Clonal Forestry Research Articles

Maximizing growth without compromising wood density: Selecting superior Norway spruce clones

The study examined a free-growing (initial stand density 400 trees ha–1), 50-year-old grafted clonal Norway spruce plantation in Eastern Latvia to assess the genetic control and variability of growth traits and wood density. The latter was used as a proxy for structural timber strength. Results showed moderately high heritability in growth traits and moderate variability in wood density among clones, with an estimated genetic coefficient of variation CVg, of 8.6%. Even when grown at a very low density on nutrient-rich soil, 85% of the trees met the density requirements for construction timber (C18 in accordance with EN 338). The negative correlation between growth traits and wood density was weak at both individual tree and clonal levels (–0.08 < rP < –0.06; –0.16 < rG < –0.09), making it feasible to select fast-growing clones with wood density required for structural timber. The observed variation underscores the importance of selective breeding to ensure optimal timber quality, with implications for enhancing sawn wood strength grades and promoting climate-resilient forestry practices. Keywords: tree breeding; structural timber; clonal forestry; wood properties; plantation forestry; climate-smart forestry

Comparative analysis of element and hormone content in zygotic embryos of Pinus elliottii and P. elliottii × P. caribaea

Somatic embryogenesis is a crucial method for achieving clonal forestry in conifers. Understanding the development of zygotic embryos is essential not only for enhancing the efficiency and quality of somatic embryogenesis, but also for advancing forestry breeding programs. This study investigated dynamic changes of element and hormone contents during ZE development of Pinus elliottii and its hybrid P. elliottii × P. caribaea. Significant differences in embryo development speed among different clones were observed. Elemental analysis was conducted using inductively coupled plasma mass spectrometry (ICP-MS) and identified 68 elements, including major, minor, and beneficial elements. In both species, the contents of potassium (K), calcium (Ca), iron (Fe), boron (B) and five beneficial elements decreased during early ZE development, while phosphorus (P) and copper (Cu) increased. Significantly higher levels of K, Ca and Fe at the initial stage, and sulfur (S) and nickel (Ni) decreased at later stages were detected in P. elliottii than in the hybrid. For the other elements, except for very few significant differences at certain stages, most differences between the two species did not reach a significant level. The contents of endogenous hormones were determined and different accumulation patterns were detected in most hormones between the two species, except abscisic acid (ABA) which simultaneously decreased with developments by stage 8. Significant differences were found in indole-3-acetic acid (IAA) contents at most stages between species, while higher levels of total cytokinin (CK) at each stage were detected in the hybrid in comparison with those in P. elliottii. As a result, lower IAA to CK ratios in the hybrid than in P. elliottii. Methyl jasmonate (JA-me) and gibberellin A3 (GA3) contents showed a similar pattern and exhibited an M-shaped fluctuation in the hybrid. Furthermore, JA-me, GA3, gibberellin A4 (GA4) and brassinolide (BR) showed significantly higher levels in the hybrid than in P. elliottii. K-means clustering and correlation analyses were used to explore relationships between elements and hormones during embryo development, revealing complex interplay in both species. These data indicate different requirement in element and hormone contents for embryogenesis and suggest species-specific media composition for each step in somatic embryogenesis. The findings provide insights into their developmental processes and informing future research and applications in somatic embryogenesis and forestry breeding.

Лесная селекция и генетическое разнообразие древесных пород

In scientific literature there are different views on the connection between forest tree breeding and genetic variability of wood species. This article has aimed to review the current Russian and foreign literary sources on the impact of breeding measures on the level of genetic diversity of forest wood species. Maintaining adequate genetic variability is necessary for adaptation to the environmental changes, as well as for long-term breeding. As soon as seed plantations are the source of improved seeds for forest regeneration, the influence of such factors as the number of clones and background pollination on the level of genetic variability of the progeny has been considered in detail. The data on the minimal clone number in seed plantations in different countries has been presented and the variability of the clones based on their fertility has been discussed. The importance of background pollination in seed plantations has been highlighted as soon as, on the one hand, it reduces the effect of breeding, but on the other hand, it increases the level of genetic variability of the progeny. A decline in genetic diversity of wood species can be caused by clone selection (which is the basis for clonal forestry). However the analysis of literary sources has shown that the reduction in genetic diversity is minimal if scientific recommendations are fulfilled. The use of the seeds from controlled cross-breeding of plus trees selected as a result of genetic evaluation (the so-called family forestry with vegetative propagation) in the somatic embryogenesis of the common spruce increases the level of genetic variability of the progeny. It has been shown that the multiple population breeding system allows to combine intensive long-term breeding and genetic conservation of wood species. The conclusion has been drawn that the implementation of optimally planned wood species breeding programs does not lead to significant narrowing of genetic diversity. On the contrary, forest tree breeding contributes to the preservation of a better gene pool, transmitting it in the process of forest regeneration through improved seeds and clones into homogeneous stands. Moreover, the objects of forest seed growing such as the archives of plus tree clones and forest seed plantations, as well as test cultures contain valuable genetic material ex situ.

