Root traits and stable isotopes as phenotyping approaches to enhance wheat adaptation to Mediterranean conditions

[eng] Wheat is a major staple food worldwide. Its cultural and economic importance is mainly highlighted in the Mediterranean region, among other regions of the world. However, wheat production is frequently challenged by environmental factors such as interannual variability in precipitation and temperatures, which translates in further shortage in water and nutrients availability. These environmental events are expected to worsen even more in the near future. Therefore, tailoring wheat cultivars that are simultaneously climate-resilient and high yielding under Mediterranean growing conditions is becoming a main focus of breeders and researchers. To this end, the main objective of the present dissertation was to identify ideotypic characteristics of wheat cultivars grown under different Mediterranean conditions through the implementation of diverse phenotyping approaches, targeting the aboveground biomass using remote and proximate sensing techniques, and the belowground biomass using shovelomics and soil coring techniques. These phenotypical platforms were further combined with stable isotopes as physiological traits assessing water and nitrogen status in different plant tissues and soil profile, as well as crop growth traits, mainly phenology, biomass and plant height, and yield components to assess potential traits to breed for in the selected idiotypic traits. Overall, phenology had a clear role in drought adaptation under the Mediterranean conditions, under wet seasons phenological durations were longer in high yielding genotypes, whereas under dry seasons, shorter days to anthesis followed by longer grain filing period were the characteristics shown by high yielding genotypes. Furthermore, predictive models integrated water status indicators (carbon isotope composition (dti3C) and canopy temperature depression (CTD)) as main explicative variables to grain yield, followed by root traits and nitrogen status. The best yielding genotypes were associated with shorter days to heading, better water status mainly through lower dti3C and higher CTD, and higher nitrogen status as demonstrated through higher growth traits (plant height and biomass), delayed senescence (higher stay green status), but also to deeper root development as shown by lower dti8O and d2H, thinner roots and root biomass distribution across soil profile. These traits altogether provided the needs in water ad nutrient sources for plant growth, and translated to higher growth, longer grain filling, better photosynthesis activities and therefore higher productivity. Furthermore, depending on water availability (irrigation vs rainfed), roots traits in the upper soil demonstrated a plastic response to their targeted environment. When support irrigation is supplied, the best yielding genotypes exhibited a dual root development with a shallower root angle and thin roots that explore the superficially and in deeper soil sections for water and nutrients capturing. In contrast, under rainfed conditions, a deep rooting is observed with steeper root angle, and thinner roots with are thinner with tendencies to extract water from deeper soil levels. Moreover, oxygen (dti8O) and hydrogen (d2H) isotope analyses of different plant tissues demonstrated similar fractionation pattern associated with evaporative processes in water tissues, whereas in the organic matter of the plant tissues, variations in dti8O were driven by evaporation, and variations in d2H values in tissues were associated with plant trophism. Chapters along this work highlighted the advantages and the limitations of shoot and root phenotyping techniques and proposed the stable isotopes as potential phenotyping traits to consider in breeding programs under Mediterranean conditions.