Metabolite variation in the lettuce gene pool: towards healthier crop varieties and food

Introduction

Lettuce (Lactuca sativa L.) is generally not specifically acknowledged for its taste and nutritional value, while its cultivation suffers from limited resistance against several pests and diseases. Such key traits are known to be largely dependent on the ability of varieties to produce specific phytochemicals.

Objectives

We aimed to identify promising genetic resources for the improvement of phytochemical composition of lettuce varieties.

Methods

Phytochemical variation was investigated using 150 Lactuca genebank accessions, comprising a core set of the lettuce gene pool, and resulting data were related to available phenotypic information.

Results

A hierarchical cluster analysis of the variation in relative abundance of 2026 phytochemicals, revealed by untargeted metabolic profiling, strongly resembled the known lettuce gene pool structure, indicating that the observed variation was to a large extent genetically determined. Many phytochemicals appeared species-specific, of which several are generally related to traits that are associated with plant health or nutritional value. For a large number of phytochemicals the relative abundance was either positively or negatively correlated with available phenotypic data on resistances against pests and diseases, indicating their potential role in plant resistance. Particularly the more primitive lettuces and the closely related wild relatives showed high levels of (poly)phenols and vitamin C, thus representing potential genetic resources for improving nutritional traits in modern crop types.

Conclusion

Our large-scale analysis of phytochemical variation is unprecedented in lettuce and demonstrated the ample availability of suitable genetic resources for the development of improved lettuce varieties with higher nutritional quality and more sustainable production.

     

<Emphasis Type="Italic">Trichoderma</Emphasis>-enriched organic fertilizer can mitigate microbiome degeneration of monocropped soil to maintain better plant growth

Background and aims

Given the worldwide effort to improve the nitrogen (N) economy of crops, it is critical to understand the mechanisms of improved N uptake which have resulted from selection pressure for grain yield in Australian wheat (Triticum aestivum L.). Changes in root system traits and N uptake were examined in nine Australian wheat varieties released between 1958 and 2007.

Methods

Wheat varieties were grown in rhizo-boxes in a glasshouse. We measured nitrogen uptake and mapped root growth and proliferation to quantify root length density (RLD), root length per plant, root biomass, specific root length, and plant nitrogen uptake per unit root length.

Results

Selection for yield reduced total RLD and total root length, and increased N uptake per unit root length that overrode the reduction in root system size, effectively explaining the increase in N uptake. Importantly, N uptake in our experiment under controlled conditions matched field measurements, reinforcing the agronomic significance of the present study.

Conclusions

Wheat varieties released in Australia between 1958 and 2007 increased their N uptake, not because of increasing their root length and RLD, but for progressively increasing the efficiency of their root system in capturing N. Our collection of varieties is therefore an interesting model to probe for variation in the affinity of the root system for nitrate.

     

Nutritional quality modulates trait variability

Background

Trait based functional and community ecology is en vogue. Most studies, however, ignore phenotypical diversity by characterizing entire species considering only trait means rather than their variability. Phenotypical variability may arise from genotypical differences or from ecological factors (e.g., nutritionally imbalanced diet), and these causes can usually not be separated in natural populations. We used a single genotype from a parthenogenetic model system (the oribatid mite Archegozetes longisetosus Aoki) to exclude genotypical differences. We investigated patterns of dietary (10 different food treatments) induced trait variation by measuring the response of nine different traits (relating to life history, morphology or exocrine gland chemistry).

Results

Nutritional quality (approximated by carbon-to-nitrogen ratios) influenced all trait means and their variation. Some traits were more prone to variation than others. Furthermore, the “threshold elemental ratio”- rule of element stoichiometry applied to phenotypic trait variation. Imbalanced food (i.e. food not able to fully meet the nutritional demands of an animal) led to lower trait mean values, but also to a higher variation of traits.

Conclusion

Imbalanced food led not only to lower trait value averages, but also to higher trait variability. There was a negative relationship between both parameters, indicating a direct link of both, average trait levels and trait variation to nutritional quality. Hence, variation of trait means may be a predictor for general food quality, and further indicate trade-offs in specific traits an animal must deal with while feeding on imbalanced diets.

