Robert Evans

Bio: Robert Evans is an academic researcher from Commonwealth Scientific and Industrial Research Organisation. The author has contributed to research in topics: Tracheid & Pinus radiata. The author has an hindex of 36, co-authored 122 publications receiving 4850 citations. Previous affiliations of Robert Evans include Cooperative Research Centre.

Rapid prediction of wood stiffness from microfibril angle and density.

Abstract: Wood quality is rapidly becoming a major consideration in tree improvement programs. Rapid, cost-effective methods will be required to cope with the large numbers of samples (increment cores) generated by such programs. Wood stiffness, or longitudinal modulus of elasticity (EL) is one ofthe most important wood properties for solid timber applications and this paper describes a rapid method for predicting EL from measurements of density and microfibril angle (MFA). Very strong linear relationships have been found between E L , measured by a sonic resonance technique, and various combinations of wood density and MFA for 104 clearwood samples of Eucalyptus delegatensis R.T. Baker. Average MFA of each sample was measured in less than 1 minute by high-speed x-ray scanning diffractometry on SilviScan-2, a prototype automated wood microstructure analyzer. Density was measured gravimetrically. A small strip cut from one end of each sample was used for MFA analysis. In this study, density variation alone accounted for 70 percent of the variation in E L , while MFA alone accounted for 86 percent. Together, MFA and density accounted for 96 percent of the variation in E L . The results of this study indicate that density, MFA, and E L could be included in tree improvement programs using instruments based on SilviScan technology.

Fasciclin-like arabinogalactan proteins: specialization for stem biomechanics and cell wall architecture in Arabidopsis and Eucalyptus

Abstract: The ancient cell adhesion fasciclin (FAS) domain is found in bacteria, fungi, algae, insects and animals, and occurs in a large family of fasciclin-like arabinogalactan proteins (FLAs) in higher plants. Functional roles for FAS-containing proteins have been determined for insects, algae and vertebrates; however, the biological functions of the various higher-plant FLAs are not clear. Expression of some FLAs has been correlated with the onset of secondary-wall cellulose synthesis in Arabidopsis stems, and also with wood formation in the stems and branches of trees, suggesting a biological role in plant stems. We examined whether FLAs contribute to plant stem biomechanics. Using phylogenetic, transcript abundance and promoter-GUS fusion analyses, we identified a conserved subset of single FAS domain FLAs (group A FLAs) in Eucalyptus and Arabidopsis that have specific and high transcript abundance in stems, particularly in stem cells undergoing secondary-wall deposition, and that the phylogenetic conservation appears to extend to other dicots and monocots. Gene-function analyses revealed that Arabidopsis T-DNA knockout double mutant stems had altered stem biomechanics with reduced tensile strength and a reduced tensile modulus of elasticity, as well as altered cell-wall architecture and composition, with increased cellulose microfibril angle and reduced arabinose, galactose and cellulose content. Using materials engineering concepts, we relate the effects of these FLAs on cell-wall composition with stem biomechanics. Our results suggest that a subset of single FAS domain FLAs contributes to plant stem strength by affecting cellulose deposition, and to the stem modulus of elasticity by affecting the integrity of the cell-wall matrix.

Polymorphisms in Cinnamoyl CoA Reductase ( CCR ) Are Associated With Variation in Microfibril Angle in Eucalyptus spp.

Abstract: Linkage disequilibrium (LD) mapping using natural populations results in higher resolution of marker-trait associations compared to family-based quantitative trait locus (QTL) studies. Depending on the extent of LD, it is possible to identify alleles within candidate genes associated with a trait. Analysis of a natural mutant in Arabidopsis has shown that mutations in cinnamoyl CoA reductase (CCR), a key lignin gene, affect physical properties of the secondary cell wall such as stiffness and strength. Using this gene, we tested whether LD mapping could identify alleles associated with microfibril angle (MFA), a wood quality trait affecting stiffness and strength of wood. We identified 25 common single-nucleotide polymorphism (SNP) markers in the CCR gene in Eucalyptus nitens. Using single-marker and haplotype analyses in 290 trees from a E. nitens natural population, two haplotypes significantly associated with MFA were found. These results were confirmed in two full-sib families of E. nitens and Eucalyptus globulus. In an effort to understand the functional significance of the SNP markers, we sequenced the cDNA clones and identified an alternatively spliced variant from the significant haplotype region. This study demonstrates that LD mapping can be used to identify alleles associated with wood quality traits in natural populations of trees.

