Influence of testing procedure on evaluation of white clover (Trifolium repens L.)

peer-reviewedThis study examined data sets derived from the white clover cultivar evaluation programmes of AFBI (N. Ireland), and DAFF (Republic of Ireland) to determine whether elite performing genotypes are identifiable, independent of test procedure and leaf size factors. Genetic variation in yield and persistency, independent of the leaf size continuum effect, was observed. Identification of elite cultivars by breeders or testers therefore required readjustment of assessment standards to account for the mostly curvilinear relationships between performance and leaf size. The different testing procedures, involving cutting or grazing at different heights, frequencies and nitrogen rates changed the relative performances between the cultivars, making it difficult to predict performance potential beyond specific test conditions. The underlying causes for these changes in rankings was considered, including sensitivity to season and location, the antagonistic affects of defoliation pressure and companion grass competition, the independence of different seasonal profiles and the probable role of other morphological characteristics. In is concluded that testing authorities must calculate the management by leaf size relationships to adjust pass/fail standards if elite performing cultivars are to be correctly indentified

A note on the comparison of three near infrared reflectance spectroscopy calibration strategies for assessing herbage quality of ryegrass

peer-reviewedPerennial ryegrass (n = 1,836), Italian ryegrass (n = 137) and hybrid ryegrass (n = 103) herbage was taken from harvested plots from the Irish national variety evaluation scheme and analysed for in vitro dry matter digestibility, water soluble carbohydrate concentration, crude protein concentration and buffering capacity. Spectral data were obtained using near infrared reflectance spectroscopy and three calibration strategies (global, species-specific or local) were utilised to relate the reference values to the spectral data. The local strategy generally provided the poorest estimation of herbage composition, with global and species-specific calibration strategies producing similarly accurate estimates of each quality trait. The higher accuracy and easier maintenance of the global strategy make it the recommended calibration method for analysing quality of ryegrass.Department of Agriculture, Food and the Marine Research Stimulus Fund (07 526

Comparison of herbage yield, nutritive value and ensilability traits of three ryegrass species evaluated for the Irish Recommended List

peer-reviewedThis study examined 169 of the newest varieties of three ryegrass species, perennial (Lolium perenne L.), Italian (Lolium multiflorum Lam.) and hybrid (Lolium boucheanum Kunth), from Recommended List trials in Ireland. The traits examined were yield, dry matter concentration, three nutritive value traits (in vitro dry matter digestibility, water-soluble carbohydrate on a dry matter basis and crude protein concentration) and two ensilability traits (buffering capacity and water soluble carbohydrate concentration on an aqueous phase basis). Varietal monocultures of each species underwent a six cut combined simulated grazing and silage management in each of two years following sowing. Perennial ryegrass yielded less than both other species in one-year-old swards, but less than only Italian ryegrass in two-year-old swards, but generally had the higher in vitro dry matter digestibility and crude protein values. Italian ryegrass displayed the most favourable ensilability characteristics of the three species with perennial ryegrass less favourable and hybrid ryegrass intermediate. Overall, despite the high yields and favourable nutritive value and ensilability traits recorded, the general differences between the three ryegrass species studied were in line with industry expectations. These findings justify assessing the nutritive value and ensilability of ryegrass species, in addition to yield, to allow farmers select species that match farming enterprise requirements.We acknowledge the Department of Agriculture, Food and the Marine for funding provided through the Research Stimulus Fund (07 526

A Survey of European Regional Adaptation in Italian Ryegrass Varieties

Ryegrass is widely adapted to cool temperate eco-zones and breeders often submit individual varieties for testing in a number of EU countries. National testing programmes often combine data from several trial sites that may differ climatically, but not from sites in other member states, despite the possibility of high ecological similarity. Given increasing interest in ‘animal value’ characters (soluble sugars, lipids, sward geometry), additional testing for these would be valuable but is prohibited by capped or declining funding. Data sharing between EU national authorities could be advantageous but is inhibited by the lack of statistically valid data on the sensitivity of each performance parameter to agro-climatic conditions across the EU. This paper, reports the preliminary stages of the ‘EuroVCU’ (herbage) desktop study of ryegrass variety performances across an extensive range of EU national test centres. Analysis of the resulting data sets quantifies the genotype by environment responses of current varieties and could provide a validated protocol for future data sharing

