Characterising Biological and Physiological Drought Signals in Diverse Parents of a Wheat Mapping Population.

Water deficit affects the growth as well as physiological and biochemical processes in plants. The aim of this study was to determine differences in physiological and biochemical responses to drought stress in two wheat cultivars-Chinese Spring (CS) and SQ1 (which are parents of a mapping population of doubled haploid lines)-and to relate these responses to final yield and agronomic traits. Drought stress was induced by withholding water for 14 days, after which plants were re-watered and maintained until harvest. Instantaneous gas exchange parameters were evaluated on the 3rd, 5th, 10th, and 14th days of seedling growth under drought. After 14 days, water content and levels of chlorophyll a+b, carotenoids, malondialdehyde, soluble carbohydrates, phenolics, salicylic acid, abscisic acid (ABA), and polyamines were measured. At final maturity, yield components (grain number and weight), biomass, straw weight, and harvest index were evaluated. Physiological and biochemical parameters of CS responded more than those of SQ1 to the 14-day drought, reflected in a greater reduction in final biomass and yield in CS. Marked biochemical differences between responses of CS and SQ1 to the drought were found for soluble carbohydrates and polyamines. These would be good candidates for testing in the mapping population for the coincidence of the genetic control of these traits and final biomass and yield.

Nutritional, environmental and economic implications of children plate waste at school: a comparison between two Italian case studies.

OBJECTIVE: This study aims at comparing two Italian case studies in relation to school children's plate waste and its implications, in terms of nutritional loss, economic cost, and carbon footprint. DESIGN: Plate waste was collected through an aggregate selective weighting method for 39 days. SETTING: Children from the first to the fifth grade from four primary schools, two in each case study (Parma and Lucca), were involved. RESULTS: With respect to the served food, in Parma the plate waste percentage was lower than in Lucca (p<0.001). Fruit and side-dishes were highly wasted, mostly in Lucca (>50%). The energy loss of the lunch meals accounted for 26% (Parma) and 36% (Lucca). Among nutrients, dietary fibre, folate and vitamin C, calcium and potassium were lost at most (26-45%). Overall, after adjusting for plate waste data, most of the lunch menus fell below the national recommendations for energy (50%, Parma; 79%, Lucca) and nutrients, particularly for fat (85%, Parma; 89%, Lucca). Plate waste was responsible for 19% (Parma) and 28% (Lucca) of the carbon footprint associated to the food supplied by the catering service, with starchy food being the most important contributor (52%, Parma; 47%, Lucca). Overall, the average cost of plate waste was 1.8 €/kg (Parma) and 2.7 €/kg (Lucca), accounting respectively for 4% and 10% of the meal full price. CONCLUSION: A re-planning of the school meals service organisation and priorities is needed to decrease the inefficiency of the current system and reduce food waste and its negative consequences.

Genetic Parameters and QTLs for Total Phenolic Content and Yield of Wheat Mapping Population of CSDH Lines under Drought Stress.

A doubled haploid population of 94 lines from the Chinese Spring × SQ1 wheat cross (CSDH) was used to evaluate additive and epistatic gene action effects on total phenolic content, grain yield of the main stem, grain number per plant, thousand grain weight, and dry weight per plant at harvest based on phenotypic and genotypic observations of CSDH lines. These traits were evaluated under moderate and severe drought stress and compared with well-watered plants. Plants were grown in pots in an open-sided greenhouse. Genetic parameters, such as additive and epistatic effects, affecting total phenolic content, were estimated for eight year-by-drought combinations. Twenty-one markers showed a significant additive effect on total phenolic content in all eight year-by-drought combinations. These markers were located on chromosomes: 1A, 1B, 2A, 2B, 2D, 3A, 3B, 3D, 4A, and 4D. A region on 4AL with a stable QTL controlling the phenolic content, confirmed by various statistical methods is particularly noteworthy. In all years and treatments, three markers significantly linked to QTLs have been identified for both phenols and yield. Thirteen markers were coincident with candidate genes. Our results indicated the importance of both additive and epistatic gene effects on total phenolic content in eight year-by-drought combinations.

Population structure in a wheat core collection and genomic loci associated with yield under contrasting environments.

A set of 96 winter wheat accessions sampled from a variety of geographic origins, including cultivars and breeding lines, were characterized with 46 genome-wide SSR loci for genetic diversity and population structure. The genetic diversity within these accessions was examined using a genetic distance-based and a model-based clustering method. The model-based analysis identified an underlying population structure comprising of four distinct sub-populations which corresponded well with distance-based groupings. Information on the population structure is taken into account in an association mapping study of grain yield from a 3-years field trial incorporating fully irrigated, rainfed and drought stress treatments. A total of 21 marker-grain yield associations (P < 0.01) were identified with nine SSR markers. Most associations were detected only in one to three environments (treatment/year combination), with an average R ( 2 ) value around 13 %. However, marker gwm484 (on chromosome 2D) was associated with yield in six environments, including irrigated, rainfed and drought stress treatments, suggesting it could be used to improve grain yield across a range of environments. Variation in grain yield at this locus was associated with earliness, early vigour, kernels per spikelet and harvest index. Microsatellite locus psp3200 (on chromosome 6D) was associated with yield in dry and hot environments, which was related to earliness, early vigour, productive tillering and total biomass per plant. Partial least squares regression, with nine environmental factors, showed that precipitation from tillering to maturity was the main environmental factor causing marker × environment associations for grain yield.

Genetic and association mapping study of wheat agronomic traits under contrasting water regimes.

