Interclonal Variation Research Articles

Leaf thermotolerance of Hevea brasiliensis clones: intra- versus interclonal variation and relationships with other functional traits.

Land surface temperature is predicted to increase by 0.2°C per decade due to climate change, although with considerable regional variability, and heatwaves are predicted to increase markedly in the future. These changes will affect where crops can be grown in the future. Understanding the thermal limits of plant physiological functioning and how flexible such limits are is thus important. Here, we report on the measurements of a core foliar thermotolerance trait, T50, defined as the temperature at which the maximum quantum yield (Fv/Fm) of photosystem II declines by 50%, across nine different Malaysian Hevea brasiliensis clones. We explore the relative importance of interclonal versus intraclonal variation in T50 as well as its association with leaf and hydraulic traits. We find very low variation in T50 within individual clones (mean intraclonal coefficient of variation (CoV) of 1.26%) and little variation across clones (interclonal CoV of 2.1%). The interclonal variation in T50 was lower than for all other functional traits considered. The T50 was negatively related to leaf mass per area and leaf dry matter content, but it was not related to hydraulic traits such as embolism resistance (P50) or hydraulic safety margins (HSM50). The range of T50 observed (42.9-46.2°C) is well above the current maximum air temperatures Tmax,obs (T50 - Tmax,obs>5.8 °C), suggesting that H. brasiliensis is likely thermally safe in this south-east Asian region of Malaysia.

Bimodal Expression Patterns, and Not Viral Burst Sizes, Predict the Effects of Vpr on HIV-1 Proviral Populations in Jurkat Cells.

ABSTRACTIntegration site landscapes, clonal dynamics, and latency reversal with or without vpr were compared in HIV-1-infected Jurkat cell populations, and the properties of individual clones were defined. Clones differed in fractions of long terminal repeat (LTR)-active daughter cells, with some clones containing few to no LTR-active cells, while almost all cells were LTR active for others. Clones varied over 4 orders of magnitude in virus release per active cell. Proviruses in largely LTR-active clones were closer to preexisting enhancers and promoters than low-LTR-active clones. Unsurprisingly, major vpr+ clones contained fewer LTR-active cells than vpr− clones, and predominant vpr+ proviruses were farther from enhancers and promoters than those in vpr− pools. Distances to these marks among intact proviruses previously reported for antiretroviral therapy (ART)-suppressed patients revealed that patient integration sites were more similar to those in the vpr+ pool than to vpr− integrants. Complementing vpr-defective proviruses with vpr led to the rapid loss of highly LTR-active clones, indicating that the effect of Vpr on proviral populations occurred after integration. However, major clones in the complemented pool and its vpr− parent population did not differ in burst sizes. When the latency reactivation agents prostratin and JQ1 were applied separately or in combination, vpr+ and vpr− population-wide trends were similar, with dual-treatment enhancement being due in part to reactivated clones that did not respond to either drug applied separately. However, the expression signatures of individual clones differed between populations. These observations highlight how Vpr, exerting selective pressure on proviral epigenetic variation, can shape integration site landscapes, proviral expression patterns, and reactivation properties.

Hydraulic traits predict stem growth across Hevea brasiliensis clones in a Malaysian climatically marginal area

Competition for land resources is forcing rubber (Hevea brasiliensis Müll. Arg.) production into more agroclimatically vulnerable zones, which are more likely to be affected by drought. It is therefore of interest to determine whether there are particularly drought resistant rubber genotypes. Established plant drought-resistance indicators include xylem resistance to embolism under water stress (P50, water potential at which 50% xylem conductivity is lost), and hydraulic safety margins (HSM50), defined as the difference between P50 and minimum leaf water potential (Pmin) under driest conditions in the year. We report here on measurements of in-situ growth performance of nine mature rubber clones at an agro-climatically marginal site in North-Western Malaysia and their hydraulic, leaf and stem traits to investigate inter-clonal variation in drought resistance and growth rate. We find that P50 varies substantially across clones, between −3.05 and −1.37 MPa, while HSM50 varied within the range of −0.11 MPa to 1.37 MPa. Similar to what has been reported across species, we find a growth-hydraulic safety trade-off between rubber clones with faster growth rates associated with a lower HSM50 and less negative P50, with one exception. Based on hierarchic linear regression we find that almost all of the best growth models include hydraulic traits, besides morphological traits, indicating that hydraulic traits are important to predict growth accurately. Furthermore, rubber genotypes with high growth rate and low hydraulic safety margin (HSM50) were associated with lower wood density, higher leaf to sapwood area and larger leaf area. Overall while there are clones that are more drought resistant and are thus suited for plantation in marginal areas, they tend to be less productive.

