Tree Growth Traits Research Articles

Precocity of fruiting in Pinus yunnanensis revealed by common garden experiment and association analysis with molecular markers

Shortening the growth cycle and maintaining high yields are the goals pursued by all breeders. Under the distinct ecological conditions of tropical and rainy and dry seasons, many plants experience the phenomenon of early flowering and fruiting under adverse conditions. However, there is still no clear conclusion as to whether early flowering and fruiting will affect the vegetative growth of plants. In this study, the vegetative and reproductive growth traits of 270 families of Pinus yunnanensis of 6 years old in common garden were analyzed. There were significant differences in phenotypic traits of different populations, indicating that the trait differences were genetically stable. The variation of vegetative growth traits mainly comes from within populations, and the variation of reproductive growth traits mainly comes among populations. The average coefficient of variation of reproductive growth traits was significantly higher than that of vegetative growth traits. There was a positive correlation between vegetative growth traits and precocity of fruiting. Ecological environment factors have impact on phenotypic variation, among which the temperature of the wettest season has the greatest impact. According to cluster analysis, the nine populations could be divided into three categories. These cluster results were not due to geographic distances, indicating the discontinuity of phenotypic variation. By association analysis, 9 and 3 SSR loci were found to be significantly associated with the trait of precocity of fruiting, respectively. Among them, PK840 locus had the highest interpretation rate for the trait of precocity of fruiting. There were 10 and 7 unique haplotypes in precocity and non-precocity of fruiting individuals, with 179 bp and 183 bp bands, respectively. According to the breeding goal of high productivity and precocity of fruiting, 54 superior families and 200 superior individuals were selected. This study explored the adaptation strategies of tree growth traits to environmental changes.

Variation in adaptation and growth among Corymbia citriodora natural-stand and landrace seed sources in southern China

ABSTRACT Corymbia citriodora subsp. citriodora has a long history of cultivation as a multipurpose tree in China and many other countries in Southeast and South Asia. Despite this history and longstanding interest in the species, published studies examining genetic variation among and/or within provenances/seed sources are scarce. Recognising this and to initiate an improvement program for this species, a field trial was established in southern coastal China in 2015 with 171 open-pollinated single mother-tree family seedlots representing five natural-stand seed sources in Australia and six planted seed sources in China. Large significant variation was found among seed sources for pest and disease resistance, survival, growth and stem form up to age 81 months. Australian seed sources were generally superior to Chinese ones for most traits. Phenotypic correlations among traits, at both the individual tree and seed-source mean levels, were favourable, with the strongest individual tree correlations found between disease susceptibility at 10 months and various tree growth traits. Overall, the variation observed in this field trial indicates the potential gains in this species from seed-source selection and ongoing breeding.

Phenomic selection in slash pine multi-temporally using UAV-multispectral imagery.

Genomic selection (GS) is an option for plant domestication that offers high efficiency in improving genetics. However, GS is often not feasible for long-lived tree species with large and complex genomes. In this paper, we investigated UAV multispectral imagery in time series to evaluate genetic variation in tree growth and developed a new predictive approach that is independent of sequencing or pedigrees based on multispectral imagery plus vegetation indices (VIs) for slash pine. Results show that temporal factors have a strong influence on the h2 of tree growth traits. High genetic correlations were found in most months, and genetic gain also showed a slight influence on the time series. Using a consistent ranking of family breeding values, optimal slash pine families were selected, obtaining a promising and reliable predictive ability based on multispectral+VIs (MV) alone or on the combination of pedigree and MV. The highest predictive value, ranging from 0.52 to 0.56, was found in July. The methods described in this paper provide new approaches for phenotypic selection (PS) using high-throughput multispectral unmanned aerial vehicle (UAV) technology, which could potentially be used to reduce the generation time for conifer species and increase the genetic granularity independent of sequencing or pedigrees.

Effect of Continuous Planting on Tree Growth Traits and Growth Stress in Plantation Forests of Eucalyptus urophylla × E. grandis

Continuous planting is the primary method for managing Eucalyptus plantations. The “space-replacing time” approach assesses growth parameters of Eucalyptus trees in China across generations, including height, diameter at breast height (DBH), slenderness ratio, trunk oblateness, and longitudinal growth strain. The findings reveal: (1) significant variations in growth strain occur among generations, with average strain increasing noticeably; and (2) growth-linked traits of Eucalyptus urophylla × E. grandis are impacted, with negative correlation between slenderness ratio and growth strain, and positive correlation between height and trunk oblateness. Factors influencing growth strain include height, slenderness, and surface longitudinal growth strain at breast height, with strong correlations observed. These parameters serve as growth strain indicators. Continuous planting affects growth traits and strain in Eucalyptus plantations. It is advisable to select trees with stable or slow growth rates and to avoid continuous planting without limits.

