Stiffness and checking of <Emphasis Type="Italic">Eucalyptus nitens</Emphasis> sawn boards: genetic variation and potential for genetic improvement

A trial was undertaken to assess the extent to which variation in sawn-board quality traits of plantation-grown Eucalyptus nitens is under genetic control and amenable to genetic improvement. Five hundred and sixty trees from 129 families and three central Victorian races were sampled from an open-pollinated progeny trial in Tasmania, Australia. Acoustic wave velocity (AWV) was assessed on standing trees and sawlogs. Wedges from disks extracted from sawlogs were assessed for basic density and checking. Processed boards from 496 of the trees were assessed for board stiffness (static modulus of elasticity, MOE), and internal and surface checking. Genetic differences among races were significant for AWV and MOE traits. The Southern race had the highest mean values for these traits. Significant additive genetic variation within races was observed in all traits, demonstrating that the quality of plantation-grown E. nitens boards could be improved through breeding. Estimated narrow-sense heritabilities were 0.85 for standing-tree AWV, 0.71 for log AWV, 0.37 for board MOE, and ranged from 0.20 to 0.52 for checking traits. A strongly positive genetic correlation (r _g = 1.05) was observed between standing-tree AWV and board MOE, indicating that AWV could be used as a selection trait to improve E. nitens board stiffness. The genetic correlation between basic density and board MOE was also positive (r _g = 0.62). However, a significant and adverse genetic correlation (r _g = 0.61) was identified between basic density and surface check length. Wood stiffness and checking traits were more-or-less genetically independent, and genetic correlations between surface and internal checking were positive but only moderate (r _g = 0.48–0.52).     

Age trends in genetic parameters for growth and wood density in <Emphasis Type="Italic">Eucalyptus globulus</Emphasis>

Genetic parameters for stem diameter and wood density were compared at selection (4–5 years) and harvest (16–17 years) age in an open-pollinated progeny trial of Eucalyptus globulus in Tasmania (Australia). The study examined 514 families collected from 17 subraces of E. globulus. Wood density was assessed on a subsample of trees indirectly using pilodyn penetration at both ages and directly by core basic density at harvest age. Significant additive genetic variance and narrow-sense heritabilities ( h_\textop² h_{\text{op}}^2 ) were detected for all traits. Univariate and multivariate estimates of heritabilities were similar for each trait except harvest-age diameter. Comparable univariate estimates of selection- and harvest-age heritabilities for diameter masked changes in genetic architecture that occurred with stand development, whereby the loss of additive genetic variance through size-dependent mortality was countered by the accentuation of additive genetic differences among survivors with age. Regardless, the additive genetic (r _a) and subrace (r _s) correlations across ages were generally high for diameter (0.95 and 0.61, respectively) and pilodyn penetration (0.77 and 0.96), as were the correlations of harvest-age core basic density with selection- and harvest-age pilodyn (r _a −0.83, −0.88; r _s −0.96, −0.83). While r _s between diameter and pilodyn were close to zero at both ages, there was a significant change in r _a from adverse at selection age (0.25) to close to zero (−0.07) at harvest age. We argue that this change in the genetic correlation reflects a decoupling of the genetic association of growth and wood density with age. This result highlights the need to validate the use of selection-age genetic parameters for predicting harvest-age breeding values.     

Mapping species differences for adventitious rooting in a <Emphasis Type="Italic">Corymbia torelliana</Emphasis> × <Emphasis Type="Italic">Corymbia citriodora</Emphasis> subspecies <Emphasis Type="Italic">variegata</Emphasis> hybrid