[spa] El trigo es un cultivo dominante en el mundo. Su importancia cultural y económica se destaca principalmente en la región Mediterránea, particularmente por lo que se refiere al trigo duro. Sin embargo, la producción del trigo está sujeta con frecuencia a diferentes factores ambientales tal como la variabilidad interanual de las precipitaciones y las temperaturas, lo que se traduce en una escasez de agua. Además, diversos modelos climáticos pronostican que estos eventos ambientales van a empeorar más en el futuro cercano, por lo tanto, desarrollar nuevos cultivares de trigo que muestran una adaptación a la sequía y elevadas temperaturas y que mantengan rendimientos altos en condiciones de cultivo Mediterráneas, permanece en el foco principal de atención de los mejoradores y fisiólogos vegetales. Con este fin, el objetivo principal de la presente tesis ha sido identificar las características ideoIpicas de los cultivares de trigo harinero y duro crecidos en diferentes condiciones Mediterráneas. Para tal fin, se implementó un conjunto de plataformas de fenotipado con el objetivo de evaluar las características de biomasa aérea mediante técnicas de teledetección remota y próxima, y las características de raíces empleando técnicas de fenotipado para su extracción de raíces. Además, se midieron los isotopos estables en diferentes partes de la planta para evaluar tanto el estado hídrico (composición isotópica de carbono) y de nitrógeno (composición isotópica de nitrógeno) del cultivo, como el funcionamiento de las raíces para extraer el agua (composiciones isotópicas de oxígeno e hidrogeno). Los parámetros que se deducen de estas técnicas de fenotipados se combinaron con aquellos de crecimiento (fenología, biomasa y altura de planta) y de los componentes del rendimiento para identificar unas características ideotipicas con alta capacidad de adaptarse a los escenarios Mediterráneos que contribuyan a desarrollar cultivares con alto rendimiento y que estén mejor adaptados a los retos climáticos futuros. En general, la fenología tuvo un papel evidente frente a la adaptación ambiental, además, dependiendo de la temporada de cultivo, los genotipos que rindieron mejor mostraron duraciones de fenología más extendidos durante temporadas húmedas, en cambio, durante temporadas secas, los genotipos con el rendimiento más alto mostraron unas duraciones de días a floración más cortas, seguidas por una duración de llenado de grano más extendida. Además, los modelos de predicción integraron el estado hídrico (a través de la composición isotópica de carbono (dti3C) y la temperatura del dosel vegetal (CTD)) como el factor principal afectando al rendimiento final, seguido por las características de las raíces y el estado de nitrógeno. Los mejores genotipos mostraron menos días entre la siembra al espigado, con un periodo de llenado de granos más largo, y se asociaron a mejores estados hídrico (menor dti3C y mayor CTD) y nitrogenado (mayor altura de plantas y biomasa), asociados a raíces más profundas (menor dti8O y d2H), lo que ha contribuido en un mejor desarrollo de la parte aérea a través de proporcionar mejor extracción de recursos hídricos y de nutrientes. Como consecuencia, estos genotipos mostraron una senescencia retrasada (mejor estado stay green), mayor biomasa aérea y crecimiento y por lo tanto mejores componentes de rendimiento y productividad de granos. Además, las características de las raíces en la capa superficial del suelo han sido afectadas por el manejo de cultivos y variabilidad estacional, debido a la alta plasticidad de este órgano, tal como se ha mostrado con el ángulo de la raíz. Aún así, se puede concluir que, bajo condiciones de riego, los genotipos con mejor rendimiento mostraron un desarrollo de raíz a la vez superficial y más profundo, con raíces más finas para explorar mayor espacio se suelo y extraer agua y nutrientes de forma más eficiente. Sin embargo, bajo condiciones de sequía, los genotipos con mejor rendimiento mostraron ángulos radiculares más cerrados, con raíces más finas lo que sugiere una tendencia a extraer el agua de secciones de suelo más profundas. Además, el análisis de las composiciones isotópicas de oxígeno (dti8O) e hidrogeno (d2H) en diferentes tejidos de la planta mostraron unos procesos de fraccionamiento parecidos en el agua de tejidos, debido a efectos evaporativos. En cambio, en la materia orgánica de tejidos, estos isótopos se comportaron de forma distinta. Las variaciones en la firma isotópica del oxígeno (dti8O) quedaron afectadas por la evaporación, mientras que en la del hidrogeno (d2H), el fraccionamiento se asoció al trofismo de la planta. Finalmente, indicar que los diferentes capítulos que se exponen en esta Tesis han destacado las capacidades y las limitaciones de las técnicas de fenotipado aéreo y de raíces, a la vez que apoyan el empleo de los isótopos estables en los programas de mejora de cultivos en condiciones mediterráneas

