Phenotypic plasticity of growth trajectory and ontogenic allometry in response to density for eucalyptus hybrid clones and families

BACKGROUND: and Aims Response to density is a crucial aspect of the ecology of trees in forests and plantations. Few studies have investigated the genetics of plasticity in response to density for growth traits such as height and circumference through development. METHODS: Two experiments were carried out in the field, the first with full-sib families of Eucalyptus urophylla x E. grandis hybrids, and the second with clones of E. tereticornis x E. grandis hybrids planted across a range of densities (625, 1111 and 2500 trees ha-1). Height, circumference and stem taper were measured through development in both experiments. Variance components were estimated and a repeated measure approach for plasticity and three different methods were used to compare the variance-covariance matrix across densities. KEY RESULTS: Genetic variance was significantly different from zero but the density x genotype interaction was significant only for clone experiments at the adult stage. Significant plasticity for three traits in both experiments was found. In the clone experiments, a significant clone x time x density interaction was found, suggesting that plasticity for growth and stem form is under genetic control. In both experiments, density did not affect environmental correlation, which remained high throughout tree development. The impact of density on genetic correlation was marked in the clone experiment, with a reduced value at lower density, but was not observed in the family trial. The differences between clones and family are mainly explained by the distribution of genetic variation within and among genotypes. CONCLUSIONS: The results suggest that plasticity for growth traits and form of tropical Eucalyptus species is under genetic control and that the environment changes genetic co-variation through ontogeny. The findings confirm that a tree population with a narrow genetic basis (represented by clones) is sensitive to a changing environment, whereas a population with a broader genetic basis (full-sib family here) exhibits a more stable reaction.     

A Study of <Emphasis Type="Italic">in vitro</Emphasis> Regeneration in Relation to Doses of Growth Regulators in Hybrids of Upland Cotton

The frequency of in vitro callus induction and plant regeneration is influenced by several factors, including composition of culture medium, explant source, and the genotype. Crosses between regenerable and non-regenerable upland cotton cultivars were evaluated for hybrid vigour towards regeneration responses, which is consequential in recalcitrant crop species like cotton where regeneration is limited only to a few cultivars. The results indicated that regenerable and non-regenerable parental cultivars had similar potential of producing callus, but differed in producing callus weight and embryogenic calli. Mean performance of crosses, regarding callus induction, callus weight, callus growth rate, percent embryo induction, and percentage of germinating embryos, deviated considerably from the performance of their parents, signifying the presence of hybrid vigour for the expression of these traits. Magnitude of hybrid vigour varied across hormonal levels. Genetic component was evident for all the traits although of lower magnitude. The results indicated that genetic component in the phenotypic expression of callus growth, percentages of embryo induction and germinating embryos was higher than that of callus induction, callus weight and percentage of embryogenic calli. Hormonal concentration in the media had affect on the degree of gene expression responsible for regeneration in upland cotton. Over, partial- and additive-dominance types of gene effects were apparent in the expression of these traits. Genotype × growth regulator level interaction caused considerable variation in the expression of regeneration responses, suggesting that determination of specific level of growth regulator concentration in the medium was necessary for a particular genotype to obtain optimum response. Genotype × explant source interaction was, however, relatively less important. Differences among genotypes for percent embryo induction were clearly evident.     

Measuring Natural Selection on Proportional Traits: Comparisons of Three Types of Selection Estimates for Resistance and Susceptibility to Herbivore Damage

To compare the strength of natural selection on different traits and in different species, evolutionary biologists typically estimate selection differentials and gradients in standardized units. Measuring selection differentials and gradients in standard deviation units or mean-standardized units facilitates such comparisons by converting estimates with potentially varied units to a common scale. In this note, I compare the performance of variance- and mean-standardized selection differentials and gradients for a unique and biologically important class of traits: proportional traits, that can only vary between zero and one, and their complements (1 minus the trait) using simple algebra and analysis of data from a field-study using morning glories. There is a systematic, mathematical relationship between unstandardized and variance-standardized selection gradients for proportional traits and their complements, but such a general relationship is lacking for mean-standardized gradients, potentially leading investigators to mistakenly conclude that a proportional change in a trait would have little effect on fitness. Despite this potential limitation, mean-standardized selection differentials and gradients represent a useful tool for studying natural selection on proportional traits, because by definition they measure how proportional changes in the mean of a trait lead to proportional changes in relative fitness.Co-ordinating editor: I. Olivieri     

Multi-species evolutionary dynamics

Dynamical attainability of an evolutionarily stable strategy (ESS) through the process of mutations and natural selection has mostly been addressed through the use of the continuously stable strategy (CSS) concept for species evolutionary games in which strategies are drawn from a continuum, and by the adaptive trait dynamics method. We address the issue of dynamical attainability of an ESS in coevolving species through the use of the concept of an ESNIS. It is shown that the definition of an ESNIS coalition for coevolving species is not in general equivalent to other definitions for CSS given in the literature. We show under some additional conditions that, in a dynamic system which involves the strategies of a dimorphic ESNIS coalition and at most two strategies that are not members of ESNIS coalition, the ESNIS coalition will emerge as the winner. In addition an ESNIS will be approached because of the invasion structure of strategies in its neighborhood. This proves that under the above conditions an ESNIS has a better chance of being attained than a strategy coalition which is a CSS. The theory developed is applied to a class of coevolutionary game models with Lotka–Volterra type interactions and we show that for such models, an ESS coalition will be dynamically attainable through mutations and natural selection if the ESS coalition is also an ESNIS coalition.Co-ordinating editor: Metz     