Genetic gain in perennial ryegrass (Lolium perenne) varieties 1973 to 2013

AbstractPerennial ryegrass (Lolium perenne) forms the basis of grassland production in temperate pastures and is globally one of the most important forage grasses. Consequently, there has been large plant breeding industry investment over the past 40 years in producing new varieties and independent testing systems designed to identify and list those with the most improved performances. This study was conducted at the Plant Testing Station, Crossnacreevy, Northern Ireland and compared the DM yield and sward density of new varieties submitted from 1973 to 2013 and grass digestibility from 1980 to 2013, under conservation and simulated grazing managements. A variety × years matrix was compiled for each parameter and comparable means between varieties never in side by side performance trials were produced. Dry matter yields showed an overall significant (p &lt; 0.001) average annual increase of 0.52 % under conservation and 0.35 % under simulated grazing, with similar gain levels within maturity groups or ploidies. These rates were not constant over time, and periods of no gain occurred in various variety groupings. Sward density of the examined varieties did not change significantly. Herbage digestibility showed no improvement over the timeframe but had the largest differences between concurrent varieties, indicating that improvements were possible in the future. The study indicated that plant breeding gains were primarily DM yield focused with sward density remaining stagnant over the 40 years, while the lack of grass digestibility improvement appeared to only require more time to overcome. Evidence of benefits and risks of variety testing influences on plant breeding objectives was discussed.</jats:p

Selection of calibration sub-sets to predict ryegrass quality using principle component analysis for near infrared spectroscopy

peer-reviewedNear infrared reflectance spectroscopy (NIRS) has become the routine method of assessing forage quality on grass evaluation and breeding programmes. NIRS requires predictive calibration models that relate spectral data to reference values developed using a calibration set (Burns et al. 2013). The samples that form the calibration set influence the accuracy and reliability of these models and need to be representative of samples that will likely be analysed (Shenk and Westerhaus, 1991; Burns et al. 2014). Analysing samples from the calibration set using reference techniques has a significant cost and time associated and needs to be considered in the context of the desired accuracy and robustness of calibration models. Calibration selection techniques can therefore maximise the accuracy and robustness of calibration models whilst reducing the number of samples requiring reference analysis. One such method is principal component analysis (PCA; Shenk and Westerhaus, 1991) whereby Shetty et al. (2012) reported that the number of samples could be reduced by up to 80% with a minimal loss in accuracy of calibration model. PCA selects representative calibration sub-sets through plotting all the samples in hyper-dimensional space, based on spectral data, and a sample is selected to represent a local neighbourhood cluster of samples for reference analysis. The aim of this research was to assess the accuracy of NIRS calibration models for buffering capacity, in vitro dry matter digestibility (DMD) and water soluble carbohydrate (WSC) content developed using calibration sub-sets selected by PCA.Funding provided by the National Development Plan, Research Stimulus Fund administrated by DAFM (RSF –07 526)

Characterisation of red-giant stars in the public Kepler data

The first public release of long-cadence stellar photometric data collected by the NASA Kepler mission has now been made available. In this paper we characterise the red-giant (G-K) stars in this large sample in terms of their solar-like oscillations. We use published methods and well-known scaling relations in the analysis. Just over 70% of the red giants in the sample show detectable solar-like oscillations, and from these oscillations we are able to estimate the fundamental properties of the stars. This asteroseismic analysis reveals different populations: low-luminosity H-shell burning red-giant branch stars, cool high-luminosity red giants on the red-giant branch and He-core burning clump and secondary-clump giants.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journa

Strain and field modulation in bilayer graphene band structure

Using an external electric field, one can modulate the bandgap of Bernal stacked bilayer graphene by breaking A-~B symmetry. We analyze strain effects on the bilayer graphene using the extended Huckel theory and find that reduced interlayer distance results in higher bandgap modulation, as expected. Furthermore, above about 2.5 angstrom interlayer distance, the bandgap is direct, follows a convex relation to electric field and saturates to a value determined by the interlayer distance. However, below about 2.5 angstrom, the bandgap is indirect, the trend becomes concave and a threshold electric field is observed, which also depends on the stacking distance.Comment: 3 pages, 5 figures - v1 and v2 are the same, uploaded twice - v3, some typos fixed and a reference adde