Assessment of Morphological Traits, Nutritional and Nutraceutical Composition in Fruits of 18 Apricot cv. Sekerpare Clones

Apricot (Prunus armeniaca L.) is one of the most important members of Prunus and its trees bears delicious and nutritious fruits during summer months in the temperate zones in the world. Apricot cultivars are propagated asexually which consists of clones. Information on inter-clonal variations in apricot cultivars can assist us in the selection of better clones from commercial cultivars. We aimed to determine morphological traits (fruit weight, seed weight, kernel weight, flesh/seed ratio, shape index, fruit firmness, color index), nutritional (sugars and organic acids) and nutraceutical (total phenolic, total flavonoids, total carotenoid and antioxidant activity) composition of 18 clones of Sekerpare apricot cultivar grown together in Kagizman district in eastern Turkey. Results showed significant differences among clones concerning most of the morphological traits, nutritional and nutraceutical compositions. Fruit weight, flesh/seed ratio and fruit firmness of clones were in range of 23.14–27.11 g, 11.21–13.14 and 3.88–5.11 kg/cm2, respectively. Fruit shape index was slightly similar among all clones which was between 0.95 and 1.03. Citric acid and sucrose were found to be the predominant organic acid and sugar among clones which varied from 728 to 915 mg/100 g and 7.11 to 9.94 g/100 g, respectively. The clone ‘KS2’ exhibited the highest level of total phenol (67.1 mg gallic acid equivalent per 100 g) and antioxidant activity (2.16 μmol trolox equivalent per g). The study confirmed the diversity among Sekerpare clones and effectiveness of combining morphological, nutritional and nutraceutical analyses in assessment of Şekerpare clones and its use for future pre-breeding programs.

Efficient Cryopreservation of Populus tremula by In Vitro-Grown Axillary Buds and Genetic Stability of Recovered Plants.

Axillary buds of in vitro microshoots were successfully frozen at –196 °C by the one-step freezing method using the protective vitrification solution 2 (PVS2). Microshoots were taken from 11 transgenic lines and three wild type lines. Influence of different explant pretreatments were analyzed from the point of their influence towards recovery after cryopreservation. It was found out that the use of axillary buds as explants after removal of the apical one increases recovery on average by 8%. The cultivation on growth medium of higher density insignificantly raises the regenerants survival rate. Pretreatment of the osmotic fluid (OF) shows the greatest influence on the survival rate. It leads to the increase in survival rate by 20%. The cryopreservation technology providing regenerants average survival rate of 83% was developed. It was based on the experimental results obtained with explant pretreatment. Incubation time in liquid nitrogen did not affect the explants survival rate after thawing. After six months cryostorage of samples their genetic variability was analyzed. Six variable simple sequence repeat (SSR) loci were used to analyze genotype variability after the freezing-thawing procedure. The microsatellite analysis showed the genetic status identity of plants after cryopreservation and of the original genotypes. The presence of the recombinant gene in the transgenic lines after cryostorage were confirmed so as the interclonal variation in the growth rate under greenhouse conditions. The developed technique is recommended for long-term storage of various breeding and genetically modified lines of aspen plants, as it provides a high percentage of explants survival with no changes in genotype.

Interclonal variation, coordination, and trade-offs between hydraulic conductance and gas exchange in Pinus radiata: consequences on plant growth and wood density.

