Showing papers in "The Journal of Agricultural Science in 2005"

The analysis of crop cultivar breeding and evaluation trials: an overview of current mixed model approaches

Abstract: The analysis of series of crop variety trials has a long history with the earliest approaches being based on ANOVA methods. Kempton (1984) discussed the inadequacies of this approach, summarized the alternatives available at that time and noted that all of these approaches could be classified as multiplicative models. Recently, mixed model approaches have become popular for the analysis of series of variety trials. There are numerous reasons for their use, including the ease with which incomplete data (not all varieties in all trials) can be handled and the ability to appropriately model within-trial error variation. Currently, the most common mixed model approaches for series of variety trials are mixed model versions of the methods summarized by Kempton (1984). In the present paper a general formulation that encompasses all of these methods is described, then individual methods are considered in detail.

Nutritional and immunological importance of colostrum for the new-born pig

Abstract: The nutritional and immunological importance of colostrum for the survival and development of the neonatal pig are reviewed. The pig is born with low body energy stores and devoid of serum immunoglobulins. Colostrum provides the piglet with both energy and maternal antibodies but its fat and protein composition is very variable. Colostrum is very digestible, and both colostral energy and nitrogen (N) are retained with a very high efficiency. Colostrum production by the sow assessed from the weight gain of the litter from birth to 24 h of age is very variable (from 1900 to 5300 g). There is no clear effect of litter size or parity, suggesting that colostrum production is a characteristic of the sow. Within a litter, colostrum consumption by the individual piglets varies considerably. It is independent of birth order, but related positively to birth weight and negatively to litter size. Other factors influencing colostrum consumption, including cold stress, premature birth and birth hypoxia, are discussed. Because of the epitheliochorial nature of the porcine placenta, the new-born piglet must acquire maternal immunoglobulin G (IgG) from ingested colostrum for passive immune protection until the immune system of the piglet becomes fully developed. Colostrum IgG concentrations in milk vary widely between individual sows both in initial concentration and in the rate at which concentrations decline during the first 24 h of life. The piglet can only absorb intact IgG prior to gut closure, which occurs in the first 24 h of life and is induced by intakes of colostrum which are insufficient to maintain piglet live-weight. As a result, the amounts of intact IgG absorbed by the piglet vary widely. The effects of colostrum consumption on neonatal survival are discussed. Consumption of colostrum in amounts sufficient to meet the energy requirement of the piglet is a major determinant for survival. Since most neonatal losses occur in the first 2 days of life, before acquisition of a maternal IgG for immune protection becomes important for survival, piglet serum IgG concentration does not correlate well with early survival but is important in later resistance to disease challenge. It is concluded that colostrum production is a good marker for the maternal quality of the sow. Future research should focus on the ability of the sow to produce more colostrum and on the possible delayed effects of passive immunisation on the health and performance of piglet at weaning and later in life.

A century of fungicide evolution

Abstract: Up until the 1940s chemical disease control relied upon inorganic chemical preparations, frequently prepared by the user. Key areas of use were horticulture and vegetable production with key targets being diseases that caused easily recognized damage. After this era and as the damaging effects of more crop diseases became obvious by the use of chemical control, the crop protection industry expanded rapidly and research to discover new active materials began in earnest. As new areas of chemistry were introduced, each one aiming to offer advantages over the previous ones, chemical families were born with research-based companies frequently adopting patent-busting strategies in order to capitalize on the developing fungicides market. Systemic fungicides offered new opportunities in disease control. The rise in Research and Development (R & D) and the increase in the number and quantity of chemicals being applied led to the introduction of regulation in the 1950s, initially on a voluntary basis, but now strictly controlled by legal obligations. In the 1960s, the market switched from horticulture and vegetables to one in which the main agricultural crops dominated. The cereal market, initially based on barley, moved to the current dominant market of wheat. The costs of R & D have risen dramatically in recent years and have become dominated not by the discovery process per se but by the provision of all the extra data needed to obtain registration. These rising costs happened at a time when markets showed little growth and are currently showing some decline. This has resulted in an industry that is continually striving to cut costs, normally by mergers and take-overs. As a consequence, many plant disease problems are not now being targeted by the industry and special measures have been introduced to ensure adequate disease control is available for these minor markets. Plant disease control will remain a necessity and fungicides will remain as a key factor in such control, although it is predicted that integrated control using chemicals, biological controls and biotechnology approaches will begin to dominate.

The fortune of a botanical curiosity – Triticale: past, present and future

Abstract: Triticale (×Triticosecale Wittmack) is the intergeneric hybrid between the female parent wheat (Triticum ssp.) and the male parent rye (Secale ssp.). The early work identifying and then producing primary and secondary triticales is described. Early wheat–rye hybrids were characterized by reproductive disorders and the cytology and meiotic characteristics have received much attention. Chromosome constitution has been studied particularly in relation to R-D substitution. Triticale has always been bred as a self-pollinating crop, although outcrossing can occur, and current cultivars are all nearly homozygous and homogeneous lines. Hybrid breeding (using cytoplasmic male sterility) makes the optimum exploitation of heterosis possible and, with the aid of molecular markers, triticale germplasm is presently being investigated to establish genetically diverse heterotic groups.The first released spring and winter cultivars were generally characterized by good disease resistance, but low grain yield, shrivelled grain, high protein content, excessive height, lodging and preharvest sprouting. Breeding effort has increased yield, reduced shrivelling and improved test weight but at the expense of protein content, which is now comparable to wheat and rye. Plant height and lodging are also now comparable to wheat and rye. Progress in reducing preharvest sprouting by genetic selection is proving difficult and slow. Triticale may be suitable for grain production and for dual purpose usage for forage and grain.The role of biotechnology in triticale improvement is described. The future of the crop, especially in low-input systems, and as raw material for industrial uses is considered.

