Male Clones Research Articles

The Origins and Vulnerabilities of Two Transmissible Cancers in Tasmanian Devils

SummaryTransmissible cancers are clonal lineages that spread through populations via contagious cancer cells. Although rare in nature, two facial tumor clones affect Tasmanian devils. Here we perform comparative genetic and functional characterization of these lineages. The two cancers have similar patterns of mutation and show no evidence of exposure to exogenous mutagens or viruses. Genes encoding PDGF receptors have copy number gains and are present on extrachromosomal double minutes. Drug screening indicates causative roles for receptor tyrosine kinases and sensitivity to inhibitors of DNA repair. Y chromosome loss from a male clone infecting a female host suggests immunoediting. These results imply that Tasmanian devils may have inherent susceptibility to transmissible cancers and present a suite of therapeutic compounds for use in conservation.

Growth and reproduction in Pinus sibirica ecotypes from Western Siberia in a common garden experiment

Experimental studies of forest trees’ intraspecies variations in reproduction and reproductive allocation are scarce. Such studies are relevant for the Siberian stone pine (Pinus sibirica Du Tour) because of the high value of its seeds and wood. To reveal growth and reproductive variations among Siberian stone pine ecotypes in relation to the climate of the provenances, we examined their growth height, crown diameter, stem volume, number of female cones, and male shoots, at different ages, in the clonal common garden experiment established in 1996 in Russia. Scions were obtained from 11 to 19 randomly selected 100–170-year old trees in each of four natural stands located on the latitudinal transect on the West Siberian plain. They were grafted onto local 4 year old Siberian stone pine seedlings and grown in a common garden experiment comprising nine plots near the southern margin of the species’ natural range. Growth traits were affected by climatic conditions in the provenances: generally, a warmer climate was associated with more rapid growth. Variation among the ecotypes at the graft age of 12 years was not large; however, it significantly increased by the age of 19. The relationship was ambiguous between reproductive traits and the climate of the provenances. The proportion of female, male and bisexual clones varied among years in all ecotypes. Most of the clones had only female cones; male clones were less common. The southern ecotype showed rapid growth and formed the lowest number of male shoots and female cones. The northern ecotype showed the weakest growth and moderate cone bearing, along with abundant male flowering. The intermediate ecotypes had a moderate growth and the highest numbers of cones, along with moderate numbers of male shoots. These results demonstrate the fundamental differences in the patterns and nature of variation in growth and reproductive traits.

Conversion and determination of sex in Vitis vinifera L. ( sylvestris )

Sex conversion in the male V. vinifera ( sylvestris ) clone 030-44 could not be attributed to germinal mutation of the major gene for sex. The differences in sex expression among male seedling vines can best be explained on the basis of an undetermined number of minor modifying genes able to shift a very sensitive threshold. The frequency of sex conversion within a given seedling vine was greatly influenced by environmental, both local and seasonal, conditions. The following facts were established in Vitis vinifera L. ( sylvestris ): (1) the male sex is heterogametic and is inherited as a simple Mendelian factor, maleness being completely dominant; (2) homozygous males are as viable as heterozygous males, they are phenotypically alike and can only be identified by breeding tests; (3) pure and hermaphroditic males are genetically alike as far as the major gene for sex is concerned; (4) sex chromosomes are not differentiated, either morphologically or physiologically. A pair of alleles, SuF and Sum, were used to explain the results obtained on selfing the hermaphroditic male clone 030-44. The gene Su F determines maleness and its allele Su m in homozygous condition determines femaleness. The gene Su F is completely dominant over its allele Sum. The genotypes of the homozygous and heterozygous males are Su F Su F and Su F Su m respectively, and that of the female is Su m Su m . The evolution of cultivated V. vinifera hermaphrodites in the light of present results is discussed.