Quantitative genetic parameters of heartwood and its chemical traits in a black pine (Pinus nigra J.F.Arnold) clonal seed orchard established in Greece

Background: Black pine (Pinus nigra J.F.Arnold) is one of the most productive conifers species for timber production in southern Europe, the Mediterranean region and Greece. Recently, the interest for its heartwood extractives content due to their medicinal properties has been renewed. Black pine can be used to produce high added value products, such as bioactive compounds produced from wood and wood waste materials. Methods: Quantitative genetic parameters were estimated for heartwood chemical traits and heartwood percentage in a 44-year-old Pinus nigra clonal seed orchard, established in Peloponnese, Greece. Results: Significant variation was found among clones and among provenances for all studied traits. Heritability on a clone mean basis was extremely high for total acetone extractives, total resin acids as for all resin acids (≥0.85), except levopimaric acid (0.47) and very high for total stilbenes, pinosylvins as for dehydroabietic acid and heartwood percentage (0.69-0.79). On an individual basis, the genetic control was moderate to high (0.53-0.62) for total acetone extractives, total resin acids as for most of resin acids (≥0.85) with dehydroabietic acid presenting low value (0.39) while levopimaric acid very low (0.15). Total stilbenes, pinosylvins and its ether derivatives as heartwood percentage exhibited low values of heritability on individual basis (0.31-0.43). The phenotypic correlation (rp) between total acetone extracts and total stilbenes was negatively weak (≤-0.173) and significant (p≤0.01) while the genetic correlation (rg) was moderate to strong (≤-0.502). The rp values between several pinosylvins were significantly (p≤0.01) moderate to strong (0.529-0.975) as were genetic correlations (0.583-0.975). Between the studied resin acids, both rp and rg values were mostly medium to strong (rp≥0.8 and rg≥0.7) and significant (p≤0.01) in the case of phenotypic correlations, with minor exceptions (levopimaric acid). Phenotypic and genetic correlations between heartwood percentage and its chemical traits were positive (being in most cases significant), except for dehydroabietic and levopimaric acid. Conclusions: The studied clones, comprising the clonal seed orchard, can be used in clonal forestry and subsequent breeding cycles, indicating high potential for advanced breeding, especially for heartwood extractives that are of high pharmaceutical and economic value.

Suitability of Eucalyptus Clones in Eastern Gangetic Plains of Uttar Pradesh, India- A Case Study in the Raebareily District, India

In India, Eucalyptus is one of the prime species in Agroforestry and farmers are mostly diverting towards clonal planting material of this species for more returns in a shorter rotation period. Eucalyptus is among the most widely cultivated forest trees in the world over 22 million hectares. Eucalyptus hybrid and E. tereticornis are the two most widely planted Eucalyptus trees in India. The area under agroforestry in India is estimated as 25.32 million ha (Mha), or 8.2 per cent of the total geographical area of the country. A total of 53.32 Mha, representing about 17.57 per cent of the total reported geographical area (TRGA) of India, could potentially be under agroforestry in the near future, thus making agroforestry a major land-use activity, after agriculture and forestry. In the recent past, clonal forestry had played a significant role in producing better production yield in a shorter time. It is also well established that the performance of Eucalyptus clones is superior over normal seed-borne plants. Therefore, there is an urgent need for improvement in the production of forest resources to meet the needs of fuel-wood, timber and wood production on a sustainable basis and increase biomass yield from farm forestry plantations. Thus, the main objective of this study was to assess the growth performance of Eucalyptus clones in the Gangetic plains of Eastern Uttar Pradesh in the Raebareily district for the identification of suitable planting material. The trial was conducted under the statistical design of Complete Randomized Blocks with 3 replicates and 3 x 2 m spacing for all 19 clones of Pragati Biotech, Punjab (413,07,526, 04, K-25, 288, 2013, 2023, 2070, 2136, 3018, 2031, P-13, P-14, P-23, P-32, P-45, P-50, P-66) of 03 eucalyptus species (E. hybrid, E. tereticornis and E. camaldulensis) along with control for all 20 treatments in respective districts. Based on growth performance parameters such as height, girth, diameter, basal area and tree volume, overall clones- P-13, P-50, P-23, 526, P-32, 3018 and P-45 performed superior over other treatments in the Raebareily district. Here, all well-performing clones of the Punjab series belonged to E. camaldulensis only whereas 3018 is E. hybrid. This study has clearly shown that the selection of clones for a particular site is very important to get maximum productivity of clonal eucalypt plantations in and around Eastern Uttar Pradesh.

