Linkage of RAPD markers to NESTUR, a stem growth index in radiata pine seedlings

 Needle-to-stem unit rate (NESTUR) is a stem growth index of conifer seedlings that measures the efficiency of stemwood production per unit of foliage growth. The random amplified polymorphic DNA (RAPD) technique was applied to haploid DNA from the megagametophytes of a full-sib radiata pine cross to find markers linked to factors controlling the NESTUR trait. Using the bulked segregant analysis approach, 23 of 933 primers displayed putative linkage to factors controlling NESTUR. Based on the genotypic analysis of 174 individuals, two quantitative trait loci (QTLs) controlling NESTUR were identified at ANOVA P-levels of 0.01–0.001. The QTLs were identified by RAPD markers OPE-06₄₅₀ and OPA-10₁₂₀₀, which were linked to each other (r=7%), and UBC-333₅₅₀, which was not linked to the other two. Linkage to components of NESTUR (increments in stem diameter and stem volume) was demonstrated for UBC-333₅₅₀, while the others were not linked to NESTUR components. Received: 18 December 1996/Accepted: 24 January 1997     

Interval mapping of quantitative trait loci affecting NESTUR, a stem growth efficiency index of radiata pine seedlings

 NESTUR (needle-to-stem unit rate) is a stem growth index of conifer seedlings that measures the efficiency of stemwood production per unit of needle growth, and is related to other seedling traits such as height, stem diameter, stem volume and needle volume. Quantitative trait loci (QTLs) affecting the expression of stem growth efficiency in radiata pine seedlings were investigated using a RAPD linkage map constructed from markers scored on haploid, megagametophytic DNA. Four putative QTLs were detected which accounted for 8.5–36.4% of the population variance. A search for evidence of epistasis, using both complete pairwise and conditional interactions, did not yield any statistically significant result. Over a 3-year period, seedlings with high-NESTUR marker alleles showed a superior growth performance of 17–40% for height, diameter and volume over those with low-NESTUR marker alleles. Received: 10 July 1997 / Accepted: 31 March 1998     

Effect of nitrogen on growth and water relations of radiata pine families

The effect of nitrogen fertilisation on growth, foliar nutrients and water relations of four families of radiata pine (Pinus radiata, D. Don) currently in the Australian breeding program was examined from age six to 11 years. At this stage, the stand was ready for commercial thinning. The annual rainfall at the site varied from 563 to 733 mm.Application of nitrogen fertiliser resulted in stem wood volume at age nine years of 178 m³ ha^-1 in the controls, compared with 228 m³ ha^-1 in plots treated with 600 kg N ha^-1. Pre-dawn needle water potential () measured in three consecutive summers (when rainfall ranged from 53 to 106 mm) were consistently higher (less water stress) in nitrogen fertilised than in control trees. Similarly, the water stress integral (S) decreased consistently with increasing levels of nitrogen, although total water use in fertilised trees would have been substantially higher because fertiliser application increased the leaf area index. The relationship between S and basal area was strong and paralleled that of foliar nitrogen concentration and basal area growth. Therefore, nitrogen application increased growth rates of trees by improving the nutrient status of trees and lowering the water stress on trees in summer.Families showed markedly different responses of basal area growth to nitrogen, ranging from an increase of 9.4% over three years for the least responsive family to 99.0% for the most responsive. There was no nitrogen × family interaction on or S suggesting that the large genetic variation in the growth response to nitrogen is mediated by factors other than water relations. These results have implications for managing highly productive plantations grown in an environment where rainfall is low compared to potential evapotranspiration.     

A differential distribution of auxin and flavonols in radiata pine stem seedlings exposed to inclination

Tree Genetics & Genomes - Gibberellins (GAs) have been widely used for many years to induce seedless grapevine and increase fruit set in production. However, the role of GAs and how they...     