Phytomers, phyllochrons, phenology and temperate cereal development

Abstract: Extensive research has been conducted on temperate cereal development since the inception of the Journal of Agricultural Science, Cambridge in 1905. This review presents an overview of the orderly and predictable development of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). It begins with the concept of building canopies by the formation, growth and senescence of phytomers (the unit comprised of the leaf, axillary bud, node and internode). Morphological naming schemes for uniquely identifying each plant part are then extended to uniquely name each phytomer unit. The role of the phyllochron (rate of leaf appearance) in synchronizing cereal development and phytomer formation is discussed, as is the use of phenology to predict the timing of the formation, growth and senescence of individual components. The complete developmental sequence of the winter wheat shoot apex correlated with growth stages is extended to spring barley. This overview discusses the abiotic factors controlling cereal development, with special attention given to key questions regarding the critical role of temperature. The review concludes with some cautious glances forward to the exciting possibilities for better understanding of mechanisms controlling the phyllochron and phenology being gained from advances in functional genomics and molecular biology.

Progress in breeding perennial clovers for temperate agriculture

Abstract: Abberton, M. T., Marshall, A. H. (2005). Progress in breeding perennial clovers for temperate agriculture: centenary review. Journal of Agricultural Science, 143 (2-3), 117-135

Evolutionary plant breeding for low input systems

Abstract: Heritable variation is at the heart of the process of evolution. However, variation is restricted in breeding for uniform crop populations using the pedigree line approach. Pedigree lines are successful in agriculture because synthetic inputs are used to raise fertility and control weeds, pests and diseases. An alternative method promoted for exploring the value of variation and evolutionary fitness in crops is to create composite cross populations. Composite cross populations are formed by assembling seed stocks with diverse evolutionary origins, recombination of these stocks by hybridization, the bulking of F1 progeny, and subsequent natural election for mass sorting of the progeny in successive natural cropping environments. Composite cross populations can provide dynamic gene pools, which in turn provide a means of conserving germplasm resources: they can also allow selection of heterogeneous crop varieties. The value of composite cross populations in achieving these aims is dependent on the outcome of mass trials by artificial and natural selection acting upon the heterogeneous mixture. There is evidence to suggest that composite cross populations may be an efficient way of providing heterogeneous crops and of selecting superior pure lines for low input systems characterized by unpredictable stress conditions.

Can Robigus defeat an old enemy? – Yellow rust of wheat

Abstract: The rust diseases have plagued cereal cultivation from the early days of domestication. Biblical accounts report on the plight of Hebrews resulting from severe rust epidemics, while the ancient Greeks and Romans made offerings to the corn god, Robigus in attempts to defeat these devastating diseases (McIntosh et al. 1995). Man's approaches to fighting plant disease have changed since the time of the Romans, but still the fight continues. While we may have won many battles, the war is not yet over.

Genetic improvement of forage crops – past, present and future

Abstract: Humphreys, M. O. (2005). Genetic improvement of forage crops - past, present and future. Journal of Agricultural Science, 143, (6), 441-448

From countrysides of production to countrysides of consumption

Abstract: The UK rural economy is increasingly driven by consumption-based demands rather than by productive land use. Such demands have been an influence on rural land use for many hundreds of years, but a range of factors, including greater wealth and mobility, have reinforced a long-standing trend for the rural economy to be consumption driven. A number of recent economic analyses and more anecdotal sources are used to furnish evidence of the importance of new consumption demands. It is argued that such demands may impact directly on land markets through land purchase for amenity, etc. and indirectly through bringing affluent people into closer proximity to diversified business opportunities. It is argued that these new economic realities are the dominant drivers of economic change and that their recognition might suggest new approaches to the support of strategies to deliver more sustainable rural development.

Explaining contradictory evidence regarding impacts of genetically modified crops in developing countries. Varietal performance of transgenic cotton in India

Abstract: A study of the commercial growing of different varieties of Bacillus thuringiensis (Bt) cotton compares the performance of growing official and unofficial hybrid varieties of Bt cotton and conventional (non-Bt) hybrids in Gujarat by 622 farmers. Results suggest that the official Bt varieties (MECH 12 and MECH 162) significantly outperform the unofficial varieties. However, unofficial, locally produced Bt hybrids can also perform significantly better than non-Bt hybrids, although second generation (F-2) Bt seed appears to have no yield advantage compared to non-Bt hybrids but can save on insecticide use. Although hybrid vigour is reduced, or even lost, with F-2 seed the Bt gene still confers some advantage. The F-2 seed is regarded as 'GM' by the farmers (and is sold as such), even though its yield performance is little better than the non-GM hybrids. The results help to explain why there is so much confusion arising from GM cotton release in India.