     

<Emphasis Type="Bold">Zinc nutrition in wheat-based cropping systems</Emphasis>

Background

Zinc (Zn) deficiency is one of the most important micronutrient disorders affecting human health. Wheat is the staple food for 35% of the world’s population and is inherently low in Zn, which increases the incidence of Zn deficiency in humans. Major wheat-based cropping systems viz. rice–wheat, cotton–wheat and maize–wheat are prone to Zn deficiency due to the high Zn demand of these crops.

Methods

This review highlights the role of Zn in plant biology and its effect on wheat-based cropping systems. Agronomic, breeding and molecular approaches to improve Zn nutrition and biofortification of wheat grain are discussed.

Results

Zinc is most often applied to crops through soil and foliar methods. The application of Zn through seed treatments has improved grain yield and grain Zn status in wheat. In cropping systems where legumes are cultivated in rotation with wheat, microorganisms can improve the available Zn pool in soil for the wheat crop. Breeding and molecular approaches have been used to develop wheat genotypes with high grain Zn density.

Conclusions

Options for improving grain yield and grain Zn concentration in wheat include screening wheat genotypes for higher root Zn uptake and grain translocation efficiency, the inclusion of these Zn-efficient genotypes in breeding programs, and Zn fertilization through soil, foliar and seed treatments.

     

QTL mapping of fruit mineral contents provides new chances for molecular breeding of tomato nutritional traits

Key message

Agronomical characterization of a RIL population for fruit mineral contents allowed for the identification of QTL controlling these fruit quality traits, flanked by co-dominant markers useful for marker-assisted breeding.

Abstract

Tomato quality is a multi-variant attribute directly depending on fruit chemical composition, which in turn determines the benefits of tomato consumption for human health. Commercially available tomato varieties possess limited variability in fruit quality traits. Wild species, such as Solanum pimpinellifolium, could provide different nutritional advantages and can be used for tomato breeding to improve overall fruit quality. Determining the genetic basis of the inheritance of all the traits that contribute to tomato fruit quality will increase the efficiency of the breeding program necessary to take advantage of the wild species variability. A high-density linkage map has been constructed from a recombinant inbred line (RIL) population derived from a cross between tomato Solanum lycopersicum and the wild-relative species S. pimpinellifolium. The RIL population was evaluated for fruit mineral contents during three consecutive growing seasons. The data obtained allowed for the identification of main QTL and novel epistatic interaction among QTL controlling fruit mineral contents on the basis of a multiple-environment analysis. Most of the QTL were flanked by candidate genes providing valuable information for both tomato breeding for new varieties with novel nutritional properties and the starting point to identify the genes underlying these QTL, which will help to reveal the genetic basis of tomato fruit nutritional properties.

     

A QTL located on chromosome 3D enhances the selenium concentration of wheat grain by improving phytoavailability and root structure

Background and aims

As an essential mineral element, selenium (Se) plays a critical role in human health. Given the low concentrations (<100 mg Se kg–1) of Se in staple crops, the identification of genetic resources with enriched Se, as well as the genes controlling Se concentration, is valuable for the marker-assisted selection of Se-rich varieties.

Methods

We determined the chromosomal quantitative trait (QTL) for Se concentration over two consecutive plant growth cycles using recombinant inbred lines (RILs) treated with two different concentrations of Se under both field-grown and hydroponic conditions.

Results

Several QTL for Se concentration were detected across the different treatments. Significant genotypic variation in the tissues of the RIL was found at Se-deficicencycondition. Notably, a QTL located on 3D (interval 214.00–218.00, Qse.sau-3D) affected root length and Se concentration in the leaves and grains, suggesting the existence of the same allele with distinctly different functions. However, the QTL for the agronomic traits measured (plant height, flowering time, and tillering number) and Se concentration were not found to be located on the same chromosomal regions, suggesting that marker-assisted selection for both traits is feasible. Se concentrations in the grains were primarily determined by the mineral transport efficiency of the lines, and the line with the highest Se concentration in the grains always possessed larger, more fibrous root systems. The concentrations of Se in the plant tissues were in the order of: root > stem > grain.

Conclusions

This is the first study to document a Se-rich synthetic wheat line, and root structure and Se grain concentration was strongly affected by QTL located on 3D.

