Glyphosate is the world's most widely used herbicide. It is nonselective and has been used to control a broad range of weed species for the past 20 yr, without the appearance of resistant weed biotypes. However, a biotype ofLolium rigidumfrom a field in Northern Victoria, Australia, in which glyphosate had been used for the past 15 yr, failed to be controlled by label recommended rates. Based on LD50values from pot dose-response experiments, this biotype exhibited resistance to glyphosate and was nearly 10-fold more resistant compared to the susceptible biotypes tested. The biotype was resistant to three different salts of glyphosate. The biotype was also nearly threefold more resistant to diclofop-methyl but was susceptible to other commonly used selective and broad-spectrum herbicides. Between the two-leaf and tillering stages of development, a susceptible biotype exhibited a small but significant decrease in tolerance to glyphosate, whereas tolerance of the resistant biotype remained unchanged with age. The resistant phenotype was verified in experiments in which seed was germinated in the presence of glyphosate. Observations on shoot and root growth of seedlings in these experiments suggested that the resistance mechanism might be associated more with the shoot than with the root.

Lavandula angustifolia (lavender) is a small woody perennial grown for essential oil, which is steam distilled from flowers. To potentially improve size of flowers and oil yield we produced and characterised autotetraploid plants. L. angustifolia seed germinated in the presence of the mitotic spindle inhibitor colchicine at concentrations of 125 mg l -1 or less resulted in plants carrying sports with larger flowers. Propagation of two sports gave rise to putative polyploid cultivars C3/2 and C6/24. Direct chromosome counts in root tip cells of seedlings from four common cultivars of L. angustifolia and the seed lot from which C3/2 and C6/24 were derived was 50 whereas C3/2 and C6/24 had greater than 90 chromosomes indicating they were autotetraploid. Ploidy level assessed by flow cytometry (FCM) of nuclei showed that 12 cultivars of L. angustifolia had similar nuclear DNA content whereas C3/2 and C6/24 had double the amount of DNA confirming autotetraploidy. The genome size (1C-value) of a diploid L. angustifolia cultivar was estimated by FCM to be 0.90 (±0.07) pg. Morphological characteristics were measured in autotetraploid and control plants. Autotetraploids had thicker peduncles, larger flowers and larger seeds than diploids. Scanning electron microscopy revealed peltate glandular trichomes were larger in the tetraploids relative to diploids. Both tetraploid and diploid cultivars had complex non-glandular trichomes on leaves and sepals and two different types of capitate glandular trichomes were identified on leaves. Autotetraploid lavenders represent useful germplasm both for commercial oil production and future breeding.

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Pseudomonas syringae pv. maculicola causes bacterial leaf spot on cruciferous plants in Australia. This is the first record confirming the identity of seven isolates currently stored as P. syringae pv. maculicola in the herbarium of the Department of Agriculture, Orange, Australia (Herb. DAR). The isolates were identified using pathogenicity testing on cauliflower and fatty acid methyl ester analysis. They clustered together using repetitive sequence-based polymerase chain reaction (rep-PCR) and PCR-restriction fragment-length polymorphism (RFLP) of the 16S − 23S internal transcribed spacer region (ITS) using seven restriction enzymes. Identification was confirmed by comparison of these isolates with known overseas isolates of P. syringae pv. maculicola , but there was significant variation in their pathogenicity and genetic structure.

Protoplasts isolated from the primary leaves of Phaseolus vulgaris L. were used in transient expression experiments to identify promoter sequences of the P. vulgaris rbcS2 gene, encoding ribulose 1,5-bisphosphate carboxylase/oxygenase small subunit, concerned with sucrose repression. The protoplasts supported high rates of expression of the chloramphenicol acetyl transferase reporter gene fused to 1433 bp of the rbcS2 5' flanking sequences. Expression was repressed by 50 mM sucrose whereas that driven by control promoters was not. Assays of promoter deletions revealed that 203 bp 5' to the transcription start site were sufficient for high rates of sucrose-repressible expression. A -187 bp deletion supported much lower rates of expression and was not subject to sucrose repression. The -203 to -187 bp region contains sequences resembling elements involved in the sugar stimulation of transcription of other genes: the SURE (sucrose response element) of plant genes and the ChoRE (carbohydrate response element) of mammalian genes. A G-box (CACGTG) located at -200 to -205 was important for high levels of sucrose-repressible expression, since deletion of a nucleotide from this element in the context of the 1433 bp promoter gave much reduced expression. However, a modified G-box (CcCGTG) in the -203 bp fusion and adjacent vector sequences remained functional. Measurements of rbcS and chalcone synthase (CHS) transcript levels in the protoplasts indicated that 4 mM sucrose was sufficient to repress or stimulate the respective genes. Further experiments suggested that metabolism of 6-carbon sugars is the signal for rbcS repression and CHS stimulation.

We have investigated the photoreceptors controlling transcription of genes encoding the small subunit (rbcS) of ribulose 1,5-bisphosphate carboxylase-oxygenase in green leaf tissue of pea (Pisum sativum). RbcS transcription was measured by hybridising labelled transcripts of isolated nuclei to rbcS cDNA clones. Transfer of green Pisum leaf tissue to darkness for 5 h causes a substantial decrease in the rate of rbcS transcription and the rate is restored rapidly when the plants are returned to white light. Low fluence rates of red light are ineffective in restoring the rate of rbcS transcription, suggesting that phytochrome alone does not fully mediate the response. Blue light is similarly effective to white light of an equal fluence rate (120 mumol m-2 s-1) in restoring the rate of rbcS transcription in the dark-treated plants, indicating that a blue light photoreceptor is involved. However, red light at the same fluence rate produces about 65% of the effect of blue or white light, showing that the blue light photoreceptor is not the only photoreceptor controlling rbcS transcription in the green leaf tissue. The identity of the photoreceptor responsible for the red light effect is discussed. Similar effects of blue and red light are observed at the level of transcript abundance in dark-grown pea leaf tissue given a brief illumination with red light, which potentiates the tissue for rapid transcript accumulation in white light.