Female Strobilus Production Research Articles

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 plasticity uncovers multiple sexual morphs in natural populations of Cedrus deodara (Roxb.) G. Don

BackgroundThe expression of gender in gymnosperms is challenging because the extent of variability in gender segregations in tree crowns and selection pressure of nature can modify the gender through time.MethodsAn in-depth investigation on spatial segregation of genders in tree crowns and sex expression of a total of 500 trees in five different natural populations of Cedrus deodara was carried out and verified the occurrence of subdioecious (co-existence of male, female, and monoecious) genders in C. deodara.ResultsFive different sexual morphs were apparent among the 500 selected individuals as (1) pure male (M): bearing only male strobili in the whole crown with 22.2%; (2) pure female (F): bearing only female strobili in the whole crown with 12.4%; (3) mixed-monoecious (MM): bearing both male and female strobili with 13.6%; (4) predominantly female (PF) with 25.6%; and (5) predominantly male (PM) with 26.2%. The occurrence of multiple sexual morphs resulted from the complex selection pressure, which increased the stability of the populations. The segregation of genders in crown layers deemed to increase the fitness that may be a mechanism for accelerating outcrossing. The results of the study suggest that the subdioecious gender expression in C. deodara is evolved through the monoecy–paradioecy pathway. The production of male strobili revealed non-significant effect of tree sizes whereas a significant effect was observed for the production of female strobili. Our study established that the total pollen and seed outputs in C. deodara changed frequently according to gender expression.ConclusionsThe size of the tree, resource availability, sex allocation, plant architecture, gender segregation in crowns, and habitat conditions are the prominent causes for gender plasticity.

Effect of giberellic acid (GA4/7) and girdling on induction of reproductive structures in Pinus patula

Aim of study: Seed production in forest tree species commonly takes a long time due to the length of the juvenile stage. Even though several treatments have been used to induce early flowering in conifer species, experience on their use in subtropical Pinus species is limited. This study aimed to evaluate the effect of GA4/7 dose (0, 1.27 and 2.54 mg cm-2) and application time (July-October), alone or in combination with partial stem girdling, on male and female strobili production in young Pinus patula Schiede ex Schltdl. et Cham. clones. Area of study: Nine clones with different flowering background of high-elevation Pinus patula growing in a six-year old seed orchard established in Central México (Aquixtla, Puebla) at 2,800 m elevation.Material and methods: Two independent flowering trials (FT1 and FT2) were carried out in the seed orchard during the 2009 and 2010 flowering cycles; similar factors were evaluated at both trials but time of application, clones tested, and experimental design used varied for each of them. Partial stem girdling was done at the base of the trunk and the GA4/7 solution was injected into the xylem above the point of girdling. The following spring, the percentage of trees with strobili and the number of strobili per tree were determined for both male and female structures.Main results: Significant differences (p ≤ 0.05) among clones in flowering capacity were found at both trials. None of the treatments applied in FT1 resulted in an increase of strobili formation, most probably because they were applied too late in the growing season. In FT2, however, application of GA4/7 combined with partial stem girdling increased the percentage of trees with strobili and the number of strobili of both sexes, particularly when applied in early July. Partial stem girdling was more effective on promoting male strobili than female ones in gibberellin-treated grafts.Research highlights: Timing of GA4/7 application and stem girdling was important, with a significant interaction with clones tested in FT2 on production of male strobili but not on female strobili. Application of 1.27 mg cm-2 GA4/7 and stem girdling in July promoted the highest percentage of trees with strobili, and increased 25-fold the number of female strobili and 5-fold the number of male strobili per tree as compared to the control treatment. Thus, operational use of this induction treatment would be valuable to increase and accelerate seed production in Pinus patula seed orchards in the region.Keywords: early flowering; gibberellins; juvenile stage; seed orchard; seed production.Abbreviations: GA: Gibberellic acid; GA4: Gibberellic acid 4; GA7: Gibberellic acid 7; GA4/7: Mix of gibberellic acids 4 and 7; FT1: Flowering trial carried out in the 2009 season; FT2: Flowering trial carried out in the 2010 season.