The possible use of n-alkanes, long-chain fatty alcohols and long-chain fatty acids as markers in studies of the botanical composition of the diet of free-ranging herbivores.

Abstract: Few methods exist for estimating quantitatively the diet composition of free-ranging herbivores. The current study examined whether long-chain fatty alcohols (alcohols) or long-chain fatty acids (acids) could be used along with n-alkanes to allow reliable diet composition estimates to be made in herbivores consuming complex diets. Twelve Scottish Blackface wether sheep housed in metabolism crates were fed four different mixtures of three plant species (three animals per mixture) for a seven-period experiment. Concentrations of cuticular wax n-alkanes, alcohols and acids were estimated in samples of individual plant species, and the faeces from animals that consumed mixtures of these species. These concentrations were then used to calculate the dietary proportions of each species by a least-squares optimization procedure. To explore the differences between the estimation methods (individual markers and their combinations), the mean squares of errors (EMS) between the actual and predicted proportions of plant species were calculated. In three out of the four mixtures, alcohols had the lowest discrepancies (lowest EMS values), followed by n-alkanes and then acids. Acids yielded the lowest discrepancy in one mixture and the highest in the others. It is concluded that, for this particular set of mixtures, alcohols had great potential to estimate composition of complex diets. However, the estimation using acids was less good and n-alkanes were of intermediate potential. Estimation from the combination of the three marker classes was always better than using the poorest individual marker.

Fungicide and cultivar affect post-anthesis patterns of nitrogen uptake, remobilization and utilization efficiency in wheat.

Abstract: Three successive field experiments (2000/01-2002/03) assessed the effect of wheat cultivar (Consort.. Hereward and Shamrock) and fungicide (epoxiconazole and azoxystrobin) applied at and after flag leaf emergence on the nitrogen in the above-ground crop (Total N) and grain (Grain N), net nitrogen remobilization from non-grain tissues (Remobilized N). grain dry matter (Grain Dill), and nitrogen utilization efficiency (NUtE(g) = Grain DM/Total N). Ordinary logistic curves were fitted to the accumulation of Grain N, Grain DM and Remobilized N against thermal time after anthesis and used to simultaneously derive fits for Total N and NUtE(g). When disease was controlled, Consort achieved the greatest Grain DM, Total N, Grain N and NUtEg; in each case due mostly to longer durations, rather than quicker rates, of accumulation. Fungicide application increased final Grain Dill.. Grant N, Total N and Remobilized N, also mostly through effects on duration rather than rate of accumulation. Completely senesced leaf laminas retained less nitrogen when fungicide had been applied compared with leaf laminas previously infected severely with brown rust (Puccinia recondita) and Septoria tritici, or with just S. tritici. Late movement of nitrogen out of fungicide-treated laminas contributed to extended duration of both nitrogen remobilization and grain N filling, and meant that increases in NUtE(g) could occur without simultaneous reductions in grain N concentration.

Growth performances, nutrient utilization and carcass traits in broiler chickens fed with a normal and a low energy diet supplemented with inorganic chromium (as chromium chloride hexahydrate) and a combination of inorganic chromium and ascorbic acid

Abstract: Diets for broiler chickens (n=90) were supplemented with chromium (CrCl3, 6H2O), either alone (0·2 mg/kg diet) or in a combination with ascorbic acid (0·2 mg Cr and 50 mg ascorbic acid/kg diet). The objectives of the study were to ascertain if ascorbic acid had any additive effect on the actions of chromium and whether chromium supplementation could alleviate the nutritional stress in the birds imposed by a reduced energy intake. The birds were fed at the recommended (Bureau of Indian Standards 1992) and at a lower plane of energy. Live-weight gain and diet utilization were higher (P<0·01) when the normal energy diet supplemented with chromium was fed. Food intake (35 days) was higher (P<0·001) in the birds fed with the low energy diet. There was an increase (P<0·01) in metabolizability due to the supplementation of chromium. The metabolizability of crude protein and total carbohydrate increased (P<0·05) when chromium and ascorbic acid were supplemented together. Chromium intake was higher (P<0·001) in the supplemented birds, especially in those fed with the low energy diet (P<0·05), though its retention was higher (P<0·05) when the normal energy diet was given. Chromium in combination with ascorbic acid also enhanced (P<0·01) chromium retention. Blood glucose (P<0·001) and plasma cholesterol (P<0·05) were lower in the supplemented birds and blood glucose was reduced further when ascorbic acid was supplemented together with chromium (P<0·01). Plasma protein increased (P<0·05) in the supplemented chickens. However, variation in the dietary energy concentration did not exert any significant effect on these blood parameters. Plasma chromium was higher (P<0·05) in the supplemented birds, though chromium had little effect in this regard with ascorbic acid. Plasma copper increased (P<0·05) when chromium was supplemented alone and increased further (P<0·05) when chromium and ascorbic acid were supplemented together. Deposition of chromium in the breast and thighs increased (P<0·05) due to supplementation. Protein content and total accretion of protein in the carcass were higher (P<0·05) when chromium was supplemented alone and with ascorbic acid. The supplemented birds had less (P<0·01) fat per 100 g of carcass irrespective of the dietary energy concentration. Weight of the hot carcass increased (P<0·05) due to chromium supplementation although dietary energy concentration did not affect this particular parameter. It was concluded that inorganic chromium supplementation (0·2 mg chromium/kg diet) might effectively enhance the growth performance, diet utilization and carcass characteristics in broiler chickens. Addition of ascorbic acid might also be beneficial in this regard. However, dietary energy concentration was more critical and to yield the maximum benefit of Cr supplementation in broiler chickens, an optimum level was essential.