Nursery Performance of Male Clones of Poplar (Populus deltoides Bartr.) under Temperate Conditions of Kashmir Valley

Nursery Performance of Male Clones of Poplar (Populus deltoides Bartr.) under Temperate Conditions of Kashmir Valley

A successful strategy to obtain artichoke hybrids

In the last half century the world population has doubled to 7 billion, while the land under cultivation increased just by 12%, from 1.37 to 1.53 billion ha. In what manner, then, did agricultural production triple? By increasing productivity, with a combination of improved agronomical practices and improved crops. In this context the exploitation of plant heterosis has been an effective approach in crop enhancement, hybrid cultivars in major crops can show more than 20% yield advantage over the best conventional ones under the same cultivation conditions. In this attempt, trying to meet commercial and industrial needs, academy (University of Tuscia, Italy) and industry (BHS, USA) encountered over again aiming to produce artichoke commercial hybrid seed through the use of male sterility. The project started in 2007, with 3 male sterile clones and 5 stable open pollinated cultivars, since then, more than 200 male sterile clones and 20 open pollinated cultivars have been developed to produce more than 500 crosses; around 30 of them, with interesting agro-morphological traits and uniformity, have been tested in different countries of the new and old world. The selected hybrids are under evaluation to assess their reproducibility and possibility of success in the global seed market. The different market requests in term of artichoke typologies and quality characteristics, which vary between the fresh market (green, purple, spiny, ovate, round heads) and the processing industry market characterized for green ovate typologies; hence it is required to allow the production/registration of a wide range of hybrids covering the different requests. Currently, one hybrid of Romanesco type, named 'Romolo' has been registered in Italy and is been sold successfully by La Semiorto Sementi srl. and its commercial firm Top Seed. The project results show how artichokes hybrids combine advantages that contribute to more vigorous plant growth, earliness, healthier plants which require lower input in pesticides and fungicides. In addition, plants from seeds are cheaper than plants derived by meristem practices. In other words, seed planting is a viable approach that makes globe artichoke friendlier both to the grower and to the environment.

High daytime temperature delays autumnal bud formation in Populus tremula under field conditions.

The effects of warming on autumnal growth cessation and bud formation in trees remain ambiguous due to contrasting observations between a range of studies under controlled conditions and field experiments. High night temperature has been reported to advance growth cessation and bud formation in several tree species grown under controlled conditions. On the other hand, some recent field experiments have shown that autumn warming delays bud formation, although the temperature parameters that could account for this effect have not been identified. In addition, dioecious species have been shown to respond differently to environmental change, and differential warming effects on the sexes have received limited attention, even more so in relation to phenology. In a data set including three separate field experiments employing either experimental warming or an elevational gradient, we tested the effect of different temperature parameters on apical, vegetative bud formation and transitions between bud stages in female and male clones of Eurasian aspen (Populus tremula). Increased temperature was found to delay bud formation, and this process was best explained by maximum daily temperature. Males were significantly delayed compared with females in forming green closed buds, a process best explained by mean 24 h temperature. Bud maturation was best explained by mean daytime temperature, and buds matured significantly faster in males than in females, possibly explaining why females and males did not differ in terms of overall bud formation. In conclusion, our data show that delayed bud formation in Eurasian aspen during autumn can be attributed to the effect of high temperature, and this effect is in contrast to most of the evidence from studies of bud development in controlled environments.

Sex-specific pattern of spatial genetic structure in dioecious and clonal tree species, Populus alba L.

Fine-scale spatial genetic structure (SGS) has profound ecological and genetic consequences for plant populations, and some studies indicate that clonal reproduction may significantly enhance SGS. Clonality is widespread among dioecious species, but little is known about the relationship between clonal reproduction and SGS in the frame of sexual dimorphism. We asked the following questions: (1) Is there a sexually dependent pattern of SGS in white poplar population? (2) What is the relationship between clonal reproduction and SGS? and (3) Does this relationship have a sex-specific component? Using 16 microsatellite markers, genetic structure including fine-scale SGS and clonality of females and males of white poplar were investigated. Significant SGS was noted for both sexes at the ramet and genet levels. At the genet level, males had 2.7-fold higher SGS than that of females. Clonality significantly contributed to SGS only in females. A sibship structure revealed with pedigree analysis and clustering-based methods among males was likely the major factor of the observed SGS. The sexes differed in their clonal growth strategies. Spatial positioning of ramets in female clones suggested foraging behavior and/or avoidance of competition, while for male clones it indicated more expansion and space colonization. The obtained results led us to conclude that sexual dimorphism in life history traits may affect the course and rate of demo-genetic processes acting in natural populations of dioecious species. To our knowledge, this is the first study demonstrating a sex-specific pattern of SGS in natural populations of dioecious species.