Stem growth reflects genetic and phenotypic differences within a tree species. The plant hydraulic system regulates the carbon economy, and therefore variations in growth and wood density. A whole-organism perspective, by partitioning the hydraulic system, is crucial for understanding the physical and physiological processes that coordinately mediate plant growth. The aim of this study was to determine whether the relationships and trade-offs between (i) hydraulic traits and their relative contribution to the whole-plant hydraulic system, (ii) plant water transport, (iii) CO2 assimilation, (iv) plant growth, and (v) wood density are revealed at the interclonal level within a variable population of 10 Pinus radiata (D. Don) clones for these characters. We demonstrated a strong coordination between several plant organs regarding their hydraulic efficiency. Hydraulic efficiency, gas exchange, and plant growth were intimately linked. Small reductions in stem wood density were related to a large increase in sapwood hydraulic efficiency, and thus to plant growth. However, stem growth rate was negatively related to wood density. We discuss insights explaining the relationships and trade-offs of the plant traits examined in this study. These insights provide a better understanding of the existing coordination, likely to be dependent on genetics, between the biophysical structure of wood, plant growth, hydraulic partitioning, and physiological plant functions in P. radiata.

Evaluation of poplar and willow clones on the experimental short rotation plantation in Kharkiv region: results of the second cultivation year

Purpose. To estimate the growth performance of poplar and willows clones on the 2nd vegetation year at short rotation plantation in the Kharkiv region, and to identify the most perspective clones for the establishing of bioenergy plantations.Methods. The growth characteristics of 2-year-old poplars (10 clones) and willows (3 clones) were analyzed on experimental plot established in 2014 due to common practice, with stem cuttings 20–25 cm long and 0.8–1.2 cm in diameter. During the analysis performed in October, diameter and height of the shoots were measured and the quantity of plants with 1, 2, and ≤ 3 shoots per plant was determined.Results. The investigations revealed significant interclonal variation in estimated growth parameters on the second vegetation year. The poplar clones ‘Huliver’, ‘Strilopodibna’, ‘Rohanska’, ‘Slava Ukrainy’ and willow clone ‘Pryberezhna’ demonstrated high growth rates. The shoot height of poplars ‘Rohanska’ and ‘Slava Ukrainy’ were 30% and 42% respectively, higher than average rates after two years of cultivation. The clones of poplars ‘Huliver’, ‘Strilopodibna’, and clone of willow ‘Pryberezhna’ had the largest diameters exceeded the average rates more than 20%. Poplars ‘Constanta’, ‘Lvivska’ and ‘Noctiurn’ demonstrated low growth. By the sprouting capacity the clones were divided into two groups: with a high level of sprouting capacity increasing significantly during the second growing season (‘Huliver’, ‘Rohanska’, ‘Druzhba’); and with low sprouting capacity within both vegetation seasons (‘Constanta’, ‘Noctiurn’ and ‘Lvivska’). In general, a comparison of the averaged growth parameters of poplars and willows revealed that the willows prevailed the poplars in height, but no significant differences in diameter and sprouting capacity were observed.Conclusions. The poplars ‘Huliver’, ‘Strilopo­dibna’, ‘Rohanska’, ‘Slava Ukrainy’ and the willow ‘Pryberezhna’ demonstrated high growth values, and poplar clones ‘Huliver’, ‘Rohanska’ and ‘Druzhba’ showed a high level of sprouting capacity. During the two growing seasons the clones of poplars ‘Constanta’, ‘Lvivska’ and ‘Noctiurn’ showed low growth rates and sprouting capacity. The results of experiments could be taken into account when establishing short-rotation plantations of bioenergy trees, in particular on plots without artificial irrigation.

