Physiological Responses of Limonium aureum Seeds to Ultra-drying

The seeds of Limonium aureum （L.） Hill. were dried from 8.92% to 2.88% moisture content in a desiccating container with silica gel. After ultra-drying the seeds were accelerated aged （50 ℃, 1 month）, and some physiological indices, including the electrical conductivity, dehydrogenase activity, superoxide dismutase （SOD）, peroxidase （POD）, glutathione reductase （GR）, ascorbate peroxidase （APX）, catalase （CAT）, volatile aldehydes and malondialdehyde （MDA） were tested. The results indicated that dehydrogenase, POD, SOD, GR, APX and CAT activities of the ultra-dry seeds were higher than the control seeds, while volatile aldehydes and malondialdehyde were lower than the control group. The results suggest that ultra-drying is beneficial for maintaining the vigor of L. aureum seeds at a high level. Thus, L. aureum seeds could be stored under ultra-dry conditions.     

Micropropagation of Limonium cavanillesii Erben, a threatened statice, from inflorescence stems

Micropropagation of Limonium cavanillesii Erben, a threatened and endemic statice species from Valencia Community (Eastern Spain), was successfully achieved using inflorescence stem pieces as initial explants. Segments 20 mm long from basal parts of immature inflorescences and with axillary buds were cut, sterilised and established in vitro. Shoots obtained from indifferentiated buds were sectioned and then transferred to Murashige and Skoog (MS) medium with 2 mg l^–1 kinetin to provide a plant stock.Shoot multiplication was achieved on MS medium with different cytokinins. The best results for shoot formation were obtained with 2–5 mg l^–1kinetin, 5 mg l^–1 6---dimethylallylaminopurine or 0.1 mg l^–1 6-benzylaminopurine, without significant differences between them. High shoot rooting (80–85%) was obtained within four weeks with indolebutyric acid or indoleacetic acid (0.1 or 0.5 mg l^–1), and also on medium without plant growth regulators. Plant survival to hardened greenhouse conditions was 90% four weeks after plantlet removal from in vitro conditions.This protocol for micropropagation of Limonium cavanillesii is very useful for conservation purposes of endangered statice species, because by using inflorescence stem as initial material it is easier to establish aseptic cultures while preserving the mother plant.     

Survival of an introduced ectomycorrhizal Laccaria bicolor strain in a European forest plantation monitored by mitochondrial ribosomal DNA analysis

Mitochondrial and nuclear genes have different inheritance, thus studies of fungal populations should use both mitochondrial and nuclear markers. Using nuclear markers, the S238N strain of the ectomycorrhizal basidiomycete Laccaria bicolor ((Maire) Orton) has been previously shown to persist for at least 10 yr after outplanting in a plantation of Douglas fir ( Pseudotsuga menziesii (Mir.) Franco) inoculated with this strain. In the present study, we have sampled 539 sporophores of Laccaria spp. from this plantation, some of which had the S238N nuclear genotype, to study mitochondrial DNA polymorphism and persistence of the inoculated S238N mitochondrial genome. Length polymorphism in fragments of the large subunit of mitochondrial ribosomal DNA (LrDNA) allowed distinction of the haplotypes present in the plantation at the species level. In addition, heteroduplex analysis and sequencing revealed intraspecific polymorphism of LrDNA among the L. bicolor sporophores and enabled specific identification of S238N LrDNA. This haplotype was only retained in sporophores carrying the S238N nuclear genome, confirming the survival of this introduced strain in a natural population.     

Effects of breeding density, synchrony, and experience on extrapair paternity in tree swallows

Breeding density, synchrony, and experience are expected toinfluence the frequency of extrapair paternity in birds. UsingDNA fingerprinting, we examined the effect of these factorson tree swallows nesting at relatively high (grids of nest-boxes)and low (solitary boxes at least 100 m from the nearest neighbor)densities and in relatively synchronous (Alberta) and asynchronous(Ontario) populations in Canada. The mean percentage of extrapairoffspring per nest did not differ significantly between birdsnesting in grids (43%, n = 22 families) and solitary boxes (57%,n = 12 families). Similarly, there was no significant differencein the mean percentage of extrapair offspring per nest betweenrelatively synchronous (60%, n = 12 Alberta families) and asynchronous(41%, n = 22 Ontario families) populations. We also found noconsistent pattern between extrapair paternity and breedingexperience among seven males and seven females examined overtwo to three breeding seasons. Female tree swallows can influencethe fertilization success of extrapair males by active selectionand rejection of copulation partners. We suggest that this abilitylimits the predicted effect of various ecological factors onthe frequency of extrapair paternity     

SPATIAL DISTRIBUTION OF A PRIMITIVELY SOCIAL BEE: DOES GENETIC POPULATION STRUCTURE FACILITATE ALTRUISM?

Exoneura bicolor is a univoltine, facultatively social bee exhibiting a solitary/quasisocial/semisocial colony polymorphism (Schwarz, 1986, 1987). Intracolony relatedness in semisocial colonies has been previously estimated at 0.49 ± 0.06 (Schwarz, 1987), although the crucial relatedness between altruists and the brood that they rear will be about half this value. This value is unlikely to be increased by the preferential rearing of only close relatives (Schwarz, 1988a) and no known morphological specializations preclude workers from reproducing in this species. Hamilton (1972, 1975) suggested that relatedness may be increased through population subdivision, if this leads to significant inbreeding and increased between-colony genetic variance. The same process may also operate at higher levels of population structure (e.g., Wade, 1978). Population structure and intracolony relatedness in E. bicolor were investigated in seven localities in southern Victoria, Australia, to determine if inbreeding at any level of population structure was contributing to relatedness between altruists and beneficiaries within these colonies. Population structure was described using hierarchical F-statistics and an identity by descent measure, developed by Queller and Goodnight (1989), was used to estimate intracolony relatedness. It was found that inbreeding was not contributing to between-group genetic variance, at any level, in a consistent manner across localities. Therefore relatedness, considered in isolation, does not seem sufficient to account for the presence of worker behavior. It is suggested that large benefits for group living may be responsible for maintaining altruistic behavior, in part, in this species. Significant heterogeneity among localities for all F-statistics estimated in our analysis was found and this may be attributable to stochastic elements such as cofounding behavior and the low percentage of males in the brood. The possible consequences of such heterogeneity in population structure for the maintenance of altruism in E. bicolor are discussed.     

Control of leaf-tip necrosis of micropropagated ornamental statice by elimination of endophytic bacteria

Summary Leaf-tip necrosis of micropropagated statice plantlets is a serious problem in commercial laboratories in Taiwan. Endophytic bacteria were detected in plantlets obtained from commercial laboratories with a leaf-tip necrosis problem. Endophytic bacteria were detected in flower stalks collected from four different statice farms at frequencies ranging from 61 to 100%. All plantlets regenerated from flower-stalk explants that tested free of endophytic bacteria did not develop leaf-tip necrosis. The most frequently detected endophytic bacteria were Pasteurella multocida, Stenotrophomonas maltophilia, and Alcaligenes sp. Most endophytic bacteria in statice plantlets were eliminated by the subculture of plantlets on medium with augmentin, cefotaxime, or augmentin plus cefotaxime. Those plantlets freed from endophytic bacteria by subculture on antibiotic-amended medium did not develop leaf-tip necrosis. Our results show that leaf-tip necrosis of micropropagated statice plantlets is associated with endophytic bacteria, and that the disease can be controlled by using explants pre-tested to be free from endophytic bacteria or by the subculture of affected plantlets on antibiotic-amended medium.