     

Bimodality of stable and plastic traits in plants

Key message

We discovered an unexpected mode of bimodal distribution of stable and plastic traits, which was consistent for homologous traits of 32 varieties of seven species both in well-irrigated fields and dry conditions.

Abstract

We challenged archived genetic mapping data for 36 fruit, seed, flower and yield traits in tomato and found an unexpected bimodal distribution in one measure of trait variability, the mean coefficient of variation, with some traits being consistently more variable than others. To determine the degree of conservation of this distribution among higher plants, we compared 18 homologous phenotypes, including yield and seed production, across different crop species grown in a common ‘crop garden’ experiment. The set included 32 varieties of tomato, eggplant, pepper, melon, watermelon, sunflower and maize. Estimates of canalization were obtained using a ‘canalization replication’ experimental design that generated multiple estimates of the coefficient of variation of traits, as well as their reaction norms in optimal and water-stressed field plots. A common pattern of bimodal distribution of stable and plastic traits was observed for all the varieties and for a wild weed (Solanum nigrum). We propose that canalization profiles of traits in a variety of taxa were ancestrally selected to maximize adaptation and reproductive success.

     

Breeding progress,variation, and correlation of grain and quality traits in winter rye hybrid and population varieties and national on-farm progress in Germany over 26 years

Key message

Grain yield of hybrid varieties and population varieties in official German variety trials increased by 23.3 and 18.1%, respectively, over the last 26 years. On-farm gain in grain yield (18.9%) was comparable to that of population varieties in variety trials, yet at a level considerably lower than in variety trials. Rye quality is subject to large year-to-year fluctuation. Increase in grain yield and decline of protein concentration did not negatively influence quality traits.

Abstract

Performance progress of grain and quality traits of 78 winter rye varieties tested in official German trials to assess the value for cultivation and use (VCU) were evaluated during 1989 and 2014. We dissected progress into a genetic and a non-genetic component for hybrid and population varieties by applying mixed models, including regression components to model trends. VCU trial results were compared with grain yield and quality data from a national harvest survey (on-farm data). Yield gain for hybrid varieties was 23.3% (18.9 dt ha^?1) and for population varieties 18.1% (13.0 dt ha^?1) relative to 1989. On-farm yield progress of 18.9% (8.7 dt ha^?1) was considerably lagging behind VCU trials, and mean yield levels were substantially lower than in field trials. Most of the yield progress was generated by genetic improvement. For hybrid varieties, ear density was the determining yield component, whereas for population varieties, it was thousand grain mass. Results for VCU trials showed no statistically significant gains or losses in rye quality traits. For on-farm data, we found a positive but non-significant gain in falling number and amylogram viscosity and temperature. Variation of grain and quality traits was strongly influenced by environments, whereas genotypic variation was less than 19% of total variation. Grain yield was strongly negatively associated with protein concentration, yet was weakly to moderately positively associated with quality traits. In general, our results from VCU trials and on-farm data indicated that increasing grain yield and decreasing protein concentration did not negatively affect rye quality traits.

     

Assessing the variation and genetic architecture of asparagine content in wheat: What can plant breeding contribute to a reduction in the acrylamide precursor?

Key message

A large genetic variation, moderately high heritability, and promising prediction ability for genomic selection show that wheat breeding can substantially reduce the acrylamide forming potential in bread wheat by a reduction in its precursor asparagine.

Abstract

Acrylamide is a potentially carcinogenic substance that is formed in baked products of wheat via the Maillard reaction from carbonyl sources and asparagine. In bread, the acrylamide content increases almost linearly with the asparagine content of the wheat grains. Our objective was, therefore, to investigate the potential of wheat breeding to contribute to a reduction in acrylamide by decreasing the asparagine content in wheat grains. To this end, we evaluated 149 wheat varieties from Central Europe at three locations for asparagine content, as well as for sulfur content, and five important quality traits regularly assessed in bread wheat breeding. The mean asparagine content ranged from 143.25 to 392.75 mg/kg for the different wheat varieties, thus underlining the possibility to reduce the acrylamide content of baked wheat products considerably by selecting appropriate varieties. Furthermore, a moderately high heritability of 0.65 and no negative correlations with quality traits like protein content, sedimentation volume and falling number show that breeding of quality wheat with low asparagine content is feasible. Genome-wide association mapping identified few QTL for asparagine content, the largest explaining 18% of the genotypic variance. Combining these QTL with a genome-wide prediction approach yielded a mean cross-validated prediction ability of 0.62. As we observed a high genotype-by-environment interaction for asparagine content, we recommend the costly and slow laboratory analysis only for late breeding generations, while selection in early generations could be based on marker-assisted or genomic selection.

