Tree Growth Traits Research Articles

Genetic relatedness among Tunisian plum cultivars by random amplified polymorphic DNA analysis and evaluation of phenotypic characters

Analysis of differentiation among local and introduced plum cultivars using morphological, pomological and RAPD markers revealed considerable genetic diversity. The phenotypic analysis shows that pomological and tree growth traits were permitted to evaluate morphological variability of plum cultivars. Ten arbitrary primers used to assay 27 cultivars revealed 143 RAPD markers. The percentage of polymorphic bands (97.28) and the resolving power (Rp) (82) showed the efficiency of used primers. The revealed RAPD markers permit to distinguish all considered cultivars and resolve homonymy problem. Cluster and principal component analysis were performed to assess patterns of diversity among cultivars and showed unstructured genetic diversity. In fact, the cultivars distribution occurs undependably of their geographic origin. The overall distribution pattern of molecular variation suggests that about 94.79% of the total variance was accounted within group component of variance. The remaining 5.21% of the variation was hierarchically structured between components due to differentiation among groups. A significant correlation ( r = 0.30; P = 0.00) was verified between morphological descriptors distance and distance generated by molecular data. These results proved the importance of both morphological and RAPD markers to elucidate in part denomination problems and elucidate relationships among cultivars. Wide phenotypic and molecular diversity found in local plum germplasm indicates a considerable potential for improving this crop. The combined analysis of phenotypic and molecular markers was a valuable tool for assessing the genetic diversity in plums.

Genomics of growth traits in forest trees

Growth traits in trees are fundamental components of adaptation in a forest ecosystem and of productivity in planted forests. A number of processes determine tree growth, which are controlled by genetic and epigenetic factors that respond dynamically to environmental signals throughout centuries. Advances in genomics have allowed an increased comprehension of the complex mechanisms of tree growth and adaptation. Yet, the application of genomics to improving forest productivity and sustainability still entails capturing a large proportion of the total genetic variation controlling the component traits. Nonetheless, genetics and genomics are unifying disciplines that will serve well to dissect the variables and mechanisms of tree growth and development.

Rapid prediction of wood crystallinity in Pinus elliotii plantation wood by near-infrared spectroscopy

Crystallinity is an important property of woody materials; it responds to tree growth traits, structure, and chemical composition, and has a significant effect on Young’s modulus, dimensional stability, density, and hardness, etc. The ability of near-infrared (NIR) spectroscopy coupled with multivariate analysis to rapidly predict the crystallinity of slash pine (Pinus elliotii) plantation wood was investigated. The results showed that the NIR data could be correlated with the X-ray diffraction (XRD)-determined crystallinity of slash pine wood by use of partial least squares (PLS) regression, producing excellent coefficients of determination, r 2, and root mean square error of calibration, RMSEC. The use of either reduced spectral ranges or the selection of certain wavelengths consistent with known chemical absorptions did not have any detrimental effect on the quality of PLS models allowing the use of inexpensive, small, and portable spectrometers. These studies show that NIR spectroscopy can be used to rapidly predict the crystallinity of slash pine wood.

Resin canal traits relevant for constitutive resistance of Norway spruce against bark beetles: environmental and genetic variability

The influence of genetic determination and environment on the variability of secondary resin canal traits was investigated on 15–19-year-old Norway spruce ( Picea abies (L.) Karst.) clones grown in Lower Austria (Pressbaum and Ulmerfeld) and southern Sweden (Knutstorp and Hermanstorp). Eleven and 20 clones were present on the two Austrian and the two Swedish sites, respectively. The sites differed in their water availability, as indicated by different annual precipitation and soil type. Resin canal traits measured were the number of epithelial cells per canal, the number of resin canals per unit tangential wood surface area, the mean resin canal area and the total resin canal area per unit tangential wood surface area. The latter three traits are known to be related to the constitutive resin flow of Norway spruce. Environment had an influence on the variability of resin canal traits but the most important factor for the variability was the tree’s genetic disposition. Within countries, clones from the drier sites (Pressbaum and Hermanstorp) showed significantly smaller resin canals. Trees from Pressbaum also had smaller total resin canal areas than trees from Ulmerfeld. The number of epithelial cells and the number of canals did not differ between sites. Resin canal traits had wide genetic variation and high broad sense heritabilities ( H 2), with values between 0.28 and 0.82. Highest heritability values were reached for the number of epithelial cells and the number of canals ( H 2 > 0.8). Genotypic correlations across trials were high for the resin canal traits and approached 1 in both the Austrian and the Swedish trials, indicating that there was little genotype by environment interaction for these traits and thus the ranking of clones was very similar in the different environments. The number of epithelial cells, the mean area and the total resin canal area showed either moderately significant positive genotypic correlations with tree growth traits or none at all. In a breeding context, our results are encouraging and indicate that high constitutive defence potential against bark beetles, such as Ips typographus, is not aligned with low volume growth. But it should be taken into consideration that environment and forestry practices can also have an impact on the resin reservoir provided by the radial resin canals.

