Testing water-soluble carbohydrate QTL effects in perennial ryegrass (Lolium perenne L.) by marker selection

Water-soluble carbohydrates (WSC) are an important factor determining the nutritional value of grass forage and development of genetic markers for selection of WSC traits in perennial ryegrass would benefit future breeding programmes. Quantitative trait loci (QTLs) for WSC have been published for an F-2 ryegrass mapping family. Markers showing significant associations with these QTLs were used to design narrow-based populations with homozygosity for target QTLs. Founders were selected from within the mapping family. The divergent populations produced were analysed for WSC content in the glasshouse and the field. There was evidence of complex interactions between WSC content and other factors and traits, including the scale of assessment, time/degree of sward establishment and other forage quality parameters. Differences between the divergent pairs of the various populations were small. However, differences observed between the founder selection groups were maintained and the roles of the QTL regions in regulating forage WSC content were confirmed. In general, the individual divergent populations exploited only a limited extent of the large phenotypic variation available within the mapping family. However, this study sets the scene for exploring the opportunities for marker-assisted breeding strategies for complex traits in obligate out-breeding species, and the challenges of doing this are discussed

Development of a Breeders’ Toolkit for Drought Resistance in a \u3cem\u3eLolium/Festuca\u3c/em\u3e Hybrid

Lolium multiflorum (Lm) is considered an ideal grass for European agriculture. However, existing high-quality forage Lm cultivars have been bred for intensive systems in benign environments, and have proved to be insufficiently robust to meet many of the environmental challenges that face extensive agriculture in more extreme conditions. Genes for persistency, tolerance of cold, drought and poor soils, can be found in currently under-exploited native Festuca ecotypes. These Festuca ecotypes cannot however compare with Lm cultivars for productivity or quality of forage under favourable conditions. Festuca glaucescens (Fg) is of Mediterranean origin and as such is adapted to drought and heat stress. The object of this work was to introgress a single chromosome segment of Fg containing genes for drought resistance into a diploid Lm background. Subsequent to the introgression of a Fg chromosome segment, Fg markers were mapped and a prototype toolkit developed to follow the genes for drought resistance through a breeding programme

Estimating Photometric Redshifts Using Support Vector Machines

We present a new approach to obtaining photometric redshifts using a kernel learning technique called Support Vector Machines (SVMs). Unlike traditional spectral energy distribution fitting, this technique requires a large and representative training set. When one is available, however, it is likely to produce results that are comparable to the best obtained using template fitting and artificial neural networks. Additional photometric parameters such as morphology, size and surface brightness can be easily incorporated. The technique is demonstrated using samples of galaxies from the Sloan Digital Sky Survey Data Release 2 and the hybrid galaxy formation code GalICS. The RMS error in redshift estimation is $<0.03$ for both samples. The strengths and limitations of the technique are assessed.Comment: 10 pages, 3 figures, to appear in the PASP, minor typos fixed to make consistent with published versio

Grass and Forage Improvement: Temperate Forages

Key points 1. Plant breeding has contributed significantly to the development of effective grassland production systems. 2. New technologies offer enhanced precision in breeding and access to wider genetic variation. 3. The requirement for more sustainable production systems will require genetic improvements in complex traits where the use of new technology will be vital

Grass and Forage Improvement: Temperate Forages

Plant breeding has contributed significantly to the development of effective grassland production systems. New technologies offer enhanced precision in breeding and access to wider genetic variation. The requirement for more sustainable production systems will require genetic improvements in complex traits where the use of new technology will be vital

\u27Stay-Green\u27 and Non-\u27Stay-Green\u27 Perennial Ryegrass in Field Swards with Different Intervals between Cuts

The purpose of this study was to investigate the effect of the \u27stay-green\u27 character, originally introduced into perennial ryegrass (Lolium perenne L.) for amenity purposes, on herbage yield, N concentration and colour in field swards of \u27stay-green\u27 forage ryegrass managed in different ways for agricultural use. The conclusions were that the introduction of the \u27stay-green\u27 character (1) confers greater greenness only at some times of year and only when there has been a sufficiently long period of regrowth, (2) is expressed only in older, as distinct from young, tillers, (3) reduces herbage yield, particularly when a long interval is allowed between defoliations, and (4) reduces the decline in the concentration of N in herbage during the latter part of a long period of regrowth

Approaches for Associating Molecular Polymorphisms with Phenotypic Traits Based on Linkage Disequilibrium in Natural Populations of \u3cem\u3eLolium Perenne\u3c/em\u3e

Association mapping relies on linkage disequilibrium (LD) between haplotypes and quantitative trait loci (QTL). The level of LD in a genome determines the resolution of this approach. In out-breeding species, LD is expected to decay rapidly, thus allowing for high-resolution mapping. It has been most extensively used in human genetics, but recent work with maize populations has demonstrated its potential in plants (Thornsberry et al., 2001; Wilson et al., 2004), and used in L. perenne to identify AFLP markers associated with a major QTL for heading date on linkage group 7 (Skøt et al., 2004). The objective of the present work is to associate allelic variation in candidate genes for heading date and water soluble carbohydrates (WSC) in natural populations of L. perenne with phenotypic variation. Both these traits are important breeding targets in ryegrass

Construction and Exploitation of a Bacterial Artificial Chromosome (BAC) Library for \u3cem\u3eLolium Perenne\u3c/em\u3e (Perennial Ryegrass)

BAC libraries are an important tool in genomics, enabling physical maps, genome sequencing, marker development and map based cloning strategies. A BAC library has therefore been generated for the temperate grass species Lolium perenne (perennial ryegrass) which compliments an existing BAC library of the closely related species, Festuca pratensis also generated by IGER. Moreover the L. perenne BAC library will provide a useful tool for grass comparative genomics to compliment the existing BAC libraries of cereal crops including rice, wheat, barley, Sorghum and maize. In particular it will allow a comparison of micro-synteny between this large genome forage crop species and the model small genome monocot species Orzya sativa

Quasi Regular Polyhedra and Their Duals with Coxeter Symmetries Represented by Quaternions I

In two series of papers we construct quasi regular polyhedra and their duals which are similar to the Catalan solids. The group elements as well as the vertices of the polyhedra are represented in terms of quaternions. In the present paper we discuss the quasi regular polygons (isogonal and isotoxal polygons) using 2D Coxeter diagrams. In particular, we discuss the isogonal hexagons, octagons and decagons derived from 2D Coxeter diagrams and obtain aperiodic tilings of the plane with the isogonal polygons along with the regular polygons. We point out that one type of aperiodic tiling of the plane with regular and isogonal hexagons may represent a state of graphene where one carbon atom is bound to three neighboring carbons with two single bonds and one double bond. We also show how the plane can be tiled with two tiles; one of them is the isotoxal polygon, dual of the isogonal polygon. A general method is employed for the constructions of the quasi regular prisms and their duals in 3D dimensions with the use of 3D Coxeter diagrams.Comment: 22 pages, 16 figure