     

Impact of the 7-bp deletion in <Emphasis Type="Italic">HvGA20ox2</Emphasis> gene on agronomic important traits in barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis> L.)

Background

Alike to Reduced height-1 (Rht-1) genes in wheat and the semi dwarfing (sd-1) gene in rice, the sdw1/denso locus involved in the metabolism of the GA, was designated as the ‘Green Revolution’ gene in barley. The recent molecular characterization of the candidate gene HvGA20ox2 for sdw1/denso locus allows to estimate the impact of the functional polymorphism of this gene on the variation of agronomically important traits in barley.

Results

We investigated the effect of the 7-bp deletion in exon 1 of HvGA20ox2 gene (sdw1.d mutation) on the variation of yield-related and malting quality traits in the population of DHLs derived from cross of medium tall barley Morex and semi-dwarf barley Barke. Segregation of plant height, flowering time, thousand grain weight, grain protein content and grain starch was evaluated in two diverse environments separated from one another by 15° of latitude. The 7-bp deletion in HvGA20ox2 gene reduced plant height by approximately 13 cm and delayed flowering time by 3–5 days in the barley segregating DHLs population independently on environmental cue. On other hand, the sdw1.d mutation did not affect significantly either grain quality traits (protein and starch content) or thousand grain weight.

Conclusions

The beneficial effect of the sdw1.d allele could be associated in barley with lodging resistance and extended period of vegetative growth allowing to accumulate additional biomass that supports higher yield in certain environments. However, no direct effect of the sdw1.d mutation on thousand grain weight or grain quality traits in barley was detected.

     

Cultivar differences in spatial root distribution during early growth in soil,and its relation to nutrient uptake - a study of wheat,onion and lettuce

Background and aims

A study was made to quantify early root development, soil exploitation and nutrient uptake in spring wheat, onion and lettuce, and their variation among cultivars. The goal was to study genetic variation in root traits making cultivars better adapted to organic production systems or other low-input systems.

Methods

Six cultivars of each species were grown in transparent tubes to allow direct observation of early root growth. The tubes were 0.3 m deep, and 0.24 m in diameter. By placing the plants close to the edge rather than at the centre of the tubes, we could quantify the spatial distribution of the root systems as well as the general root growth and nutrient uptake.

Results

Root growth of wheat and lettuce was faster than root growth of onion, and onion showed little capacity for horizontal root system development. Significant variation in early root growth and horizontal spread of the root system was found among cultivars of all three species. In general, cultivars with strong growth and high volume of soil exploitation showed higher average nutrient concentrations.

Conclusion

Early shoot growth, root growth and nutrient uptake are intrinsically linked, making it difficult to determine whether improved root growth was the primary cause of improved performance. However, we did find cultivars where the strong root growth and superior root distribution seemed to be the driver for improved overall growth.

     

Breeding progress,genotypic and environmental variation and correlation of quality traits in malting barley in German official variety trials between 1983 and 2015

Key message

Evaluation of breeding progress for spring barley varieties in Germany showed that both grain yield and malting quality were considerably improved during the last 33 years, and that genetic effects of protein concentration and malting traits were not associated.

Abstract

Based on historical data, this study aimed to investigate yield potential and malting quality of 187 varieties tested and released in German registration trials to evaluate the value for cultivation and use (VCU) during 1983–2015, and to quantify the environmental variability and the association among traits. We used mixed linear models with multiple linear regression terms to dissect genetic and non-genetic trend components. Grain yield increased by 43% (23.4 dt ha^?1) in VCU trials and 35% (14.0 dt ha^?1) on-farm relative to 1983. All yield components contributed significantly. Malting quality was also considerably improved by 2.3% for extract content up to 25.1% for friability, relative to 1983, nearly completely due to new varieties. Total variability of individual traits was very different between traits (2.4–24.4% relative to 1983). The relative influence of genotypes on total variation was low for grain yield and its components, whereas it was considerably larger for other traits. We found remarkable differences between phenotypic and genetic correlation coefficients for grain yield and protein concentration with malting traits. The observed positive phenotypic relation between grain yield and malting quality can be attributed to a shift of selection and environmental effects, but genetic correlations showed a negative association. Genetic effects of protein concentration and malting quality were not correlated indicating that both were not genetically linked. Considerable yield progress and improvement of malting quality were achieved despite of their weak to moderate negative genetic dependence.