Assessing 62 Chinese Fir (Cunninghamia lanceolata) Breeding Parents in a 12-Year Grafted Clone Test

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is one of the major commercial conifer species in China. The present study concentrated on the assessment of growth, wood property traits, and strobili number in a 12-year grafted clone test of 62 Chinese fir breeding parents, aiming to describe the variation and correlations between these traits and to identify parent clones with the highest potential for future breeding. The results indicate that all of the growth (height, diameter at breast height, stem volume, crown-width) and wood property (wood basic density and hygroscopicity) traits varied significantly (p < 0.01) among clones, with coefficients of variation ranging from 7.6% to 30.6%. Furthermore, these traits consistently had a moderate to high (0.39–0.87) repeatability estimate (broad-sense heritability). Remarkable clonal differences were also observed for the production of male and female strobili. Phenotypic correlations among growth traits were strong (p < 0.01) and positive. Significantly negative correlations (p < 0.01 or 0.05) were found between wood basic density and growth (except for height) and hygroscopicity. The production of male and female strobili appeared to be significantly (p < 0.01) positively correlated with each other. A notable number of faster-growing parent clones were identified (n = 30); 11 of these had higher density wood with an average realized gain of 10.5% in diameter, and a 5.4% gain in wood basic density. When selection was made for growth and strobili, 10 faster-growing parent clones with medium to high production of female strobili were identified.

Variation and Stability in Female Strobili Production of a First-Generation Clonal Seed Orchard of Chinese Pine (Pinus tabuliformis)

Abstract Seed orchards of Chinese pine, Pinus tabuliformis, are in a transition period from first generation to advanced generation. During this crucial period, evaluation of seed production in seed orchards is essential. Female strobili production is an important factor in seed production. This study examined the variation and stability in female strobili production in a first-generation clonal seed orchard of Chinese pine in years 9, 10, 13, 14, 20 and 21 after grafting in 1974. The results showed significant variation in female strobili production among clones, years, and interactions between clones and years. Correlations in female strobili production between years were significant. The repeatability for female strobili production within the examined years ranged from 0.47 to 0.87. The relative stability of female strobili production varied among clones, with regression coefficients among individual clones and an environmental index ranging from 0.13 to 2.81. The productivity index in different clones ranged from -1.09 to 1.83. Yield stability of female strobili among clones could be estimated from female strobili production. Clones could be divided into three groups according to their stability and productivity parameters. The results of this research provide guidance for evaluating clones in existing seed orchards, as well as some basic information for seed orchard management and advanced-generation seed orchard establishment.

Variation in sexual reproduction in Taxus cuspidata Sieb. & Zucc

Male and female strobilus production and seed production were measured in multiple years in three natural populations of Taxus cuspidata in Japan. Our goal was to record variation in these parameters among individuals, among populations, and from year to year in this species, which is defined as dioecious. We also wished to determine whether cosexual individuals occurred in the sampled T. cuspidata populations. Male and female strobilus production varied significantly among male and female individuals, respectively, and individuals had significant annual variation in male and female strobilus production. Significant variation in male and female strobilus production was also recorded in comparisons among T. cuspidata populations. In some populations, males were significantly larger than females, but this result was not consistently observed. No cosexual individuals were recorded in any of the populations studied. Correlations among reproductive variables and measured vegetative characters were generally non-significant at all sites and in most years, with a few exceptions. When compared with other Taxus species, strobilus ratios in T. cuspidata were less male biased (2.3 male strobili per female strobilus in T. cuspidata versus 8.7 and 7.0 male strobili per female strobilus in Taxus brevifolia and Taxus canadensis, respectively). Seed production efficiency was comparable to T. brevifolia, but less than half of that recorded for T. canadensis, the only species of the genus that has individuals that are typically cosexual.

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.

