Unlocking genetic insights: Evaluating wheat RILs for physiobiochemical traits under terminal heat stress conditions

BACKGROUND

The increasing impacts of heat stress on wheat production due to climate change has entailed the development of heat-resilient crop varieties. To address this, two hundred recombinant inbred lines (RILs) derived from a cross between WH711/WH1021 were evaluated in a randomized block design (RBD) with two replications at CCSHAU, Hisar, during 2018-19 under heat stress and non-stress conditions. Heat stress was induced by altering the date of sowing so that the grain filling stage coincide with heat stress.

RESULTS

Heat stress adversely affects RILs performance, as illustrated by alterations in phenotypic traits. Highest coefficients of variations were recorded for TAA, CTD 1, WUE, CTD 2, Cc and A under non-stress and heat stress conditions whereas gs, WUEi and GY under non-stress and SPAD 1, SPAD 2, GY and NDVI 2 under heat-stress conditions recorded moderate estimates of coefficient of variations. CTD 2, TAA, E, WUE and A displayed a significant occurrence of both high heritability and substantial genetic advance under non-stress. Similarly, CTD 2, NDVI 2, A, WUEi, SPAD 2, gs, E, Ci, MDA and WUE exhibited high heritability with high genetic advance under heat-stress conditions.

CONCLUSIONS

Complementary and duplicate types of interactions with number of controlling genes were observed for different parameters depending on the traits and environments. RILs 41, 42, 59, 74, 75, 180 and 194 were categorized as heat tolerant RILs. Selection preferably for NDVI 1, RWC, TAA, A, E and WUEi to accumulate heat tolerance favorable alleles in the selected RILs is suggested for development of heat resilient genotypes for sustainable crop improvement. The results showed that traits such as such as NDVI, RWC, TAA, A, E, and WUEi, can be effective for developing heat-resilient wheat genotypes and ensuring sustainable crop improvement.

Genetic modification strategies for enhancing plant resilience to abiotic stresses in the context of climate change

Enhancing the resilience of plants to abiotic stresses, such as drought, salinity, heat, and cold, is crucial for ensuring global food security challenge in the context of climate change. The adverse effects of climate change, characterized by rising temperatures, shifting rainfall patterns, and increased frequency of extreme weather events, pose significant threats to agricultural systems worldwide. Genetic modification strategies offer promising approaches to develop crops with improved abiotic stress tolerance. This review article provides a comprehensive overview of various genetic modification techniques employed to enhance plant resilience. These strategies include the introduction of stress-responsive genes, transcription factors, and regulatory elements to enhance stress signaling pathways. Additionally, the manipulation of hormone signaling pathways, osmoprotectant accumulation, and antioxidant defense mechanisms is discussed. The use of genome editing tools, such as CRISPR-Cas9, for precise modification of target genes related to stress tolerance is also explored. Furthermore, the challenges and future prospects of genetic modification for abiotic stress tolerance are highlighted. Understanding and harnessing the potential of genetic modification strategies can contribute to the development of resilient crop varieties capable of withstanding adverse environmental conditions caused by climate change, thereby ensuring sustainable agricultural productivity and food security.

Transcriptomic Analysis Provides Novel Insights into the Heat Stress-Induced Response in Codonopsis tangshen

Codonopsis tangshen Oliv (C. tangshen) is a valuable traditional Chinese medicinal herb with tremendous health benefits. However, the growth and development of C. tangshen are seriously affected by high temperatures. Therefore, understanding the molecular responses of C. tangshen to high-temperature stress is imperative to improve its thermotolerance. Here, RNA-Seq analysis was performed to investigate the genome-wide transcriptional changes in C. tangshen in response to short-term heat stress. Heat stress significantly damages membrane stability and chlorophyll biosynthesis in C. tangshen, as evidenced by pronounced malonaldehyde (MDA), electrolyte leakage (EL), and reduced chlorophyll content. Transcriptome analysis showed that 2691 differentially expressed genes (DEGs) were identified, including 1809 upregulated and 882 downregulated. Functional annotations revealed that the DEGs were mainly related to heat shock proteins (HSPs), ROS-scavenging enzymes, calcium-dependent protein kinases (CDPK), HSP-HSP network, hormone signaling transduction pathway, and transcription factors such as bHLHs, bZIPs, MYBs, WRKYs, and NACs. These heat-responsive candidate genes and TFs could significantly regulate heat stress tolerance in C. tangshen. Overall, this study could provide new insights for understanding the underlying molecular mechanisms of thermotolerance in C. tangshen.