Genetic variation in branchlet carbon and nitrogen isotope composition and nutrient concentration of 11-year-old hoop pine families in relation to tree growth in subtropical Australia

Genetic variation in tree growth and branchlet carbon isotope composition (δ 13C), nitrogen (N) isotope composition (δ 15N) and nutrient (N, P, K, Ca, Mg, Mn, Fe, Cu and Zn) concentration of 11-year-old hoop pine ( Araucaria cunninghamii Ait. ex D. Don) half-sib families were examined at two contrasting sites (31 families with 8 blocks sampled at a wet site and 27 families with 9 blocks at a dry site) in south-east Queensland, Australia. Genetic correlations were determined between the tree growth traits, between the physiological traits, and between the physiological and growth traits. The potential of using these tree physiological traits was evaluated for assisting in selection of elite hoop pine families with improved water-use efficiency (WUE) as reflected in branchlet δ 13C, nutrient (particularly N)-use efficiency (NUE) and tree growth. At the wet site there was significant genetic variation in tree growth, branchlet δ 13C, nutrient concentration and mineral concentration among the 11-year-old hoop pine families, with heritability estimates ranging from 0.26 to 0.72. At the dry site, there was also significant genetic variation in some of the corresponding variables with heritability estimates ranging from 0.26 to 0.54. There seemed to be significant family variation in branchlet δ 15N at the dry site ( P=0.068), with a moderate heritability estimate of 0.21, but not at the wet site. Some strong genetic correlations were also found between the tree growth traits, between the physiological traits, and between the tree growth and the physiological traits. Tree WUE and branchlet nutrient concentrations were significantly influenced by rainfall and soil fertility. Branchlet δ 15N at the wet site was significantly lower than that at the dry site, suggesting that soil microbial–plant interactions might play a role in discriminating soil available 15N in favor of 14N for tree uptake (lower δ 15N in plant tissues) at the wet site. Branchlet δ 13C δ 15N and nutrient (particularly N) concentration show promise as physiological and nutritional traits for assisting in the selection of elite hoop pine families with improved tree WUE, NUE and growth for the more water- and nutrient-limited environments in subtropical Australia.

Genetics of Eucalyptus wood properties

Traditional methods of assessing wood properties are both destructive and expensive, limiting the numbers of samples that can be processed. Over the past decade, non-destructive sampling techniques and new assessment methods have been developed leading to a large in- crease in the numbers of trees and traits that can be evaluated. This technology has enabled the assessment of progeny trials to determine the pat- terns of variation, degree of genetic control and economic importance of many wood traits, leading to the inclusion of wood properties in many eucalypt-breeding programs. Issues addressed in this paper include the potential markets and products for plantation eucalypts leading to a defi- nition of which wood properties should be assessed for a range of products. Current recommendations for non-destructive sampling for basic density, fibre length and predicted pulp yield in Eucalyptus globulus and E. nitens are provided. Other non-destructive assessment techniques are illustrated including cellulose content, acoustic testing methods for wood stiffness and SilviScan X-ray densitometry and diffraction analysis for density and microfibril angle. The degree of genetic control for wood properties is compared to tree growth traits and a series of issues and chal- lenges for the future presented. eucalypt / breeding / wood quality / genetic parameters / non-destructive sampling

Allozyme variation in interior Douglas-fir: association with growth and resistance to western spruce budworm herbivory

We used starch gel electrophoresis to investigate levels of genetic variation between trees of interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca) that were phenotypically resistant versus susceptible to defoliation by the western spruce budworm (Choristoneura occidentalis Freeman). We also investigated the association between allozyme variation and tree growth traits. Overall, the phenotypically resistant trees had a lower allelic heterozygosity (p = 0.020) compared with susceptible trees. However, this difference between resistant and susceptible trees primarily occurred at the Buena Vista, Colorado, site rather than the Deckers, Colorado, and Jacob Lake, Arizona, sites. Among 25 loci we examined, the resistant trees also had a higher frequency of the most common alleles (p = 0.057) and a higher proportion of homozygous genotypes, especially at loci FEST-1 (p = 0.004), ACO-1 (p = 0.080), and 6PGD-1 (p = 0.084). The higher allelic heterozygosity in susceptible trees was mainly due to their higher proportion of uncommon and (or) rare alleles. Compared with susceptible trees, resistant trees had higher mean radial growth rates (p = 0.047) and less temporal variability in growth rate over 25 years (p = 0.037). Mean radial growth rate and average tree heterozygosity were not related at any site (p = 0.316). Relationships between temporal variability in growth rate and tree heterozygosity were inconsistent among sites. Our results suggest that phenotypic differences in resistance of interior Douglas-fir to western spruce budworm defoliation are partly caused by genetic differences among trees.