Short communication. Flowering induction by GA4/7 application and mineral fertilization in a Pinus radiata D. Don seed orchard in Sergude (Galicia)

Application of gibberellins GA4/7 was an efficient method of promoting female strobilus production in a three year old clonal radiata pine seed orchard in northern Spain. Four clones were selected including one poor flowering clone, one intermediate flowering clone and two good flowering clones, according to this annual flower account (2000). The gibberellins were applied in July and in August (2000) by stem injection of an ethanolic solution of GA4/7. There were no differences in the effectiveness of application on the different dates. Gibberellins produced an increase in the mean number of female cones, that was more effective in poor flowering clones, and a significant decrease in the percentage of empty seeds in poor and intermediate flowering clones in the next harvests. The seed orchard was divided into three zones according to the slope, and was fertilized with NPK 15-5-20 at one of three times (May, June or July 2000) for promoting male flowering in the seed orchard. Regardless of time of application, fertilization resulted in a 3-fold increase in the mean number of male cones produced, without female production effect.

Effect of Foliar-Applied Gibberellin A3 on Male and Female Strobilus Production and Cone and Seed Quality in Western Redcedar (Thuja plicata Donn)

Abstract Western redcedar (Thuja plicata Donn) foliar-applied gibberellin A3 (GA3) induction trials were performed over a 4-year period at a number of different seed orchards in coastal British Columbia. The effects of GA3 timing, concentration, and frequency on male and female strobilus production, as well as timing on seed quality, were studied. Male and female strobili were induced over the complete span of shoot elongation from May to August, indicative of a less-precise induction period than species in the Pinaceae family. Female strobilus production was correlated with shoot increment, such that maximum cone production was associated with maximum shoot elongation. In addition, seed quality decreased with decreasing shoot increments in August. For operational efficiency, a one-time foliar application of 200 mg/l GA3 is sufficient for adequate female strobilus production. To increase the female-to-male strobilus ratio, a two-time foliar application of GA3 mid-May and mid-July, concentrating on vigorous shoots, is recommended. Results are discussed in relation to seed orchard management techniques that may potentially influence selfing rates.

Graft survival and promotion of female and male strobili by topgrafting in a third-cycle slash pine (Pinus elliottiivar.elliottii) breeding program

A total of 2561 slash pine ( Pinus elliottii Engelm. var. elliottii) grafts were topgrafted in the winter of 2003 and evaluated in January of 2004. The objectives of this study were to understand the effect of the genetic material and crown position on survival and flowering response of topgrafts. Also, the effects of geographic direction, branch order, and scion age on topgraft response were assessed. Topgrafting was an effective tool for promoting both female and male strobili. The genetic material (scion and interstock clones) and the crown position had large effects on the promotion of female flowering and topgraft survival. More than 23% of the total variation in female flowering and 16.3% of the total variation in topgraft survival were due to differences among scion clones and among interstock clones, respectively. The highest survival rate was reached by grafting in the mid-top followed by the top crown position. Grafting in the top of the crown was highly superior in promoting female strobili followed by the mid-top position. First-order branches showed a significantly superior production of female strobili. Chronologically older scions, from selections made in the first and second generations of the tree improvement program, produced more female and male strobili than third-cycle forward selections.

Analysis of the parental reproductive balance in a Pinus pinaster Ait. seed orchard

The number of female and male strobili were assessed for 22 clones in a Pinus pinaster Ait. seed orchard along four consecutive years. The data showed that differences for the production of both female and male strobili among clones were very large and statistically significant for all years examined. Differences in female strobili production among clones were more variable than in male strobili. Pearson’ s correlations between years were highly significant. Both correlations between female and male flowers were moderate and positive for all 4 years. Broad-sense heritabilities for flower production on an individual ramet basis varied from 0.14 to 0.50, while those on a clone-mean basis were much higher, from 0.39 to 0.82. Maleness index indicated high sexual symmetry (Mi= 0.47-0.49). The results are useful for planning further activities in the seed orchard such as pruning, roguing or selective cone harvest.