Quantitative trait loci (QTL) detection was carried out for adventitious rooting and associated propagation traits in a second-generation outbred Corymbia torelliana × Corymbia citriodora subspecies variegata hybrid family (n = 186). The parental species of this cross are divergent in their capacity to develop roots adventitiously on stem cuttings and their propensity to form lignotubers. For the ten traits studied, there was one or two QTL detected, with some QTL explaining large amounts of phenotypic variation (e.g. 66% for one QTL for percentage rooting), suggesting that major effects influence rooting in this cross. Collocation of QTL for many strongly genetically correlated rooting traits to a single region on linkage group 12 suggested pleiotropy. A three locus model was most parsimonious for linkage group 12, however, as differences in QTL position and lower genetic correlations suggested separate loci for each of the traits of shoot production and root initiation. Species differences were thought to be the major source of phenotypic variation for some rooting rate and root quality traits because of the major QTL effects and up to 59-fold larger homospecific deviations (attributed to species differences) relative to heterospecific deviations (attributed to standing variation within species) evident at some QTL for these traits. A large homospecific/heterospecific ratio at major QTL suggested that the gene action evident in one cross may be indicative of gene action more broadly in hybrids between these species for some traits.     

Genetic stability of wood density and diameter in <Emphasis Type="Italic">Pinus radiata</Emphasis> D. Don plantation estate across Australia

Genetic variation for wood quality traits and diameter growth for radiata pine (Pinus radiata D. Don) at age 20/21 years was estimated from eight trials in Australia. The traits studied were wood density, acoustic time-of-flight (an indirect measure of stiffness) and diameter at breast height (DBH). Wood density and DBH exhibited significant additive genetic variation whereas non-additive effects were not significantly different from zero. Time of flight was also not significantly different from zero for both additive and non-additive effects, respectively. Average single-site heritability estimates (±SE) for wood density and DBH were 0.38 ± 0.10 and 0.16 ± 0.08, respectively. Pooled-site heritability estimates for wood density and DBH were 0.38 ± 0.10 and 0.08 ± 0.10, respectively. For density, there was little evidence of genotype-by-environment interaction (GEI) across the eight trials at the additive level (type B additive genetic correlation; r _BADD = 0.73 ± 0.08) and type B genetic correlation for full-sib families (r _BFS = 0.64 ± 0.08). In contrast, the type B additive genetic correlation for DBH was lower, (r _BADD = 0.51 ± 0.14), suggesting evidence of GEI. However, type B genetic correlation for full-sib families was moderate (0.63 ± 0.11) for DBH, suggesting that there may be some stable full-sib families. On the basis of the results of this study, GEI should be considered in order to optimise deployment of improved germplasm in Australia.     

The influence of predator regime on reproductive traits in <Emphasis Type="Italic">Gammarus</Emphasis> <Emphasis Type="Italic">pulex</Emphasis> populations

Selection on traits conferring reduced predation may be opposed by selection on other traits associated with reproduction. Here, we examined the hypothesis that traits associated with reproduction in Gammarus pulex are driven by predation. We studied G. pulex originating from ponds with two different kinds of predator regimes: (1) ponds with fish—often large, non-gap-limited predators and (2) ponds without fish where invertebrates are the dominant predators—often small, gap-limited predators with a much more restricted prey size range. We examined the body size of males and females in G. pulex amplexus pairs originating from fish and fishless ponds. We also examined, in the laboratory, their mating success, the number of offspring per female and offspring mortality under different rearing conditions, with or without fish cue. Mating success, defined as the percentage of amplexus pairs that produced live offspring, was higher for G. pulex from fishless ponds independent of rearing condition. Individuals from fish ponds were larger and they produced a higher number of offspring which tended to be related to female body size. Offspring mortality was higher in populations from fish ponds compared to populations from fishless ponds. Despite the higher offspring mortality, females from fish ponds had a higher number of offspring alive after 13 weeks, which is the approximate time it takes for G. pulex to reach maturity. Our data imply that no trade-off between reducing body size to reduce mortality caused by fish and maximising reproductive success exist in G. pulex from fish ponds. The strategy with many offspring may be the correct strategy in fishponds where predation pressure generally is higher than in fishless ponds.     