Effects of genotype and environment on seed yield and quality of rice

Abstract: Seed yield and seed quality determine much of the value of rice (Oryza sativa L.) crops to the producers. The effects of genotype and environment on seed yield and quality were investigated using 12 rice genotypes grown during 3 years (2000–2003) at four different sowing dates in India, where detailed environmental data were collected. Yield, seed weight, proportion of seed setting and quality in terms of potential seed longevity, proportion of discoloured seeds, seed leachate conductivity and percentage germination were evaluated. The results were subjected to analysis of variance and the influence of environmental factors was evaluated by correlation analysis. Analysis of variance suggested that proportion of seed setting, seed leachate conductivity, potential seed longevity, percentage seed germination and proportion of seed discoloration were influenced more by environmental effects than by genotypic effects. In contrast, yield, panicle number, seed weight, and proportion of high-density grains were influenced more by genotypic than by environmental effects. The significant interaction effects of genotype and environment for all characteristics were attributed to differential resistance of genotypes to lodging (caused by increased plant height, low radiation and excessive rain at the time of grain filling) and were associated with fewer panicles harvested, lower seed setting and lower seed weight. Correlation analysis suggested that warm weather conditions with high solar radiation and without excessive rains during grain filling stage gave the best rice seed yield with high quality.

Possibilities of near infrared reflectance spectroscopy for the prediction of organic carbon concentrations in grassland soils

Abstract: For the determination of soil organic carbon (OC) concentrations, the availability of a fast, low-cost analysis method is required. The aim of the present study was to evaluate the possibilities of near infrared reflectance spectroscopy (NIRS) to build a spectral database and to develop calibrations for the prediction of organic carbon concentrations in grassland soils. NIRS spectra of 1626 soil samples from different grasslands (both agricultural and natural) were collected between 1100 and 2500 nm. NIRS calibrations were developed with modified partial least square regression and tested with independent validation samples. The best equations were obtained with the first derivative of the spectra without scatter corrections. For the global calibration, containing the samples of all origins, the standard errors of calibration (SEC) and of prediction (SEP) were respectively 3.70 g OC/kg dry soil (R 2 =0.89) and 3.95 g OC/kg dry soil (R 2 =0.88). The ratio of the standard deviation of the reference validation data to the SEP (RPD), indicating the performance of the calibration, was 2.9. Dividing the samples into groups according to their practice (agricultural or natural grassland), improved SEP by 5.8 and 7.7%, respectively. Dividing the samples into texture groups (clay, silt, sand) improved SEP for agricultural grassland by, on average, 7.4% and for natural grassland by 16.2%.

The role of fractures and lipids in the seed coat in the loss of hardseededness of six Mediterranean legume species

Abstract: Changes in the seed coat morphology of 12 annual legumes were studied using environmental scanning electron microscopy (ESEM). The seeds of Biserrula pelecinus L. cv. Casbah, Ornithopus sativus cv. Cadiz, Trifolium clypeatum L., T. spumosum L., T. subterraneum L. cv. Bacchus Marsh, Trigonella balansae Boiss. & Reuter., Trigonella monspeliaca L. and Vicia sativa subsp. amphicarpa Dorthes (morthes.) were examined by ESEM after exposure to field conditions for 6 months, while those of Medicago polymorpha L. cv. Circle Valley, Trifolium clypeatum L., T. glanduliferum Boiss., T. lappaceum L., T. spumosum L., and T. subterraneum L. cv. Dalkeith, were examined after 2 years' exposure. The entry of water into seeds was followed by covering various parts of the seed coat with petroleum jelly and soaking the treated seeds in dyes. As the seeds softened over time, more and larger fractures appeared on the seed coat. Water entered the seed either through fractures, over the seed coat as a whole or through the lens. It is hypothesized that the formation of fractures occurs after physicochemical changes in the seed coat, probably associated with changes in the amount and nature of seed coat lipids. The newly matured whole seeds of M. polymorpha cv. Circle Valley, T. clypeatum, T. glanduliferum, T. lappaceum, T. spumosum, and T. subterraneum cv. Dalkeith were analysed for lipid content in 1997. The seed coats of T. subterraneum cv. Dalkeith and T. spumosum were separated from the cotyledons and examined in detail for lipid content. The lipid content of whole seeds ranged from 48 (T. lappaceum) to 167 mg/g (T. subterraneum cv. Dalkeith). Total lipid of the whole seeds of T. subterraneum cv. Dalkeith and T. glanduliferum declined by about 9 mg/g over 2 years, while in T. spumosum it declined by about 17 mg/g. In contrast, the major fatty acids in the seed coat declined by 0.67 mg/g over the 2 years. Change in seed coat lipids showed a marked similarity to changes in hardseededness for both T. subterraneum cv. Dalkeith and T. spumosum. The results strongly suggest that seed softening is associated with loss of lipids in the seed coat, because lipids have physical characteristics that are altered at temperatures experienced in the field.