Agronomical and analytical trait data assessed in a set of quinoa genotypes growing in the UAE under different irrigation salinity conditions

The importance of quinoa has been emphasized considerably in the recent decades, as a highly nutritional crop seed that is tolerant to salinity and amenable to arid agronomical conditions. The focus of this paper is to provide raw and a supplemental data of the research article entitled "Agronomic performance of irrigated quinoa in desert areas: comparing different approaches for early assessment of salinity stress" [1], aiming to compare different approaches for early detection, at the genotypic and crop levels, of the effect of salinity caused by irrigation on the agronomic performance of this crop. A set of 20 genotypes was grown under drip irrigation in sandy soil, amended with manure, at the International Center for Biosaline Agriculture (UAE) for two weeks, after which half of the trial was submitted to irrigation with saline water and this was continued until crop maturity. After eight weeks of applying the two irrigation regimes, pigment contents were evaluated in fully expanded leaves. The same leaves were then harvested, dried and the stable carbon and nitrogen isotope compositions (δ13C and δ15N) and the total nitrogen and carbon contents of the dry matter analyzed, together with ion concentrations. At maturity yield components were assessed and yield harvested. Data analysis demonstrated significant differences in genotypes response under each treatment, within all assessed parameters. The significant level was provided using the Tukey-b test on independent samples. The present dataset highlights the potential use of different approaches to crop phenotyping and monitoring decision making

Dataset of above and below ground traits assessed in Durum wheat cultivars grown under Mediterranean environments differing in water and temperature conditions

Ideotypic characteristics of durum wheat associated with higher yield under different water and temperature regimes were studied under Mediterranean conditions. The focus of this paper is to provide raw and supplemental data from the research article entitled "Durum wheat ideotypes in Mediterranean environments differing in water and temperature conditions" [1], which aims to define specific durum wheat ideotypes according to their responses to different agronomic conditions. In this context, six modern (i.e. post green revolution) genotypes with contrasting yield performance (i.e. high vs low yield) were grown during two consecutive years under different treatments: (i) winter planting under support-irrigation conditions, (ii) winter planting under rainfed conditions, (iii) late planting under support-irrigation. Trials were conducted at the INIA station of Colmenar de Oreja (Madrid). Different traits were assessed to inform about water status (canopy temperature at anthesis and stable carbon isotope composition (delta C-13) of the flag leaf and mature grains), root performance (root traits and the oxygen isotope composition (delta O-18) in the stem base water), phenology (days from sowing to heading), nitrogen status/photosynthetic capacity (nitrogen content and stable isotope composition (delta N-15) of the flag leaf and mature grain together with the pigment contents and the nitrogen balance index (NBI) of the flag leaf), crop growth (plant height (PH) and the normalized difference vegetation index (NDVI) at anthesis), grain yield and agronomic yield components. For most of the parameters assessed, data analysis demonstrated significant differences among genotypes within each treatment. The level of significance was determined using the Tukey-b test on independent samples, and ideotypes were modelled from the results of principle component analysis. The present data shed light on traits that help to define specific ideotype characteristics that confer genotypic adaptation to a wide range of agronomic conditions produced by variations in planting date, water conditions and seasonThis study was supported by the Spanish projects PID2019-106650RB-C21 and PCIN-2017-063, from the Ministerio de Ciencia e Innovacion, Spain. FZR is a recipient of a research grant (FI-AGAUR) sponsored by the Agency for Management of University and Research Grants (AGAUR) in collaboration with the University of Barcelona (UB) . We thank the personnel from the exper-imental station of INIA at Colmenar de Oreja (Aranjuez) for their continued support of our re-search. We thank the members of the Integrative Crop Ecophysiology Group for their assistance during the data assessment of the study. We extend our thanks to The Water Research Institute (IdRA) for their financial support to cover laboratory analyses. JLA acknowledges support from ICREA Academia, Generalitat de Catalunya, Spain. We thank Dr. J.Voltas from the University of Lleida, Spain, for his support with the delta 18O water analyses