Local Adaptation and the Effects of Isolation and Population Size – the Semelparous Perennial <Emphasis Type="Italic">Carlina vulgaris</Emphasis> as a Study Case

We made a reciprocal transplantation experiment with Carlina vulgaris, among 12 semi-natural grassland sites situated in southwest Sweden. The fate of seeds and seedlings were followed during 2 years. Local adaptation was investigated both by native superiority over non-natives, and by comparing the observed performance of a population to the fitted value of a reduced statistical model that showed the populations’ performance at all sites and the performance of all other populations at its home site. The latter method indicates presence of local adaptation even when natives are inferior to introduced populations as long as the negative difference in fitness between the populations is smaller at the native population’s home site. The strength of local adaptation was measured as the ratio of the observed to the expected performance in reduced statistical models and regressed on the degree of isolation and population size. We found no evidence of local adaptation in terms of native superiority compared to non-natives, but with the relative method we found one of six fitness components, juvenile survival, to be 6% higher for natives at their home sites compared to how they performed at other sites and how others performed at their site. Further, our results indicate that both isolation and population size have a positive effect on the process of local adaptation. Co-ordinating editor: J. Tuomi     

<Emphasis Type="Italic">Agropyron elongatum</Emphasis> chromatin localization on the wheat chromosomes in an introgression line

The introgressed small-chromosome segment of Agropyron elongatum (Host.) Neviski (Thinopyrum ponticum Podp.) in F₅ line II-1-3 of somatic hybrid between common wheat (Triticum aestivum L.) and A. elongatum was localized by sequential fluorescence in situ hybridization (FISH), genomic in situ hybridization (GISH) and karyotype data. Karyotype analysis offered basic data of arm ratios and relative lengths of 21 pairs of chromosomes in parent wheat Jinan177 and hybrid II-1–3. Using special high repetitive sequences pSc119.2 and pAs1 for FISH, the entire B- and D-genome chromosomes were detected. The FISH pattern of hybrid II-1-3 was the same as that of parent wheat. GISH using whole genomic DNA from A. elongatum as probe determined the alien chromatin. Sequential GISH and FISH, in combination with some of the karyotype data, localized the small chromosome segments of A. elongatum on the specific sites of wheat chromosomes 2AL, 1BL, 5BS, 1DL, 2DL and 6DS. FISH with probe OPF-03₁₂₉₆ from randomly amplified polymorphic DNA (RAPD) detected E-genome chromatin of A. elongatum, which existed in all of the small chromosome segments introgressed. Microsatellite primers characteristic for the chromosome arms above were used to check the localization and reveal the genetic identity. These methods are complementary and provide comprehensive information about the genomic constitution of the hybrid. The relationship between hybrid traits and alien chromatin was discussed.     

A hybrid, broad-spectrum inhibitor of Colorado potato beetle aspartate and cysteine digestive proteinases

Protein engineering approaches are currently being devised to improve the inhibitory properties of plant proteinase inhibitors against digestive proteinases of herbivorous insects. Here we engineered a potent hybrid inhibitor of aspartate and cysteine digestive proteinases found in the Colorado potato beetle, Leptinotarsa decemlineata Say. Three cathepsin D inhibitors (CDIs) from stressed potato and tomato were first compared in their potency to inhibit digestive cathepsin D-like activity of the insect. After showing the high inhibitory potency of tomato CDI (M(r) approximately 21 kDa), an approximately 33-kDa hybrid inhibitor was generated by fusing this inhibitor to the N terminus of corn cystatin II (CCII), a potent inhibitor of cysteine proteinases. Inhibitory assays with recombinant forms of CDI, CCII, and CDI-CCII expressed in Escherichia coli showed the CDI-CCII fusion to exhibit a dual inhibitory effect against cystatin-sensitive and cathepsin D-like enzymes of the potato beetle, resulting in detrimental effects against 3rd-instar larvae fed the hybrid inhibitor. The inhibitory potency of CDI and CCII was not altered after their fusion, as suggested by IC(50) values for the interaction of CDI-CCII with target proteinases similar to those measured for each inhibitor. These observations suggest the potential of plant CDIs and cystatins as functional inhibitory modules for the design of effective broad-spectrum, hybrid inhibitors of herbivorous insect cysteine and aspartate digestive proteinases.     

Antimalarial activity of thiophenyl- and benzenesulfonyl-dihydroartemisinin

Each diastereomer of 10-thiophenyl- and 10-benzenesulfonyl-dihydroartemisinin was synthesized from artemisinin in three steps, and screened against chloroquine-resistance and chloroquine-sensitive Plasmodium falciparum. Three of the four tested compounds were found to be effective. Especially, 10 beta-benzenesulfonyl-dihydroartemisinin showed stronger antimalarial activity than artemisinin.