Genetic Parameters and Genotype–Environment Interactions in Paulownia Clonal Tests in Temperate and Subtropical Regions of China

Clonal forestry has developed rapidly in recent years and already plays a significant role in commercial tree plantations worldwide. Clonal breeding requires accurate assessments of genetic parameters, together with measurements of clonal productivity, stability, and adaptably. However, relevant studies for clones of Paulownia spp. genotypes are rare. We therefore conducted clonal tests on twenty Paulownia clones established at three sites in the temperate and subtropical regions of China. Trees were planted in a randomized block design, with four replications in each site, twenty plots in each block, and six to eight individuals of the same clone in each plot. We measured the trunk diameter at breast height (DBH), total trunk height (Ht), and individual stand volume of 7-year-old trees to estimate genetic parameters and analyze genotype–environment interactions. A combined analysis of variance indicated that clonal, site, and clone–site interactions significantly affected the three growth traits. Clonal heritability and individual heritability were 0.35–0.84 and 0.07–0.30, respectively. The phenotypic and genetic correlation coefficients among the growth traits were 0.46–0.93 and 0.85–0.99, respectively. There were extremely significant positive linear relationships between the best linear unbiased predictors for DBH and the original DBH values (R2 > 0.98). Clones 10, 2, 18, and 13 were selected for deployment based on a selection intensity of 1.4, GGE biplots, and the relative performance of harmonic means on genotypic values analysis. For these clones, the genetic gains in DBH, Ht, and volume were 18.05%, 21.46%, and 46.03%, respectively. These results provide useful information for the selection of Paulownia clones at the target sites and will provide a sound basis for improving Paulownia clonal breeding programs in the future.

Genetic Variation in Tropical Tree Species and Plantations: A Review

The global efforts to restore tropical forests and their productive and ecological functions through plantation forestry largely depend on the available genetic variation in the tree species used to establish the plantations. However, there is limited information on the levels and trends of the genetic variation and variability of different plantation tree species in the tropics. Therefore, this study reviews several marker-based studies that have investigated genetic variation. Most of the top economic species like Eucalyptus tereticornis and Mansonia altissima are attributed to low levels of genetic diversity, while others like Pinus caribaea and Swietenia macrophylla still exhibit high expected heterozygosity across different populations. However, the levels of genetic diversity assessed may depend on the markers used. Microsatellites, i.e., simple sequence repeats (SSRs), mostly give higher estimates when compared to other polymerase chain reaction-based markers. Other factors that typically contribute to the directional pattern of genetic variation in tropical tree species and populations include their distribution, density, seed dispersal, succession, and reproduction. Also, anthropogenic impacts like logging and fragmentation have contributed to the vast genetic base reduction of many tropical species and populations. Having adequate genetic variation within the plantation populations is significant in improving their fitness, resilience, fecundity, productivity, and other ecological functions. It also provides a basis for tree improvement and breeding in plantation forests. Although clonal forestry is becoming widespread and considered highly productive, it is attributed to specific economic, technical, and ecological risks, such as the increased spread of pests and diseases. Therefore, further discussions and recommendations to maximise genetic diversity in tropical (clonal) plantations are provided.

