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Jordan G.J.,University of Tasmania | Brodribb T.J.,University of Tasmania | Blackman C.J.,University of Tasmania | Blackman C.J.,Macquarie University | Weston P.H.,The Royal Botanic Gardens and Domain Trust
American Journal of Botany | Year: 2013

Premise of study: The mechanisms by which plants tolerate water defi cit are only just becoming clear. One key factor in drought tolerance is the ability to maintain the capacity to conduct water through the leaves in conditions of water stress. Recent work has shown that a simple feature of the leaf xylem cells, the cube of the thickness of cell walls divided by the lumen width (t/b) 3, is strongly correlated with this ability. • Methods: Using ecologically, phylogenetically, and anatomically diverse members of Proteaceae, we tested the relationships between (t/b) 3 and climate, leaf mass per unit area, leaf area, and vein density. To test relationships at high phylogenetic levels (mostly genus), we used phylogenetic and nonphylogenetic single and multiple regressions based on data from 50 species. We also used 14 within-genus species pairs to test for relationships at lower phylogenetic levels. • Key results: All analyses revealed that climate, especially mean annual precipitation, was the best predictor of (t/b) 3. The variation in (t/b) 3 was driven by variation in both lumen diameter and wall thickness, implying active control of these dimensions. Total vein density was weakly related to (t/b) 3 but unrelated to either leaf area or climate. Conclusions: We conclude that xylem reinforcement is a fundamental adaptation for water stress tolerance and, among evergreen woody plants, drives a strong association between rainfall and xylem anatomy. The strong association between (t/b) 3 and climate cannot be explained by autocorrelation with other aspects of leaf form and anatomy that vary along precipitation gradients. © 2013 Botanical Society of America. Source

Callaghan S.E.,Agriculture Section | Puno V.I.,University of Sydney | Williams A.P.,Agriculture Section | Weir B.S.,Landcare Research | And 11 more authors.
Australasian Plant Disease Notes | Year: 2016

Fusarium oxysporum f.sp. niveum is reported for the first time in the Lao PDR. It was isolated from watermelons (Citrullus lanatus) in Songkhon district, Savannahkhet province following a limited ad hoc survey during January and February of 2015. Infected plants showed symptoms of wilt, vascular discolouration, necrosis in the collar region, lower stem base and upper taproot regions, and whole plant death. Identification of the pathogen was confirmed through phylogenetic analysis of the EF1-α locus and a pathogenicity test satisfying Koch’s postulates. © 2016, Australasian Plant Pathology Society Inc. Source

Pinaria A.G.,Sam Ratulangi University | Laurence M.H.,The Royal Botanic Gardens and Domain Trust | Burgess L.W.,University of Sydney | Liew E.C.Y.,The Royal Botanic Gardens and Domain Trust
Plant Pathology | Year: 2015

Vanilla stem rot, caused by Fusarium oxysporum f. sp. vanillae (Fov), is the main constraint to increasing vanilla production in the major vanilla-producing countries, including Indonesia. The current study investigated the origin of Fov in Indonesia using a multigene phylogenetic approach. Nineteen Fov isolates were selected to represent Indonesia, the Comoros, Mexico and Réunion Island. The translation elongation factor 1 alpha gene and the mitochondrial small subunit ribosomal RNA gene phylogenies resolved the Fov isolates into three distinct clades in both phylogenetic species of the F. oxysporum species complex, indicating a polyphyletic pattern of evolution. In addition, Fov isolates from Indonesia were also polyphyletic. These results suggest that the vanilla stem rot pathogen in Indonesia has a complex origin. The implications for disease management are discussed. © 2015 British Society for Plant Pathology. Source

Laurence M.H.,University of Sydney | Summerell B.A.,The Royal Botanic Gardens and Domain Trust | Burgess L.W.,University of Sydney | Liew E.C.Y.,The Royal Botanic Gardens and Domain Trust
Fungal Biology | Year: 2014

Fusarium oxysporum is an important plant and human pathogenic ascomycetous group, with near ubiquity in agricultural and non-cultivated ecosystems. Phylogenetic evidence suggests that F. oxysporum is a complex of multiple morphologically cryptic species. Species boundaries and limits of genetic exchange within this complex are poorly defined, largely due to the absence of a sexual state and the paucity of morphological characters. This study determined species boundaries within the F. oxysporum species complex using Genealogical Concordance Phylogenetic Species Recognition (GCPSR) with eight protein coding loci. GCPSR criteria were used firstly to identify independent evolutionary lineages (IEL), which were subsequently collapsed into phylogenetic species. Seventeen IELs were initially identified resulting in the recognition of two phylogenetic species. Further evidence supporting this delineation is discussed. © 2014 The British Mycological Society. Source

Puno V.I.,University of Sydney | Laurence M.H.,The Royal Botanic Gardens and Domain Trust | Guest D.I.,University of Sydney | Liew E.C.Y.,The Royal Botanic Gardens and Domain Trust
Australasian Plant Pathology | Year: 2015

Phytophthora multivora, a recently described species recovered from declining natural ecosystems in Western Australia, was detected in the natural site of the rare and endangered Wollemi pine in New South Wales. The Phytophthora species was identified based on morphology and sequence analysis of the rDNA ITS and mitochondrial DNA cox1 regions. A pathogenicity trial to test the susceptibility of Wollemi pine to P. multivora resulted in symptoms equal in extent to those caused by P. cinnamomi, a known pathogen of Wollemi pine. Post-trial dry root weight analysis of P. multivora and P. cinnamomi inoculated plants revealed no significant difference between species, as both significantly reduced root mass compared to uninoculated plants. P. multivora was shown to be a pathogen of the Wollemi pine, and the implications on protecting this endangered species in the wild are discussed. © 2015, Australasian Plant Pathology Society Inc. Source

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