Growth phenology and mating system of maritime pine (Pinus pinaster Aiton) in central Spain

The study of the mating systems of forest species is important both in forest management and breeding. In this work, we analyzed the phenology of diameter growth, the phenology of female and male flowering, and the seed yield in a native stand of maritime pine (from Meseta Castellana provenance) during the years 1999 and 2000. Maritime pine showed a long vegetative period in the study area (8.6 months). The male flowering period lasted 15 days whereas the female flowering lasted four weeks. Maximum pollen production occurred when most female strobili reached their maximum receptivity. Individual female strobilus production was medium-high in the studied stand (annual mean about 30 strobili per tree) and there was a remarkable correlation between both years. During the studied period, a high seed yield was observed (300,000 seeds/ha estimated in year 2000) and no limitation to natural regeneration due to mating system is expected

Clonal and annual variation of flower production and composition of gamete gene pool in a clonal seed orchard ofPinus densiflora

The numbers of female and male strobili were assessed for 99 clones in a Pinus densiflora Sieb. et Zucc. seed orchard for four consecutive years. The data showed that differences for the production of both female and male strobili among clones were very large and statistically significant for all years examined. The most abundant quartile of clones produced 48.1 and 37.3% of the total female and male strobili, respectively, averaged over the 4-year period. Differences in female strobilus production among clones were more variable than in male. Pearson's correlations between years for flower production were positive for all combinations of years. Spearman's rank correlation coefficients between years with moderate female flowers were highly significant. Both correlations between female and male flowers were moderate and positive for all 4 years. Broad-sense heritabilities for flower production on an individual ramet basis varied from 0.19 to 0.41, while those on a clone-mean basis were much higher, from 0.57 to 0.80. Maleness index showed that sexual symmetry in good and poor flower years deviated more from the ideal panmictic situation than that in intermediate years. Parental balance curves showed that orchard clones contributed more equally to the seed crop when flower production was moderate.

Predicting Pinus radiata female strobilus production for seed orchard site selection in New Zealand

A ground-based estimate was made of the number of emergent female strobili carried by 74 open-grown stands (10–12 years old) of Pinus radiata growing across a range of latitudes and altitudes of the South Island and North Island of New Zealand. The intent of this study was to develop and evaluate an empirical model to describe the relationship between environmental variables and emergent female strobilus numbers. The model suggested that variability in female strobilus number was necessarily associated with climate and site factors. Temperature and to a lesser extent rainfall variables were associated with the number of seed cone-buds that achieved anthesis in the spring. The step-wise multiple regression analysis selected mean minimum February temperature, integrated soil water stress (February–March), accumulated growing degree days (weighted against spring rainfall prior to seed cone-bud initiation), in that order. The first variable was found to explain around 54% of the variance in strobilus numbers across sites, while taken together all of the variables explained 64% of among-site variability. Model evaluation was carried out across both similar eastern South Island sites and different North Island sites at which it was developed. It was found to predict strobilus counts accurately across the South Island sites, but less accurately across the warmer North Island sites. Mean minimum February temperature was still the most important predictor of strobilus production across sites, but this relationship was non-linear. Thus, a non-linear modelling approach was adopted to better fit the model across regions New Zealand-wide. Long term nation-wide data for mean minimum February temperature were then used in a climate modelling system to generate a temperature map for New Zealand, to assist with seed orchard site selection. This map illustrated that oceanic (as opposed to semi-continental) environments around the New Zealand coast are likely to be the most productive sites for seed orchard production. Contrary to a priori perceptions, the northern regions of the North Island were depicted to offer a greater number of candidate sites for seed orchard siting than the more south eastern semi-arid regions of New Zealand.

Clonal and annual variation of flower production and composition of gamete gene pool in a clonal seed orchard of <i>Pinus densiflora</i>

The numbers of female and male strobili were assessed for 99 clones in a Pinus densiflora Sieb. et Zucc. seed orchard for four consecutive years. The data showed that differences for the production of both female and male strobili among clones were very large and statistically significant for all years examined. The most abundant quartile of clones produced 48.1 and 37.3% of the total female and male strobili, respectively, averaged over the 4-year period. Differences in female strobilus production among clones were more variable than in male. Pearson's correlations between years for flower production were positive for all combinations of years. Spearman's rank correlation coefficients between years with moderate female flowers were highly significant. Both correlations between female and male flowers were moderate and positive for all 4 years. Broad-sense heritabilities for flower production on an individual ramet basis varied from 0.19 to 0.41, while those on a clone-mean basis were much higher, from 0....

