Analyzing and identifying unusual observations in modified liu estimator using global influence technique

Influence concepts have an important place in linear regression models and case deletion is a useful method for assessing the influence of single case. The influence measures in the presence of multicollinearity were discussed under the linear regression models when the errors structure is uncorrelated and homoscedastic. When modified Liu estimator (MLE) is used to mitigate the effects of multicollinearity, the influence of observations can be drastically modified. In this research paper it is aimed to analyze global influence techniques to detect influential observations in MLE. To illustrate the methodologies derived in this research paper a multicollinearity real data set was used to identify influential observations using global influence techniques derived in this research paper

Tradeoff between Biomass and Flavonoid Accumulation in White Clover Reflects Contrasting Plant Strategies

An outdoor study was conducted to examine relationships between plant productivity and stress-protective phenolic plant metabolites. Twenty-two populations of the pasture legume white clover were grown for 4½ months during spring and summer in Palmerston North, New Zealand. The major phenolic compounds identified and quantified by HPLC analysis were glycosides of the flavonoids quercetin and kaempferol. Multivariate analysis revealed a trade-off between flavonoid accumulation and plant productivity attributes. White clover populations with high biomass production, large leaves and thick tap roots showed low levels of quercetin glycoside accumulation and low quercetin:kaempferol ratios, while the opposite was true for less productive populations. The latter included stress-resistant ecotypes from Turkey and China, and the analysis also identified highly significant positive relationships of quercetin glycoside accumulation with plant morphology (root:shoot ratio). Importantly, a high degree of genetic variation was detected for most of the measured traits. These findings suggest merit for considering flavonoids such as quercetin as potential selection criteria in the genetic improvement of white clover and other crops

Epistatic Association Mapping in Homozygous Crop Cultivars

The genetic dissection of complex traits plays a crucial role in crop breeding. However, genetic analysis and crop breeding have heretofore been performed separately. In this study, we designed a new approach that integrates epistatic association analysis in crop cultivars with breeding by design. First, we proposed an epistatic association mapping (EAM) approach in homozygous crop cultivars. The phenotypic values of complex traits, along with molecular marker information, were used to perform EAM. In our EAM, all the main-effect quantitative trait loci (QTLs), environmental effects, QTL-by-environment interactions and QTL-by-QTL interactions were included in a full model and estimated by empirical Bayes approach. A series of Monte Carlo simulations was performed to confirm the reliability of the new method. Next, the information from all detected QTLs was used to mine novel alleles for each locus and to design elite cross combination. Finally, the new approach was adopted to dissect the genetic basis of seed length in 215 soybean cultivars obtained, by stratified random sampling, from 6 geographic ecotypes in China. As a result, 19 main-effect QTLs and 3 epistatic QTLs were identified, more than 10 novel alleles were mined and 3 elite parental combinations, such as Daqingdou and Zhengzhou790034, were predicted

Pattern analysis of the diversity of morphological plant attributes and herbage yield in a world collection of white clover (Trifolium repens L.) germplasm characterised in a summer moisture stress environment of Australia

