Ionomic and metabolic responses of wheat seedlings to PEG-6000-simulated drought stress under two phosphorus levels

Exploring drought tolerance for germination traits of diverse wheat genotypes at seedling stage: a multivariate analysis approach

Wheat holds crucial global importance as a staple food in many regions. Drought stress significantly impedes seed germination of wheat. The lack of drought-tolerant wheat varieties hampers wheat production, especially in arid regions of the world. This study investigated seed germination and seedling growth in eighty wheat genotypes under moisture stress stimulated by polyethylene glycol (PEG6000). The study included two osmotic potentials induced by PEG-20% (ψ: -0.491 MPa) and PEG-25% (ψ: -0.735 MPa), as well as a control set without PEG. The data showed that dehydration caused by polyethylene glycol generally had an adverse effect on the morphological characteristics of wheat seedlings by causing substantial losses during the early germination stage. The results acquired from analysis of variance explained highly significant variances (p < 0.01) across genotypes (G), PEG-Treatments (TPEG), and interactions between genotypes and PEG-Treatments (G x TPEG) for all observed variables. Moisture deficit radically affected all studied seedling traits of bread wheat under rising osmotic stress, with germination percentage (GP), shoot length (SL), root length (RL), coleoptile length (CL), seedling length (SDL), root fresh weight (FRW), root dry weight (DRW), shoot fresh weight (FSW), shoot dry weight (DSW), seedling biomass (SBM) and seedling vigor index (SVI) reduced by about 30-95% compared to control (PEG-0%) to the maximum induced osmotic stress at -0.735 MPa. The coefficient of relative inhibition (CRI) rose in response to osmotic stress, demonstrating growth inhibition. Boxplots demonstrated a considerable decline under stress, although scatter plots and correlation matrices revealed significant positive associations for most seedling traits, except CRI. The histograms for most variables showed a wider value range and more diversified distribution patterns. Principal component analysis (PCA) and genotype by trait biplot emphasized that PC1 represented 94.29% of the cumulative variation, with an eigenvalue of 11.31 out of 12 components. The heatmap displayed diverse genotype and trait characteristics, indicating higher values for drought resistance and lower values for susceptibility in genotype performance. As indicated by a range of multivariate analyses, the wheat lines NR-499, NARC-2009 and Pakistan-2013 stood out as the most drought-tolerant among the genotypes; whereas Borlaug-2016, NR-514 and NR-516 were found to be highly susceptible, whereas SBM, SDL, SVI and CRI have been found key indicators for subsequent screening. These tolerant wheat lines offer promising potential for developing drought-tolerant varieties that could thrive in arid regions, thereby strengthening wheat production in water-stressed environments. Integrating these findings into breeding programs is crucial for realizing the potential of drought-tolerant wheat varieties in transforming global wheat production.

Study of the genetic variability of durum wheat (Triticum durum Desf.) in the face of combined stress: water and heat

The devastating effects and extent of abiotic stress on cereal production continue to increase globally, affecting food security in several countries, including Tunisia. Heat waves and the scarcity of rainfall strongly affect durum wheat yields. The present study aims to screen for tolerance to combined water and heat stresses in durum wheat at the juvenile stage. Three combined treatments were tested, namely: T0 (100% field capacity (FC) at 24 °C), T1 (50% FC at 30 °C), and T2 (25% FC at 35 °C). The screening was carried out based on morphological, physiological, and biochemical criteria. The results showed that the combined stress significantly affected all the measured parameters. The relative water content (RWC) decreased by 37.6% under T1 compared to T0. Quantum yield (Fv/m) and photosynthetic efficiency (Fv/0) decreased under severe combined stress (T2) by 37.15% and 37.22%, respectively. Under T2 stress, LT increased by 63.7%. A significant increase in osmoprotective solutes was also observed, including proline, which increased by 154.6% under T2. Correlation analyses of the combination of water and heat stress confirm that the traits RWC, chlorophyll b content, Fv/m, proline content, Fv/0 and leaf temperature can be used as reliable screening criteria for the two stresses combined. The principal component analysis highlighted that Aouija tolerates the two levels of stresses studied, while the genotypes Karim and Hmira are the most sensitive. The results show that the tolerance of durum wheat to combined water and heat stress involves several adaptation mechanisms proportional to the stress intensity.