Seasonal Changes in Interclone Variation Following Ozone Exposure on Three Major Gene Pools: An Analysis of Cryptomeria Japonica Clones

Recently, there has been a continuous increase in the concentration of tropospheric ozone in urban forests in Japan. Since monoterpenes are precursors to ozone, we need to evaluate the effects of ozone exposure on all tree species that are considered to be sources of monoterpenes. Cryptomeria japonica, which is the most widely planted afforestation tree, is classified into three different gene pools. However, the interclone variation for seasonal changes in the ozone exposure effect has not been evaluated. Thus, free-air ozone enhancement experiments were conducted using three representative clones of C. japonica in the summer and winter. After exposure to twice the ozone concentration in the ambient atmosphere, the effect on the monoterpene emission rate was found to be considerably different among the clones and for the different seasons. The monoterpene emission rate after ozone exposure increased in winter and summer in the native clones (Donden and Yakushima) in the snow area and heavy rain area, respectively. Since monoterpenes are antibacterial substances, each clone adapted sensitivity to stress during each season upon considerable damage. These results suggest that not only differences between tree species but also differences between clones are important for evaluating seasonal variation characteristics after ozone exposure.

Biomass Yield and Fuel Properties of Different Poplar SRC Clones

The goal of the research was to determine the biomass yield and fuel properties of ten different poplar clones. The research was conducted in an experimental plot established in Forest Administration Osijek, Forest Office Darda, in the spring of 2014. The layout of the plot consisted of three repetitions per clone with 40 plants per repetition in spacing 3x1 m. Based on the DBH distribution, in the early spring of 2018, one sample tree of an average DBH per repetition was selected, thus forming a sample of 30 trees. Average survival rate of the investigated trees after four vegetation periods was 74.54 ±13.85% ranging from 52.08% (Koreana) to 91.67% (SV885 and SV490). Average DBH of the sample trees was 8.2 ±1.9 cm, height 9.3 ±1.8 m and root collar diameter 10.7 ±1.9 cm. Moisture content in fresh state (just after the felling) ranged from 51.6% (Hybride 275) to 55.9% (SV885). Bark content averaged 18.4%, from 15.4% (Baldo) to 21.1% (V 609). Average nominal density of the sampled trees amounted to 383.5 ±35.9 kg/m3. Bark ash content was on average ten times higher (6.44 ±0.65%) than wood ash content (0.64 ±0.07%) resulting in average ash content of 1.7 ±0.1% (taking the bark content into account). The clone SV490 showed the highest biomass yield with 15.8 t/ha/year, while the lowest biomass yield was recorded for the clone Hybride 275 with 2.8 t/ha/year. High inter-clonal productivity variation stresses the importance of selection work to find the most appropriate clones with the highest productivity potential for the given area where the poplar SRC plantations are to be established. Due to high initial moisture content, if direct chipping harvesting systems are preferred, wood chips could be efficiently used in CHP (Combined Heat and Power) plants that operate on the principle of biomass gasification (where a gasifier is coupled to a gas engine to produce electric power and heat). In several CHP gasification plants operating in Croatia, wood chips with high initial moisture content (from traditional poplar plantations) are used as a feedstock that has to be pre-dried using the surplus heat. In this respect SRC poplar wood chips could make an ideal feedstock supplement.

Inter-clonal Variation in Copper Sensitivity in Bosmina longirostris with Different Exposure Histories

An acquisition of metal tolerance in cladocerans related to the historical exposure has been well documented for the genera Daphnia and Ceriodaphnia, which are frequently used in ecotoxicological studies. However, small-sized cladocerans are rarely investigated for the inter-clonal variation in metal sensitivity, whereas they often dominate zooplankton community in many lakes and ponds, and even in eutrophicated rivers. We investigated the influence of historical copper exposure on the copper sensitivity of Bosmina longirostris. Copper sensitivity was compared among three clones originating from a site (Lake Yanaka), which located at downstream of historically contaminated river (Watarase River) and clones from five different reservoirs. For reference, the background copper concentration (as Cu2+ activity) at each site and its toxicity to Daphnia magna were estimated by metal speciation and the biotic ligand model (BLM), respectively. Less copper-sensitive Bosmina clones were obtained only from Lake Yanaka, although the background copper concentrations were far below the lethal levels. The results suggested the variability in copper-sensitivity in B. longirostris and its association with historical copper contamination.