Genetic diversity and in vitro assessment of salt tolerance responses and associated changes in gene expression of male poplar (Populus) trees

ABSTRACTIn vitro evaluation of salinity effects on male aspen clone W52 (Populus tremula L.) and the hybrid aspen clone T89 (Populus tremula L. × Populus tremuloides ‘Michx’) were investigated after seawater treatments (control, and ‘concentrations’ of 8.0, 12.0 and 14.0 dS/m). A salinity level of 14.0 dS/m was found to be lethal. All the vegetative parameters of both Populus clones were significantly decreased at 12.0 dS/m. The amounts of pigments and percentages of K+ and Na+, as well as peroxidase activity in the plantlets, were determined as indicators for salt stress tolerance. Also, a genetic diversity study between the two Populus clones using inter-simple sequence repeat (ISSR)-PCR analysis showed specific marker bands for the W52 clone with high molecular sizes: 1900, 1500, 1150, and 1000 bp. Furthermore, the level of transcription factor homeodomain-leucine zipper III_1 (PagHD-ZIPIII_1) gene transcripts was positively affected in response to salt stress and influenced by genotypes. Hence, the response of the two clones to salt stress was associated with the up-regulation of PagHD-ZIPIII_1 gene which could be a good candidate for in vitro selection for salt tolerance genotypes. Generally, the clone T89 is more salinity tolerant compared to the clone W52.

22 SEMEN AND REPRODUCTIVE PROFILES OF CLONED ANATOLIAN GREY CATTLE

Anatolian grey cattle (endangered native Anatolian cattle) as 1 male (clone 1) and 4 females (clones 2–5) were produced from cells of 1 male and 1 female cattle by somatic cell nuclear transfer (SCNT) in a previous study. In this study, we examined the reproductive potential of these cloned animals, which are now 4 and 5 years old. The parameters evaluated by phase contrast microscopy for motility, TUNEL for DNA fragmentation, eosin staining for viability, Hoechst 33258 staining and hypo-osmotic swelling test (HOST) for membrane integrity, and fluorescein isothiocyanate-Pisum sativum agglutinin (FITC-PSA) for acrosome integrity of frozen-thawed spermatozoa, as well as birth and survival of calves following insemination with frozen-thawed semen of cloned and nuclear donor bull and normal bull. Six ejaculates and 3 samples per ejaculate from each bull were tested, and the Mann-Whitney U test was used to analyse the data. The spermatological parameters of cloned bull semen – volume, concentration, and motility of fresh – were within accepted limits for artificial insemination (4.60 ± 0.47 mL, 1.55 ± 0.21 × 109 spermatozoa mL–1, 80.00 ± 1.07%, respectively). Frozen-thawed sperm motility and viability rate were higher in the cloned bull (56.6%, 56.7%) than in its nuclear donor (47%, 43%; P < 0.05). Intact membrane and DNA fragmentation rate of cloned bull and its nuclear donor bull sperm were similar (P > 0.05) but the intact acrosome rate of cloned bull was higher than that of its nuclear donor (P < 0.05). Low rates in frozen-thawed sperm of nuclear donor can be related to storage time of sperm which were frozen 5 years before. One (clone 4) of the cloned grey heifers was artificially inseminated with frozen semen from nuclear donor bull and the other (clone 5) was naturally mated with a Holstein bull. Two healthy calves were delivered naturally. When same cloned cows (clones 4–5) and 2 other cloned heifers (clones 2–3) were artificially inseminated with frozen semen of the cloned grey bull, clones 2 and 4 gave birth to 2 healthy female calves. One cloned cow (clone 3) aborted in the third month of gestation and other one (clone 5) is currently 8 months pregnant. Two calves of clone 4 and 5 are 17 months old and 2 other calves of clone 2 and 4 are now 6 and 1 months old. Except for clone 3, our results show that cloned Anatolian grey bull and cows produced from frozen cells in gene bank have normal fertility.