The opportunity of using durum wheat landraces to tolerate drought stress: screening morpho-physiological components

Local genetic resources could constitute a promising solution to overcome drought stress. Thus, eight (8) durum wheat landraces and one improved variety were assessed for drought tolerance in pots under controlled conditions. Three water treatments were tested: control (100 % of the field capacity (FC)), medium (50 % FC) and severe (25 % FC) stress. The assessment was carried out at the seedling stage to mimic stress during crop set-up. Results showed that increased water stress led to a decrease in biomass and morpho-physiological parameters and an increase in antioxidant enzyme activities. Severe water stress decreased the chlorophyll fluorescence parameters, relative water content (RWC) and water potential of the investigated genotypes by 56.45, 20.58, 50.18 and 139.4 %, respectively. Besides, the phenolic compounds content increased by 169.2 % compared to the control. Catalase and guaiacol peroxidase activities increased 17 days after treatment for most genotypes except Karim and Hmira. A principal component analysis showed that the most contributed drought tolerance traits were chlorophyll fluorescence parameters, RWC and electrolyte conductivity. Unweighted pair group method with arithmetic mean clustering showed that the landraces Aouija, Biskri and Hedhba exhibited a higher adaptive response to drought stress treatments, indicating that water stress-adaptive traits are included in Tunisian landraces germplasm.

NtNCED3 regulates responses to phosphate deficiency and drought stress in Nicotiana tabacum

Plants are sessile and encounter to abiotic environmental stressors, such as nutrient deficiency and drought stress. Identifying stress tolerance genes and their mechanisms is vital to ensuring plant survival. In this study, we characterized NCED3 in the tobacco plant Nicotiana tabacum, a key enzyme in the biosynthesis of abscisic acid that is widely involved in abiotic stress responses, using overexpression and RNA interference knockdown. Overexpression of NtNCED3 promoted primary root development, leading to increased dry weight, root-to-shoot ratio, photosynthetic capacity, and acid phosphatase activity, coinciding with highly increased phosphate uptake capability under low phosphate conditions. Under both drought and extreme phosphate deficiency conditions, the phosphate starvation response preceded the drought stress response. However, under high phosphate conditions, the drought stress phenotype emerged before the symptoms of phosphate deficiency. Plants overexpressing NtNCED3 grew better than the wild-type and NtNCED3 knockdown plants, with more developed root systems and higher biomass, phosphorus content, and hormone content. This study provides evidence that NtNCED3 enzyme participates in plant responses to phosphate deficiency and drought stress in N. tabacum, and NtNCED3 may serve as a potentially valuable gene for genetic modification of plant tolerance to both drought stress and phosphate starvation.

Multi-Omics Uncover the Mechanism of Wheat under Heavy Metal Stress

Environmental pollution of heavy metals has received growing attention in recent years. Heavy metals such as cadmium, lead and mercury can cause physiological and morphological disturbances which adversely affect the growth and quality of crops. Wheat (Triticum aestivum L.) can accumulate high contents of heavy metals in its edible parts. Understanding wheat response to heavy metal stress and its management in decreasing heavy metal uptake and accumulation may help to improve its growth and grain quality. Very recently, emerging advances in heavy metal toxicity and phytoremediation methods to reduce heavy metal pollution have been made in wheat. Especially, the molecular mechanisms of wheat under heavy metal stress are increasingly being recognized. In this review, we focus on the recently described epigenomics, transcriptomics, proteomics, metabolomics, ionomics and multi-omics combination, as well as functional genes uncovering heavy metal stress in wheat. The findings in this review provide some insights into challenges and future recommendations for wheat under heavy metal stress.