Evolution of dispersal and life history strategies – <Emphasis Type="Italic">Tetrahymena</Emphasis> ciliates

Background  

Considerable attention has focused on how selection on dispersal and other core life-history strategies (reproductive effort, survival ability, colonization capacity) may lead to so-called dispersal syndromes. Studies on genetic variation in these syndromes within species could importantly increase our understanding of their evolution, by revealing whether traits co-vary across genetic lineages in the manner predicted by theoretical models, and by stimulating further hypotheses for experimental testing. Yet such studies remain scarce. Here we studied the ciliated protist Tetrahymena thermophila, a particularly interesting organism due to cells being able to transform into morphs differing dramatically in swim-speed. We investigated dispersal, morphological responses, reproductive performance, and survival in ten different clonal strains. Then, we examined whether life history traits co-varied in the manner classically predicted for ruderal species, examined the investment of different strains into short- and putative long-distance dispersal, while considering also the likely impact of semi-sociality (cell aggregation, secretion of 'growth factors') on dispersal strategies.     

Identification of a major QTL for time of initial vegetative budbreak in apple (<Emphasis Type="Italic">Malus</Emphasis> x <Emphasis Type="Italic">domestica</Emphasis> Borkh.)

In the Western Cape region of South Africa, dormancy release and the onset of growth does not occur normally in apple (Malus x domestica Borkh.) trees during spring due to the mild winter conditions experienced and fluctuations in temperatures experienced during and between winters. In this region, the application of chemicals to induce the release of dormancy forms part of standard orchard management. Increasing awareness of the environmental impact of chemical sprays and global warming has led to the demand for new apple cultivars better adapted to local climatic conditions. We report the construction of framework genetic maps in two F1 crosses using the low chilling cultivar ‘Anna’ as common male parent and the higher chill requiring cultivars ‘Golden Delicious’ and ‘Sharpe’s Early’ as female parents. The maps were constructed using 320 simple sequence repeats, including 116 new markers developed from expressed sequence tags. These maps were used to identify quantitative trait loci (QTL) for time of initial vegetative budbreak (IVB), a dormancy related characteristic. Time of IVB was assessed four times over a 6-year period in ‘Golden Delicious’ x ‘Anna’ seedlings kept in seedling bags under shade in the nursery. The trait was assessed for 3 years on adult full-sib trees derived from a cross between ‘Sharpe’s Early’ and ‘Anna’ as well as for 3 years on replicates of these seedlings obtained by clonal propagation onto rootstocks. A single major QTL for time of IVB was identified on linkage group (LG) 9. This QTL remained consistent in different genetic backgrounds and at different developmental stages. The QTL may co-localize with a QTL for leaf break identified on LG 3 by Conner et al. (1998), a LG that was, after the implementation of transferable microsatellite markers, shown to be homologous to the LG now known to be LG 9 (Kenis and Keulemans 2004). These results contribute towards a better understanding regarding the genetic control of IVB in apple and will also be used to elucidate the genetic basis of other dormancy related traits such as time of initial reproductive budbreak and number of vegetative and reproductive budbreak.     

Discovery of <Emphasis Type="Italic">Ophiostoma tsotsi</Emphasis> on <Emphasis Type="Italic">Eucalyptus</Emphasis> wood chips in China

Ophiostoma species such as O. quercus are the most frequent causal agents of sapstain of freshly felled hardwood timber and pulpwood. Many species are regarded as economically important agents of wood degradation. The aim of this study was to identify a collection of Ophiostoma isolates, resembling O. quercus, found on stained Eucalyptus pulpwood chips in China. DNA sequences of the internal transcribed spacer regions, including the 5.8S region, of the ribosomal DNA, and parts of the β-tubulin and elongation factor-1α genes, revealed that the isolates were not O. quercus. Surprisingly, they represented O. tsotsi, a wound-infesting fungus recently described from hardwoods in Africa. In addition, sequence data from an isolate from agarwood in Vietnam, identified in a previous study as belonging to an unknown Pesotum species, were also shown to represent O. tsotsi. A high level of genetic variability was observed among isolates of both O. quercus and O. tsotsi. This was unexpected and suggests that both species have been present in Asia for a significant amount of time.     

