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Kulheim C.,Australian National University | Padovan A.,Australian National University | Hefer C.,University of British Columbia | Krause S.T.,Martin Luther University of Halle Wittenberg | And 4 more authors.
BMC Genomics | Year: 2015

Background: Terpenoids are abundant in the foliage of Eucalyptus, providing the characteristic smell as well as being valuable economically and influencing ecological interactions. Quantitative and qualitative inter- and intra- specific variation of terpenes is common in eucalypts. Results: The genome sequences of Eucalyptus grandis and E. globulus were mined for terpene synthase genes (TPS) and compared to other plant species. We investigated the relative expression of TPS in seven plant tissues and functionally characterized five TPS genes from E. grandis. Compared to other sequenced plant genomes, Eucalyptus grandis has the largest number of putative functional TPS genes of any sequenced plant. We discovered 113 and 106 putative functional TPS genes in E. grandis and E. globulus, respectively. All but one TPS from E. grandis were expressed in at least one of seven plant tissues examined. Genomic clusters of up to 20 genes were identified. Many TPS are expressed in tissues other than leaves which invites a re-evaluation of the function of terpenes in Eucalyptus. Conclusions: Our data indicate that terpenes in Eucalyptus may play a wider role in biotic and abiotic interactions than previously thought. Tissue specific expression is common and the possibility of stress induction needs further investigation. Phylogenetic comparison of the two investigated Eucalyptus species gives insight about recent evolution of different clades within the TPS gene family. While the majority of TPS genes occur in orthologous pairs some clades show evidence of recent gene duplication, as well as loss of function. © 2015 Külheim et al.; licensee BioMed Central.

Aveling T.A.S.,Forestry and Agricultural Biotechnology Institute | Govender V.,Forestry and Agricultural Biotechnology Institute | Kandolo D.S.,Forestry and Agricultural Biotechnology Institute | Kritzinger Q.,University of Pretoria
Journal of Agricultural Science | Year: 2013

The quality of seed is dependent on two very broad aspects: how healthy (disease-free) a seed is and its field performance (germination and vigour). The objective of the present study was to evaluate the effect of pesticidal seed treatments of maize (Zea mays L.) on seed germination and vigour, and on greenhouse emergence in the presence of Fusarium graminearum Schw. Maize seeds were treated with four pesticides: Apron® XL (metalaxyl), Thiram (thiram), Celest® XL (fludioxonil, metalaxyl) and Apron ® Star 42 WS (thiamethoxam, metalaxyl, difenoconazole). Viability and vigour of the treated seeds were determined. Thereafter, seeds were planted under greenhouse conditions. The control consisted of water-treated seeds. None of the pesticides reduced the standard germination under laboratory conditions and none had any effect on the quantity of leachate (measured as conductivity) or moisture content of the seeds. The different treatments also had no effect on germination or on seedling weight increase among treatments after rapid imbibition and there was no difference in germination among treatments following the cold test. The proportion of diseased plants harvested from F. graminearum inoculated soil was significantly reduced by Apron® Star 42 WS and Celest® XL. The vigour tests indicated that none of the pesticides tested affected the seeds negatively and that plant biomass in the presence of the pathogen, F. graminearum, was increased after the application of the pesticides to the seeds, with the exception of seeds treated with Apron® XL. Copyright © Cambridge University Press 2012.

Reeksting B.J.,University of Pretoria | Reeksting B.J.,Forestry and Agricultural Biotechnology Institute | Taylor N.J.,University of Pretoria | van den Berg N.,University of Pretoria | van den Berg N.,Forestry and Agricultural Biotechnology Institute
South African Journal of Botany | Year: 2014

Losses in the production of avocado (Persea americana (Mill.)) are incurred due to Phytophthora root rot (PRR), a disease of the feeder roots that results in tree-dieback and eventual tree death. Avocado is also a flood-sensitive species and flooding exacerbates the effects of PRR. The avocado industry relies on the use of rootstocks tolerant to PRR to minimise losses. The present study compared the gas exchange and chlorophyll fluorescence responses of avocado rootstock plants of 'Dusa™', the current South African industry standard, with 'Duke 7', and the selections R0.12 and R0.06 which show reduced and superior tolerance to PRR, respectively. A decline in stomatal conductance (gs) and net CO2 assimilation (PN) over the 30day evaluation period were early responses to flooding. 'Dusa™', the more tolerant rootstock plants, demonstrated a better recovery in PN and gs in response to inoculation; however, both rootstocks performed poorly under flooded conditions. A decline in PN in infected 'Duke 7' plants appeared to be associated with stomatal limitations due to reduced stomatal conductance. The decline in PN and gs was not apparent in infected 'Dusa™' plants. Non-stomatal limitations to PN in rootstock plants exposed to flooding were also evident as indicated by increases in the ratio of internal to atmospheric CO2 concentrations (Ci/Ca). Impaired photosynthetic capacity in flooded rootstock plants was reflected by reduced photosystem II efficiency and photochemical quenching. In comparison to 'Dusa™', R0.12 rootstock plants showed reduced PN and gs following inoculation with Phytophthora cinnamomi whereas the more tolerant R0.06 rootstock plants revealed sustained photosynthetic activity. Interestingly R0.06 was the only rootstock able to maintain PN and gs in non-inoculated, flooded plants. © 2014 South African Association of Botanists.

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