Evaluation of variability in human kidney organoids

The utility of human pluripotent stem cell-derived kidney organoids relies implicitly on the robustness and transferability of the protocol. Here we analyze the sources of transcriptional variation in a specific kidney organoid protocol. Although individual organoids within a differentiation batch showed strong transcriptional correlation, we noted significant variation between experimental batches, particularly in genes associated with temporal maturation. Single-cell profiling revealed shifts in nephron patterning and proportions of component cells. Distinct induced pluripotent stem cell clones showed congruent transcriptional programs, with interexperimental and interclonal variation also strongly associated with nephron patterning. Epithelial cells isolated from organoids aligned with total organoids at the same day of differentiation, again implicating relative maturation as a confounder. This understanding of experimental variation facilitated an optimized analysis of organoid-based disease modeling, thereby increasing the utility of kidney organoids for personalized medicine and functional genomics.

Genome-wide mutation detection by interclonal genetic variation

Genetic toxicology assays estimate mutation frequencies by phenotypically screening for the activation or inactivation of endogenous or exogenous reporter genes. These reporters can only detect mutations in narrow areas of the genome and their use is often restricted to certain in vitro and in vivo models. Here, we show that Interclonal Genetic Variation (ICGV) can directly identify mutations genome-wide by comparing sequencing data of single-cell clones derived from the same source or organism. Upon ethyl methanesulfonate (EMS) exposure, ICGV detected greater levels of mutation in a dose- and time-dependent manner in E. coli. In addition, ICGV was also able to identify a ∼20-fold increase in somatic mutations in T-cell clones derived from an N-ethyl-N-nitrosourea (ENU)-treated rat vs. a vehicle-treated rat. These results demonstrate that the genetic differences of single-cell clones can be used for genome-wide mutation detection.

PHYSICAL AND MECHANICAL EVALUATION OF 8-YEARS-OLD ACACIA HYBRID (A. Mangium x A. Auriculiformis) CLONES FOR VARIOUS END USES

Currently, clonal of forest tree is gaining importance due to the yield improvement and low variability in different wood characteristics. Hybrid trees from clonal forest are importantly characterized in term of wood quality for finding suitable uses. Accordingly, three clones (HD3, K47, H4) of 8-year-old Acacia hybrid (Acacia mangium × A. auriculiformis) were evaluated for inter-clonal comparison of its wood quality by evaluating their physical and mechanical properties as per Indian Standards. All tree clones were studied at breast high including diameter, heartwood content, and physical and mechanic properties. The Dbh of all three clones was around 30–35% and 60–70% greater than pure forms of A. auriculiformis and A. mangium of the same age, respectively. The volumetric shrinkage of all three clones was found to vary from 7.8 to 8.6%. The low shrinkage values may be attributed to higher dimensional stability of the wood of these clones. The data obtained in green and air-dry conditions were used to calculate ‘suitability indices' with respect to teak (Tectona grandis) which was taken as a reference wood for comparison in India. All the suitability indices that these clones were either comparable or slightly lower than those of pure forms of A. auriculiformis and A. mangium. Less inter-clonal variation was observed in most of the suitability indices. Though, all the three clones were exclusively grown for their use in pulp and paper industry, but the comparative suitability figures for different end uses indicate that these clones could also be used for certain non-structural applications such as tool handles, light packing cases, pallets and light furniture.

Host-genotype dependent gut microbiota drives zooplankton tolerance to toxic cyanobacteria

The gut microbiota impacts many aspects of its host’s biology, and is increasingly considered as a key factor mediating performance of host individuals in continuously changing environments. Here we use gut microbiota transplants to show that both host genotype and gut microbiota mediate tolerance to toxic cyanobacteria in the freshwater crustacean Daphnia magna. Interclonal variation in tolerance to cyanobacteria disappears when Daphnia are made germ-free and inoculated with an identical microbial inoculum. Instead, variation in tolerance among recipient Daphnia mirrors that of the microbiota donors. Metagenetic analyses point to host genotype and external microbial source as important determinants of gut microbiota assembly, and reveal strong differences in gut microbiota composition between tolerant and susceptible genotypes. Together, these results show that both environmentally and host genotype-induced variations in gut microbiota structure mediate Daphnia tolerance to toxic cyanobacteria, pointing to the gut microbiota as a driver of adaptation and acclimatization to cyanobacterial harmful algal blooms in zooplankton.