The effects of agroforestry practices on fiber attributes in <Emphasis Type="Italic">Populus nigra</Emphasis> var. <Emphasis Type="Italic">betulifolia</Emphasis>

The effects of intercropping with alfalfa and initial tree spacing on fiber properties in Populus nigra var. betulifolia are reported on the basis of a study of 15 trees. The trees were harvested from an agroforestry trial near Karaj city, Iran. Treatments included four initial spacings of 3 m × 4 m, 3 m × 6.7 m, 3 m × 8 m, and 3 m × 10 m intercropped with alfalfa as nitrogen-fixing plant, as well as one 3 m × 4 m treatment without alfalfa. Results showed that initial spacing and intercropping with alfalfa increased the growth rate. Also, alfalfa-intercropping had increasing effects on all fiber dimensions, especially on diameter and wall thickness. The effect of initial spacing on fiber attributes based on ring numbers was not statistically significant; however, whole-disk fiber length, weighted by ring area, was increased with stem diameter. The reason for this increase may be traced to the fact that much of the basal area of fast-growing trees is concentrated in farther rings from the pith that have longer fibers. Clear correlation was not found between fiber length and growth rate and therefore, no firm conclusion can be made in this regard.     

Genetic microheterogeneity and phenotypic variation of <Emphasis Type="Italic">Helicobacter pylori</Emphasis> arginase in clinical isolates

Background  

Clinical isolates of the gastric pathogen Helicobacter pylori display a high level of genetic macro- and microheterogeneity, featuring a panmictic, rather than clonal structure. The ability of H. pylori to survive the stomach acid is due, in part, to the arginase-urease enzyme system. Arginase (RocF) hydrolyzes L-arginine to L-ornithine and urea, and urease hydrolyzes urea to carbon dioxide and ammonium, which can neutralize acid.     

Identification of a <Emphasis Type="Italic">Rice stripe necrosis virus</Emphasis> resistance locus and yield component QTLs using <Emphasis Type="Italic">Oryza sativa</Emphasis> × <Emphasis Type="Italic">O. glaberrima</Emphasis> introgression lines

Background  

Developing new population types based on interspecific introgressions has been suggested by several authors to facilitate the discovery of novel allelic sources for traits of agronomic importance. Chromosome segment substitution lines from interspecific crosses represent a powerful and useful genetic resource for QTL detection and breeding programs.     

Potential chromosomal introgression barriers revealed by linkage analysis in a hybrid of <Emphasis Type="Italic">Pinus massoniana</Emphasis> and <Emphasis Type="Italic">P. hwangshanensis</Emphasis>

Background  

Exploring the genetic mechanisms underlying speciation is a hot topic in modern genetics and evolutionary studies. Distortion of marker transmission ratio is frequently ascribed to selection against alleles that cause hybrid incompatibility. The natural introgression between P. massoniana and P. hwangshanensis and their distribution ranges lead to the emergence of the two species as desirable organisms to study the genetic mechanisms for speciation.     

Construction of a reference molecular linkage map of globe artichoke (<Emphasis Type="Italic">Cynara cardunculus</Emphasis> var. <Emphasis Type="Italic">scolymus</Emphasis>)