Superior Clone Selection in a Eucalyptus Trial Using Forest Phenotyping Technology via UAV-Based DAP Point Clouds and Multispectral Images

The quantitative, accurate and efficient acquisition of tree phenotypes is the basis for forest “gene-phenotype-environment” studies. It also offers significant support for clarifying the genetic control mechanisms of tree traits. The application of unmanned aerial vehicle (UAV) remote sensing technology to the collection of phenotypic traits at an individual tree level quantitatively analyses tree phenology and directionally evaluates tree growth, as well as accelerating the process of forest genetics and breeding. In this study, with the help of high-resolution, high-overlap, multispectral images obtained by an UAV, combined with digital elevation models (DEMs) extracted from point clouds acquired by a backpack LiDAR, a high-throughput tree structure and spectral phenotypic traits extraction and a genetic selection were conducted in a trial of Eucalyptus clones in the State-owned Dongmen Forest Farm in the Guangxi Zhuang Autonomous Region. Firstly, we validated the accuracy of extracting the phenotypic parameters of individual tree growth based on aerial stereo photogrammetry point clouds. Secondly, on this basis, the repeatability of the tree growth traits and vegetation indices (VIs), the genetic correlation coefficients between the traits were calculated. Finally, the eucalypt clones were ranked by integrating a selection index of traits, and the superior genotypes were selected and their genetic gain predicted. The results showed a high accuracy of the tree height (H) extracted from the digital aerial photogrammetry (DAP) point cloud based on UAV images (R2 = 0.91, and RMSE = 0.56 m), and the accuracy of estimating the diameter at breast height (DBH) was R2 = 0.71, and RMSE = 0.75 cm. All the extracted traits were significantly different within the tree species and among the clones. Except for the crown width (CW), the clonal repeatability (Rc) of the traits were all above 0.9, and the individual repeatability values (Ri) were all above 0.5. The genetic correlation coefficient between the tree growth traits and VIs fluctuated from 0.3 to 0.5, while the best clones were EA14-15, EA14-09, EC184, and EC183 when the selection proportion was 10%. The purpose of this study was to construct a technical framework for phenotypic traits extraction and genetic analysis of trees based on unmanned aerial stereo photography point clouds and high-resolution multispectral images, while also exploring the application potential of this approach in the selective breeding of eucalypt clones.

Long-term water use efficiency and non-structural carbohydrates of dominant tree species in response to nitrogen and water additions in a warm temperate forest.

Nitrogen (N) deposition tends to accompany precipitation in temperate forests, and vegetation productivity is mostly controlled by water and N availability. Many studies showed that tree species response to precipitation or N deposition alone influences, while the N deposition and precipitation interactive effects on the traits of tree physiology, especially in non-structural carbohydrates (NSCs) and long-term water use efficiency (WUE), are still unclear. In this study, we measured carbon stable isotope (δ13C), total soluble sugar and starch content, total phenols, and other physiological traits (e.g., leaf C:N:P stoichiometry, lignin, and cellulose content) of two dominant tree species (Quercus variabilis Blume and Liquidambar formosana Hance) under canopy-simulated N deposition and precipitation addition to analyze the changes of long-term WUE and NSC contents and to explain the response strategies of dominant trees to abiotic environmental changes. This study showed that N deposition decreased the root NSC concentrations of L. formosana and the leaf lignin content of Q. variabilis. The increased precipitation showed a negative effect on specific leaf area (SLA) and a positive effect on leaf WUE of Q. variabilis, while it increased the leaf C and N content and decreased the leaf cellulose content of L. formosana. The nitrogen-water interaction reduced the leaf lignin and total phenol content of Q. variabilis and decreased the leaf total phenol content of L. formosana, but it increased the leaf C and N content of L. formosana. Moreover, the response of L. formosana to the nitrogen-water interaction was greater than that of Q. variabilis, highlighting the differences between the two dominant tree species. The results showed that N deposition and precipitation obviously affected the tree growth strategies by affecting the NSC contents and long-term WUE. Canopy-simulated N deposition and precipitation provide a new insight into the effect of the nitrogen-water interaction on tree growth traits in a temperate forest ecosystem, enabling a better prediction of the response of dominant tree species to global change.

