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In Chile, durum wheat is cultivated in high-yielding Mediterranean environments, therefore breeding programs have selected cultivars with high yield potential in addition to grain quality. The genetic progress in grain yield (GY) between 1964 and 2010 was 72.8 kg ha−1 per year. GY showed a positive and significant correlation with days to heading, kernels per unit ground area and thousand kernel weight. The gluten and protein content tended to decrease with the year of cultivar release. The correlation between the δ13C of kernels and GY was negative and significant (−0.62, p < 0.05, for all cultivars; and −0.97, p < 0.001, excluding the two oldest cultivars). The yield progress (genetic plus agronomic improvements) of a set of 40−46 advanced lines evaluated between 2006 and 2015 was 569 kg ha−1 per year. Unlike other Mediterranean agro-environments, a longer growing cycle together with taller plants seems to be related to the increase in the GY of Chilean durum wheat during recent decades.

This study evaluates the changes caused by breeding in the genotype by environment (G × E) interaction of the durum wheat varieties most widely cultivated in Spain after the Green Revolution. A set of 12 cultivars was tested in 27 environments, which are understood as the combination of different sites, years, and treatments (water regime and planting dates), representative of the durum wheat growing conditions in Spain with average grain yields (GY) ranging between 2.8 and 9.1 Mg ha−1. The most important environmental factors affecting the G × E interaction for yield were themaximum and the mean temperature during the entire crop cycle. An improvement in genetic yield was observed in warm environments and under optimal water conditions that resemble those where the germplasm originated (essentially as advanced lines) before its release in Spain. Therefore, the adaptation of semi-dwarf durum in Spain has shown a tendency to specific adaptation rather than large-scale adaptation. Two different patterns of selection have been reported due the G × E interaction and changes in the ranking of genotypes: in the high yielding environments (GY > 5 Mg ha−1), plants favor increased water uptake, with higher levels of transpiration and more open stomata (more negative values of carbon isotope composition, δ13C, and higher canopy temperature depression, CTD), whereas, in low yielding environments (GY < 5 Mg ha−1) plants close their stomata and favor greater water use efficiency (less negative δ13C values and lower CTD values).

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 (δ13C) of the flag leaf and mature grains), root performance (root traits and the oxygen isotope composition (δ18O) in the stem base water), phenology (days from sowing to heading), nitrogen status/photosynthetic capacity (nitrogen content and stable isotope composition (δ15N) 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 season.

Durum wheat production is seriously threatened by Fusarium head blight (FHB) attacks in Tunisia, and the seed coating by bio-agents is a great alternative for chemical disease control. This study focuses on evaluating, under field conditions, the effect of seed coating with Trichoderma harzianum, Meyerozyma guilliermondii and their combination on (i) FHB severity, durum wheat grain yield and TKW in three crop seasons, and (ii) on physiological parameters and the carbon and nitrogen content and isotope composition in leaves and grains of durum wheat. The results indicated that the treatments were effective in reducing FHB severity by 30 to 70% and increasing grain yield with an increased rate ranging from 25 to 68%, compared to the inoculated control. The impact of treatments on grain yield improvement was associated with higher NDVI and chlorophyll content and lower canopy temperature. Furthermore, the treatments mitigated the FHB adverse effects on N and C metabolism by resulting in a higher δ13Cgrain (13C/12Cgrain) and δ15Ngrain (15N/14Ngrain). Overall, the combination outperformed the other seed treatments by producing the highest grain yield and TKW. The high potency of seed coating with the combination suggests that the two microorganisms have synergetic or complementary impacts on wheat.

Coating seeds with bio-control agents is a potentially effective approach to reduce the usage of pesticides and fertilizers applied and protect the natural environment. This study evaluated the effect of seed coating with Meyerozyma guilliermondii, strain INAT (MT731365), on seed germination, plant growth and photosynthesis, and plant resistance against Fusarium culmorum, in durum wheat under controlled conditions. Compared to control plants, seed coating with M. guilliermondii promoted the wheat growth (shoot and roots length and biomass), and photosynthesis and transpiration traits (chlorophyll, ɸPSII, rates of photosynthesis and transpiration, etc.) together with higher nitrogen balance index (NBI) and lower flavonols and anthocyanins. At 21 days post infection with Fusarium, M. guilliermondii was found to reduce the disease incidence and the severity, with reduction rates reaching up to 31.2% and 30.4%, respectively, as well as to alleviate the disease damaging impact on photosynthesis and plant growth. This was associated with lower ABA, flavonols and anthocyanins, compared to infected control. A pivotal function of M. guilliermondii as an antagonist of F. culmorum and a growth promoter is discussed.