Age-related changes in the expression of QTLs for growth in radiata pine seedlings

 Haploid megagametophytes from a full-sib cross of Pinus radiata were used to construct a genetic linkage map for radiata pine based on random amplified polymorphic DNA (RAPD) markers. The map, which was made from 222 markers, was used to carry out a QTL analysis of growth using measurements made on seedlings from which these megagametophytes were collected at an early germination stage. Trends in the expression of QTLs for stem diameter, volume and height were compared using measurements made at 5 months of age, and at 1, 2 and 3 years of age. None of the observed trends showed complete stability, i.e. none of the putative QTL positions detected at any one age was strongly expressed at all of the four stages of measurement. However, 45% of the trends showed partial stability, i.e. putative QTLs significant at one age were also detected at a subsequent age. Trends in QTL expression with age followed one of three patterns: (1) putative QTLs at some locations showed a gradual linear increase in influence from 5 months of age and were highest at 3 years of age; (2) QTLs detected at 5 months of age gradually became less significant with age; and (3) some putative QTLs showed a curvilinear increase in effect from 5 months of age, reaching their peak expression at 1 to 2 years, and sometimes were still detected at 3 years of age. Received: 10 July 1997 / Accepted: 31 March 1998     

The influence of simulated shadelight and daylight on growth, development and photosynthesis of Pinus radiata, Agathis australis and Dacrydium cupressinum

Abstract. Juvenile seedlings, micropropagated plantlets, and adult rooted cuttings of Pinus radiata, together with seedlings of Agathis australis and Dacrydium cupressinum, were grown under either high (670/μmol m^?2 s^?1) or low (200 μmol m^?2 s^?1) photosynthetic photon flux density (PPFD) and, at low PPFD, under three red:far-red (R/FR) conditions, approximately simulating canopy shadelight, daylight and one intermediate value. In all types of P. radiata, a shade-intolerant species, stem height and diameter, stem and needle dry weight, and apical dominance were markedly increased by a reduction in R:FR ratio while fascicle density was decreased. In contrast, these increases were considerably less for the shade-tolerant D. cupressinum and moderately tolerant A. australis. With the exception of the P. radiata seedlings, height growth was greatest in all species under high compared to low PPFD for daylight R:FR ratio conditions. Total shoot (or plant) dry weight was increased approximately two-fold in all species and types by the higher PPFD. Shoot extension rates were negatively correlated with calculated phytochrome photoequilibrium with P. radiata, the most shade-intolerant species, having the highest change in rate per unit change in photoequilibrium (i.e. very responsive), and D. cupressinum, the most shade tolerant species evaluated, having the smallest change (i.e. largely unresponsive). Within the spectral quality treatments at low PPFD, it is suggested that higher rates of dry matter accumulation under the low R:FR ratio were the result of reduced mutual shading of adjacent leaves as a consequence of photomorphogenically-controlled internode lengths rather than of enhanced photosynthesis per se. The significance of the results is discussed in relation to planting stock management in nurseries, the management of forest canopies for understorey seedling growth, and to the construction of representative growth simulation models. Consequences for controlled environment lighting are also considered.     

Changes in soil CO2 and O2 concentrations when radiata pine is grown in competition with pasture or weeds and possible feedbacks with radiata pine root growth and respiration

This study examined the reciprocal effects of growing ryegrass, lotus and other weed species in competition with radiata pine on soil CO₂ and O₂ concentrations and on the growth and root respiration of the radiata pine. Soil O₂ concentrations decreased and soil CO₂ concentrations increased with increasing soil depth. Radiata pine plus competing species slightly reduced soil O₂ concentrations and markedly increased soil CO₂ concentrations (up to 40 mmol mol⁻¹) compared with radiata pine alone. The dry weights of shoots and roots, and the root respiration rates of radiata pine grown with competing vegetation were much less than those for radiata pine alone. This probably was not solely caused by competition for nutrients water or light since adequate water and nutrients were supplied to all treatments and the radiata pine overtopped the competing vegetation. When radiata pine roots were raised in NaHCO₃ solutions equivalent to a range of CO₂ concentrations, succinate dehydrogenase activity (a metabolic indicator of mitochondrial respiration) and elongation rates of roots decreased as CO₂ concentrations increased from 0 to 40 mmol mol⁻¹. This suggests that the elevated CO₂ concentrations found in the experiments in soil was the cause, at least in part, of the reduced growth of radiata pine in competition with other species. This revised version was published online in June 2006 with corrections to the Cover Date.     