Leaf metabolic response to water deficit in Pinus pinaster Ait. relies upon ontogeny and genotype

Pinus pimaster Aiton displays marked heteroblasty during its vegetative phase, showing complex interactions between developmental processes and environmental adaptation, with a patent differentiation in functional performance according to leaf type resulting from heteroblasty. In this work, untargeted quantitative metabolic profiling in adult and juvenile needles of four water-deficit stressed P. pinaster genotypes was investigated to know if metabolic responses to drought are genotype-dependent and vary according to the stage of needle ontogeny.Among the changes in metabolome, it highlights the increase of osmotically active substances, as well as the overproduction of antioxidant compounds by up-regulating ascorbate, shikimate/phenylalanine and phenylpropanoid metabolic pathways. Moreover, significant inter-clonal quantitative variations were also found at different levels, in both primary and secondary metabolism pathways, although terpenoids and specially flavonoids showed the highest significance. A surprising result was the ontogenetic changes in metabolic profiles. Juvenile needles contain significant higher levels of UV screener and antioxidant flavonoids. The level of drought tolerance of a genotype and the ontogenetic stage were important factors in determining the drought-induced level of flavonoid increase in needles of a given genotype. Regarding terpenoids, the significant drought-induced accumulation of neutral diterpenes in juvenile needles, and mono- and sesquiterpenes in adults, was genotype dependent regardless its degree of drought tolerance.These results point to flavonoids as very versatile metabolites in maritime pine needle, acting like important compounds modulating not only drought acclimation but also changes in needle metabolism associated with developmental processes such as heteroblasty.

The influence of facultative endosymbionts on honeydew carbohydrate and amino acid composition of the black bean aphid Aphis fabae

AbstractThe facultative endosymbionts Hamiltonella defensa and Regiella insecticola are commonly found in aphids. They are linked with various ecological benefits but generally occur at low prevalence, which indicates a possible harbouring cost. Little is known about how the presence of facultative endosymbionts is reflected in honeydew composition. Honeydew is the key mediator of the mutualism between aphids and their tending ants. The present study examines whether endosymbionts have an influence on aphid honeydew quality by comparing the amino acid and carbohydrate concentrations between infected and uninfected aphids. To this end, two genetic lines of the aphid Aphis fabae Scopoli are experimentally infected with different strains of Hamiltonella and Regiella. Infected aphids are shown to have reduced concentrations of amino acids in the honeydew compared with uninfected aphids. However, the presence of endosymbionts has no effect on the absolute amount of carbohydrates produced. Nevertheless, interclonal variation in honeydew composition between aphid genotypes is observed for both carbohydrate and amino acid production. These results imply that the nutritional value of honeydew depends on aphid genotype, as well as on the presence of secondary bacterial endosymbionts, which suggests that there is a physiological cost of harbouring endosymbionts and which could also impact aphid attractiveness to tending ants.

T-cell stimuli independently sum to regulate an inherited clonal division fate

In the presence of antigen and costimulation, T cells undergo a characteristic response of expansion, cessation and contraction. Previous studies have revealed that population-level reproducibility is a consequence of multiple clones exhibiting considerable disparity in burst size, highlighting the requirement for single-cell information in understanding T-cell fate regulation. Here we show that individual T-cell clones resulting from controlled stimulation in vitro are strongly lineage imprinted with highly correlated expansion fates. Progeny from clonal families cease dividing in the same or adjacent generations, with inter-clonal variation producing burst-size diversity. The effects of costimulatory signals on individual clones sum together with stochastic independence; therefore, the net effect across multiple clones produces consistent, but heterogeneous population responses. These data demonstrate that substantial clonal heterogeneity arises through differences in experience of clonal progenitors, either through stochastic antigen interaction or by differences in initial receptor sensitivities.