Comparison of Gene Expression Changes in Three Wheat Varieties with Different Susceptibilities to Heat Stress Using RNA-Seq Analysis

Wheat is highly susceptible to heat stress, which significantly reduces grain yield. In this study, we used RNA-seq technology to analyze the transcript expression at three different time-points after heat treatment in three cultivars differing in their susceptibility to heat stress: Jopum, Keumkang, and Olgeuru. A total of 11,751, 8850, and 14,711; 10,959, 7946, and 14,205; and 22,895, 13,060, and 19,408 differentially-expressed genes (log2 fold-change > 1 and FDR (padj) < 0.05) were identified in Jopum, Keumkang, and Olgeuru in the control vs. 6-h, in the control vs. 12-h, and in the 6-h vs. 12-h heat treatment, respectively. Functional enrichment analysis showed that the biological processes for DEGs, such as the cellular response to heat and oxidative stress—and including the removal of superoxide radicals and the positive regulation of superoxide dismutase activity—were significantly enriched among the three comparisons in all three cultivars. Furthermore, we investigated the differential expression patterns of reactive oxygen species (ROS)-scavenging enzymes, heat shock proteins, and heat-stress transcription factors using qRT-PCR to confirm the differences in gene expression among the three varieties under heat stress. This study contributes to a better understanding of the wheat heat-stress response at the early growth stage and the varietal differences in heat tolerance.

Heat Stress at Early Reproductive Stage Differentially Alters Several Physiological and Biochemical Traits of Three Tomato Cultivars

Global warming is predicted to be increased in the upcoming years, resulting in frequent heatwaves or hot days worldwide, which can seriously affect crop growth and productivity. The responses of heat stress to several photophysiological and biochemical traits in three tomato cultivars were investigated in a pot experiment, and the heat tolerance capability of these cultivars was evaluated based on the investigated traits. The experiment was followed by a factorial completely randomized design, and the factors were (i) tomato cultivars (BARI Hybrid Tomato-5, BARI Tomato-14, and BARI Tomato-15) and (ii) heat stress (control and heat). The plants of three tomato cultivars were exposed to short-term heat stress (four days at 38/25 °C day/night temperature) at the flowering stage. The measured traits such as dry mass, leaf greenness (SPAD), maximum photochemical efficiency of photosystem II (Fv/Fm), photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E), leaf chlorophyll, and carotenoid content were significantly declined, while the catalase and ascorbate peroxidase activities were increased by heat stress in all three tomato cultivars except BARI Tomato-15, which showed unaltered gs, E, and carotenoids. The percent reduction (over control) in SPAD, Fv/Fm, A, total chlorophyll, and total carotenoids was significantly lower (11, 06, 25, 34, and 19%, respectively), whereas the percent increase in catalase and ascorbate peroxidase activities was substantially higher (70 and 72%, respectively) in BARI Tomato-15 than in other cultivars. Based on the measured physiological and biochemical traits, the cultivar BARI Tomato-15 showed better heat tolerance than the other cultivars.

Elevated CO2 modulates the effect of heat stress responses in Triticum aestivum by differential expression of isoflavone reductase-like (IRL) gene

Two wheat genotypes forming high and low biomass (HB and LB), exhibiting differential expression of an isoflavone reductase-like (IRL) gene, and resulting in contrasting grain yield under heat stress field conditions, were analyzed in detail for their responses under controlled heat and elevated CO2 conditions. Significant differences in IRL expression between the two lines were hypothesized to be the basis of their differential performance under the tested conditions and their stress tolerance potential. By a holistic approach integrating advanced cell physiological phenotyping of the antioxidative and phytohormone system in spikes and leaves with measurements of ecophysiological and agronomic traits, the genetic differences of the genotypes in IRL expression were assessed. In response to heat and elevated CO2, the two genotypes showed opposite regulation of IRL expression, which was associated with cytokinin concentration, total flavonoid contents, activity of superoxide dismutase, antioxidant capacity and photosynthetic rate in leaves and cytokinin concentration and ascorbate peroxidase activity in spikes. Our study showed that IRL expression is associated with wheat yield performance under heat stress at anthesis, mediated by diverse physiological mechanisms. Hence, based on our results, the IRL gene is a promising candidate for developing genetic markers for breeding heat-tolerant wheat.

Biochemical, Physiological, and Productive Response of Greenhouse Vegetables to Suboptimal Growth Environment Induced by Insect Nets

Simple Summary

Global warming jeopardizes agriculture, which must satisfy the demands of the world’s expanding population for both staple and high-quality products while ensuring increased sustainability. Environmental and regulatory pressure has prompted farmers to convert their production strategies towards sustainable agriculture systems, by introducing for instance, integrated pest management strategies. Insect nets are a suitable tool for pest control but require careful assessment of their effects on the generated microclimate. The low porosity, mandatory for proper exclusion, results in suboptimal airflow and in temperature rise with detrimental effects on crop production and quality. The biochemical and morpho-physiological changes induced by high-temperature impact vegetable crop performance and product quality in advanced growing systems, and also represent a challenge for the most impoverished developing countries of the world, which rely on local horticultural products as a key source of dietary diversity.