     

Neuronal network analyses reveal novel associations between volatile organic compounds and sensory properties of tomato fruits

Introduction

The process of tomato (Solanum lycopersicum) breeding has affected negatively the fruit organoleptic properties and this is evident when comparing modern cultivars with heirloom varieties. Flavor of tomato fruit is determined by a complex combination of volatile and nonvolatile metabolites that is not yet understood.

Objectives

The aim of this work was to provide an alternative approach to exploring the relationship between tomato odour/taste and volatile organic compounds (VOCs).

Methods

VOC composition and organoleptic properties of seven Andean tomato landraces along with an edible wild species (Solanum pimpinellifolium) and four commercial varieties were characterized. Six hedonic traits were analyzed by a semitrained sensory panel to describe the organoleptic properties. Ninety-four VOCs were analyzed by headspace solid phase microextraction/gas chromatography–mass spectrometry (HS/SPME/GC–MS). The relationship between sensory data and VOCs was explored using an Artificial Neural Networks model (Kohonen Self Organizing Maps, omeSOM).

Results and Conclusion

The results showed a strong preference by panelists for tomatoes of landraces than for commercial varieties and wild species. The predictive analysis by omeSOM showed 15 VOCs significantly associated to the typical and atypical tomato odour and taste. Moreover, omeSOM was used to predict the relationship of VOC ratios with sensory data. A total of 108 VOC ratios out of 8837 VOC ratios were predicted to be contributing to the typical and atypical tomato odour and taste. The metabolic origin of these flavor-associated VOCs and the metabolic point or target for breeding strategies were discussed.

     

Improving the baking quality of bread wheat by genomic selection in early generations

Key message

Genomic selection shows great promise for pre-selecting lines with superior bread baking quality in early generations, 3 years ahead of labour-intensive, time-consuming, and costly quality analysis.

Abstract

The genetic improvement of baking quality is one of the grand challenges in wheat breeding as the assessment of the associated traits often involves time-consuming, labour-intensive, and costly testing forcing breeders to postpone sophisticated quality tests to the very last phases of variety development. The prospect of genomic selection for complex traits like grain yield has been shown in numerous studies, and might thus be also an interesting method to select for baking quality traits. Hence, we focused in this study on the accuracy of genomic selection for laborious and expensive to phenotype quality traits as well as its selection response in comparison with phenotypic selection. More than 400 genotyped wheat lines were, therefore, phenotyped for protein content, dough viscoelastic and mixing properties related to baking quality in multi-environment trials 2009–2016. The average prediction accuracy across three independent validation populations was r = 0.39 and could be increased to r = 0.47 by modelling major QTL as fixed effects as well as employing multi-trait prediction models, which resulted in an acceptable prediction accuracy for all dough rheological traits (r = 0.38–0.63). Genomic selection can furthermore be applied 2–3 years earlier than direct phenotypic selection, and the estimated selection response was nearly twice as high in comparison with indirect selection by protein content for baking quality related traits. This considerable advantage of genomic selection could accordingly support breeders in their selection decisions and aid in efficiently combining superior baking quality with grain yield in newly developed wheat varieties.

     

Rhizoplane microbiota of superior wheat varieties possess enhanced plant growth-promoting abilities

BACKGROUND

Microbes affect the growth of plants. In this study, the diversity and plant growth-supporting activities of wheat rhizospheric bacteria were examined.

METHODS

Sampling was performed thrice at different phases of plant growth. Microbes associated with the rhizoplane of three wheat varieties (Seher, Lasani, and Faisalabad) were cultured and assessed for their plant growth-promoting abilities based on auxin production, hydrogen cyanide production, phosphate solubilization, and nitrogen fixation.