The genome organization of globe artichoke (Cynara cardunculus var. scolymus), unlike other species belonging to Asteraceae (=Compositae) family (i.e. sunflower, lettuce and chicory), remains largely unexplored. The species is highly heterozygous and suffers marked inbreeding depression when forced to self-fertilize. Thus a two-way pseudo-testcross represents the optimal strategy for linkage analysis. Here, we report linkage maps based on the progeny of a cross between globe artichoke (C. cardunculus var. scolymus) and cultivated cardoon (C. cardunculus var. altilis). The population was genotyped using a variety of PCR-based marker platforms, resulting in the identification of 708 testcross markers suitable for map construction. The male map consisted of 177 loci arranged in 17 major linkage groups, spanning 1,015.5 cM, while female map was built with 326 loci arranged into 20 major linkage groups, spanning 1,486.8 cM. The presence of 84 loci shared between these maps and those previously developed from a cross within globe artichoke allowed for map alignment and the definition of 17 homologous linkage groups, corresponding to the haploid number of the species. This will provide a favourable property for QTL scanning; furthermore, as 25 mapped markers (8%) correspond to coding regions, it has an additional value as functional map and might represent an important genetic tool for candidate gene studies in globe artichoke.     

Water relations advantages for invasive <Emphasis Type="Italic">Rubus</Emphasis> <Emphasis Type="Italic">armeniacus</Emphasis> over two native ruderal congeners

Despite species in the Rubus fruticosus complex (wild blackberry) being among the most invasive plants globally in regions with large annual fluctuations in water availability, little is known about their water relations. We compared water relations of a prominent member of the complex, R. armeniacus (Himalayan blackberry), with species native to the Pacific Northwest of North America (PNW), R. spectabilis (salmonberry) and R. parviflorus (thimbleberry). In eight stands of each species located near Portland, Oregon, USA, we measured mid-day hydraulic resistance (R _plant), and daily time series of stomatal conductance (g _s), leaf water potential (Ψ_lf), and environmental conditions at four time periods spanning the 2007 growing season. Although all species maintained Ψ_lf above −0.5 MPa in spring, R. armeniacus maintained less negative Ψ_lf (≥−1.0 MPa) than the natives in summer, a factor attributable to advantages in both its root and shoot systems. R _plant of R. armeniacus was ≤0.1 MPa mmol⁻¹ m² s for the duration of the study, and approximately 25–50% of R _plant for the native species in summer. R. armeniacus had higher g _s compared to the native species throughout the spring and summer, with approximately twice their rates in summer. Our R _plant and g _s results show that R. armeniacus has access to more water during PNW summers than congeneric natives, allowing it to maintain high water-use, and potentially helping it achieve higher growth and reproductive rates. Water relations may therefore be a critical component of the competitive and invasive success of R. armeniacus and other R. fruticosus species worldwide.     

Additive and non-additive genetic parameters from clonally replicated and seedling progenies of<Emphasis Type="Italic"> Eucalyptus globulus</Emphasis>

The first estimates of the importance of epistatic effects within Eucalyptus globulus were obtained from analysis of clonally replicated full-sib progeny tests grown in Portugal. Parents comprised diverse selections from the Portuguese landrace. Variance components were estimated for 4-year-old diameter growth and pilodyn penetration, an indirect measure of wood density, both key traits in the pulpwood breeding objective. The experimental components of variance were used to estimate heritabilities and proportions of the phenotypic variance due to dominance and epistasis. The additive variance was the only significant genetic component affecting either diameter or pilodyn. Estimates of the additive, dominance and epistatic effects accounted for 8–10%, 0–4% and 0.4% of the phenotypic variance in diameter, and for 11–17%, 0% and 5% of the phenotypic variance in pilodyn, respectively. A comparison of residual coefficients of variation within seedling and cloned progenies indicated that C effects within clones were not a serious source of random variability. Despite the test sites encompassing a diverse range of locations, no important genotype by environment interaction was detected. The results suggested that an improvement strategy combining both recurrent selection for additive genetic merit and clonal testing may be adequate for optimizing genetic gains from this genetic base.Communicated by O. Savolainen     

Direct gene transfer study and transgenic plant regeneration after electroporation into mesophyll protoplasts of <Emphasis Type="Italic">Pelargonium</Emphasis> <Emphasis Type="Italic">×</Emphasis> <Emphasis Type="Italic">hortorum</Emphasis>, ‘Panaché Sud’