Broadening the Gene Pool of Cocoa (Theobroma cacao L.) Progenies with Guiana Clones: Establishment and Precocity Traits

Guiana (GU) cocoa is one of the recently identified genetic groups with high resistance to black pod diseases. The objective of this study was to estimate combining abilities of selected GU clones for traits related to establishment ease and precocity. Three tester clones were crossed with eight GU clones as males in a 3 x 8 factorial mating design to produce F1 progenies. These progenies were evaluated together with four standard varieties at two locations in Ghana for percentage survival, stem growth, jorquette height, canopy spread, flowering intensity, and pod number. The GU progenies surpassed on average the standards for all traits except for jorquette height at one location. Preponderance of additive effects was manifested as significant general combining ability (GCA) estimates of female and male clones for all traits. The specific combining ability (SCA) was significant only for flowering intensity, stem growth, and pod number. GU 341H and GU 225V contributed positively to GCA effects for all traits studied. Based on establishment and precocity traits, the Guiana population represents a suitable genetic resource for broadening the genetic base of cocoa breeding.

Clonal genetic structure and diversity in populations of an aquatic plant with combined vs. separate sexes

Clonality is often implicated in models of the evolution of dioecy, but few studies have explicitly compared clonal structure between plant sexual systems, or between the sexes in dioecious populations. Here, we exploit the occurrence of monoecy and dioecy in clonal Sagittaria latifola (Alismataceae) to evaluate two main hypotheses: (i) clone sizes are smaller in monoecious than dioecious populations, because of constraints imposed on clone size by costs associated with geitonogamy; (ii) in dioecious populations, male clones are larger and flower more often than female clones because of sex-differential reproductive costs. Differences in clone size and flowering could result in discordance between ramet- and genet-based sex ratios. We used spatially explicit sampling to address these hypotheses in 10 monoecious and 11 dioecious populations of S.latifolia at the northern range limit in Eastern North America. In contrast to our predictions, monoecious clones were significantly larger than dioecious clones, probably due to their higher rates of vegetative growth and corm production, and in dioecious populations, there was no difference in clone size between females and males; ramet- and genet-based sex ratios were therefore highly correlated. Genotypic diversity declined with latitude for both sexual systems, but monoecious populations exhibited lower genotypic richness. Differences in life history between the sexual systems of S.latifolia appear to be the most important determinants of clonal structure and diversity.

UV‐B and temperature enhancement affect spring and autumn phenology in Populus tremula

Perennial plants growing at high latitudes synchronize growth and dormancy to appropriate seasons by sensing environmental cues. Autumnal growth cessation, bud set and dormancy induction are commonly driven by the length of photoperiod and light quality, and the responses are modified by temperature. However, although ultraviolet (UV)-B radiation is well known to affect plant growth and development, information on the effects on bud phenology is scarce. We examined the separate and combined effects of enhanced temperature and UV-B on autumnal bud set and spring bud break in female and male clones of Populus tremula in an outdoor experiment in Joensuu, Eastern Finland. Enhancements of UV-B and temperature were modulated to +30% and +2 °C, respectively, from June to October 2012. Enhanced UV-B accelerated bud set, while increased temperature delayed it. For both UV-B and temperature, we found sex-related differences in responsiveness. Temperature increase had a stronger delaying effect on bud maturation in male compared with female clones. Also, male clones were more responsive to UV-B increase than female clones. Increasing autumnal temperature enhanced bud break in spring for both sexes, while UV-B enhanced bud break in male clones. In conclusion, we found that UV-B affected phenological shifts in P. tremula, and that temperature and UV-B affected genders differently.