Remote sensing techniques and stable isotopes as phenotyping tools to assess wheat yield performance: effects of growing temperature and vernalization

This study compares distinct phenotypic approaches to assess wheat performance under different growing temperatures and vernalization needs. A set of 38 (winter and facultative) wheat cultivars were planted in Valladolid (Spain) under irrigation and two contrasting planting dates: normal (late autumn), and late (late winter). The late plating trial exhibited a 1.5 °C increase in average crop temperature. Measurements with different remote sensing techniques were performed at heading and grain filling, as well as carbon isotope composition (δ13C) and nitrogen content analysis. Multispectral and RGB vegetation indices and canopy temperature related better to grain yield (GY) across the whole set of genotypes in the normal compared with the late planting, with indices (such as the RGB indices Hue, a* and the spectral indices NDVI, EVI and CCI) measured at grain filling performing the best. Aerially assessed remote sensing indices only performed better than ground-acquired ones at heading. Nitrogen content and δ13C correlated with GY at both planting dates. Correlations within winter and facultative genotypes were much weaker, particularly in the facultative subset. For both planting dates, the best GY prediction models were achieved when combining remote sensing indices with δ13C and nitrogen of mature grains. Implications for phenotyping in the context of increasing temperatures are further discussed

Defining durum wheat ideotypes adapted to Mediterranean environments through remote sensing traits

An acceleration of the genetic advances of durum wheat, as a major crop for the Mediterranean region, is required, but phenotyping still represents a bottleneck for breeding. This study aims to define durum wheat ideotypes under Mediterranean conditions by selecting the most suitable phenotypic remote sensing traits among different ones informing on characteristics related with leaf pigments/photosynthetic status, crop water status, and crop growth/green biomass. A set of 24 post–green revolution durum wheat cultivars were assessed in a wide set of 19 environments, accounted as the specific combinations of a range of latitudes in Spain, under different management conditions (water regimes and planting dates), through 3 consecutive years. Thus, red–green–blue and multispectral derived vegetation indices and canopy temperature were evaluated at anthesis and grain filling. The potential of the assessed remote sensing parameters alone and all combined as grain yield (GY) predictors was evaluated through random forest regression models performed for each environment and phenological stage. Biomass and plot greenness indicators consistently proved to be reliable GY predictors in all of the environments tested for both phenological stages. For the lowest-yielding environment, the contribution of water status measurements was higher during anthesis, whereas, for the highest-yielding environments, better predictions were reported during grain filling. Remote sensing traits measured during the grain filling and informing on pigment content and photosynthetic capacity were highlighted under the environments with warmer conditions, as the late-planting treatments. Overall, canopy greenness indicators were reported as the highest correlated traits for most of the environments and regardless of the phenological moment assessed. The addition of carbon isotope composition of mature kernels was attempted to increase the accuracies, but only a few were slightly benefited, as differences in water status among cultivars were already accounted by the measurement of canopy temperature

Durum wheat ideotypes in Mediterranean environments differing in water and temperature conditions

Ideotypic characteristics of durum wheat associated with higher yield under different water and temperature regimes were studied under Mediterranean conditions. Six semi-dwarf cultivars with contrasting agronomic performance were grown during two consecutive years under winter-planted rainfed and winter-planted support-irrigation conditions and a late-planting trial under support irrigation, at the INIA station of Colmenar de Oreja (Madrid). Different traits were assessed to inform on: water status, root performance, phenology, photosynthetic capacity, crop growth, grain yield and agronomic yield components. Under support irrigation and normal planting, genotypes with higher grain yield exhibited better water status (lower δ13C and canopy temperature), assimilation of more superficial water (higher δ18O), earlier heading and greater plant height and ear density. Under water-limited conditions (rainfed), the best genotypes also exhibited better water status (lower δ13C) and earlier heading, but higher specific root length with extraction of water from deeper soil layers (lower δ18O), more efficient N metabolism (higher δ15N and NBI) and consequently stronger growth (plant height and NDVI), and greater ear density and thousand grain weight. Under warmer conditions (late planting), the best genotypes also exhibited better water status (lower δ13C) and greater plant height and photoprotective mechanisms (higher flavonoid content and lower chlorophyll content). However, the strong differences in drought between consecutive years determined other specific ideotypic traits within each of the three growing conditions and the particular year. Our study suggests specific ideotypes when breeding durum wheat under different agronomic scenarios, but also stresses that interannual variation in water conditions, typical of Mediterranean conditions, should be taken into account

