In vitro germination of wheat pollen on raffinose medium

Wheat pollen gave up to 81.7 % germination when cultured on a 0.7 % agar medium containing 100 mg 1−1 H3BO3, 300 mg 1−1 CaCl2.2H2O and 0.75 M raffinose. On this medium at 25°C, germination started within 5 min and tubes reached a mean maximum length of 200 μm after 1 h. Maltose supported 27.9% germination, while sucrose gave at most 6.8%. Pollen on media with fructose, galactose, dextrose or lactose failed to germinate

Canker disease in Corymbia calophylla (Marri) in the south west of Western Australia

Cankering of marri in the southern forests of Western Australia is causing concern as it is increasing considerably in severity and geographic range. The contribution of canker fungi to stem, branch and tree death has not been studied in detail, and the causal agent(s) is yet to be determined (1). This project examined disease incidence and associated pathogens

Heterotrophic carbon gain and mineral nutrition of the root hemi-parasiteSantalum albumL. in pot culture with different hosts

This paper examines heterotrophic gain of carbon and mineral composition of Santalum album partnered singly in pot culture with three beneficial woody N2-fixing hosts and a nonbeneficial eucalypt host. Based on dry matter gains of the parasite at 33 weeks, Sesbaniaformosa proved the best host followed by Acacia ampliceps and A. trachycarpa while no improvement in growth was seen with Eucalyptus camaldulensis as a host in comparison with Santalum grown without a host. Numbers of haustoria formed by Santalum on roots of different hosts were poorly correlated with host quality. A small proportion of haustoria on legume hosts were attached to root nodules. Santalum partnered with any host or grown alone exhibited self-parasitism where haustoria attached to its own root system. Based on net C and N gains of Santalum and the C : N ratios of xylem solutes of Santalum, the heterotrophic gains of C from xylem of the three beneficial legume hosts over a nine week period were equivalent to 57.9% of total carbon (35.9 g C plant-1) on A. ampliceps, 45.5% (12.7 g C plant-1) on A. trachycarpa and 34.6% (29.9 g C plant-1) on S. formosa. Assays of leaf, stem, bark and root tissue of Santalum and its hosts and net increases in mineral contents of Santalum over the first nine weeks of the study showed that parasitism on beneficial hosts increased the mineral contents of the parasite, with evidence of net gains in certain elements (e.g. Ca, K, P, Na) being greatest when associated with hosts richest in the corresponding element. Foliage of Santalum was extraordinarily rich in Na and in some cases also in P and N in comparison with associated hosts. Net losses or only small gains of P, K, Ca and Na over the study interval in Santalum grown alone or associated with the eucalypt indicated poor ability for nutrient uptake through its own root system. Regression analysis showed incremental gains of N, C and Na, leaf area, content of K, N and Na in foliage of the parasite and root : shoot ratio to be excellent predictors of growth benefit from different hosts. Examples of stepwise regression analysis are provided indicating how such data might be employed for monitoring growth and host benefit under future plantation cultures of the parasite

In vitro propagation of Eucalyptus species

Introduction The importance of eucalypts and reasons for tissue culture Eucalypts are Australia's most distinctive plant group. They are contained within the genus Eucalyptus which consists of over 500 named species, with more as yet unnamed (Brooker & Kleinig 1983; 1990 Chippendale 1988). The natural distribution of the genus is almost completely confined to the Australian continent and Tasmania with only two species, E. deglupta and E. urophylla, occurring naturally in other countries. Since European settlement of Australia, seeds of eucalypts have been sent to countries throughout the world and they are now commonly grown in tropical and temperate areas for timber, pulp wood, eucalyptus oil, fuelwood, charcoal and as ornamentals. Exploitation of eucalypts outside Australia was initiated by the French. During the nineteenth century, eucalypts were planted in Europe and North America, and European imperial governments introduced them to colonies in South America, Africa and Asia. The presence of eucalypts in some of these countries is now so familiar to the native peoples that many consider them to be indigenous (Zacharin 1978). Although eucalypts in early plantations often grew very quickly the wood was sometimes of poor quality due to wood splitting and distortion (Clarke 1957; Penfold & Willis 1961; Pryor 1976). In many cases this was because the species chosen were inappropriate for local climatic and edaphic conditions (Evans 1980; Durand-Cresswell et al. 1982), the trees had been planted for the wrong purposes (Penfold & Willis 1961; Pryor 1976), or given incorrect fertilisers (Savory 1962; Stone 1968). The poor quality of the wood led to a slump in enthusiasm for growing eucalypts until about 1945 when world demand for pulpwood started to increase (Pryor 1976). Today the major uses of eucalypt wood are for fuelwood and pulpwood. There has been a 150 fold increase in pulpwood production from eucalypts since the early 1960s (Molleda 1984). They are now the most widely planted hardwood group in the world (Boland et al. 1984; Eldridge et al. 1993)