RESULTS

Bacterial load (CFU/mL) declined, and the succession of bacterial diversity occurred as the plants aged. Most auxin-producing bacteria and the highest concentrations of auxin (77 μg/mL) were observed during the second sampling point at the tillering stage. The Seher variety harbored the most auxin-producing as well as phosphate-solubilizing bacteria. Most of the bacteria belonged to Bacillus and Pseudomonas. Planomicrobium, Serratia, Rhizobium, Brevundimonas, Stenotrophomonas, and Exiguobacterium sp. were also found.

CONCLUSION

These results suggest that the rhizoplane microbiota associated with higher-yield plant varieties have better plant growth-promoting abilities as compared to the microbiota associated with lower-yield plant varieties.

     

Co-managing soil and plant pathogens: effects of organic amendments on soil fertility and fungal pathogen survival

Backgrounds and aims

Interactions between plants can be both positive and negative, denoting facilitation and competition. Although facilitative effects of having legume neighbours (focus on yield productivity) are well studied, a better mechanistic understanding of how legumes interact with non-legumes in terms of root distribution is needed. We tested the effects of neighbour identity, its spatial location, as well as the effects of plant order of arrival on above and belowground traits and root distribution.

Methods

We performed a rhizotron experiment (4 weeks duration) in which we grew maize alone, with only a legume, only another grass, or with both species and tracked roots of the plant species using green and red fluorescent markers.

Results

Maize grew differently when it had a neighbour, with reduced development when growing with wheat compared to alone. Growing with a legume generally equated to the same outcome as not having a neighbour. Roots grew towards the legume species and away from the wheat. Order of arrival affected aboveground traits to a certain extent, but its effects on maize roots were dependent on spatial location.

Conclusions

Our study provides evidence of facilitation, showing the importance of the identity of the neighbours, together with their spatial location, and how order of arrival can modulate the outcome of these initial interactions.

     

Accelerating wheat breeding for end-use quality with multi-trait genomic predictions incorporating near infrared and nuclear magnetic resonance-derived phenotypes

Key message

Using NIR and NMR predictions of quality traits overcomes a major barrier for the application of genomic selection to accelerate improvement in grain end-use quality traits of wheat.

Abstract

Grain end-use quality traits are among the most important in wheat breeding. These traits are difficult to breed for, as their assays require flour quantities only obtainable late in the breeding cycle, and are expensive. These traits are therefore an ideal target for genomic selection. However, large reference populations are required for accurate genomic predictions, which are challenging to assemble for these traits for the same reasons they are challenging to breed for. Here, we use predictions of end-use quality derived from near infrared (NIR) or nuclear magnetic resonance (NMR), that require very small amounts of flour, as well as end-use quality measured by industry standard assay in a subset of accessions, in a multi-trait approach for genomic prediction. The NIR and NMR predictions were derived for 19 end-use quality traits in 398 accessions, and were then assayed in 2420 diverse wheat accessions. The accessions were grown out in multiple locations and multiple years, and were genotyped for 51208 SNP. Incorporating NIR and NMR phenotypes in the multi-trait approach increased the accuracy of genomic prediction for most quality traits. The accuracy ranged from 0 to 0.47 before the addition of the NIR/NMR data, while after these data were added, it ranged from 0 to 0.69. Genomic predictions were reasonably robust across locations and years for most traits. Using NIR and NMR predictions of quality traits overcomes a major barrier for the application of genomic selection for grain end-use quality traits in wheat breeding.

     

A combination of stomata deregulation and a distinctive modulation of amino acid metabolism are associated with enhanced tolerance of wheat varieties to transient drought

Introduction

Mediterranean winter crops are commonly and increasingly exposed to irregular rainfall and high temperatures, which lead to transient drought events of different degrees, adversely affecting growth and yield. Hence, exploring the diverse degrees of tolerance to drought existing in the crop and the molecular strategies behind it is pivotal for the development of ad hoc breeding programs.

Objective

We investigated the physiological and metabolic response of six commercial wheat cultivars to transient water stress at the tillering and grain-filling stages.

Methods

Drought experiments in lysimeters were set up at two developmental stages including six wheat cultivars. Newly expanded youngest leaves and flag leaves were sampled during the drought and following recovery. Metabolite profiles were generated using a GC–MS based protocol. Data on transpiration were continually acquired by measuring the weight variation of pots using electronic temperature compensated load cells.