Variation in Flowering Behaviour and Honey Bee Visitation on Eucalyptus Clones

With the adoption of clonal forestry by the farmers on large tracts in north-western India, the reports of negligible flowering in Eucalyptus clonal plantations need to be analysed. This study reports the results from the experimental trial involving 14 clones replicated thrice in randomized block design with plot size of 5 trees. Floral buds appeared from June and continued up to July. Profuse flowering was recorded only on three clones i.e., PE-7, PE-8 and PE-9. On the other hand, no floral buds could be seen on C-72, C-413, PE-12 and PE-14. All the four honey bee species i.e., Apis mellifera L. (Italian honey bee), A. dorsata F. (rock bee), A. cerana indica F. (Indian honey bee) and A. florea (little bee) visited the flowers. The frequency of their visit was maximum (7.3/ 2 min) during the afternoon (1 pm) and the lowest (4.9) in the evening. The maximum honey bee visitation was observed on clone PE-9.

Propagation by stem cuttings of 20 seedlots of Eucalyptus camaldulensis and the likelihood of a seedlot × propagation system interaction

ABSTRACT In clonal forestry, eucalypts are propagated by stem cuttings on a large scale. Six-month-old seedlings of 20 seedlots of Eucalyptus camaldulensis were propagated by stem cuttings and segregated according to their pre-harvest position (apical, mid-position and apical) in the parent shoot. ‘Rooted (%)’ – the number of cuttings rooted as a percentage of the original number – was compared to climatic data from near the sites of seed collection. Seedlot mean rooted (%) tended to vary with the warmth of the native climate, suggesting that warm-climate seedlots were less well-adapted to the cool conditions that prevailed. Apical cuttings had the highest rooted (%) compared to mid-position and basal cuttings, suggesting variation in the unrooted survival of cuttings rather than in the rooting ability of the survivors. The results indicate the likelihood of seedlot propagation system interactions in E. camaldulensis when propagated by stem cuttings.

Rapid growth in clonal Juglans nigra L. is most closely associated with early foliation, robust branch architecture, and protandry

The advantages of clonal forestry have been well described, but little progress has been made in the identification of phenotypes best suited to this method in high-value hardwood species. The genetic variation within, clonal repeatability (broad-sense heritability) of, and Pearson's correlations among phenological, morphological, physiological, and growth traits (N = 22) of black walnut (Juglans nigra L.) were investigated using 25 grafted clonal genotypes. The trees were grown at wide spacing (4.6 m × 6.1 m) in an intensively managed plantation in north-central Indiana, USA. Clonal effect was significant (p < 0.05) for most traits except gas exchange variables. Many phenological traits showed high clonal repeatability (Rc2 > 0.70), including foliation dates, first female bloom, first pollen shed, and crown retention rate (autumnal defoliation). Some traits showed moderate repeatability (0.35 < Rc2 < 0.7), such as branch angle, branch frequency, tree diameter, height, anthracnose severity, and foliar carbon and nitrogen concentration. Net CO2 assimilation rate and stomatal conductance had low repeatability (Rc2 < 0.35). We observed a previously unreported association between sexual morph and tree stem growth, i.e., protandrous trees generally grew faster than protogynous trees. This association between sexual morph and stem growth may be an evolutionary consequence of differences in reproductive costs in protandrous versus protogynous trees, and needs to be tested in other monoecious woody species. Overall, our analyses indicated that the following traits are associated with rapid stem growth: 1) early foliation; 2) early male flowering or late female flowering, i.e., more likely a protandrous variety; 3) large average branch diameter; 4) high branch frequency; 5) small (more vertical) average branch angle; 6) early leaf fall; 7) low later-season foliar carbon concentration; and 8) large number of small fruits and seeds. These traits may be used, with further testing, to define a biomass ideotype for J. nigra.