The influence of the lower Ob River runoff on radial growth of trees

The influence of the Ob River runoff in its lower reaches on the radial growth of main forest-forming tree species-the Siberian spruce (Picea obovata Ledeb.), Siberian stone pine (Pinus sibirica Du Tour.), and larch (Larix sibirica Ledeb.)-was studied in the north of Western Siberia in various test sites both at the riverside and at a distance of 3 to 80 km from the Ob River floodplain. Differences in responses of the radial growth to air temperature in October and repeated frost damage of tree annual rings are observed in the Siberian spruce and Siberian stone pine depending on the distance from the river. The correlations of the radial growth of trees and frost damage with the effect of the Ob River runoff are discussed.     

Effects of radial growth, tree age, climate, and seed origin on wood density of diverse jack pine populations

Several models of the effects of silviculture, radial growth, and tree age on wood density have been developed, but they have rarely considered the roles of diverse seed origins and climate. We developed a model to test the effects of radial growth, tree age, climate, and seed-source origins on wood density in 21 diverse populations of jack pine in a common garden in Petawawa, Ontario, Canada over the last 24 years using a linear mixed-effects model. Although we found significant differences in wood density among diverse seed origins, there were no differences between seed origins having the same ring age and ring width, indicating an indirect effect on wood density of seed-source origin via radial growth. High variation in wood density among trees within the same population and between populations indicated high genetic control of wood density. The climate effect was significant on wood density in all populations, but smaller when radial growth was controlled. Climate effect did not differ significantly among populations. Precipitation in July negatively affected latewood density, whereas precipitation in May in the current year and September of the previous year negatively affected earlywood density. We concluded that a single model of jack pine wood density and radial growth could be used, either controlling for climate effects or not, as the relationship between wood density and radial growth is preserved among the diverse populations, and the climate effect controlling for radial growth in the model was only slight.     

Stand- and tree-level determinants of the drought response of Scots pine radial growth

Characterizing the responses of key tree species to extreme climatic events may provide important information for predicting future forest responses to increased climatic variability. Here we aimed at determining which tree- and stand-level attributes were more closely associated with the effect of a severe drought on the radial growth of Scots pine, both in terms of immediate impact and recovery after the drought event. Our dataset included tree-ring series from 393 plots located close to the dry limit of the species range. Time series analysis and mixed-effects models were used to study the growth of each tree and its detailed response to a severe drought event that occurred in 1986. Our results showed that the radial growth responses of Scots pine were determined primarily by tree-level characteristics, such as age and previous growth rate, and secondarily by stand basal area and species richness, whereas local climate had a relatively minor effect. Fast-growing trees were more severely affected by the drought and retained proportionally lower growth rates up to three years after the episode. In absolute terms, however, fast-growing trees performed better both during and after the event. Older trees were found to be less resilient to drought. The effect of stand basal area and species richness indicated that competition for resources worsened the effects of drought, and suggested that the effect of interspecific competition may be particularly detrimental during the drought year.     

Effect of hydrothermal conditions of permafrost soil on radial growth of larch and pine in Central Yakutia

Results of an investigation of radial growth of Larix cajanderi Mayr and Pinus sylvestris L. in Central Yakutia are presented. The time span of the constructed tree-ring chronologies is more than 200 years. Dendroclimatological analysis revealed a close relationship of tree growth on permafrost soils with climatic factors and soil hydrothermal conditions. A significant correlation of radial growth of larch and pine trees in Central Yakutia with soil temperature and moisture at various depths was found for the first time by statistical analysis.     

Inferring relatedness and heritability using molecular markers in radiata pine

A set of eight unlinked microsatellite markers was used to estimate relatedness among 355 individuals of a Pinus radiata breeding population. The average performance of open-pollinated progeny of each individual, for wood density, was considered to represent the phenotype of all 355 individuals. Marker-based estimates of relationship were compared with the pedigree-based coefficients of relationships. The phenotypic similarity among all pairs of individuals was regressed on marker-estimated relatedness to estimate the inheritance of wood density. The marker-based estimate of heritability was compared with that obtained using classical quantitative genetic methods. Overall, a low correlation (0.13) was observed between marker-based and pedigree-based estimates of relatedness. After discarding negative estimates of relatedness, the average coefficient of relationship among known groups of maternal half-sibs, full-sibs and unrelated individuals, increased from 0.24 to 0.29 (0.25 expected), from 0.43 to 0.48 (0.50 expected) and from –0.04 to 0.15 (0 expected), respectively. Marker-based and conventional estimates of heritability of wood density were 0.79 and 0.38, respectively. However, by using only marker loci with expected Hardy–Weinberg frequencies, marker-based estimate of heritability was 0.33, which is very similar to that obtained from conventional approaches. The use of molecular markers to understand quantitative genetic variation is discussed.     