Evaluation of Genomic Prediction Algorithms for Reducing Selection and Breeding Cycles in Shea Tree (Vitellaria Paradoxa)

The focus of this study was to determine the genomic prediction (GP) algorithms with the highest prediction accuracies for reducing the breeding and selection cycles in <i>Vitellaria paradoxa</i>. The efficiency of the GP algorithms were compared to evaluate five Shea tree growth traits in 708 genotypes with 30734 Single Nucleotide Polymorphic (SNPs) markers, which were reduced to 27063 after removing duplicates. Five hundred forty-nine (77.54%) Shea tree training population and 159 (22.46%) training population were genotyped for 30734 single nucleotide polymorphisms (SNPs) and phenotyped for five Shea tree growth traits. We built a model using phenotype and marker data from a training population by optimizing its genomic prediction accuracy for effectiveness of GS. The phenotype and marker data were used for cross validation of the prediction accuracies of the different models. Prediction accuracies varied among the genomic prediction algorithms based on the five phenotypic traits. We determined the best genomic algorithm that is more suitable for reduction of selection and breeding cycles in <i>Vitellaria paradoxa</i>. The GP algorithms were evaluated and we conclude that rrBLUP is the best for improving the prediction accuracy for reducing the breeding cycle in Shea tree.

Integrating genome-wide association mapping of additive and dominance genetic effects to improve genomic prediction accuracy in Eucalyptus.

Genome-wide association studies (GWAS) is a powerful and widely used approach to decipher the genetic control of complex traits. Still, a significant challenge for dissecting quantitative traits in forest trees is statistical power. This study uses a population consisting of 1,123 samples derived from two successive generations of crosses between Eucalyptus grandis (W. Hill) and E. urophylla (S.T. Blake). All samples have been phenotyped for growth and wood property traits and genotyped using the EuChip60K chip, yielding 37,832 informative single nucleotide polymorphisms (SNPs). We use multi-locus GWAS models to assess additive and dominance effects to identify markers associated with growth and wood property traits in the eucalypt hybrids. Additive and dominance association models identified 78 and 82 significant SNPs across all traits, respectively, which captured between 39 and 86% of the genomic-based heritability. We also used SNPs identified from the GWAS and SNPs using less stringent significance thresholds to evaluate predictive abilities in a genomic selection framework. Genomic selection models based on the top 1% SNPs captured a substantially greater proportion of the genetic variance of traits compared with when we used all SNPs for model training. The prediction ability of estimated breeding values improved significantly for all traits when using either the top 1% SNPs or SNPs identified using a relaxed p value threshold (p<10-3 ). This study also highlights the added value of incorporating dominance effects for identifying genomic regions controlling growth traits in trees. Moreover, integrating GWAS results into genomic selection method provides enhanced power relative to discrete associations for identifying genomic variation potentially valuable for forest tree breeding.

Effects of Slope Aspect and Rainfall on Belowground Deep Fine Root Traits and Aboveground Tree Height.

The vertical root distribution and rooting depth are the main belowground plant functional traits used to indicate drought resistance in arid and semiarid regions. The effects of the slope aspect on the aboveground traits are visible but not the belowground deep root traits. We aimed to investigate the fine root traits of the locust tree (Robinia pseudoacacia L.) planted on southerly and northerly aspects, and the variations in the rooting depth in regions with different rainfall, as well as assessing how deep rooting, might affect the response to drought in a loess region. We selected three study sites with different rainfall amounts, with six sampling plots at each site (three each with southerly and northerly aspects). Soil core samples were collected down to the depth where no roots were present. The locust trees tended to develop deeper fine roots rather than greater heights. The tree height and diameter were greater for locust trees on northerly aspects, whereas trees on southerly aspects had significantly deeper rooting depths. Fine root traits (root length, root area, and root dry weight density) were higher in the southerly aspect for both Changwu and Ansai, but lower in Suide. The ratio of the root front depth tree height ranged from 1.04 to 3.17, which was higher on southerly than northerly aspects, and it increased as the rainfall decreased. Locust tree growth traits (belowground fine root and aboveground tree height) were positively correlated with the mean annual rainfall. The soil moisture content of the topsoil decreased as the rainfall decreased, but the pattern varied in the deep layer. Our results suggest that the variations in the belowground rooting depth under different slope aspects may be related to plant survival strategies. The vertical extension of the rooting depth and tree height may be key functional traits that determine plant growth in drought-prone regions.

