100 research outputs found
The genetical examination of 'Grasslands Ariki' ryegrass Lolium ((multiflorum x perenne) x perenne) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science
'Grasslands Ariki' ryegrass - Lolium [(multiflorum x perenne) x perenne] - has been established in New Zealand as a successful pasture variety. While some genetic parameters were determined during its breeding programme, no diallel cross analyses have been performed on 'Ariki'. It was for this reason that this particular experiment was suggested to me. The inclusion of two treatments arose from a cynical remark passed by W. Harris, regarding the failure on the part of plant breeders to use simulated swards. The experiment was designed to determine the levels of genotype-by-environment interaction in 'Ariki' ryegrass. [FROM INTRODUCTION
Caucasian Clover (\u3cem\u3eTrifolium ambiguum\u3c/em\u3e) Is Persistent in New Zealand Montane, Improved Rangeland But Requires Regular Sulphur Application for Productivity
Frequent grazing by sheep reduced caucasian clover cover and rhizome mass in ryegrass pasture
The responses of hexaploid caucasian clover
(Trifolium ambiguum) to four contrasting grazing
regimes were compared with those of white clover
(T. repens) in an endophytic (Neotyphodium lolii)
hybrid ryegrass pasture on a fertile lowland site.
After 2 years, frequent grazing (set stocking) by
sheep reduced caucasian clover cover to 10%
compared with 25.5% in infrequent grazing
(rotational grazing) treatments (mean spelling time
25 days). Similarly, frequent grazing reduced
caucasian clover rhizome plus root dry weight (780
kg DM/ha when sampled to 100 mm depth in
frequently grazed plots, compared with 3220 kg
DM/ha for infrequent). Under frequent grazing
treatments, mean white clover cover was 21%,
under infrequent hard grazing it was 26% and under
lax infrequent grazing it was 14%. The reduction
in ryegrass tiller population from 5720/m² in the
infrequently and laxly grazed treatments to 4150/
m² in the frequently hard grazed pastures indicated
the severity of that hard grazed treatment. These
results show that in lowland ryegrass pastures on
high fertility sites, the stoloniferous growth form
of white clover may be superior to the rhizomatous
strategy of caucasian clover when grazing by sheep
is frequent throughout spring, summer and autumn
Fast and Accurate Power Estimation of FPGA DSP Components Based on High-level Switching Activity Models
When designing DSP circuits, it is important to predict their power consumption early in the design flow in order to reduce the repetition of time consuming design phases. High-level modelling is required for fast power estimation when a design is modified at the algorithm level. This paper presents a novel high-level analytical approach to estimate logic power consumption of arithmetic components implemented in FPGAs. In particular, models of adders and multipliers are presented in detail. The proposed methodology considers input signal correlation and glitching produced inside the component. It is based on an analytical computation of the switching activity in the component which takes into account the component architecture. The complete model can estimate the power consumption for any given clock frequency, signal statistics and operands’ word-lengths. Compared to other proposed power estimation methods, the number of circuit simulations needed for characterizing the power model of the component is highly reduced. The accuracy of the model is within 10% of low-level power estimates given by the tool XPower, and it achieves better overall performance
Genetic diversity of selected genes that are potentially economically important in feral sheep of New Zealand
Background: Feral sheep are considered to be a source of genetic variation that has been lost from their
domestic counterparts through selection.
Methods: This study investigates variation in the genes KRTAP1-1, KRT33, ADRB3 and DQA2 in Merino-like feral
sheep populations from New Zealand and its offshore islands. These genes have previously been shown to
influence wool, lamb survival and animal health.
Results: All the genes were polymorphic, but no new allele was identified in the feral populations. In some of
these populations, allele frequencies differed from those observed in commercial Merino sheep and other breeds
found in New Zealand. Heterozygosity levels were comparable to those observed in other studies on feral sheep.
Our results suggest that some of the feral populations may have been either inbred or outbred over the duration
of their apparent isolation.
Conclusion: The variation described here allows us to draw some conclusions about the likely genetic origin of
the populations and selective pressures that may have acted upon them, but they do not appear to be a source of
new genetic material, at least for these four genes.This research was supported by the Brian Mason Scientific and Technical
Trust
Dynamic partial reconfigurable hardware architecture for principal component analysis on mobile and embedded devices
Towards an optimal sampling strategy for assessing genetic variation within and among white clover (Trifolium repens L.) cultivars using AFLP
Cost reduction in plant breeding and conservation programs depends largely on correctly defining the minimal sample size required for the trustworthy assessment of intra- and inter-cultivar genetic variation. White clover, an important pasture legume, was chosen for studying this aspect. In clonal plants, such as the aforementioned, an appropriate sampling scheme eliminates the redundant analysis of identical genotypes. The aim was to define an optimal sampling strategy, i.e., the minimum sample size and appropriate sampling scheme for white clover cultivars, by using AFLP data (283 loci) from three popular types. A grid-based sampling scheme, with an interplant distance of at least 40 cm, was sufficient to avoid any excess in replicates. Simulations revealed that the number of samples substantially influenced genetic diversity parameters. When using less than 15 per cultivar, the expected heterozygosity (He) and Shannon diversity index (I) were greatly underestimated, whereas with 20, more than 95% of total intra-cultivar genetic variation was covered. Based on AMOVA, a 20-cultivar sample was apparently sufficient to accurately quantify individual genetic structuring. The recommended sampling strategy facilitates the efficient characterization of diversity in white clover, for both conservation and exploitation
Ocean Acidification at High Latitudes: Potential Effects on Functioning of the Antarctic Bivalve Laternula elliptica
Ocean acidification is a well recognised threat to marine ecosystems. High
latitude regions are predicted to be particularly affected due to cold waters
and naturally low carbonate saturation levels. This is of concern for organisms
utilising calcium carbonate (CaCO3) to generate shells or skeletons.
