection in host ponderosa pine populations because they preferentially attack trees with specific genetically determined traits and because target trees suffer significant reductions in several fitness components.

Relationship between gibberellin A4/7 concentration, time of treatment, and crown position on flowering of Piceaglauca

Treatment with the gibberellin mixture A4 and A7 (GA4/7) enhanced female flowering on mature white spruce (Piceaglauca (Moench) Voss). Time of treatment, crown position, and GA4/7 concentration influenced treatment success. GA4/7 treatment initiated before meristematic differentiation began (late June) enhanced female strobilus production, whereas those initiated after late June were ineffective. Shoots treated with 250 mg•L−1 GA4/7 bore significantly more female strobili than shoots that received 500 mg•L−1. Treatment did not affect female production on uppermost crown positions, male strobilus production, or seed yield per cone. Female strobili predominated from axillary buds centrally located on untreated shoots. GA4/7 treatments that enhanced female production shifted the distribution of strobili to more distal shoot positions.

Sexual zonation in the crown of Piceaglauca and the flowering response to exogenous GA4/7

Strobili distribution on crowns of 8- and 9-year-old white spruce (Piceaglauca (Moench) Voss) was evaluated and modified by gibberellin A4/7 (GA4/7) applied as a foliar spray to branches in the transitional (female → male) zone and strictly male zone. Treatment with GA4/7 increased female strobili production 6.2-fold and male strobili production 2.4-fold on branches in the transitional zone. On male zone branches treated with GA4/7, female strobili were induced and male strobili production increased sixfold.