Heritable variation in tree growth and needle vegetation indices of slash pine (Pinus elliottii) using unmanned aerial vehicles (UAVs)

Vegetation indices (VIs) are mainly associated with plant yield, and yield-related physiological traits can assist in breeding selection. Tree breeding programs require a rapid assessment of a large number of individual trees across multiple regions. Unmanned aerial vehicle (UAV) multispectral platforms combined with high spatial, temporal and spectral resolutions can readily assess the VIs at various plant growth phases, which has been deeply detailed for evaluating the physiological status of agricultural crops and forest stands. However, the underlying genetics of foliar spectral bands, VIs and growth traits from a large scale of samples, especially in the case of forest trees, have been less investigated. In this paper, two sites of slash pine breeding populations were completely investigated to monitor the spectral bands, VIs, and tree growth traits. This allows us to determine the genotypic variation of these traits and to estimate the heritability (h2). The results show that the estimated h2 ranges from 0.04 to 0.36, and the site may affect tree growth because the traits between two sites come to different h2 values. At the two sites, the h2 values of the green red difference vegetation index (GNDVI) and anthocyanin reflectance index (ARI) at Site 1 and the red edge chlorophyll index (RECI), leaf chlorophyll index (LCI), red green blue vegetation index (RGBVI), normalized difference red edge index (NDRE), NIR and red edge at Site 2 were less than 0.1. However, breeding selection is still possible for most VIs and growth traits at both sites based on different breeding targets and families (families 3, 5, 10, 11, 14 and 17 at Site 1 and 4, 6, 8, 19 and 13 at Site 2 for optimal spectral bands; families 2, 8, 7, 13, 16, and 18 at Site 1 and 6, 7, 11, 14, 15, 18, and 20 at Site 2 for optimal VIs; families 8 and 16 at Site 1 and families 7 and 18 at Site 2 for optimal growth traits) with a variety of optimal traits are selected. This paper demonstrates the potential use of UAV-based imagery technologies in the breeding selection of slash pine trees.

Influence of tree height and diameter on wood basic density, cellulose and fibre characteristics in Melia dubia Cav. families

In the present study, phenotypic and genotypic correlations between tree growth traits (height, diameter and biomass) with some of the important wood quality parameters such as basic density, cellulose content, lignin content and fibre characteristics, viz. length, diameter, lumen diameter, double cell wall thickness and fibre content, were worked out using data from ten families of five-year-old Melia dubia raised by seed sources of ten superior candidate plus trees (CPTs). Result showed that medium to strong genetic and phenotypic correlations were recorded within and between growth traits and wood quality parameters studied. Direct positive strong association was observed between tree biomass with height and its diameter. Similarly, basic density of wood was phenotypically and genotypically associated with cellulose content, fibre length and fibre content; furthermore, all these parameters showed negative association with lignin content, fibre diameter, lumen diameter and double cell wall thickness. Genetic correlation showed that wood quality parameters, viz. basic density, cellulose content, fibre length and fibre content, were positively influenced by the height and diameter of trees. Thus, these parameters may be considered while selecting superior genotypes of M. dubia for better pulp and paper quality.

Site Classification of Eucalyptus urophylla × Eucalyptus grandis Plantations in China

Background and Objectives: It is important to match species needs with site conditions for sustainable forestry. In Eucalyptus urophylla × Eucalyptus grandis plantations in southern Yunnan, China, species-site mismatches have led to inappropriate expansion and management, which has degraded forests and decreased efficiency in plantation production. Further research is needed to understand the relationship between tree growth and site productivity. We empirically explored site features and classified site types within these plantations in southern Yunnan. Our objective was to develop a theoretical basis for improving site selection for afforestation, and to establish intensive management in that region. Materials and Methods: 130 standard plots were set up in 1−15-year-old eucalyptus plantations in Pu’er and Lincang. We used quantification theory to examine the relationship between dominant tree growth traits and site factors. Hierarchical cluster analysis and canonical correlation analysis were applied to classify sites and evaluate the growth potential of E. urophylla × E. grandis plantations, respectively. Results: The multiple correlation coefficient between eight site factors (altitude, slope, slope position, aspect, soil depth, texture, bulk density, and litter thickness) and the quantitative growth of the dominant tree was 0.834 (p &lt; 0.05). Slope position, altitude, and soil depth were the main factors contributing to the variation in stand growth. Plantation growth was best on lower slopes at relatively low altitude, where thick and weathered red soil layers existed. Conversely, the poorest plantations were located on upper slopes at higher altitude, with a thin semi-weathered purple soil layer. The soil factors total nitrogen (N) and potassium (K), trace boron (B), copper (Cu), and zinc (Zn) content, available phosphorous (P), and organic matter content in the soil influenced plantation growth. Conclusions. The addition of N, P, and K fertilizer as well as trace elements such as B, Cu, and Zn can promote the productivity of these plantations.

