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Yanco, Australia

Herron G.A.,Elizabeth Macarthur Agricultural Institute | Langfield B.J.,Elizabeth Macarthur Agricultural Institute | Tomlinson T.M.,Elizabeth Macarthur Agricultural Institute | Mo J.,Yanco Agricultural Institute
Australian Journal of Entomology

Field strains of Thrips tabaci Lindeman were collected from bulb onion in New South Wales, Queensland and South Australia and returned to the laboratory for culturing and subsequent bioassay to determine chemical specific responses. Chemicals tested included diazinon, dimethoate, λ-cyhalothrin and methidathion with imidacloprid and spinetoram evaluated to establish reliable susceptible baseline responses. Reference (susceptible) responses were compared back with those previously published and for all insecticides more susceptible strains were found for resistance comparison. Results for methidathion in particular were found to be significantly different from those reported previously. These differences influenced resistance factor calculation considerably. A high 49-fold methidathion resistance was detected, a result consistent with anecdotal grower concerns of poor product performance against T. tabaci. Resistance to diazinon remains generally low with all strains tested showing <6-fold at the LC 50 level. LC 50 dimethoate resistance peaked at 17-fold. Maximum (56-fold) λ-cyhalothrin resistance was significantly less than previously found but responses were very heterogeneous implying resistance could very quickly increase. Worryingly, the difference in imidacloprid responses between the least and most tolerant was 41-fold although the chemical is neither used nor registered for use against T. tabaci. We consider such a high and significant difference in response to imidacloprid is most likely caused by an unknown cross-resistance that may compromise any future development of imidacloprid for use against T. tabaci. Thrips remain susceptible to spinetoram. © 2011 Industry and Investment NSW; Journal compilation © 2011 Australian Entomological Society. Source

Damunupola J.W.,University of Peradeniya | Ratnayake K.,University of Queensland | Joyce D.C.,University of Queensland | Joyce D.C.,Sunshine Coast Mail Center | Irving D.E.,Yanco Agricultural Institute
Functional Plant Biology

Early desiccation limits the vase life of Acacia cut flowers and foliage and may be attributable to poor hydraulic conductivity (K h) of the cut stems. Acacia holosericea A.Cunn. ex G.Don has been adopted as the test species to investigate the postharvest water relations of the genus Acacia. To understand potential constraints on K h, xylem conduits in cut A. holosericea stems were anatomically characterised by light and scanning and transmission electron microscopy. Vessels with simple perforation plates and tracheids were the principal water conducting cells. Bordered vestured intervessel pits were present in xylem vessel elements. The majority of conduits (89%) were short at 15cm long. Only 2% were 15-16cm in length. Mean xylem conduit diameter was 77±0.9m and the diameter profile showed a normal distribution, with 29% of diameters in the range of 70-80μm. Simple perforation plates can offer relatively low resistance to water flow. On the other hand, bordered vestured pits and short xylem conduits can confer comparatively high resistance to water flow. Overall, the presence of bordered vestured pits, together with a high proportion of short xylem conduits and high stomatal densities (232 ± 2mm-2) on unifacial phyllodes, could contribute to early dehydration of A. holosericea cut foliage stems standing in vase water. Further research will relate these anatomical features with changes in K h and transpiration of cut foliage stems. © 2011 CSIRO. Source

Dinh S.Q.,University of Queensland | Dinh S.Q.,Australian Department of Primary Industries and Fisheries | Joyce D.C.,University of Queensland | Irving D.E.,Yanco Agricultural Institute | Wearing A.H.,University of Queensland
Plant Pathology