Promotion of Lateral Female Strobili Production in Pinus densiflora by Cytokinin Application at a Specific Stage

BAP (N 6-benzylaminopurine) was sprayed 5, 10 and 15 times at four different periods to promote flowering of a grafted Japanese red pine (Pinus densiflora) clone. Four stages were I, August 4 to September 1; II, September 6 to October 4; III, October 5 to November 14 and IV, November 30 to December 28, in 1994. Concentration of BAP was 250 mg/l. In May, 1995, no apical female strobili were observed at the top of the new shoots in any treatment. However, BAP application at stage III (floral differentiation period) produced lateral female and bisexual strobili at the lower part of new shoots. The numbers of lateral female and bisexual strobili were 87 out of 147 to 234 out of 162 new shoots. Frequency of BAP application did not affect the numbers. Marked decrease in number of male strobili induced by BAP application at stages I and II was observed. In contrast, the number of new shoots was increased by the BAP application at the above stages. Treatment at stage III and IV did not affect significantly the number of male strobili and new shoots. These results indicate that BAP application at stage III specifically induces the development of lateral female and bisexual strobili in Japanese red pine.

Floral response of Piceaglauca to gibberellin A4/7, napthaleneacetic acid, root-pruning, and biennial treatment

The floral response of 6-year-old seedling white spruce (Piceaglauca (Moench) Voss.) was evaluated after treatment in 1981 with the gibberellin mixture of A4 and A7 (GA4/7), napthaleneacetic acid (NAA), and root-pruning. To evaluate the effectiveness of biennial treatment, trees treated in 1981 were again treated in 1983 and compared with a second group of trees treated only in 1983. Trees treated in 1981 with 500 mg•L−1 GA4/7 plus 25 mg•L−1 NAA and root-pruning averaged 42 female strobili per tree and control trees remained vegetative. Root-pruning significantly reduced terminal shoot growth and shoot water potential. No male strobili were produced on study trees. Trees treated in 1981 and again in 1983 were as productive (based on female counts) as trees treated only in 1983. Two treatments in 1983 significantly enhanced female strobilus production over the control: (i) 500 mg•L−1 GA4/7 alone and (ii) 250 mg•L−1 GA4/7 plus root-pruning. These treatments averaged 150 and 192 female strobili per tree, respectively; control trees averaged 30. Biennial treatment with GA4/7 and root-pruning can effectively continue to increase female cone production of white spruce.

Inheritance and correlations of frost injury, growth, flowering, and cone characteristics in white spruce, Piceaglauca (Moench) Voss

White spruce progenies from the Lake States (61) and from the Ottawa River Valley, Ontario (31), were tested in north-central Wisconsin. Transplants were raised in nurseries in Wisconsin and Ontario and planted in 1969 in an open field after thorough weed control. Observations in the Wisconsin nursery and in the field between 1971 and 1979 are reported. They included heights, frost damage, spring vegetative growth phenology, strobili production, and three cone characteristics. The discussion concentrates on the relationships between heights and the other measured characteristics. Frost damage proved difficult to assess. In the year of frost, damage is severe, a 50% growth reduction, and the fastest growing trees are most severely damaged. However, in environments with only occasional late spring frosts, permanent damage is negligible. Spring growth initiation was not correlated significantly with total height growth or frost damage. Breeding of late-flushing genotypes that can avoid frost damage is questionable in spite of the high heritability for flushing. Female strobili production was substantial at age 10 years, male production was not. Even so, generation turnovers of 10–15 years may be possible. The impact of fecundity on growth potential is discussed as it relates to multigeneration breeding.

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.