Genetic interactions among Pto-miR319 family members and their targets influence growth and wood properties in Populus tomentosa

MicroRNAs (miRNAs) play crucial roles in all aspects of plant growth and development, but the genetic interactions of miRNAs and their target genes in woody plants are largely unknown. Here, we integrated association genetics and expression profiling to decipher the allelic variations and interactions of the Pto-MIR319 family of miRNAs and 12 putative Pto-miR319 target genes related to wood formation in 435 unrelated individuals of Populus tomentosa Carrière (Chinese white poplar). Expression pattern analysis showed that among all pairings between expressions of pre-miRNA of Pto-MIR319 members and targets, 70.0% showed negative correlation of expression levels (r = - 0.944 to 0.674, P < 0.01) in eight tissues and organs of poplar, suggesting that Pto-miR319 may participate in the regulatory network of wood formation. Single SNP-based association studies identified 137 significant associations (P < 0.01, Q < 0.1), representing 126 unique SNPs from Pto-MIR319 members and their targets, with 10 tree growth traits, revealing that these genetic factors have common roles related to wood formation. Epistasis analysis uncovered 105 significant SNP-SNP associations (P < 0.01) influencing the 10 traits, demonstrating the close genetic interactions between Pto-MIR319 family members and the 12 Pto-miR319 target genes. Notably, one common SNP, in the precursor region of Pto-MIR319e, affected the stability of Pto-MIR319e's secondary structure by altering the stem-loop structure and minimum free energy, contributing to variations in the expression of Pto-MIR319e and Pto-miR319e target genes. This study enriches the understanding of the functions of miR319 family miRNAs in poplar and exemplifies a feasible approach to exploring the genetic effects underlying miRNA-mRNA interactions related to complex traits in trees.

Update of Genetic Linkage Map and QTL Analysis for Growth Traits in Eucommia ulmoides Oliver

Eucommia ulmoides (Tu-chung) is an economically and ecologically important tree species which has attracted worldwide attention due to its application in pharmacology, landscaping, wind sheltering and sand fixation. Molecular marker technologies can elucidate the genetic mechanism and substantially improve the breeding efficiency of E. ulmoides. The current research updated the original linkage map, and quantitative trait loci (QTL) analysis was performed on tree growth traits measured over 10 consecutive years in an E. ulmoides F1 population (“Xiaoye” × “Qinzhong No.1”). In total, 452 polymorphic markers were scored from 365 simple sequence repeat (SSR) primers, with an average of 1.24 polymorphic markers per primer combination. The integrated map was 1913.29 cM (centimorgan) long, covering 94.10% of the estimated genome and with an average marker density of 2.20 cM. A total of 869 markers were mapped into 19 major independent linkage groups. Growth-related traits measured over 10 consecutive years showed a significant correlation, and 89 hypothetical QTLs were forecasted and divided into 27 distinct loci. Three traits for tree height, ground diameter and crown diameter detected 25 QTLs (13 loci), 32 QTLs (17 loci) and 15 QTLs (10 loci), respectively. Based on BLASTX search results in the NCBI database, six candidate genes were obtained. It is important to explore the growth-related genetic mechanism and lay the foundation for the genetic improvement of E. ulmoides at the molecular level.