Rapid measurement of the transverse dimensions of tracheids in radial wood sections from Pinus radiata

Abstract: A new analytical Instrument has been developed for rapid measurement of the transverse dimensions of tracheids in Australian plantation-grown Pinus radiata. The Instrument combines scannwig x-ray microdensitometry and image analysis to produce radial profiles of tracheid diameter, wall thickness, coarseness and other wood mo hological characteristics. The tracheid diameter and density measurements are performed automatically on polished radial wood sections cut from increment cores. Corrections are made for the unavoidable deviations from radial alignment of the cores. The initial purpose of the Instrument is to provide comprehensive Information for tree breeding and silvicultural programs with particular emphasis on pulping and papermaking characteristics.

Cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance

Abstract: Although measurements of crystallinity index (CI) have a long history, it has been found that CI varies significantly depending on the choice of measurement method. In this study, four different techniques incorporating X-ray diffraction and solid-state 13C nuclear magnetic resonance (NMR) were compared using eight different cellulose preparations. We found that the simplest method, which is also the most widely used, and which involves measurement of just two heights in the X-ray diffractogram, produced significantly higher crystallinity values than did the other methods. Data in the literature for the cellulose preparation used (Avicel PH-101) support this observation. We believe that the alternative X-ray diffraction (XRD) and NMR methods presented here, which consider the contributions from amorphous and crystalline cellulose to the entire XRD and NMR spectra, provide a more accurate measure of the crystallinity of cellulose. Although celluloses having a high amorphous content are usually more easily digested by enzymes, it is unclear, based on studies published in the literature, whether CI actually provides a clear indication of the digestibility of a cellulose sample. Cellulose accessibility should be affected by crystallinity, but is also likely to be affected by several other parameters, such as lignin/hemicellulose contents and distribution, porosity, and particle size. Given the methodological dependency of cellulose CI values and the complex nature of cellulase interactions with amorphous and crystalline celluloses, we caution against trying to correlate relatively small changes in CI with changes in cellulose digestibility. In addition, the prediction of cellulase performance based on low levels of cellulose conversion may not include sufficient digestion of the crystalline component to be meaningful.

Status and Prospects of Association Mapping in Plants

Abstract: There is tremendous interest in using association mapping to identify genes responsible for quantitative variation of complex traits with agricultural and evolutionary importance. Recent advances in genomic technology, impetus to exploit natural diversity, and development of robust statistical analysis methods make association mapping appealing and affordable to plant research programs. Association mapping identifi es quantitative trait loci (QTLs) by examining the marker-trait associations that can be attributed to the strength of linkage disequilibrium between markers and functional polymorphisms across a set of diverse germplasm. General understanding of association mapping has increased signifi cantly since its debut in plants. We have seen a more concerted effort in assembling various association-mapping populations and initiating experiments through either candidategene or genome-wide approaches in different plant species. In this review, we describe the current status of association mapping in plants and outline opportunities and challenges in complex trait dissection and genomics-assisted crop improvement. L arge-scale genome-wide association analyses of major human diseases have yielded very promising results, corroborating fi ndings of previous candidategene association studies and identifying novel disease loci that were previously unknown (Th e Wellcome Trust Case Control Consortium, 2007). Th e same strategy is being exploited in many plant species thanks to the dramatic reduction in costs of genomic technologies. In contrast to the widely used linkage analysis traditional mapping research in plants, association mapping searches for functional variation in a much broader germplasm context. Association mapping enables researchers to use modern genomic technologies to exploit natural diversity, the wealth of which is known to plant geneticists and breeders but has been utilized only on a small scale before the genomics era. Owing to the ease of producing large numbers of progenies from controlled crosses and conducting replicated trials with immortal individuals (inbreds and recombinant inbred lines, RILs), association mapping in plants may prove to be more promising than in human or animal genetics. In the current review,

Standardized precipitation evapotranspiration index (SPEI) revisited: parameter fitting, evapotranspiration models, tools, datasets and drought monitoring

Abstract: 48 pags., 25 figs. Available online 21 December 2013. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0088