Sensing the physical and nutritional status of the root environment in the field : a review of progress and opportunities

Abstract: The challenge that faces agriculture at the start of the 21st Centuary is to provide security of food production in a sustainable way. Achieving this task is difficult enough, but against a background of climate change, it becomes a moving target. However, one certainty is that soil factors that limit crop growth must be taken into account as new strategies for crop management are developed. To achieve this, it is necessary to measure the physical and nutritional status of the root environment in the field. Before considering measurement methods, our understanding of how the plant interacts with its soil environment is reviewed, so that it is clear what needs to be measured. Soil strength due to soil drying is identified as an important stress that limits agricultural productivity. The scope to measure Soil factors that directly affect plant growth is reviewed. While in situ sensors are better developed, progress in the development of remote sensors of soil properties are also reviewed. A robust approach is needed to interpret soil measurements at the field scale and here geostatistics has much to offer. The present review takes a forward look and explores how our understanding of plant responses to soil conditions, the newly emerging sensing technologies and geostatistical tools can be drawn together to develop robust tools for Soil and crop management. This is not intended to be an exhaustive review. Instead, file authors focus on those aspects that they consider to be most important and where the greatest progress is being made.

Thermal time for phenological development of four maize hybrids grown off-season in a subtropical environment

Abstract: A common method to describe maize phenology during the vegetative phase is to determine the number of leaves. The thermal interval between the appearance of successive leaves, called the phyllochron, is critical for predicting the duration of vegetative development. In general, there is a high correlation between the final number of initiated leaves and the duration from sowing to silking. The development of a crop depends on temperature and photoperiod and genetic response to these environmental factors, thus bio-meteorological indices are needed to describe this process. The goal of this study was to obtain a better understanding of the phyllochron and its impact on the final number of leaves. A second objective was to evaluate three thermal indices for predicting the duration of sowing to silking and silking to physiological maturity for four maize hybrids grown off-season in a subtropical region of the Southern Hemisphere (Sao Paulo State, Brazil). The modified general thermal index (mGTI) was compared with the classical thermal time concept (TT) with two sets of cardinal temperatures, including TT(10) with 10 °C as minimum base temperature (Tb) and TT(8) with 8 °C as Tb. Three field experiments that included four hybrids with different relative maturity ratings were conducted during the autumn and winter growing seasons of 2001 and 2002 at the University of Sao Paulo, in Piracicaba, SP, Brazil. Phenology was recorded daily. Also, an independent evaluation of three methods for estimating phenology was conducted with data obtained from the variety trials of the ‘Instituto Agronomico’ for four regions of the State of Sao Paulo, Brazil. The results indicated that the value for the phyllochron was about 50 °Cd/leaf until approximately the appearance of the 12th leaf, and then declined. For estimating the planting to silking period, the TT(10) method resulted in a coefficient of variation (CV) of 2·01%, while for TT(8) the CV was 1·37% and for mGTI the CV was 1·04%. For the period from silking to physiological maturity, the CV was 2·91% for the TT(10), 2·64% for the TT(8) and 2·01% for the mGTI method. All CVs were very small, suggesting that there was only a slight difference between algorithms. It can be concluded from this study that the mGTI can be used for estimating both silking and physiological maturity dates for maize grown off-season in subtropical regions of Brazil because it resulted in the smallest CV. However, additional studies with different maize hybrids are necessary to confirm the advances in estimating the main phenological phases for maize based on the mGTI.

The changing context for agricultural science

Abstract: There are many agricultures, and diverse components of each, so a journal of agricultural science must encompass a wide and ever-changing range of disciplines. The Journal of Agricultural Science, Cambridge, has done this in exemplary fashion from its very first issue one hundred years ago, which opened with Roland Biffen’s (1905) paper on the use in wheat breeding of Mendel’s recently rediscovered laws of inheritance. Another premonitory paper in that issue, on calcium cyanamide, was, as its author A. D. Hall (1905) put it : ‘ the first attempt on a commercial scale to bring atmospheric nitrogen into a state of combination, to manufacture, in fact, an artificial manure containing N derived from the air’. Much of the progress in agriculture in the following century, during which the average yield of wheat in the UK has risen from 2 to 8 tonnes per hectare, has been due to the synergistic interactions between these two areas of research, and with other branches of agricultural science encompassed by this journal. The journal’s history over the first 75 years was surveyed by Bell (1980), and illustrates well the continuing shifts in disciplinary emphasis and perspectives as agriculture has evolved. In recent years this evolution has been even more apparent among the books reviewed than in the papers published.