Studies of potential effects of future levels of pCO2 on high latitude
calcifiers are at present limited, and there is little understanding of their
potential to acclimate to these changes. We describe a laboratory experiment
to compare physiological and metabolic responses of a key benthic bivalve, Laternula
elliptica, at pCO2 levels of their natural environment
(430 µatm, pH 7.99; based on field measurements) with those predicted
for 2100 (735 µatm, pH 7.78) and glacial levels (187 µatm, pH
8.32). Adult L. elliptica basal metabolism (oxygen consumption
rates) and heat shock protein HSP70 gene expression levels
increased in response both to lowering and elevation of pH. Expression of
chitin synthase (CHS), a key enzyme involved in synthesis
of bivalve shells, was significantly up-regulated in individuals at pH 7.78,
indicating L. elliptica were working harder to calcify in
seawater undersaturated in aragonite (ΩAr = 0.71),
the CaCO3 polymorph of which their shells are comprised. The different
response variables were influenced by pH in differing ways, highlighting the
importance of assessing a variety of factors to determine the likely impact
of pH change. In combination, the results indicate a negative effect of ocean
acidification on whole-organism functioning of L. elliptica
over relatively short terms (weeks-months) that may be energetically difficult
to maintain over longer time periods. Importantly, however, the observed changes
in L. elliptica CHS gene expression provides evidence for
biological control over the shell formation process, which may enable some
degree of adaptation or acclimation to future ocean acidification scenarios
A combined functional and structural genomics approach identified an EST-SSR marker with complete linkage to the Ligon lintless-2 genetic locus in cotton (Gossypium hirsutum L.)
<p>Abstract</p> <p>Background</p> <p>Cotton fiber length is an important quality attribute to the textile industry and longer fibers can be more efficiently spun into yarns to produce superior fabrics. There is typically a negative correlation between yield and fiber quality traits such as length. An understanding of the regulatory mechanisms controlling fiber length can potentially provide a valuable tool for cotton breeders to improve fiber length while maintaining high yields. The cotton (<it>Gossypium hirsutum </it>L.) fiber mutation Ligon lintless-2 is controlled by a single dominant gene (<it>Li<sub>2</sub></it>) that results in significantly shorter fibers than a wild-type. In a near-isogenic state with a wild-type cotton line, <it>Li<sub>2 </sub></it>is a model system with which to study fiber elongation.</p> <p>Results</p> <p>Two near-isogenic lines of Ligon lintless-2 (<it>Li<sub>2</sub></it>) cotton, one mutant and one wild-type, were developed through five generations of backcrosses (BC<sub>5</sub>). An F<sub>2 </sub>population was developed from a cross between the two <it>Li<sub>2 </sub></it>near-isogenic lines and used to develop a linkage map of the <it>Li<sub>2 </sub></it>locus on chromosome 18. Five simple sequence repeat (SSR) markers were closely mapped around the <it>Li<sub>2 </sub></it>locus region with two of the markers flanking the <it>Li<sub>2 </sub></it>locus at 0.87 and 0.52 centimorgan. No apparent differences in fiber initiation and early fiber elongation were observed between the mutant ovules and the wild-type ones. Gene expression profiling using microarrays suggested roles of reactive oxygen species (ROS) homeostasis and cytokinin regulation in the <it>Li<sub>2 </sub></it>mutant phenotype. Microarray gene expression data led to successful identification of an EST-SSR marker (NAU3991) that displayed complete linkage to the <it>Li<sub>2 </sub></it>locus.</p> <p>Conclusions</p> <p>In the field of cotton genomics, we report the first successful conversion of gene expression data into an SSR marker that is associated with a genomic region harboring a gene responsible for a fiber trait. The EST-derived SSR marker NAU3991 displayed complete linkage to the <it>Li<sub>2 </sub></it>locus on chromosome 18 and resided in a gene with similarity to a putative plectin-related protein. The complete linkage suggests that this expressed sequence may be the <it>Li<sub>2 </sub></it>gene.</p
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