Botrytis cinerea infects waxflower (Chamelaucium spp.) flowers and can induce them to abscise from their petioles before disease becomes evident. Botrytis cinerea infection of flowers was studied on two waxflower cultivars by light and electron microscopy. Pot-grown waxflower flowers were harvested, inoculated with aqueous suspensions of B. cinerea conidia, incubated at 20-22°C and >95% RH and examined within 96h post-inoculation (hpi). Conidial germination on petals started 4hpi, penetration via germ tube tips was 6hpi and protoappressoria were formed 8hpi. Germination on petals approximately doubled every 4-6h to 18hpi. Conidial germination was ca. 50% at 22-24hpi. Botrytis cinerea infected most waxflower flower organs, including petals, anthers and filaments, stigma and hypanthium, within 24hpi. Hyaline and lobate appressoria were observed 36hpi. Infection cushions on stamen bases were formed 36hpi by saprophytic hyphae that originated from anthers. This infection process can give rise to tan-coloured symptoms typical of botrytis disease that radiate from this part of the flower. Subcuticular hyphae were present at high density near stamen bases and evidently resulted from multiple penetrations from single infection cushions. The subcuticular hyphae grew within the hypanthium and towards the centre of the floral tube. When flower abscission occurred, floral tube tissues close to the abscission zone remained uninfected. This observation infers possible transmission of a signal (e.g. ethylene) upon B. cinerea infection. Thus, B. cinerea causes flower abscission apparently as a defence response. © 2010 The Authors. Plant Pathology © 2010 BSPP. Source

Kharabian-Masouleh A.,Southern Cross University of Australia | Waters D.L.E.,Southern Cross University of Australia | Reinke R.F.,Yanco Agricultural Institute | Reinke R.F.,Charles Sturt University | Henry R.J.,University of Queensland
Plant Biotechnology Journal

High-throughput sequencing of pooled DNA was applied to polymorphism discovery in candidate genes involved in starch synthesis. This approach employed semi- to long-range PCR (LR-PCR) followed by next-generation sequencing technology. A total of 17 rice starch synthesis genes encoding seven classes of enzymes, including ADP-glucose pyrophosphorylase (AGPase), granule starch synthase (GBSS), soluble starch synthase (SS), starch branching enzyme (BE), starch debranching enzyme (DBE) and starch phosphorylase (SPHOL) and phosphate translocator (GPT1) from 233 genotypes were PCR amplified using semi- to long-range PCR. The amplification products were equimolarly pooled and sequenced using massively parallel sequencing technology (MPS). By detecting single nucleotide polymorphism (SNP)/Indels in both coding and noncoding areas of the genes, we identified genetic differences and characterized the SNP/Indel variation and distribution patterns among individual starch candidate genes. Approximately, 60.9 million reads were generated, of which 54.8 million (90%) mapped to the reference sequences. The average coverage rate ranged from 12708 to 38300 times for SSIIa and SSIIIb, respectively. SNPs and single/multiple-base Indels were analysed in a total assembled length of 116403bp. In total, 501 SNPs and 113 Indels were detected across the 17 starch-related loci. The ratio of synonymous to nonsynonymous SNPs (Ka/Ks) test indicated GBSSI and isoamylase 1 (ISA1) as the least diversified (most purified) and conservative genes as the studied populations have been through cycles of selection. This report demonstrates a useful strategy for screening germplasm by MPS to discover variants in a specific target group of genes. © 2011 The Authors. Plant Biotechnology Journal © 2011 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd. Source

Eyre J.X.,University of Queensland | Joyce D.C.,University of Queensland | Irving D.E.,Yanco Agricultural Institute
Journal of Horticultural Science and Biotechnology

Backhousia myrtifolia is a species native to Australia that shows potential as a cut flower crop. During Spring and Summer, it bears numerous small florets with prominent white sepals and glossy deep-green foliage. B. myrtifolia is harvested either when tight white buds are present in the centre of the star-shaped sepals, or following bud burst, after the petals and stamens have abscised to leave only the sepals.Wilting and brown-to-black discolouration of the flowers and foliage can markedly reduce stem quality. Several forms of discolouration were characterised over the 2004 - 2006 flowering seasons and were collectively termed 'post-harvest browning syndrome'. Further research based on the symptomatology described herein is required to elucidate the causal agent(s). Source

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