A rapid and inexpensive method for surface sterilisation of Ecklonia radiata (Phaeophyta) for tissue culture

Sections of the thallus of the brown alga Ecklonia radiata (C. Ag.) J. Ag. were surface sterilised for tissue culture by dipping in 70% ethanol for 30 s, followed by sterile deionised water for 30 min. A high percentage of aseptic viable explants could be obtained using this treatment, and growth in vitro was initiated

Tissue culture of brown seaweed

The harvesting of macrophyte algae (seaweeds) is well established and on a world-wide scale more than 180,000 tonnes dry weight of algae such as the phaeophytes Laminaria, Undaria,Sargassum and Macrocystis, the red algae Eucheuma, Gracilaria and Porphyra, and the green algae Ulva, Monostroma and Caulerpa are harvested annually. Much of this algal biomass comes from farmed rather than wild species. The red and brown algae are the source of the phycocolloids agar, alginate, agarose and carrageenan which are of fundamental importance to the development of biotechnology; i.e. for the culture of microorganisms (agar), for the separation of biomolecules (alginate and agarose) and for the production of food products (agar, carrageenan, alginate). The successful large-scale cultivation of these algae requires, amongst other things, the ability to select fast growing and disease resistant strains which produce large quantities of the desired phycocolloid. To this purpose classical plant breeding programs are being carried out, however these are slow and the production of superior cultivars takes much time and effort (Van der Meer 1988). In recent years there has therefore been much interest in developing protoplast and tissue culture systems which would allow more rapid selection and propagation of suitable cell lines, the possibility of producing hybrids by cell fusion and new strains by genetic engineering (Polne-Fuller and Gibor 1987b, Le Gallet al. 1990). Work in our laboratory has concentrated mainly on the brown algal genera Ecklonia and Cystophora. Ecklonia was chosen because it is easily obtained and is a potential source of alginate, and Cystophora, a genus endemic to Australia and New Zealand, because previous studies indicated that this genus appears to be a good source of tocopherols and tocotrienols (Gregson et al. 1977, Kazlauskas et al. 1981, unpubl. results). The tocopherols are of interest and also provide a convenient model for the study of the production of secondary metabolites in algal tissue culture. In this paper we describe some of our findings on the tissue culture of these species and on their tocopherol content

Transposable elements: Powerful contributors to angiosperm evolution and diversity

Transposable elements (TEs) are a dominant feature of most flowering plant genomes. Together with other accepted facilitators of evolution, accumulating data indicate that TEs can explain much about their rapid evolution and diversification. Genome size in angiosperms is highly correlated with TE content and the overwhelming bulk (>80%) of large genomes can be composed of TEs. Among retro-TEs, long terminal repeats (LTRs) are abundant, whereas DNA-TEs, which are often less abundant than retro-TEs, are more active. Much adaptive or evolutionary potential in angiosperms is due to the activity of TEs (active TE-Thrust), resulting in an extraordinary array of genetic changes, including gene modifications, duplications, altered expression patterns, and exaptation to create novel genes, with occasional gene disruption. TEs implicated in the earliest origins of the angiosperms include the exapted Mustang, Sleeper, and Fhy3/Far1 gene families. Passive TE-Thrust can create a high degree of adaptive or evolutionary potential by engendering ectopic recombination events resulting in deletions, duplications, and karyotypic changes. TE activity can also alter epigenetic patterning, including that governing endosperm development, thus promoting reproductive isolation. Continuing evolution of long-lived resprouter angiosperms, together with genetic variation in their multiple meristems, indicates that TEs can facilitate somatic evolution in addition to germ line evolution. Critical to their success, angiosperms have a high frequency of polyploidy and hybridization, with resultant increased TE activity and introgression, and beneficial gene duplication. Together with traditional explanations, the enhanced genomic plasticity facilitated by TE-Thrust, suggests a more complete and satisfactory explanation for Darwin’s “abominable mystery”: the spectacular success of the angiosperms

Genetic diversity and phylogenetic relationships within Eucalyptus marginata (Myrtaceae)

The eucalypt species Eucalyptus marginata which is harvested for high quality timber comprises three subspecies recognized by morphological characters; E. marginata ssp. marginata, ssp. thalassica, and ssp. elegantella. Genetic diversity and phylogenetic relationships between the subspecies were examined using anonymous nuclear RFLP loci, with Eucalyptus staerei included as an outgroup in the phylogenetic analysis. The level of diversity within the nuclear genome was lower than that found in comparative studies with other eucalypts (A = 2. 7, H4 = 0.345). Most of the variation occurred with ill the populations (96. 9%, H4 = 0.334) The two populations sampled for each of ssp. thalassica and ssp. elegantella clustered together in the UPGMA analysis, however there was little differentiation between the three subspecies overall (D = 0.029). Eucalyptus marginata was clearly distinct from its closest relative E. staerei (0 = 0.16). There is little genetic support for the separation of the subspecies