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Mareeba, Australia

Jones L.M.,Northern Australia Quarantine Strategy NAQS | Grice K.R.E.,Center for Tropical Agriculture | Davis R.I.,Northern Australia Quarantine Strategy NAQS
Australasian Plant Pathology | Year: 2010

Five pathogen-host leaf tissue combinations were used to determine whether dried plant disease material(γ) irradiated at a level of 25 kGy retains diagnostic value when subjected to selected polymerase chain reaction-based assays. Diagnostic amplification of nucleic acids from all anticipated positive samples was successful following γ irradiation. Variability in results is discussed in relation to sample handling. © Australasian Plant Pathology Society 2010.

Hardner C.M.,University of Queensland | Wright C.,Agri Science Queensland | Bally I.,Center for Tropical Agriculture
Acta Horticulturae | Year: 2013

Fruit weight is considered an important factor determining consumer choice in mango and other fruit. In this study, breeding values for average fruit weight were predicted for 29 parents and their ancestors from a seedling progeny trial established in northern Queensland using multivariate linear mixed model approaches that incorporated a pedigree. The trial was conducted over 6 seasons from 1999/2000 to 2005/2006 assessing average fruit weight in 1615 progeny (an average of 433 progeny per season) from 40 families made up of 29 cultivar combinations. Different means, breeding values and residual effects were estimated for each season using a factor analytic approach. Average fruit weights were not significantly different among seasons, however, there was a significant (p = 0.003) effect of year of planting. Additive genetic effects were large with average narrow sense heritability of 0.79. Family effects were very small and not significant. Breeding values were very strongly correlated among seasons (rg = 0.98), however, there was no strong correlation in non-genetic effects on the average fruit weight of progeny among seasons (re = 0.29) suggesting that environmental impacts on average fruit weight may differ between years. The estimated breeding values indicated that on average, progeny from crosses with the cultivars 'Keitt' and 'Kent' produced the largest fruit and progeny from 'Creeping' and 'Williard' produced the smallest fruit. Implications for mango breeding are discussed. © ISHS 2013.

Richards A.E.,CSIRO | Brackin R.,University of Queensland | Lindsay D.A.J.,Center for Tropical Agriculture | Schmidt S.,University of Queensland
Austral Ecology | Year: 2012

Fire is an important driver of nutrient cycling in savannas. Here, we determined the impact of fire frequency on total and soluble soil nitrogen (N) pools in tropical savanna. The study sites consisted of 1-ha experimental plots near Darwin, Australia, which remained unburnt for at least 14years or were burnt at 1-, 2- or 5-year intervals over the past 6years. Soil was analysed from patches underneath tree canopies and in inter-canopy patches at 1, 12, 28, 55 and 152days after fire. Patch type had a significant effect on all soil N pools, with greater concentrations of total and soluble (nitrate, ammonium, amino acids) N under tree canopies than inter-canopy patches. The 'time since the last fire' had no significant effect on N pools. Fire frequency similarly did not affect total soil N but it did influence soluble soil N. Soil amino acids were most prominent in burnt savanna, ammonium was highest in infrequently burnt (5-year interval) savanna and nitrate was highest in unburnt savanna. We suggest that the main effect of fire on soil N relations occurs indirectly through altered tree-grass dynamics. Previous studies have shown that high fire frequencies reduce tree cover by lowering recruitment and increasing mortality. Our findings suggest that these changes in tree cover could result in a 30% reduction in total soil N and 10-60% reductions in soluble N pools. This finding is consistent with studies from savannas globally, providing further evidence for a general theory of patchiness as a key driver of nutrient cycling in the savanna biome. © 2012 Ecological Society of Australia.

Vawdrey L.L.,Center for Wet Tropics Agriculture | Male M.,PO Box 482 | Grice K.R.E.,Center for Tropical Agriculture
Crop Protection | Year: 2015

Results from the first of two artificially inoculated field experiments showed foliar applications of copper hydroxide (Blue Shield Copper) at 600g a.i./100L-1 (0% infected fruit), copper hydroxide+metalaxyl-M (Ridomil Gold Plus.) at 877.5g a.i./100L-1 (0.27%), metiram+pyraclostrobin (Aero) at 720g a.i./100L-1 (0.51%), chlorothalonil (Bravo WeatherStik) at 994g a.i./100L-1 (0.63%) and cuprous oxide (Nordox 750 WG) at 990g a.i./100L-1 (0.8%) of water significantly reduced the percentage of infected fruit compared to potassium phosphonate (Agri-Fos 600) at 1200g a.i./100L-1 (8.22%), dimethomorph (Acrobat) at 108g a.i./100L-1 (11.18%) and the untreated control (16%). Results from the second experiment showed fruit sprayed with copper hydroxide (Champ Dry Prill) at 300 (2.0% infected fruit), 375 (0.4%) and 450g a.i./100L-1 (0.6%) and metiram+pyraclostrobin (Aero) at 360 (2.8%), 480 (0.6%) and 600g a.i./100L-1 of water (1.0%) significantly reduced the percentage of infected fruit compared to the untreated control (19.4%). Foliar sprays of copper hydroxide at 375g a.i./100L-1 in rotation with chlorothalonil at 994g a.i./100L-1 every two weeks is now recommended to growers for controlling Phytophthora fruit rot of papaya. © 2014.

Katoh H.,Japan National Agriculture and Food Research Organization | Davis R.,Northern Australia Quarantine Strategy | Smith M.W.,Bundaberg Research Station | Weinert M.,Center for Tropical Agriculture | Iwanami T.,Japan National Agriculture and Food Research Organization
Annals of Applied Biology | Year: 2012

Japanese isolates of 'Candidatus Liberibacter asiaticus' have been shown to be clearly differentiated by simple sequence repeat (SSR) profiles at four loci. In this study, 25 SSR loci, including these four loci, were selected from the whole-genome sequence and were used to differentiate non-Japanese samples of 'Ca. Liberibacter asiaticus' (13 Indian, 3 East Timorese, 1 Papuan and 8 Floridian samples). Out of the 25 SSR loci, 13 were polymorphic. Dendrogram analysis using SSR loci showed that the clusters were mostly consistent with the geographical origins of the isolates. When single nucleotide polymorphisms (SNPs) were searched around these 25 loci, only the upstream region of locus 091 exhibited polymorphism. Phylogenetic tree analysis of the SNPs in the upstream region of locus 091 showed that Floridian samples were clustered into one group as shown by dendrogram analysis using SSR loci. The differences in nucleotide sequences were not associated with differences in the citrus hosts (lime, mandarin, lemon and sour orange) from which the isolates were originally derived. © 2012 Association of Applied Biologists.

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