PERBANYAKAN VEGETATIF TUSAM (Pinus merkusii Jungh et de Vriese) DENGAN TEKNIK CANGKOK

Pinus merkusii is a main species for produce pine resin in Indonesia. Clone of Pinus merkusii on progeny trial establishing by Perhutani has identified can produce high yielderresin up to 100 gr/tree/3 days. Clonal forestry needs applied propagation method that easy dan economically on operational level. One of propagation method selected was by air layering. This research work were to obtained genetic materials and to get information number of live percent of seedling from air layering from high yielder resin Pinus merkusii subline when the mother trees reach 12 years old. The research was conducted in Perum Perhutani KPH Banyumas Barat, RPH Samudra on year 2020 with Completely Randomized Design (CRD). The result of this research showed that rooting ability on Pinus merkusii 12 years old mother trees have signifiant differences between subline. Rooting ability of seedling generated by air layering method were 29% (subline SG2), 24% (subline JB2), 18% (subline SL2) and 11% (subline SM2) with an average of 18% and heritability of rooting ability by air layering was 0,44.&#x0D;

Fate of forest tree biotechnology facing climate change

Abstract Woody plants have been cultured in vitro since the 1930s. After that time much progress has been made in the culture of tissues, organs, cells, and protoplasts in tree species. Tree biotechnology has been making strides in clonal propagation by organogenesis and somatic embryogenesis. These regeneration studies have paved the way for gene transfer in forest trees. Transgenics from a number of forest tree species carrying a variety of recombinant genes that code for herbicide tolerance, pest resistance, lignin modification, increased woody bio-mass, and flowering control have been produced by Agrobacterium-mediated and biolistic methods, and some of them are undergoing confined field trials. Although relatively stable transgenic clones have been produced by genetic transformation in trees using organogenesis or somatic embryogenesis, there were also unintended unstable genetic events. In order to overcome the problems of randomness of transgene integration and instability reported in Agrobacterium-mediated or biolistically transformed plants, site-specific transgene insertion strategies involving clustered regularly interspaced short palindromic repeats (CRISPR-Cas9) platform offer prospects for precise genome editing in plants. Nevertheless, it is important to monitor phenotypic and genetic stability of clonal material, not just under greenhouse conditions, but also under natural field conditions. Genetically modified poplars have been commercialized in China, and eucalypts and loblolly pine are expected to be released for commercial deployment in USA. Clonal forestry and transgenic forestry have to cope with rapid global climate changes in the future. Climate change is impacting species distributions and is a significant threat to biodiversity. Therefore, it is important to deploy Strategies that will assist the survival and evolution of forest tree species facing rapid climate change. Assisted migration (managed relocation) and biotechnological approaches offer prospects for adaptation of forest trees to climate change.

An advanced protocol for the establishment of plantlets originating from somatic embryos in Pinus massoniana.

This study describes critical factors affecting germination of somatic embryos and plantlet regeneration in Pinus massoniana. Somatic embryos from the same embryogenic line 27 of P. massoniana were used as test materials. The supplementation of activated charcoal (AC) in the medium was essential for the germination of mature somatic embryos, while the addition of excessive AC to the medium was prohibitive for somatic embryo germination. The highest germination rate was found on the medium containing 10g/l AC, and the addition of 5g/l AC to the medium was optimal to the growth of germinating somatic embryos. Thidiazuron (TDZ) was linearly related to the number of sprouting axillary buds. However, the growth of sprouting buds was retarded when > 4µmol/l TDZ was added into culture medium. Exogenous plant growth regulators added to the medium significantly improved the root regeneration capacity of shoots. The highest root regeneration rate was observed under the treatment of 1.2µmol/l ɑ-naphthaleneaceticacid (NAA) plus 2µmol/l paclobutrazol (PBZ), reaching 96.3%. One year after the field transfer, the growth performance of plant height, caliper, and survival rate for rooted shoots was significantly better than that of plantlets directly developed via somatic embryogenesis. The presented results provide useful instruction for the establishment of plantlets originating from somatic embryos, and would be able to make a great contribution to the clonal forestry of P. massoniana.

A comparative study on grey relational analysis and C5.0 classification algorithm on adventitious rhizogenesis of Eucalyptus