Glucosinolate assessment in Brassica oleracea leaves by near-infrared spectroscopy

Abstract: Glucosinolates and their hydrolysis products are of great concern because they are responsible for many of both the beneficial and harmful properties of glucosinolate-containing plants. Cabbage (Brassica oleracea L.) is a species highly consumed as a leaf vegetable in many countries showing high qualitative and quantitative differences in glucosinolate composition among cultivars. The standard analytical techniques for determining glucosinolate composition using conventional methods lead to high costs, labour input and delays, all of which affect both the availability of data and the taking of swift decisions. In contrast, near-infrared spectroscopy (NIRS) has emerged as a rapid and cost-effective technique of analysis for many agro-food products. In this work we test the potential of NIRS for screening the total glucosinolates (t-GSL), gluconapin (GNA), gluconasturtiin (GNAST) and neoglucobrassicin (NGBS) contents of cabbage leaf cultivars coming from Portugal and Spain. NIRS calibrations resulted in coefficients of determination and standard deviation to standard error of cross-validation ratio of 0·83 and 2·38 for t-GSL; 0·70 and 1·85 for GNA; 0·62 and 1·63 for GNAST; and 0·60 and 1·58 for NGBS, respectively. An examination of the loadings of the equation for t-GSL suggested that O-H groups of water, C-H combinations of the methylene group and also N-H groups of amides were the molecular associations most strongly used in modelling total glucosinolates. It was concluded that NIRS shows a high potential as an analytical method for total and individual glucosinolate routine analysis in cabbage.

Effect of quebracho tannin on faecal egg counts and worm burdens of temperate sheep with challenge nematode infections

Abstract: Three animal experiments were carried out to investigate the effect of condensed tannins (CT) on parasitic gastrointestinal (GI) nematode infections of sheep. Experiment 1 investigated the long-term effect of varying dietary levels (0–80 g/kg diet) of quebracho tannin (QT) on faecal egg counts (FEC) and feed consumption of lambs with experimental Haemonchus contortus infection. Dietary QT did not cause significant reductions in FEC although at high inclusions of QT there was an indication of a reduction in FEC. Some undesirable effects of tannins were also observed; feed consumption was significantly reduced (P 0·05) on small intestinal T. colubriformis although similar effects to those seen in Experiment 2 on H. contortus were observed, suggesting that the location of the nematodes in the gut might be important. Apart from reducing feed consumption, the drench caused some physiological changes in the gut, particularly an increase in faecal water and mucus content, which were more marked following the drench than seen in the dietary inclusion trial. In conclusion, unlike dietary inclusion, QT worked more quickly and more effectively against H. contortus when administered as drench; T. colubriformis may require a higher dose or a prolonged exposure to the drench. The present findings suggest that it may be possible, perhaps with limited use of synthetic anthelmintics, to design appropriate feeding strategies using tannins to alleviate the problem of nematode infections in small ruminants. This may be particularly relevant to the tropics and subtropics where many species of plants contain high levels of tannins and where extracts high in tannins are readily available.

Past developments and future opportunities in the design and analysis of crop experiments

Abstract: A review of papers on the statistical design and analysis of experiments published in the Journal of Agricultural Science, Cambridge, over the last 100 years is presented. The development of significant ideas in the practical design of field experiments is reviewed. Some possible future developments in the design of spatial field trials and computer-aided design of experiments are discussed.

Grain yield, straw yield and economic value of tall and semi-dwarf durum wheat cultivars in Algeria

Abstract: In cereal-livestock farming systems of North Africa and West Asia the straw of durum wheat [Triticum turgidum (L.) Thell. ssp. turgidum conv. durum (Desf.) MacKey] is frequently used for feeding animals during the dry season and may enhance the sustainability and the flexibility of farming in various respects. In Algeria the average sale price per unit weight of the durum straw is around 30% of that of grain. Six tall and 18 semi-dwarf locally well-adapted cultivars were grown in the season 2000/01 at five Algerian locations representing the main durum wheat cropping areas to verify: (i) the impact of straw yield on the economic merit of cultivars for recommendation and (ii) the interest of tall v. semi-dwarf plant types for breeding. The tall material comprised four cultivars derived from local landraces and two old varieties. The semi-dwarf germplasm originated from CIMMYT, ICARDA or various Mediterranean countries. In the economic assessment the straw value was expressed in terms of grain-equivalent, defining an economic yield as: grain yield+(0.30 x straw yield). The merit of individual cultivars was markedly affected by ignoring or taking into account the straw yield. On average, tall germplasm had a moderate (about 3 %) but significant (P<0.02) economic advantage over semi-dwarf material as a result of much higher straw yield (+25%) and aerial biomass (+12%) and somewhat lower grain yield (-7%). However, three semi-dwarf varieties from CIMMYT were top-ranking for economic yield. They possessed outstanding aerial biomass and similar harvest index compared with the mean response of other semi-dwarf germplasm. On average, the tall germplasm showed higher grain yield stability (P <0.01), lower straw yield stability (P<0.01) and slightly higher stability of economic yield (P<0.11) than the semi-dwarf group as measured by Shukla's stability variance. Grain yield was negatively correlated with straw yield (r=-0.41, P<0.05), and was not correlated with aerial biomass, in the whole set of cultivars. However, it was not correlated with straw yield, and was positively correlated with aerial biomass (r=0.61, P<0.01), within the semi-dwarf germplasm. Information on straw yield can improve the targeting of cultivars for cereal-livestock farming systems. Breeding for these systems may target either a tall type within semi-dwarf material (i.e. a tall dwarf'), or a truly tall plant type.

