Jennifer A. McComb

Stimulation of synthesis and release of swainosonine from transformed roots of Swainsona galegifolia.

Transformed root cultures of Swainsona galegifolia were established for swainsonine production. Stimulation of production of swainsonine and its release into the culture medium was achieved using copper sulphate, reduction of medium pH and supply of swainsonine precursors. The yield of control cultures (0.3 g of roots grown in 15 ml medium for 30 days) was 79 micrograms swainsonine with only a trace of swainsonine in the medium. After treatment with 1 mM copper sulphate for two days before harvest on day 30, 155 micrograms of swainsonine was produced, of which 14.3 micrograms was in the medium. Reduction of medium pH from 5.7 to 2.7 for one day before harvest resulted in 159 micrograms of swainsonine (47 micrograms in the medium). Supplementation with 2 mM malonic acid for 12 days before harvest resulted in 187 micrograms total swainsonine (34 micrograms in the medium), while 2 mM pipecolic acid for six days before harvest gave the highest swainsonine yield (220 micrograms total, 43 micrograms in the medium). The increased yields were achieved through small increases in biomass, as well as increases in the level of swainsonine synthesis.

Comparisons of growth of Eucalyptus camaldulensis from seeds and tissue culture: root, shoot and leaf morphology of 9-month-old plants grown in deep sand and sand over clay

Comparisons of early growth of tissue culture clones and seedlings of Eucalyptus camaldulensis indicated strong morphological differences between genotypes within the species, but no architectural differences, either above-or below-ground, were attributable to micropropagation. Clonal 9-month-old plants were less variable than seedling populations. Both seed-origin plants and clonal-origin plants generally developed a number of deep sinker roots and showed equal ability to penetrate heavy clay soils. One clonal line, however, had a compact habit and a root architecture concentrated in the upper 20 cm of the soil profile. Under favourable nutrient and water conditions, the largest of the 9-month-old plants from both seed and tissue culture exceeded 2.5 m in height, produced more than 500 g of above-ground biomass and developed root lengths exceeding 8 km. Clonal Eucalyptus camaldulensis have advantages in plantation conditions with saturated, saline and heavy soil conditions.

Phosphite induces expression of a putative proteophosphoglycan gene in Phytophthora cinnamomi

The phosphate analogue phosphite is widely used to control diseases of plants caused by oomycete pathogens such as those within the genus Phytophthora. Phosphite inhibits zoospore production and growth of P. cinnamomi. However, very little is known about the underlying mechanism of action. In the present study, we grew P. cinnamomi in Ribero’s liquid medium with 0.1 mM phosphate, with and without 5 μg phosphite/mL, and used differential display reverse transcriptase-PCR (DDRT-PCR) to identify P. cinnamomi genes that are transcriptionally repressed or induced by phosphite. By using this technique, four differentially expressed bands were identified. However, quantitative measurement of the amount of mRNA transcript by RT-PCR revealed that only one gene was actually phosphite inducible. On the basis of the homology of the deduced amino acid sequence, this gene encodes a proteophosphoglycan. The remaining three bands did not show differential expression.

Inoculation of Eucalyptus marginata Donn ex Sm. (jarrah) clones with Phytophthora cinnamomi Rands in vitro and under glasshouse conditions

Jarrah trees surviving on jarrah dieback sites or seedlings surviving inoculation with Phytophthora cinnamomi under glasshouse conditions were propagated using tissue culture techniques. Clones and seedlings of jarrah were inoculated with zoospores in vitro and under glasshouse conditions. When inoculated in vitro individual clones showed a consistent response, between trials, with regard to time to infection. After inoculation in the glasshouse all seedlings became infected and had reduced growth, but the level of infection of the root system and the reduction in the growth of the plants varied between clones.