5 DISRUPTION OF THE HIGH MOBILITY GROUP AT-HOOK 2 (HMGA2) GENE IN SWINE REDUCES POSTNATAL GROWTH

The high mobility group AT-hook 2 (HMGA2) protein has been shown to be a crucial gene for cell growth, proliferation, and apoptosis; HMGA2 is also a strong biological candidate for growth, because mutations in this gene alter body size in mice and humans. Compared with wild-type controls, adult mice lacking HMGA2 are 60% smaller, and adult heterozygous mutants are 20% smaller. In humans, HMGA2 has been associated with adult and childhood height without any other deleterious effect. Additionally, a microdeletion in the HMGA2 gene in a human patient resulted in short stature, with no dysmorphologies and normal puberty. In order to determine the effect of HMGA2 on fetal and adult growth in pigs, a transgenic pig line deficient in HMGA2 expression was generated by gene targeting in fetal fibroblasts (FF). Using a targeting vector carrying a reporter gene, and homology arms specific to HMGA2, heterozygous mutant cell lines were generated. The cell lines were then used to generate 6 heterozygous females by somatic cell nuclear transfer (SCNT). Bodyweights and lengths from snout to base of tail were measured every 2 weeks for a year for mutant (n = 6) and wild-type farm gilts (n = 6). Data were analysed by one-way ANOVA. As in mice, disruption of one allele of the HMGA2 gene resulted in 25% reduction in weight (P < 0.0001) and 14% reduction in length (P < 0.0001). Early in postnatal growth (2 months), weights of mutants were not different than wild-type. However, mutants were 20 to 35% lighter (P < 0.05) during mid stages (6 months) and 25 to 30% (P < 0.0001) in late stages (3 months). The same insertional mutation generated 8 heterozygous male clones by SCNT. In addition, 7 nontransgenic males from the same FF line were generated as SCNT controls. Bodyweights and lengths were measured every 2 weeks for 30 weeks for HMGA2 heterozygous mutants (n = 8), control SCNT (n = 7) and wild-type farm boars (n = 5). The weight curve of boars showed similar pattern as for mutant gilts. At 30-week postnatal stage, mutants were 17% (P < 0.05) and 16% (P < 0.05) lighter in weight compared with littermate and wild-type animals, respectively. We are presently developing homozygous HMGA2 mutant lines. Currently, 3 of 6 heterozygous gilts have been bred with heterozygous boars, with 1 confirmed pregnancy. The expectation is that the homozygous animals will, like mice, be 60% smaller than the wild-type animals. The approach described here will result not only in a valuable large-animal model of dwarfism, but also in a tool to reduce the size of existing transgenic and nontransgenic swine lines. This, in turn, will increase the receptivity of valuable transgenic lines by the biomedical community. Funding for this work was provided by NIH grant R21-OD010553 to JP.

Floral Biology and Interspecific and Intergeneric Crossability of Teasle Gourd

Information on fruit setting in teasle gourd [Momordica subangulata Blume subsp. renigera (G. Don) WJJ de Wilde] has received little attention, and the precise nature of its breeding system has never been described. A study was undertaken on the pollination mechanism, fruit setting, and interspecific and intergeneric crossability for genetic improvement of teasle gourd. The first flower produced by the male clone reached full bloom 75 days after emergence from the soil; those produced by female clones required an average of 53 days. Number of nodes producing the first flower varied from plant to plant and subsequent flowers also did not develop in any definite sequence. The time required by male and female flower buds to reach anthesis was 15 and 10 days, respectively. Opening of either type of flower occurred between 6 and 7 am, and dehiscence of anthers began at time of opening of female flower. The stigma became receptive 12 hours before anthesis. No fruit set was obtained by hybridization between teasle gourd and other cucurbits, indicating little likelihood for recombination of desirable characters from others cucurbits into teasle gourd using fresh pollen.

Sex allocation in a polyembryonic parasitoid with female soldiers: an evolutionary simulation and an experimental test.