Genomic prediction in contrast to a genome-wide association study in explaining heritable variation of complex growth traits in breeding populations of Eucalyptus

BackgroundThe advent of high-throughput genotyping technologies coupled to genomic prediction methods established a new paradigm to integrate genomics and breeding. We carried out whole-genome prediction and contrasted it to a genome-wide association study (GWAS) for growth traits in breeding populations of Eucalyptus benthamii (n =505) and Eucalyptus pellita (n =732). Both species are of increasing commercial interest for the development of germplasm adapted to environmental stresses.ResultsPredictive ability reached 0.16 in E. benthamii and 0.44 in E. pellita for diameter growth. Predictive abilities using either Genomic BLUP or different Bayesian methods were similar, suggesting that growth adequately fits the infinitesimal model. Genomic prediction models using ~5000–10,000 SNPs provided predictive abilities equivalent to using all 13,787 and 19,506 SNPs genotyped in the E. benthamii and E. pellita populations, respectively. No difference was detected in predictive ability when different sets of SNPs were utilized, based on position (equidistantly genome-wide, inside genes, linkage disequilibrium pruned or on single chromosomes), as long as the total number of SNPs used was above ~5000. Predictive abilities obtained by removing relatedness between training and validation sets fell near zero for E. benthamii and were halved for E. pellita. These results corroborate the current view that relatedness is the main driver of genomic prediction, although some short-range historical linkage disequilibrium (LD) was likely captured for E. pellita. A GWAS identified only one significant association for volume growth in E. pellita, illustrating the fact that while genome-wide regression is able to account for large proportions of the heritability, very little or none of it is captured into significant associations using GWAS in breeding populations of the size evaluated in this study.ConclusionsThis study provides further experimental data supporting positive prospects of using genome-wide data to capture large proportions of trait heritability and predict growth traits in trees with accuracies equal or better than those attainable by phenotypic selection. Additionally, our results document the superiority of the whole-genome regression approach in accounting for large proportions of the heritability of complex traits such as growth in contrast to the limited value of the local GWAS approach toward breeding applications in forest trees.

Tree growth traits and social status affect the wood density of pioneer species in secondary subtropical forest.

Wood density (WD) is not only an important parameter to estimate aboveground biomass but also an indicator of timber quality and plant adaptation strategies to stressful conditions (i.e., windthrow, pests, and pathogens). This study had three objectives: (1) to compare WD among seven subtropical tree species; (2) to determine how tree growth traits may influence possible differences in WD between the pioneer and shade‐tolerant species; and (3) to examine whether or not WD differs by tree social status (dominant vs. suppressed trees) within species. To do this, 70 trees were destructively harvested. From each tree, disks at different stem heights were obtained and subjected to a method of stem analysis to measure whole tree level WD. The results showed that WD differed significantly among the seven species (p < .001). Their average WD was 0.537 g/cm3, ranging from 0.409 g/cm3 for Choerospondias axillaris to 0.691 g/cm3 for Cyclobalanopsis glauca. The average WD of the four pioneer species (0.497 ± 0.13 g/cm3) was significantly lower (p < .01) than that of the three shade‐tolerant species (0.589 ± 0.12 g/cm3). The WD of the pioneers had a significant positive correlation with their stem diameter at breast height (DBH), tree height (H), and tree age, but WD had a significant negative correlation with relative growth rate (RGR). In contrast, the WD of the shade‐tolerant tree species had no significant relationships with DBH, H, tree age, or RGR. The dominant trees of the pioneer species had a higher WD than the suppressed trees, whereas the shade‐tolerant species had a lower WD for dominant trees than the suppressed trees. However, the differences in WD between dominant and suppressed trees were not significant. Taken together, the results suggest that classifying species into pioneer and shade‐tolerant groups to examine the effects of tree growth traits and social status could improve our understanding of intra‐ and interspecific variation in WD among subtropical tree species.

Inheritance of growth and survival in two 9-year-old, open-pollinated progenies of an advanced breeding population of Chinese firs in southeastern China

Tree growth traits (tree height, DBH and stem volume) and survival from two 9-year-old, open-pollinated progeny tests of Chinese fir were investigated for heritability, genotype × environment interaction, age-age genetic correlation and selection efficiency. The 97 and 79 families planted at two sites were collected from the third-cycle seed orchard. Individual heritability was estimated between 0.05 and 0.21 for tree height, DBH, and volume and between 0.45 and 1.0 for survival. Family heritability was between 0.20 and 1.14. Significant genotype × environment interaction was observed for the three growth traits. Type B genetic correlation was between 0.41 and 0.67 with an increasing trend as tree grows. High age-age genetic correlation was observed with correlation reaching 0.9 after age 4 for height, DBH, and volume. The genetic gains were estimated at 3.26, 3.39 and 5.98 % for tree height, DBH, and volume with 10 % selection intensity. The implication for advanced tree breeding in Chinese fir is discussed.