Effect of constant photoperiods on the laying performance of broiler breeders allowed conventional or accelerated growth

Abstract: An experiment was conducted at the University of KwaZulu–Natal to assess the effect of constant photoperiods on sexual maturity and egg-laying performance in broiler breeders given two levels of control-feeding during the rearing phase. Cobb broiler breeder females were grown to reach 2·1 kg body weight at 17 or 21 weeks, and maintained on 10, 11, 12, 13, 14 or 16-h photoperiods from 2 days to 68 weeks of age. There were no significant interactions between photoperiod and growth rate for any production parameter. The time required reaching 2·1 kg increased proportionally with photoperiod but, because of delayed sexual development, birds on longer photoperiods consumed more feed to, and were heavier at, sexual maturity than shorter daylengths. The longer-photoperiod birds also had inferior rates of lay in the first half of the cycle, but superior in the second, which, together with the photoperiodic effects on maturity, resulted in birds on 11, 13 or 14 h producing most eggs to 68 weeks, and those on 16 h fewest. It is possible that the pattern of egg production was due to some of the birds on [ges ]13-h photoperiods becoming photorefractory, having a mid-cycle pause, and then spontaneously resuming egg production in the latter half of the cycle. However, a hinge-analysis of current and other data to the more usual depletion age of 60 weeks showed that the combined effects of photoperiod on sexual maturity and egg production resulted in constant 10-h birds producing the highest number of eggs, with numbers decreasing by 3·6 eggs/h of photoperiod above the hinge and 7·8 eggs/h of photoperiod below it. Mean egg weight increased by 0·4 g/h of photoperiod, but the proportion of abnormally large and floor eggs and the incidence of mortality were unaffected by daylength. For each photoperiod, accelerated growth resulted in body weights being heavier than controls at sexual maturity, despite the mean age at maturity being 10 days earlier for the faster-growing birds. Body weights for the two growth groups were not significantly different at 68 weeks. Faster-growth birds consumed 1 kg less feed to 2·1 kg body weight, but 1·3 kg more feed to sexual maturity and 2·7 kg more to 68 weeks, and produced 6 more eggs than, but had similar patterns of egg production to, the conventionally managed controls. Mean egg weight, the proportion of floor eggs and the incidence of mortality were similar for both groups. Notwithstanding that the overall production of abnormally large eggs was low (1·1 eggs per bird); the faster-growing birds produced significantly more than the controls. Egg weight was positively influenced by age at sexual maturity, body weight at sexual maturity and photoperiod, but was unaffected by rate of growth to 2·1 kg per se.These findings show that there are differences between broiler breeders and egg-type pullets in their response to constant photoperiods. It is likely that the factors responsible for these differences, particularly in terms of sexual development, are the exhibition of photorefractoriness by, and the retardational effects of controlled feeding on, broiler breeders.

Effects of long-term administration of recombinant bovine somatotropin on milk production and plasma insulin-like growth factor and insulin in crossbred Holstein cows

Abstract: The objective of the study was to determine the in vivo relationship between the long-term administration of recombinant bovine somatotropin (rbST), circulating levels of IGF-I and insulin, mammary blood flow and other variables relevant to milk synthesis, in crossbred, Holstein cattle. Ten first-lactation, non-pregnant, crossbred, Holstein dairy cattle were divided into two groups of five animals each: an experimental group and a control group. Animals in each group were fed with rice straw, treated with 5 kg urea dissolved in 100 litres water per 100 kg dry rice straw as the source of roughage. Four consecutive study periods were carried out in each group. These consisted of a pretreatment period (45 days postpartum before lactation peak) and three treatment periods during early lactation (105 days postpartum), mid-lactation (165 days postpartum) and late lactation (225 days postpartum). During the treatment periods, animals that had completed 60 days of lactation were injected subcutaneously at fortnightly intervals with 500 mg of recombinant bovine somatotropin (rbST) (POSILAC, Monsanto, USA) in the experimental group, while animals in the control group were injected subcutaneously at fortnightly intervals with 800 mg of sterile sesame oil, without rbST, as a placebo. During the pretreatment period, there were no significant differences in plasma concentrations of IGF-I, insulin and other parameters between the control group and the experimental group. During the treatment periods, the increase in the concentration of plasma IGF-I in rbST treated animals was significantly higher than in the control animals throughout the lactation period. Plasma glucose, protein and triglyceride concentrations in each group remained stable throughout the study. The total daily dry matter intakes were not significantly different between the groups. Milk yield increased by 20% with rbST treatment and it was 22% greater than that of the control animals receiving placebo in early lactation. Milk yield of rbST treated animals rose to a peak in early lactation and then gradually declined. In late lactation, milk yield of rbST-treated animals decreased by 19% as compared with early lactation. Udder plasma flow and udder blood flow markedly increased with rhST treatment and there were no significant changes in the control animals. The ratio of udder blood flow to the rate of milk production increased in mid- and late lactation in controls and the rbST treated animals. These findings suggest that the short persistency of lactation in rbST treated animals was similar to that in the control animals receiving placebo. Changes in milk production during the progress of lactation in rbST treated animals might not be controlled systemic;lily only but also locally within the mammary gland. The lack of effect of higher plasma IGF-I levels on persistency of lactation in rbST treated animals, may be due to changes in the pattern of IGF-I binding proteins and paracrine production inhibiting IGF-I action.