Parasitoid wasps are convenient subjects for testing sex allocation theory. However, their intricate life histories are often insufficiently captured in simple analytical models. In the polyembryonic wasp Copidosoma koehleri, a clone of genetically identical offspring develops from each egg. Male clones contain fewer individuals than female clones. Some female larvae develop into soldiers that kill within-host competitors, while males do not form soldiers. These features complicate the prediction of Copidosoma’s sex allocation. We developed an individual-based simulation model, where numerous random starting strategies compete and recombine until a single stable sex allocation evolves. Life-history parameter values (e.g., fecundity, clone-sizes, larval survival) are estimated from experimental data. The model predicts a male-biased sex allocation, which becomes more extreme as the probability of superparasitism (hosts parasitized more than once) increases. To test this prediction, we reared adult parasitoids at either low or high density, mated them, and presented them with unlimited hosts. As predicted, wasps produced more sons than daughters in all treatments. Males reared at high density (a potential cue for superparasitism) produced a higher male bias in their offspring than low-density males. Unexpectedly, female density did not affect offspring sex ratios. We discuss possible mechanisms for paternal control over offspring sex.

RNAi-mediated Knockdown of <i>Xist</i> Does Not Rescue the Impaired Development of Female Cloned Mouse Embryos

In mice, one of the major epigenetic errors associated with somatic cell nuclear transfer (SCNT) is ectopic expression of Xist during the preimplantation period in both sexes. We found that this aberrant Xist expression could be impeded by deletion of Xist from the putative active X chromosome in donor cells. In male clones, it was also found that prior injection of Xist-specific siRNA could significantly improve the postimplantation development of cloned embryos as a result of a significant repression of Xist at the morula stage. In this study, we examined whether the same knockdown strategy could work as well in female SCNT-derived embryos. Embryos were reconstructed with cumulus cell nuclei and injected with Xist-specific siRNA at 6–7 h after oocyte activation. RNA FISH analysis revealed that siRNA treatment successfully repressed Xist RNA at the morula stage, as shown by the significant decrease in the number of cloud-type Xist signals in the blastomere nuclei. However, blastomeres with different sizes (from “pinpoint” to “cloud”) and numbers of Xist RNA signals remained within single embryos. After implantation, the dysregulated Xist expression was normalized autonomously, as in male clones, to a state of monoallelic expression in both embryonic and extraembryonic tissues. However, at term there was no significant improvement in the survival of the siRNA-injected cloned embryos. Thus, siRNA injection was largely effective in repressing the Xist overexpression in female cloned embryos but failed to rescue them, probably because of an inability to mimic consistent monoallelic Xist expression in these embryos. This could only be achieved in female embryos by applying a gene knockout strategy rather than an siRNA approach.

Sex ratios and clonal growth in dioecious Populus euphratica Oliv., Xinjiang Prov., Western China

Using a microsatellite assay, we investigated sex ratios at three levels (apparent, intrinsic, genet) for Populus euphratica stands in Xinjiang, China and possible consequences of sex-specific costs of reproduction in terms of clonal growth and individual growth or mortality. Sex ratios at all levels tended to be male biased (60 % of 3,295 flowering trees were male), although male excess was least pronounced at the genet level (52 % of 850 genets were male). Male clones comprised significantly more (708 vs. 572) trees than female clones. Reproductive investment was measured in terms of carbon (C) and nitrogen (N) contents of male and female reproductive organs: single flowers or fruit capsules, whole inflorescences or infructescences, and whole branches of ca. 2 cm diameter. Male flowers and catkins require less N than female fruits and catkins, but on average only 16 % of female catkins develop into fruits. This changes the measured investment for reproduction at branch level: now male branches spent 3.3 times more N than their female counterparts. This coincides with the annual increment of branches, measured as a possible trade-off for costs of reproduction: female branches needed 2 years less to reach a diameter of 2 cm. We conclude that full fruit set of females would give males a heavy comparative advantage, but frequent abortion of whole infructescences by females seems to be a powerful mechanism to compensate a higher reproductive effort, thus avoiding a pronounced runaway effect by more vigorous clonal growth of male trees over a long time.