Soil and tree species traits both shape soil microbial communities during early growth of Chinese subtropical forests

A better understanding of the linkages between aboveground and belowground biotic communities is needed for more accurate predictions about how ecosystems may be altered by climate change, land management, or biodiversity loss. Soil microbes are strongly affected by multiple factors including local abiotic environmental conditions and plant characteristics. To find out how soil microbial communities respond to multiple facets of the local soil and plant environment, we analysed soil lipid profiles associated with three-year-old monocultures of 29 tree species. These species are native of the diverse subtropical forests of southeast China and greatly vary in functional traits, growth or biomass characteristics, and phylogenetic relatedness. Along with the traits of each tree species, we also determined the soil and plot characteristics in each monoculture plot and tested for phylogenetic signals in tree species-specific microbial indicators. Microbial community structure and biomass were influenced by both soil properties and plant functional traits, but were not related to the phylogenetic distances of tree species. Specifically, total microbial biomass, indicators for fungi, bacteria, and actinomycetes were positively correlated with soil pH, soil organic nitrogen, and soil moisture. Our results also indicate that leaf dry matter content and the leaf carbon to nitrogen ratio influence multivariate soil microbial community structure, and that these factors and tree growth traits (height, crown or basal diameter) positively promote the abundances of specific microbial functional groups. At the same time, a negative correlation between leaf nitrogen content and Gram positive bacterial abundance was detected, indicating plant–microbial competition for nitrogen in our system. In conclusion, even at early stages of tree growth, soil microbial community abundance and structure can be significantly influenced by plant traits, in combination with local soil characteristics.

Agronomic and qualitative evaluation of some olive selections derived from a breeding program

A breeding olive program has been established in 1994 at Egypt by crossing between local and foreign cultivars for selection and evaluation to get new genotypes for table, oil, or dual purpose varieties. Future work is planned to evaluate the adaptation of the most promising selection to different environments. During three successive years (2011-2013) progenies from crosses between cvs. (Leccio x Toffahi), (Coratina x Toffahi), (Toffahi x Arbiquine) and (Arbiquine x Toffahi) were evaluated. The progenies have been analyzed for some tree growth traits (shoot length, shoot thickness, number of nodes/shoot, internodes length, leaf traits (average number of leaves/shoot, leaf surface area, leaf shape), flowering-entity (flowering time, the length of inflorescence, number of total flowers/ inflorescence, number of perfect flowers/inflorescence, number of staminate flowers/ inflorescence, sex ratio, and fruit set/m), drupe traits (tree yield, fruit shape, fruit weight, seed weight, flesh weight, flesh/seed, moisture and oil content (oil percent in fresh weight and oil percent in dry weight) and rooting capability. From the obtained data, it can be concluded that some valuable selections have been resulted. Such progenies were No. 51, 62, and 63 for table olive; progenies No 36, 49, 109 and 121 for oil and No. 34, 35, 108, 110 and 111 for dual purpose. Furthermore, selected progenies were propagated and planted in three locations, to evaluate their performance in different geographical areas. Performance included i.e., tree growth, yield, fruit characteristics, oil content and oil compositions in fatty acids. There comes the necessity to study quantities and qualitative traits of olive production for the most important selections.

Behaviour of some olive accessions resulting from an olive improvement program

The olive (Olea europaea) is one of the most important oleaginous crops of the Mediterranean basin. Increased demand for olive oil creates a need for new olive varieties to help meet the requirements of the global market. Rapid technological changes in olive growing have increased interest in breeding programs and new cultivars. A breeding program aimed at selecting new dual purpose (i.e. oil and table olive) cultivars, began in Egypt in 1994. A three successive years evolution (2011, 2012 and 2013) was conducted on progenies resulted from crosses between (Koronaki x Hamed), (Manzanello x Hamed) (Picual x Hamed) and (Arbquine x Hamed). The progenies have been analyzed for some tree growth traits, growth, blooming, fruiting, fruit quality and rootability. The obtained data, concluded that some valuable selections have resulted from this study progenies No. 73, 91 and 100 for table olive, whereas progenies No. 42, 47, 71, 89 and 98 for oil besides, progenies No. 57 and 59 for dual purpose. Thereupon, it is preferable to propagate all the best selected progenies and planted in three locations, in order to evaluate their performance (i.e., tree growth, yield, fruit characteristics, oil content and oil compositions in fatty acids) in different geographical areas. It remains necessary to study quantities and qualitative traits of olive production in more detail, for the most interesting selections.