On-Chip Clonal Analysis of Glioma-Stem-Cell Motility and Therapy Resistance

Enhanced glioma-stem-cell (GSC) motility and therapy resistance are considered to play key roles in tumor cell dissemination and recurrence. As such, a better understanding of the mechanisms by which these cells disseminate and withstand therapy could lead to more efficacious treatments. Here, we introduce a novel micro-/nanotechnology-enabled chip platform for performing live-cell interrogation of patient-derived GSCs with single-clone resolution. On-chip analysis revealed marked intertumoral differences (>10-fold) in single-clone motility profiles between two populations of GSCs, which correlated well with results from tumor-xenograft experiments and gene-expression analyses. Further chip-based examination of the more-aggressive GSC population revealed pronounced interclonal variations in motility capabilities (up to ∼4-fold) as well as gene-expression profiles at the single-cell level. Chip-supported therapy resistance studies with a chemotherapeutic agent (i.e., temozolomide) and an oligo RNA (anti-miR363) revealed a subpopulation of CD44-high GSCs with strong antiapoptotic behavior as well as enhanced motility capabilities. The living-cell-interrogation chip platform described herein enables thorough and large-scale live monitoring of heterogeneous cancer-cell populations with single-cell resolution, which is not achievable by any other existing technology and thus has the potential to provide new insights into the cellular and molecular mechanisms modulating glioma-stem-cell dissemination and therapy resistance.

Above- and below-ground biomass partitioning and fine root morphology in juvenile Sitka spruce clones in monoclonal and polyclonal mixtures

Six juvenile Sitka spruce (Picea sitchensis (Bong.) Carr) clones were grown in monoclonal (pure) and polyclonal mixtures (mixed) in a field experiment to assess effects of clonal diversity on above- and below-ground growth, biomass partitioning and fine root morphology. Shoot height and root collar diameter were measured twice annually and after the second year 48 clones were destructively harvested. Fine roots were divided into 10 diameter classes, for each of which morphological characteristics were calculated from digitized images. Competitive interactions arising from deployment type were found to significantly increase fine root surface area in mixed plots and fine root length in pure plots for two fine root diameter classes for some clones. Competitive interactions were also found to significantly alter relationships between above- and below-ground variables and reduce the strength and significance of relationships among root traits in mixed plots. Significant inter-clonal variation for many above- and below-ground parameters was also observed. The two most productive clones, in terms of height and diameter growth, differed significantly in biomass partitioning suggesting that a high degree of variation occurs among Sitka spruce clones, which may affect stand productivity and uniformity.

Assessment of inter-population genetic diversity and preliminary evaluation of suitable clones of teak (Tectona grandis Linn. F.)

Productivity, uniformity and sustainability are the three important characters of the clonally propagated plants. With the increased use of clonal technology, the scarcity of wood products evidently decreased which has also led to reduced pressure on natural forests and ecosystem. However, the success of clonal technology rests on wise selection and deployment of suitable clones by studying the inter-population genetic diversity. The present study was conducted in a clonal seed orchard (CSO) of teak (Tectona grandis Linn. F.) comprising of 13 different clones to estimate the inter-clonal variation in terms of growth performance and genetic variability at 32 and 33 years of age. Clone ORANP2 exhibited maximum DBH (26.61cm), height (23.69 m), and stem volume (235.40 m3ha-1) with MAI of 7.133 m3ha-1year-1. The highest CAI of DBH (1.08 cm) and volume (18.558m3/ha) was reported in ORANP5 and ORANR3, respectively. The study found that clone ORANP2 is a superior genotype and thus can be recommended for vegetative multiplication and ex-situ mass planting in reforestation programmes. Both heritability and genetic advance values were low for all the plant traits studied (DBH, height and stem volume) indicating that these traits are of less use for a tree breeder for furthering the selection and breeding process on teak or other tropical hardwood species across globe.