Information on the variation available for different plant attributes has enabled germplasm collections to be effectively utilised in plant breeding. A world sourced collection of white clover germplasm has been developed at the White Clover Resource Centre at Glen Innes, New South Wales. This collection of 439 accessions was characterised under field conditions as a preliminary study of the genotypic variation for morphological attributes; stolon density, stolon branching, number of nodes. number of rooted nodes, stolon thickness, internode length, leaf length, plant height and plant spread, together with seasonal herbage yield. Characterisation was conducted on different batches of germplasm (subsets of accessions taken from the complete collection) over a period of five years. Inclusion of two check cultivars, Haifa and Huia, in each batch enabled adjustment of the characterisation data for year effects and attribute-by-year interaction effects. The component of variance for seasonal herbage yield among batches was large relative to that for accessions. Accession-by-experiment and accession-by-season interactions for herbage yield were not detected. Accession mean repeatability for herbage yield across seasons was intermediate (0.453). The components of genotypic variance among accessions for all attributes, except plant height, were larger than their respective standard errors. The estimates of accession mean repeatability for the attributes ranged from low (0.277 for plant height) to intermediate (0.544 for internode length). Multivariate techniques of clustering and ordination were used to investigate the diversity present among the accessions in the collection. Both cluster analysis and principal component analysis suggested that seven groups of accessions existed. It was also proposed from the pattern analysis results that accessions from a group characterised by large leaves, tall plants and thick stolons could be crossed with accessions from a group that had above average stolon density and stolon branching. This material could produce breeding populations to be used in recurrent selection for the development of white clover cultivars for dryland summer moisture stress environments in Australia. The germplasm collection was also found to be deficient in genotypes with high stolon density, high number of branches high number of rooted nodes and large leaves. This warrants addition of new germplasm accessions possessing these characteristics to the present germplasm collection

Variation among low rainfall white clover (Trifolium repens l.) accessions for morphological attributes and herbage yield

The importance of passport data on rainfall at collection sites of accessions as a guide to identifying germplasm to be used in the genetic improvement was assessed by using 40 white clover accessions from the germplasm collection at Glen Innes, New South Wales. This set together with 2 standard cultivars, Haifa and Huia, were evaluated in the field. The objectives were to: (i) estimate the magnitude of genotypic variation among accessions for morphological attributes and herbage yield in a dryland summer rainfall environment; and (ii) compare estimates of genotypic variation for, and correlations among, the attributes and herbage yield for the 40 accessions with results from a study based on a random sample of accessions from the same collection. Herbage yield was measured in 4 seasons (autumn 1992-summer 1993) together with stolon and other plant attributes which were measured in 1 season (summer 1993). There was significant (

An introduction to markers, quantitative trait loci (QTL) mapping and marker-assisted selection for crop improvement: The basic concepts

Recognizing the enormous potential of DNA markers in plant breeding, many agricultural research centers and plant breeding institutes have adopted the capacity for marker development and marker-assisted selection (MAS). However, due to rapid developments in marker technology, statistical methodology for identifying quantitative trait loci (QTLs) and the jargon used by molecular biologists, the utility of DNA markers in plant breeding may not be clearly understood by non-molecular biologists. This review provides an introduction to DNA markers and the concept of polymorphism, linkage analysis and map construction, the principles of QTL analysis and how markers may be applied in breeding programs using MAS. This review has been specifically written for readers who have only a basic knowledge of molecular biology and/or plant genetics. Its format is therefore ideal for conventional plant breeders, physiologists, pathologists, other plant scientists and students

Genotypic variation for stolon and other morphological attributes of white clover (Trifolium repens L.). Populations and their influence on herbage yield in the summer rainfall region of New South Wales

A random sample of 60 germplasm accessions from the Australian white clover germplasm collection was characterized in the field at Glen Innes, N.S.W. Genotypic variation for stolon and other morphological attributes was measured in one season. Herbage yield was evaluated over seven seasons to quantify the magnitude of accession-by-season interaction. There were significant (P < 0.01) differences among accessions, seasons, and accession-by-season interactions for herbage yield. Classification was used to group the accessions on their seasonal herbage yield. A summer active group, a winter active group and a group showing autumn activity for herbage yield were identified. There was significant (P < 0.01) variation among accessions for all plant attributes measured and their accession mean repeatability was moderate to high. There were strong genotypic correlations among the morphological attributes. Five of the morphological attributes (stolon density, stolon branching, plant spread, plant height, stolon thickness and leaf length) expressed a strong genotypic correlation with average herbage yield over seven seasons. The genotypic variation estimated for herbage production and plant attributes signifies the potential of the collection to be used as a source of variation for the genetic improvement of productivity and perenniality of white clover for Australian environments