The optimization of plant hormone application to achieve better rhizogenesis in eucalypt cuttings has been demonstrated using a machine learning approach. This study focuses on reducing the human bias in treatment selection in case of adventitious rhizogenesis in eucalypts. The effect of different concentrations of indole-3-butyric acid (IBA) on rhizogenesis was studied and differential responses of genotypes to treatments were observed. Stem cuttings of six different Eucalyptus genotypes were administered with different concentrations and duration of IBA treatments and subsequently multiple parameters, like total length of root system (TLRS), number of roots, shoot to root ratio, etc. were measured using image analysis and manual measurements. A rule-based model and classification tree forming the basis for the C5.0 algorithm was used to eliminate “Human Bias” from the selection procedure. A top-down greedy search approach applied in the whole training set which selected the best feature as the root node and resulted in splitting the data set into smaller subsets. It was subsequently compared with our multiple-attribute decision-making (MADM) model i.e. GRA. The data were trained and tested, and the confidence value report demonstrated a high accuracy level of the decision trees. This suggests the potential use of artificial intelligence in clonal forestry. As per our results, lowering the concentration of auxin and increasing the duration of exposure produced better root quality in E. camaldulensis and hybrids (reciprocal hybrids of E. tereticornis and E. camaldulensis), while the opposite effect was observed in E. tereticornis clones. Therefore, the use of machine learning algorithms could significantly increase the accuracy of treatment selection and provide the optimum results for individual genotypes.

Effects of Cutting, Pruning, and Grafting on the Expression of Age-Related Genes in Larix kaempferi

Grafting, cutting, and pruning are important horticultural techniques widely used in the establishment of clonal forestry. After the application of these techniques, some properties of the plants change, however, the underlying molecular mechanisms are still unclear. In our previous study, 27 age-related transcripts were found to be expressed differentially between the juvenile vegetative (1- and 2-year-old) and adult reproductive (25- and 50-year-old) phases of Larix kaempferi. Here, we re-analyzed the 27 age-related transcripts, cloned their full-length cDNA sequences, and measured their responses to grafting, cutting, and pruning. After sequence analysis and cloning, 20 transcription factors were obtained and annotated, most of which were associated with reproductive development, and six (LaAGL2-1, LaAGL2-2, LaAGL2-3, LaSOC1-1, LaAGL11, and LaAP2-2) showed regular expression patterns with L. kaempferi aging. Based on the expression patterns of these transcription factors in L. kaempferi trees subjected to grafting, cutting, and pruning, we concluded that (1) cutting and pruning rejuvenate the plants and change their expression, and the effects of cutting on gene expression are detectable within 14 years, although the cutting seedlings are still maturing during these years; (2) within three months after grafting, the rootstock is more sensitive to grafting than the scion and readily becomes mature with the effect of the scion, while the scion is not readily rejuvenated by the effect of the rootstock; and (3) LaAGL2-2 and LaAGL2-3 are more sensitive to grafting, while LaAP2-2 is impervious to it. These findings not only provide potential molecular markers to assess the state of plants but also aid in studies of the molecular mechanisms of rejuvenation.

The effects of rooting media, IBA, and clones on rooting ability of Teak’s shoot cutting

Clonal forestry of teak in the community forest could increase the forest productivity where the shoot cutting was one of the vegetative propagation methods to propagate and maintain the superior clone of teak. However, the major problem on the shoot cutting of teak was the difference in rooting ability among rooting media, IBA (Indolebutyric Acid) and selected superior of teak clone. The research was conducted on split-split plot design with 10 individual as replication on each treatment. The main plot was two rooting media (cocopeat:rice husk 2:1/A; and soil:sand:compost 3:2:1/B). The subplot was IBA hormone concentration (0 ppm, 50 ppm, 100 ppm, 150 ppm) and the sub-sub plot was 11 clones of teak. The result showed that the rooting ability of teak was affected by all of treatments and interaction among them (P < 0.05), except for the interaction between IBA dosage and clone (P >0.05). The primary and secondary root length showed that clone and interaction between media and clone were significantly different (P < 0.05), while the media was only significantly different for secondary root length (P < 0.05). However, the number of primary and secondary root was not affected by the treatments (P>0.05). Moreover, the best result of rooting ability of teak for rooting media, IBA and was the cocopeat:rice husk (70,53%), IBA 150 ppm (53.18%) and clone WG2 (85%), respectively. It suggested that the seedling production of superior teak through the shoot cutting method depended on the rooting media, IBA concentration, and the specific of teak clone.