Results

The tillering stage in wheat is more sensitive to droughts than the grain filling stage. The former stage was characterized by pronounced metabolic alterations also during recovery from the drought, and plants exhibited reduced transpiration. Notably, cultivars varied considerably in their susceptibility to drought. Exceptionally only in cv Zahir was transpiration not reduced at tillering. During recovery, the transpiration rate of Yuval and Zahir was not significantly affected, while except Ruta the other varieties maintained lower values. At grain-filling, a moderate decrease in transpiration in response to drought was evident in Bar-Nir, Yuval and Zahir varieties as compared with the stronger response of Gedera, Galil and Ruta. The transpiration trend during recovery remained lower than the control plants, particularly in Gedera and Zahir, while it reached higher values than control plants in Yuval and Ruta varieties. Metabolite profiling of leaves across cultivars showed varietal specific trends of response. Particularly during tillering, amino acid metabolism was differentially regulated across cultivars. For instance, Ruta and Zahir exhibited major changes in central carbon nitrogen metabolism during stress response, accumulating large amounts of proline and threonine during tillering, while in Bar-Nir a general decrease in relative amino acid content was noted. Changes in stress related GABA were common to Galil, Ruta, Yuval and Zahir. Desiccation related raffinose family oligosaccharides were mostly associated with a later stage of grain-filling and recovery stages of response.

Conclusion

The results indicate the occurrence of stage-dependent metabolic diversification along with a physiological response during transient droughts among wheat cultivars. It can be concluded that the most tolerant cultivar was Zahir, where a combination of stomatal closure deregulation and a significant accumulation rate of stress-related metabolites were evident.

     

Discovery of A-type procyanidin dimers in yellow raspberries by untargeted metabolomics and correlation based data analysis

Introduction

Raspberries are becoming increasingly popular due to their reported health beneficial properties. Despite the presence of only trace amounts of anthocyanins, yellow varieties seems to show similar or better effects in comparison to conventional raspberries.

Objectives

The aim of this work is to characterize the metabolic differences between red and yellow berries, focussing on the compounds showing a higher concentration in yellow varieties.

Methods

The metabolomic profile of 13 red and 12 yellow raspberries (of different varieties, locations and collection dates) was determined by UPLC–TOF-MS. A novel approach based on Pearson correlation on the extracted ion chromatograms was implemented to extract the pseudospectra of the most relevant biomarkers from high energy LC–MS runs. The raw data will be made publicly available on MetaboLights (MTBLS333).

Results

Among the metabolites showing higher concentration in yellow raspberries it was possible to identify a series of compounds showing a pseudospectrum similar to that of A-type procyanidin polymers. The annotation of this group of compounds was confirmed by specific MS/MS experiments and performing standard injections.

Conclusions

In berries lacking anthocyanins the polyphenol metabolism might be shifted to the formation of a novel class of A-type procyanidin polymers.

     

Selection for water-soluble carbohydrate accumulation and investigation of genetic × environment interactions in an elite wheat breeding population

Key message

Water-soluble carbohydrate accumulation can be selected in wheat breeding programs with consideration of genetic × environmental interactions and relationships with other important characteristics such as relative maturity and nitrogen concentration, although the correlation between WSC traits and grain yield is low and inconsistent.

Abstract

The potential to increase the genetic capacity for water-soluble carbohydrate (WSC) accumulation is an opportunity to improve the drought tolerance capability of rainfed wheat varieties, particularly in environments where terminal drought is a significant constraint to wheat production. A population of elite breeding germplasm was characterized to investigate the potential for selection of improved WSC concentration and total amount in water deficit and well-watered environments. Accumulation of WSC involves complex interactions with other traits and the environment. For both WSC concentration (WSCC) and total WSC per area (WSCA), strong genotype × environment interactions were reflected in the clear grouping of experiments into well-watered and water deficit environment clusters. Genetic correlations between experiments were high within clusters. Heritability for WSCC was larger than for WSCA, and significant associations were observed in both well-watered and water deficit experiment clusters between the WSC traits and nitrogen concentration, tillering, grains per m², and grain size. However, correlations between grain yield and WSCC or WSCA were weak and variable, suggesting that selection for these traits is not a better strategy for improving yield under drought than direct selection for yield.