Effect of nitrogen fertilization on the expression of slow-blasting resistance in rice

Abstract: The development of rice blast disease in four slow-blasting (SB) genotypes was compared with that in the fast-blasting (FB) genotype Karuna, under natural field epidemics over a period of 3 years at five levels of nitrogen, in order to determine if the application of high doses of nitrogen influenced the expression of disease progress in the SB types. The treatment effects were compared through estimation of nine parameters viz. (i) lesion number (LN); (ii) area under disease progress curve (AUDPC); (iii) relative area under disease progress curve (RAUDPC); (iv) logistic apparent infection rate (r); (v) Gompertz apparent infection rate (k); (vi) logit line intercept (logit-a); (vii) gompit line intercept (gompit-a); (viii) time required for the disease to reach 0·25 severity in logistic (T25r); and (ix) Gompertz (T25k) models. There was a significant increase in LN, AUDPC, RAUDPC, r and k with increased levels of nitrogen application in all genotypes, but the rate of increase in disease severity was much lower in SB genotypes than the FB one and did not lead to breakdown of resistance in the SB genotypes, since severity level was much below the economic injury level. Among the nine derived parameters for evaluation of resistance LN, AUDPC, RAUDPC, r and k were best. The AUDPC and RAUDPC had lower degrees of error variance compared with the other parameters and hence were considered superior measures for characterization of disease progress curves.

Agronomic evaluation and performance of flax varieties for industrial fibre production

Abstract: Flax fibre for industrial purposes differs from that for linen production, although the agronomic factors that influence fibre development and which factors are most important for industrial fibre production have still to be defined. A description of variations in the performance of fibre flax varieties is also necessary as current guidance relates to the European market rather than the UK. Field trials were sown in 2002 and 2003 at the Henfaes Research Centre in north Wales, investigating 29 and 26 varieties, respectively, of European fibre flax and dual-purpose flax varieties. In 2002 a nitrogen treatment was included in the trial with two treatments, 40 kg/ha and 80 kg/ha. Varieties were evaluated for 20 agronomic and fibre production variables, and the differences between the varieties were analysed using analysis of variance (ANOVA) and principal components analysis (PCA). The higher nitrogen rate was found to increase crop lodging, although some varieties were found to be more susceptible than others. Environment had a strong influence on crop success, with some varieties showing more year to year stability than others. PCA allowed those varieties that were the highest yielding, highest fibre producers and showed the best stability across the 2 years to be identified. Understanding the agronomic results presented and discussed here is important if fibre flax production is to become economically viable in the UK.

Genetic analysis of stomatal conductance in upland cotton (Gossypium hirsutum L.) under contrasting temperature regimes

Abstract: Stomatal conductance plays an important role in the heat avoidance mechanism of crop plants. Stomatal conductance in cotton is genetically determined and has been shown to be associated with heat resistance and higher yields. Experiments were carried out with six generations (parental, F 1 , F 2 and back crosses) of three upland cotton crosses under heat-stressed and non-stressed greenhouse and field regimes, to understand the inheritance pattern of stomatal conductance as affected by contrasting temperature regimes. The results revealed significant variation for stomatal conductance due to generations and generation x temperature regime interaction in the three crosses. In general, heat stress reduced stomatal conductance and available genetic variability. Temperature regimes exerted a significant effect on the expression of the genes responsible for stomatal conductance. High temperature or heat stress favoured the expression of genes having additive effects, while absence of heat stress favoured those having dominant effects in two of the three crosses evaluated. The third cross showed the opposite reaction. The results suggest that genes controlling stomatal conductance in the parents of the first two crosses (MNH-552, HR109-RT. CIM-448, CRIS-19) were different from those controlling stomatal conductance in FH-900 and N-Karishma, the parents of the third cross. The selection efficiency of stomatal conductance in segregating populations was likely to be affected by the complexity of its inheritance, environmental dependency, and presence of substantial non-allelic and genotype x temperature regime interactions.

Genetic analysis of physical grain quality characters in sorghum

Abstract: Sorghum is grown the world over for both human and animal consumption. Recently, the increase in grain production has slowed; simultaneously, its marketability has declined. Grain size is one of the most important determinants of grain yield and market price in India. One important factor responsible for the decline in consumption of sorghum in India is the inferior quality of rainy season produce. Consumers prefer post rainy season sorghums as the grains are bold, round and lustrous in appearance. Any improvement in the quality of rainy season sorghum grain would help it to fetch higher market prices. In the present study, the genetics of important grain quality characteristics such as grain size, grain shape and lustre were studied using two crosses based on elite sorghum lines 463B and AKMS 14B, and a germplasm line, IS 17600, during 2001 at the National Research Centre for Sorghum, Hyderabad, India. Generation mean analysis and frequency distribution studies revealed that grain size is governed by dominant genes that are polygenic in nature. Predominance of dominance and epistatic interactions in both crosses indicates that selection for higher grain size would be more effective if the dominance and epistatic effects are first reduced by a few generations of selfing. Biparental mating is suggested for developing homozygous bold grain lines. Round grain shape is governed by a single dominant gene and grain lustre by two complementary recessive genes. The study suggested that developing a sorghum hybrid with bold, round grain is feasible provided either of the parents has bold and/or round grain. However, for the hybrid to be lustrous, both parents need to be lustrous and homozygous for the alleles conferring grain lustre at a common locus. With the possibility of development of sorghum hybrids with bold, round and lustrous grain, there is scope for improvement in consumer preference of rainy season sorghum grain.