Advantage of clonal deployment in Norway spruce (Picea abies (L.) H. Karst)

Key messageThere is considerable genetic gain of tree volume from clonal deployment in Norway spruce (Picea abies(L.) H. Karst) and clonal deployment will have at least 50% more or double genetic gain than the seedling deployment.ContextGenetic parameters and genetic gains for wood quality and growth traits were estimated in six large clonal progeny trials.AimsDevelop the optimal clonal deployment strategy of Norway spruce in Sweden.MethodsWood quality and growth traits were measured in all clonal trials and additive and non-additive genetic variances are partitioned.ResultsAdditive and non-additive genetic variances were equally important for growth traits while non-additive variance was small or not significant for wood quality trait. The genetic gain predicted for clonal deployment was greater than any of the other four deployment strategies. Selecting the top 1% of tested clones (clonal forestry) would have 48.4% and 134.6% more gain than the gain predicted for the seedling deployment of selected full-sib families and half-sib family (family forestry), respectively, at the same selection intensity.ConclusionThis study highlights that testing of 30–40 clones per family would maximize the realized genetic gain for different clonal selection scenarios, either selecting the best ten or 20 clones without any co-ancestry restrictions or selecting the best single clone from each of the best ten or 20 families (e.g., co-ancestry restriction). Clonal mean selection and vegetative deployment are the most effective.

New technique for the early production of Araucaria angustifolia grafted plants

Abstract: The objective of this work was to evaluate the grafting of Araucaria angustifolia in two container volumes and at three heights. Rootstocks with 30±5.0 cm were grafted with 4.0±1.0-cm buds in 110 and 280-cm3 plastic tubes (containers) at three heights (5.0±1.0, 10±1.0, and 15±1.0 cm). There was a reduction in graft survival as the height of the grafting point increased, and the lower volume limited the development of the root system. Therefore, grafting at 5.0±1.0 cm in 280-cm3 containers brings new perspectives to improve the clonal forestry of the species, with a significant reduction in plants production time (of up to 12 months), as well as in production costs, used materials, and physical area.

Optimization of rhizogenesis for in vitro shoot culture of Pinusmassoniana Lamb.

The rooting capacity of Pinusmassoniana is poor, especially for mature trees, and has prevented the development of clonal forestry for P.massoniana. In this study, we varied explant types, subculture times and exogenous hormones for plantlet regeneration and assessed shoots for rooting rate and root number for P.massoniana. Following five repetitive grafts, new shoots from grafts used as explant sources were rejuvenated as observed from juvenile shoot morphology and anatomy, leading to greatly enhanced plant regeneration in comparison to that of mature materials from 26-year-old P.massoniana trees. The rooting capacity of subcultured shoots increased with successive subcultures, reaching a peak at 20 subcultures with 35–40 days per subculture. However, rooting performance was significantly reduced after 30 subcultures. The addition of naphthaleneacetic acid (NAA) plus indoleacetic acid in the medium improved the root number, but the combination of exogenous NAA with paclobutrazol (PBZ) increased rooting rate and root number. We thus greatly improved the rooting capacity of mature P.massoniana trees by optimizing explant types (rejuvenated), subculture times (20 subcultures, 35–40 days per subculture) and addition of NAA + PBZ to the rooting medium. The conditions can be used for efficient plantlet regeneration of P.massoniana.

The origin and genetic variability of vegetatively propagated clones identified from old planted trees and plantations of Thujopsis dolabrata var. hondae in Ishikawa Prefecture, Japan

Clonal plantations of Thujopsis dolabrata var. hondae have been established in Ishikawa Prefecture, Japan, since at least the 1800s. Historical planting of the species has led to the development of vegetatively propagated local cultivars, which originated from ‘donor’ trees that have often been conserved in sacred groves or avenues at shrines and temples. These donor trees must have been selected from natural populations. In this study, we estimated the origin and genetic variability of clones identified among old planted trees and clonal plantations of T. dolabrata var. hondae, using 19 microsatellite markers. We discovered 12 clones among old planted trees, including 5 identical to members of a set of 14 we previously identified in plantations (giving 21 clones in total). Based on analyses combining assignment and exclusion tests, we inferred origins of 8 of those 21 clones: 6 may have originated from a natural population distributed in Ishikawa, 1 from Hokkaido and Aomori, and the other from Iwate and Yamagata, suggesting the clones constituting cultivars have multiple origins. The clones identified in plantations have significantly lower genetic variability and higher relatedness, indicating that clones of cultivars have a much narrower genetic base than those of natural populations. We suggest new clones selected from natural populations elsewhere, as well as Ishikawa, are needed for future breeding of T. dolabrata var. hondae to develop clonal forestry for this species.