Genetic analyses and association mapping were performed on a winter wheat core collection of 96 accessions sampled from a variety of geographic origins. Twenty-four agronomic traits were evaluated over 3 years under fully irrigated, rainfed and drought treatments. Grain yield was the most sensitive trait to water deficit and was highly correlated with above-ground biomass per plant and number of kernels per m(2). The germplasm was structured into four subpopulations. The association of 46 SSR loci distributed throughout the wheat genome with yield and agronomic traits was analyzed using a general linear model, where subpopulation information was used to control false-positive or spurious marker-trait associations (MTAs). A total of 26, 21 and 29 significant (P < 0.001) MTAs were identified in irrigated, rainfed and drought treatments, respectively. The marker effects ranged from 14.0 to 50.8%. Combined across all treatments, 34 significant (P < 0.001) MTAs were identified with nine markers, and R(2) ranged from 14.5 to 50.2%. Marker psp3200 (6DS) and particularly gwm484 (2DS) were associated with many significant MTAs in each treatment and explained the greatest proportion of phenotypic variation. Although we were not able to recognize any marker related to grain yield under drought stress, a number of MTAs associated with developmental and agronomic traits highly correlated with grain yield under drought were identified.

The genetics of nitrogen use in hexaploid wheat: N utilisation, development and yield.

A genetic study is presented for traits relating to nitrogen use in wheat. Quantitative trait loci (QTLs) were established for 21 traits relating to growth, yield and leaf nitrogen (N) assimilation during grain fill in hexaploid wheat (Triticum aestivum L.) using a mapping population from the cross Chinese Spring x SQ1. Glutamine synthetase (GS) isozymes and estimated locations of 126 genes were placed on the genetic map. QTLs for flag leaf GS activity, soluble protein, extract colour and fresh weight were found in similar regions implying shared control of leaf metabolism and leaf size. Flag leaf traits were negatively associated with days to anthesis both phenotypically and genetically, demonstrating the complex interactions of metabolism with development. One QTL cluster for GS activity co-localised with a GS2 gene mapped on chromosome 2A, and another with the mapped GSr gene on 4A. QTLs for GS activity were invariably co-localised with those for grain N, with increased activity associated with higher grain N, but with no or negative correlations with grain yield components. Peduncle N was positively correlated, and QTLs co-localised, with grain N and flag leaf N assimilatory traits, suggesting that stem N can be indicative of grain N status in wheat. A major QTL for ear number per plant was identified on chromosome 6B which was negatively co-localised with leaf fresh weight, peduncle N, grain N and grain yield. This locus is involved in processes defining the control of tiller number and consequently assimilate partitioning and deserves further examination.

Genetic diversity of the Novi Sad Wheat Core Collection revealed by microsatellites.

In recent years, considerable emphasis has been placed on the development of microsatellites to be used for a variety of objectives. Parental genetic diversity is a crucial requisition to derive desirable and superior progenies from crossing and selection. In order to determine desirable genotypes for hybridization, 710 wheat genotypes from the Novi Sad Core Collection, originating from 38 countries, have been evaluated during the 1993-2000 period. During those seven growth seasons, 54 agronomical, morphological, physiological and other traits have been evaluated in field and controlled conditions. In each year, the field experiment comprised 3-7 replications, while for each field replication the plot size was 1.2 m(2). Based on the results from this evaluation, 96 genotypes with the highest phenotypic variation for 26 of the very important traits for wheat breeding programmes in Yugoslavia and the UK, were identified for screening with microsatellites. A set of 36 microsatellite markers was used, covering all three wheat genomes and all 42 chromosomes. For the 36 microsatellites, a total of 46 loci and 366 alleles were detected, with the average number of 7.96 alleles per locus. For 35 loci, null alleles were detected. The association of microsatellite data with phenotypic data, for 6 important traits for wheat breeding (stem height, earliness, resistance to leaf rust and powdery mildew, sedimentation value and protein content), as well as the potential for their implementation in marker assisted selection (MAS) in wheat breeding programmes for both Yugoslavia and UK are discussed.

Abscisic acid is correlated with the leaf growth inhibition of four genotypes of maize differing in their response to salinity.

In this paper we tested the hypothesis that the leaf growth reduction of salt-stressed maize is regulated by the abscisic acid (ABA) concentrations in the growing zone of the leaf. Leaf elongation rate (LER) of maize (Zea mays L.) was rapidly inhibited by salinity (80 mM NaCl), and the (+)-ABA concentration increased significantly in the growing zone of the leaf. Upon removal of salinity, ABA concentrations decreased rapidly in the growing zone and LER increased to control levels. Four maize genotypes differing in their responses to salinity were compared over a range of leaf ABA concentrations. (+)-ABA concentrations in the growing zone of the leaf were highly correlated with LER inhibition for all four genotypes. However, the sensitivity of LER to leaf ABA concentrations differed amongst the genotypes. Thus, for each genotype, ABA concentrations in the growing zone of the leaf were a good predictor of maize LER response to salinity.

Corrigendum to: Abscisic acid is correlated with the leaf growth inhibition of four genotypes of maize differing in their response to salinity.

In this paper we tested the hypothesis that the leaf growth reduction of salt-stressed maize is regulated by the abscisic acid (ABA) concentrations in the growing zone of the leaf. Leaf elongation rate (LER) of maize (Zea mays L.) was rapidly inhibited by salinity (80 mM NaCl), and the (+)-ABA concentration increased significantly in the growing zone of the leaf. Upon removal of salinity, ABA concentrations decreased rapidly in the growing zone and LER increased to control levels. Four maize genotypes differing in their responses to salinity were compared over a range of leaf ABA concentrations. (+)-ABA concentrations in the growing zone of the leaf were highly correlated with LER inhibition for all four genotypes. However, the sensitivity of LER to leaf ABA concentrations differed amongst the genotypes. Thus, for each genotype, ABA concentrations in the growing zone of the leaf were a good predictor of maize LER response to salinity.