Effect of irrigation salinity and ecotype on the growth, physiological indicators and seed yield and quality of Salicornia europaea

The euhalophyte species Salicornia europaea is cultivated for oilseed and as a fodder crop in various parts of the world. In saline coastal environments it possesses great potential for the subsistence of the most disadvantaged farmers. We investigated the effect of salinity levels in irrigation water on the germination capacity, shoot biomass and seed productivity as well as diverse quality traits (nitrogen content in shoots and seeds and fatty acids, in seeds) and physiological traits (stable carbon and nitrogen isotopes and ion content) of two accessions collected in the United Arab Emirates (UAE). The three salinity levels tested were irrigation with fresh water (0.3 dS m−1), brackish water (25 dS m−1) and sea water (40 dS m−1). In addition, a hypersaline condition (80 dS m−1) was also tested for germination. The best germination rates were achieved with seeds exposed to fresh and brackish water, while imbibition with sea water decreased germination by half and hypersaline water inhibited it almost totally. However, the best irrigation regime in terms of biomass and seed yield involved brackish water. Moreover, rising salinity in the irrigation increased the stable isotope composition of carbon (δ13C) and nitrogen (δ15N), together with the Na+ and K+ of shoots and seeds, and the lipid levels of seeds, while the total nitrogen content and the profile of major fatty acids of seeds did not change. Differences between the two ecotypes existed for growth and seed yield with the best ecotype exhibiting lower δ13C and higher K+ in both shoots and seeds, lower Na+ and higher δ15N in shoots, and lower N in seeds, together with differences in major fatty acids. Physiological mechanisms behind the response to irrigation salinity and the ecotypic differences are discussed in terms of photosynthetic carbon and nitrogen metabolism

Heterosis and reciprocal effects for physiological and morphological traits of popcorn plants under different water conditions

In spite of the benefits of heterosis in maize breeding, little is known about the physiological mechanisms of this phenomenon and its genetic control under different water regimes. This study aimed to understand the heterosis effects on plant growth, the photosynthetic and transpiration traits, and the root traits of four inbred popcorn lines and their hybrids, including their reciprocal combinations. Plants were grown in lysimeters, inside a rain shelter, under two water conditions (water stress - WS; well-watered - WW) until anthesis. Plant growth traits included shoot biomass, plant height, and leaf area. Photosynthetic traits comprised leaf pigment and total nitrogen content, chlorophyll fluorescence, gas exchange, water use efficiency and stomatal index and density, along with the stable carbon (δ13C) and nitrogen (δ15N) isotope compositions of the last developed leaf. Root weight density and specific root length were also recorded. Greater heterosis effects were observed for traits related to plant growth and root weight density, and specifically under WS. Traits related to root weight density in deeper soil layers benefited markedly from heterosis, but there were no advantages in terms of stomatal conductance and water status in general. Apparently, only δ13C supported a better water status under WS, and was observed in the hybrids in particular. Non-additive gene effects were predominant in controlling of most of the growth and root traits studied, supporting the conclusion that the heterosis effect is especially favorable under water-limiting conditions. Moreover, the choice of the female parent is essential for traits related to gas exchange when breeding for better resilience to drought