Photosynthesis, temperature and radial growth of Scots pine in northern Finland: identifying the influential time intervals

We analyzed the statistical dependence between temperature, the state of functional substances (S), estimated photosynthetic production and the radial growth of Scots pine in northern Finland. Annual sums of these variables were calculated for intervals consisting of consecutive calendar days. For daily mean temperature, all possible intervals between 1 April of the previous year and 31 August of the current year were tested. For S and the daily photosynthetic production, the tested range included days from April to October of the previous year and from April to August of the current year. These sums were compared with tree-ring indices using the Pearson correlation coefficient over the period 1906–2002. The highest correlations (r = 0.64) between daily mean temperature and growth indices were obtained for current-year periods starting 22 June and ending 28 July. For S, a temperature-derived variable describing the instantaneous photosynthetic capacity of Scots pine, the respective interval was from 5 July to 31 July (r = 0.63). The daily photosynthetic production of Scots pine was estimated for 1906–2002 using the PhenPhoto model. The interval during which the estimated daily photosynthetic production of Scots pine produced the highest correlation with growth indices (r = 0.56) was from 5 July to 27 July. Previous-year values of each variable were also significantly correlated to annual growth indices. The intervals with highest correlations were in May–June for each variable, and the correlations were rather low—between 0.3 and 0.4. We also tested selection criteria based on intervals that do not consist of consecutive calendar days, but results did not show notable improvements over the customarily used continuous intervals.     

The influence of wind on branch characteristics of Pinus radiata

Measurements taken from trees growing in exposed and sheltered areas within two structurally similar forests were used to investigate the influence of wind on branch characteristics of mature New Zealand-grown Pinus radiata. A widely used branch model was used to remove the influence of treatment and site differences in tree stem diameter and height, so that the influence of wind on branch diameter could be examined. At site 1 average windspeed in the exposed treatment exceeded average windspeed in the sheltered treatment by 62%. When averaged across sites, mean branch diameter, branch index (mean diameter of the largest branch, in each of the four azimuthal quadrants) and largest branch diameter in exposed areas significantly exceeded values for trees in sheltered areas by 9 mm (25%), 42 mm (54%), and 72 mm (72%), respectively. Treatment and site differences in tree stem diameter and height partially accounted for the observed increases in branch diameter. However, after these effects were removed by the model, branch diameter in exposed areas still significantly exceeded that in sheltered areas by 21 mm for branch index and 44 mm for the largest branch. Treatment and site variation in this residual branch diameter was almost entirely attributable to topographical exposure to 1 km, a variable which has been found to be strongly correlated to windspeed. Possible reasons for these observed wind-induced increases in branch diameter are discussed.

Dicyclohexylamine uptake and effects on polyamine content in cultured cotyledons of radiata pine

Excised cotyledons of radiata pine ( Pinus radiata D. Don) were cultured in the presence or absence of benzyladenine and two concentrations of dicyclohexylamine, a potent inhibitor of spermidine synthesis in animals and bacteria. Cellular levels of the drug and of putrescine, spermidine and spermine were determined by dansylation followed by thin layer chromatography. The rate of uptake of the drug was rapid during the first 6 h of incubation and then diminished; nevertheless, its cellular content increased with time in culture and uptake was greater if more was present in the medium. Cotyledons cultured on benzyladenine-containing media accumulated more dicyclohexylamine than on benzyladenine-free media and this resulted in toxic side-effects. The drug had no significant effect on the elongation growth occurring in the absence of the hormone. In cotyledons treated with the drug, spermidine levels fell to zero after a 5- to 10-day exposure. Putrescine increased transiently at 24 h and then declined significantly. Spermine levels also declined to 11% of control values by day 5 and remained low throughout. Except for a marked decrease in all three polyamines during the first 24 h of culture, all control cotyledons maintained significantly higher polyamine levels than dicyclohexylamine-treated ones.