Different eco-physiological responses between male and female Populus deltoides clones to waterlogging stress

Sex-related variations in response to waterlogging stress between male clones ( Populus deltoides CL. ‘Juba’) and female clones ( P. deltoides CL. ‘Danhong’) in a semi-controlled environment were investigated. All tested plants survived after a ten-week waterlogging treatment with 5 cm of water above the soil surface. This suggests that the two clones belonged to waterlogging-tolerant species, so that they can be applied in the construction of riparian protection forests and the restoration of wetlands. Compared with well-watered treatment, waterlogging treatment significantly decreased shoot height, stem diameter, leaf number, mean leaf area, total leaf area, relative water content (RWC), specific leaf area (SLA), total chlorophyll concentration (chlorophyll a + b, TC), carotenoids (Caro), net photosynthetic rate ( A), stomatal conductance ( gs), instantaneous water use efficiency (WUEi), maximum efficiency of PSII ( F v/ F m), maximum effective quantum yield of PSII (Yield), and soluble sugar content and significantly increased levels of superoxide anion radical ( O 2 - ), hydrogen peroxide (H 2O 2), proline, reducing sugar, peroxidase (POD) activity, and superoxide dismutase (SOD) activity. The effects of waterlogging on chlorophyll a/chlorophyll b ratio, TC/Caro ratio, intercellular CO 2 concentration ( Ci), transpiration ( E), photochemical quenching coefficient (qP), and non-photochemical quenching coefficient (qN) were not significant. In well-watered conditions, females had significantly faster growth rate and higher TC, Caro, and A than males. In contrast, males exhibited higher values of RWC and WUEi; less reductions in SLA, TC, Caro, and A; higher levels of POD and SOD activities; higher proline and reducing sugar contents; and lower O 2 - and H 2O 2 levels than females under waterlogging conditions. Findings indicate that males have better cellular defense mechanisms against damage caused by waterlogging stress than females, whereas females were more responsive to waterlogging stress than males.

NextGen sequence analysis of two sex-linked P. tremuloides genomic regions on chromosome 19

Material and methods Using DNA probes derived from these SSR markers, two BAC clones were isolated from a BAC library of the P. tremuloides male clone (Pakull B. et al., 2011, Can. J. For. Res. 41, 245-253) and further analyzed by454 sequencing (GATC Biotech AG). The generated single end reads were assembled to contigs using Newbler and Mira. The set of combined contigs (Newbler and Mira) of each BAC was subjected to scaffolding by SeqMan Pro (DNASTAR Lasergene) together with the related BAC end sequences created by Sanger sequencing (Pakull B. et al., 2011, Can. J. For. Res. 41, 245-253). The subsequent combination of the created scaffolds to BAC consensus sequences was assisted by Sanger sequencing of PCR amplified scaffold ends and connections.

Performance and variability patterns in wood properties and growth traits in the parents, F1 and F2 generation hybrid clones of Populus deltoides

The performance and variability patterns in the wood element’s dimensions, specific gravity and growth parameters namely ramet height and GBH were evaluated in 16 clones of parents, F1 and F2 hybrids of Populus deltoides Bartr. ex Marsh. Ramet radial variations were non-significant, while inter-clonal variations due to interaction of clone/replication were significant for all the wood traits except vessel element length. Inter-clonal variations were significant only for fiber length and fiber wall thickness. Fiber length and specific gravity were significantly higher in female, while wall thickness and vessel element length were higher in male clones. Female parents (G48 and S7C8) showed higher fiber length and specific gravity than of the male parent (G3), while vessel diameter and wall thickness were higher in male parent (G3). There is not much difference in fiber length and vessel element’s dimensions among the parents, F1 and F2 generation hybrid clones. Specific gravity did not showed any trend for parents, F1 and F2 generations. Generally female clones showed higher growth rate. Broad sense heritability for wood traits ranged from 0.143 (fiber length) to 0.505 (fiber wall thickness), while for growth traits it was 0.374 (GBH) and 0.418 (height). Genetic gain for all the wood and growth traits was positive for most of the wood traits. The highly divergent male clone (78) and female clones (S7C8, G48, W/A 49) in number of combinations could be used for developing new hybrids of desired wood traits to develop new clones.