Knowledge of the function of the ear as a key organ in the uptake, remobilization and partitioning of nitrogen is essential for understanding its contribution to grain filling and thus guiding future breeding strategies. In this work, four Chinese winter wheat genotypes were grown on a 15N-enriched nutrient solution. N absorption and further remobilization to the flag leaf, the ear and the mature grains were calculated via the 15N atom % excess. The results indicated that the high yields of the Chinese wheat genotype were determined by higher grain numbers per ear, with greater plant height and a larger ear size, while the thousand-grain weight did not affect grain yield. In the mature grains, 66.7% of total N was remobilized from the pre-anthesis accumulation in the biomass, while the remaining 33.3% was derived from the N taken up during post-anthesis. From anthesis to 2 weeks after the anthesis stage, the flag leaf remobilized 3.67 mg of N outwards and the ear remobilized 3.87 mg of N inwards from the pre-anthesis accumulation in each plant. The positive correlation between ear Nrem and grain Nrem indicated that the ear was an important organ for providing N to the grain, whereas the remobilized N stream from the leaves was not correlated with grain Nrem, thus indicating that flag leaf N was not translocated directly to the grain. The grain Nrem was negatively correlated with the ear N concentration throughout grain filling, which suggested that higher-yielding genotypes had better sink activity in the ear, while Rubisco played a critical role in N deposition. Therefore, to improve yield potential in wheat, the N accumulation in the ear and the subsequent remobilization of that stored N to the grains should be considered. N accumulation and remobilization in the ear may at least be valuable for Chinese breeding programs that aim at optimizing the sink/source balance to improve grain filling.

Septoria leaf blotch (SLB) is considered one of the most devastating diseases affecting global wheat production. Biostimulant application is among the modern approaches in plant protection to overcome the impact of SLB’s fungicide resistance. In this manner, the effect of coating seeds with thyme essential oil or Paraburkholderia phytofirmans PsJN strain on SLB severity and yield components (spikes/m2, straw yield (SY), grain yield (GY) and thousand kernel weight (TKW)) were assessed under field conditions for 3 years. The effect on physiological traits and nitrogen and carbon isotope composition (δ15Ngrain, δ13Cgrain) and nitrogen and carbon content (Ngrain, Cgrain) of grains was assessed in one year of study. The increasing SLB severity decreased all yield components, increased δ15Ngrain and Cgrain content and slightly decreased δ13Cgrain as the resulting effect of Zymoseptoria tritici inducing stomatal opening and leaf necrosis. Across the years, both treatments alleviated the SLB adverse impact by reducing SLB severity, increasing spikes/m2, SY, GY and TKW. Both treatments ameliorated grain quality by increasing Cgrain content and decreasing δ13Cgrain and δ15Ngrain. The difference between the performance of thyme oil or PsJN strain in terms of intensity and stability is discussed and considered to be linked to the different triggered systemic resistance and the associated amount of costs deriving from resource allocation towards defense processes.

Coating seeds with biostimulants is among the promising approaches in crop production to increase crop tolerance to drought stress. In this study, we evaluated the potential of coating durum wheat seeds of the cultivar ‘Karim’ with thyme essential oil on enhancing seed germination and seedling growth, and on plant growth promotion and induction of drought resistance. Coated seeds were pre-germinated, grown in hydroponics, and grown in pots under controlled well-watered and progressive water/nutrient stress conditions. Seed coating with thyme oil increased germination rate and enhanced seedling growth development in hydroponics. In the pot experiment, thyme oil increased, when well watered, root and shoot development, chlorophyll, nitrogen balance index (NBI), abscisic acid (ABA), anthocyanins and flavonoids in leaves, decreased nitrogen isotope composition (δ15N) and increased carbon isotope composition (δ13C) of shoots. Increasing water/nutrient stress in control plants induced higher accumulation of ABA and anthocyanins coupled with a transient decrease in chlorophyll and NBI, a decrease in shoot and root development, the Normalized Difference Vegetation Index (NDVI), shoot C content, δ15N, and an increase in δ13C, revealing the avoidance strategy adopted by the cultivar. Thyme oil had the potential to enhance the avoidance strategy by inducing roots elongation, reducing the loss of shoot and roots dry matter and chlorophyll, maintaining balanced NBI, an decreasing anthocyanins, flavonoids, and δ13C via maintaining lower ABA-mediated-stomatal closure. Thyme oil increased shoot N content and δ15N indicating preferential uptake of the 15N enriched NH4+. Coating seeds with thyme oil is suggested as a promising alternative approach to improve plant’s water and nutrient status and to enhance drought resistance.

Vegetation indices and canopy temperature are the most usual remote sensing approaches to assess cereal performance. Understanding the relationships of these parameters and yield may help design more efficient strategies to monitor crop performance. We present an evaluation of vegetation indices (derived from RGB images and multispectral data) and water status traits (through the canopy temperature, stomatal conductance and carbon isotopic composition) measured during the reproductive stage for genotype phenotyping in a study of four wheat genotypes growing under different water and nitrogen regimes in north Algeria. Differences among the cultivars were reported through the vegetation indices, but not with the water status traits. Both approximations correlated significantly with grain yield (GY), reporting stronger correlations under support irrigation and N-fertilization than the rainfed or the no N-fertilization conditions. For N-fertilized trials (irrigated or rainfed) water status parameters were the main factors predicting relative GY performance, while in the absence of N-fertilization, the green canopy area (assessed through GGA) was the main factor negatively correlated with GY. Regression models for GY estimation were generated using data from three consecutive growing seasons. The results highlighted the usefulness of vegetation indices derived from RGB images predicting GY.