Abstract

Environmental pressure poses a major challenge to the agricultural sector, which requires the development of cultivation techniques that can effectively reduce the impact of abiotic stress affecting crop yield and quality (e.g., thermal stress, wind, and hail) and of biotic factors, such as insect pests. The increased consumer interest in premium-quality vegetables requires the implementation of sustainable integrated pest management (IPM) strategies towards an ever-increasing insect pressure, also boosted by cultivation under protected structures. In this respect, insect nets represent an excellent, eco-friendly solution. This review aims to provide an integrative investigation of the effects of the insect screens in agriculture. Attention is dedicated to the impact on growth, yield, and quality of vegetables, focusing on the physiological and biochemical mechanisms of response to heat stress induced by insect screens. The performance of insect nets depends on many factors—foremost, on the screen mesh, with finer mesh being more effective as a barrier. However, finer mesh nets impose high-pressure drops and restrict airflow by reducing ventilation, which can result in a detrimental effect on crop growth and yield due to high temperatures. The predicted outcomes are wide ranging, because heat stress can impact (i) plant morpho-physiological attributes; (ii) biochemical and molecular properties through changes in the primary and secondary metabolisms; (iii) enzymatic activity, chloroplast proteins, and photosynthetic and respiratory processes; (iv) flowering and fruit settings; (v) the accumulation of reactive oxygen species (ROSs); and (vi) the biosynthesis of secondary biomolecules endowed with antioxidant capacity.

Physiological, biochemical, and molecular mechanisms of heat stress tolerance in plants

High temperature (HT) stress is a major environmental stress that limits plant growth, metabolism, and productivity worldwide. Plant growth and development involve numerous biochemical reactions that are sensitive to temperature. Plant responses to HT vary with the degree and duration of HT and the plant type. HT is now a major concern for crop production and approaches for sustaining high yields of crop plants under HT stress are important agricultural goals. Plants possess a number of adaptive, avoidance, or acclimation mechanisms to cope with HT situations. In addition, major tolerance mechanisms that employ ion transporters, proteins, osmoprotectants, antioxidants, and other factors involved in signaling cascades and transcriptional control are activated to offset stress-induced biochemical and physiological alterations. Plant survival under HT stress depends on the ability to perceive the HT stimulus, generate and transmit the signal, and initiate appropriate physiological and biochemical changes. HT-induced gene expression and metabolite synthesis also substantially improve tolerance. The physiological and biochemical responses to heat stress are active research areas, and the molecular approaches are being adopted for developing HT tolerance in plants. This article reviews the recent findings on responses, adaptation, and tolerance to HT at the cellular, organellar, and whole plant levels and describes various approaches being taken to enhance thermotolerance in plants.

Productivity of a doubled haploid winter wheat population under heat stress

Breeding of new winter wheat cultivars with good heat tolerance requires better understanding of the genetic background of heat tolerance. In the present work the effect of heat stress on the 6th day after heading was investigated in a doubled haploid (DH) population arising from a cross between heat-sensitive (Plainsman V) and heat-tolerant (Mv Magma) cultivars. Averaged over the population, heat stress was found to result in a significant reduction in biomass, grain yield and grain number per plant, and in thousand-kernel weight (TKW) and harvest index. High temperature had the greatest effect on the grain yield, with a drop of 36.2% compared with the control. This could be attributed jointly to significant reductions in the TKW of the main ear and in the grain number of the side tillers. The relationship between the yield parameters was confirmed by the positive correlations obtained for the lines in the population. The diverse levels of heat tolerance in the different lines were confirmed by the significant differences in the reduction in the chlorophyll content (SPAD index) of the flag-leaves and in yield parameters. The changes in yield components in stress condition, however, can be still the most effective tools for heat stress evaluation.

Relationship between biotic stress tolerance and protective compounds in wheat genotypes

Large numbers of wheat genotypes were grown under field conditions and screened for biotic stress tolerance and certain protective compounds. It was found that both the salicylic acid and polyamine contents of the investigated genotypes varied over a wide range, while the antioxidant enzyme activities showed a similar pattern in the different genotypes. In order to investigate stress-induced changes in salicylic acid and polyamine contents, samples were collected from plants artificially inoculated with leaf rust (Puccinia triticina), on which natural powdery mildew [Blumeria graminis (DC.) Speer f. sp. tritici Em. Marchal] infection also appeared. Biotic stress mostly resulted in elevated levels of total salicylic acid and polyamines in all the genotypes. The activities of various antioxidant enzymes showed similar changes after infection regardless of the genotype. The investigation was aimed at detecting a relationship between the level of stress tolerance and the contents of protective compounds, in particular salicylic acid and polyamines.

Drought tolerance in cereals in terms of water retention, photosynthesis and antioxidant enzyme activities

Experiments were carried out on three bread wheat varieties, one barley and one durum wheat variety grown in pots in the phytotron and subjected to water withdrawal for 7 days during grain-filling. Leaf water loss, net assimilation rate and transpiration showed marked differences, allowing the genotypes to be ranked. Although the most resistant variety had the highest activity for ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR) and glutathione-S-transferase (GST), which did not rise further in response to drought and the most susceptible variety had the lowest values, which increased to the greatest extent under drought, the level of sensitivity could not be predicted for all the genotypes from the enzyme activity values alone. The largest increases were recorded for the APX, CAT and GR activities. In most genotypes the GR activity was correlated with that of GST, CAT and APX. Changes in the enzyme activities were observed after a decline in transpiration and photosynthesis. The range of soil moisture values over which the antioxidant enzyme activity levels remained relatively unchanged was a better indication of tolerance to drought than either basic or stress-induced activity levels.