Direct genetic transformation of mesophyll protoplasts was studied in Pelargonium × hortorum. Calcein and green-fluorescent protein (GFP) gene were used to set up the process. Electroporation (three electric pulses from a 33-μF capacitor in a 250-V cm⁻¹ electric field) was more efficient than PEG 6000 for membrane permeation, protoplast survival and cell division. Transient expression of GFP was detected in 33–36% of electroporated protoplasts after 2 days and further in colonies. A protoplast suspension conductivity of >1,500 μS cm⁻¹ allowed high colony formation and plant regeneration. Stable transformation was obtained using the plasmid FAJ3000 containing uidA and nptII genes. When selection (50 mg l⁻¹ kanamycin) was achieved 6 weeks after electroporation, regenerated shoots were able to grow and root on 100 mg l⁻¹ kanamycin. The maximum transformation efficiency was 4.5%, based on the number of colonies producing kanamycin-resistant rooted plants or 0.7% based on the number of cultured protoplasts. Polymerase chain reaction (PCR) analysis on in vitro micropropagated plants showed that 18 clones out of 20 contained the nptII gene, while the uidA gene was absent. These results were confirmed after PCR analyses of five glasshouse-acclimatized clones.     

Metabolism of arabinogalactan from siberian larch by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> yeast

The ability of Saccharomyces cerevisiae yeast to utilize arabinogalactan (AG) from Siberian larch wood was studied, as well as the influence of phenolic impurities on the rate of its utilization. It was shown that arabinogalactan was intensively involved in the yeast metabolism, and the degradation extent of the polymer chain depended on both the method of purification of the AG sample and the amount of phenolic impurities in this sample.     

<Emphasis Type="Italic">Pseudocercospora griseola</Emphasis> Causing Angular Leaf Spot on <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> Produces 1,8-Dihydroxynaphthalene-Melanin

Pseudocercospora griseola is the causal agent of angular leaf spot of common bean (ALS). It has undergone parallel coevolution with its host and two major groups have been defined, “Andean” (P. griseola f. griseola) and “Mesoamerican” (P. griseola f. mesoamericana). The aim of this study was to analyze the nature and the level of the dark pigment synthesized by the representatives of each group. After 21 days of incubation on potato dextrose agar medium, P. griseola f. griseola isolate S3b developed colonies with diameters of 17.5 ± 1.3 mm and concentric rings of pigmentation. Isolate T4 of P. griseola f. mesoamericana presented smaller colonies (9.9 ± 0.3 mm) with a uniform dark-gray color. Both isolates, S3b and T4, produced the same pigment, a 1,8-dihydroxynaphthalene-melanin, although different in quantity and structural features as suggested by the IR spectrum. The P. griseola f. griseola isolate S3b had a higher growth rate and melanin content as well as smaller sensitivity to melanin synthesis inhibitors compared to the isolate T4 of P. griseola f. mesoamericana. These results suggest a possible link between melanin and growth in P. griseola.     

Hybridization between <Emphasis Type="Italic">Alouatta caraya</Emphasis> and <Emphasis Type="Italic">Alouatta guariba clamitans</Emphasis> in captivity

Hybridization between Alouatta spp. has been suggested at contact zones of A. palliata and A. pigra in Mexico and of A. caraya and A. guariba clamitans in Brazil and Argentina. Whereas genetic data confirmed hybridization between the former pair of species, hybrid individuals of the latter pair have been putatively identified on the basis of a mosaic pelage color. In this paper, we describe the first confirmed cases of hybridization between a female A. guariba clamitans and a male A. caraya. One hybrid male was born in 2007 and one hybrid female was born in 2009 with distinct coat colors. The male resembled the newborn color pattern characteristic of A. guariba clamitans, whereas the female resembled the newborn pattern of A. caraya. The birth and survival of the male hybrid for a year and a half indicated the viability of the heterogametic sex.