Physiology Of Wheat Research Articles

Wheat physiology predictor: predicting physiological traits in wheat from hyperspectral reflectance measurements using deep learning

BackgroundThe need for rapid in-field measurement of key traits contributing to yield over many thousands of genotypes is a major roadblock in crop breeding. Recently, leaf hyperspectral reflectance data has been used to train machine learning models using partial least squares regression (PLSR) to rapidly predict genetic variation in photosynthetic and leaf traits across wheat populations, among other species. However, the application of published PLSR spectral models is limited by a fixed spectral wavelength range as input and the requirement of separate custom-built models for each trait and wavelength range. In addition, the use of reflectance spectra from the short-wave infrared region requires expensive multiple detector spectrometers. The ability to train a model that can accommodate input from different spectral ranges would potentially make such models extensible to more affordable sensors. Here we compare the accuracy of prediction of PLSR with various deep learning approaches and an ensemble model, each trained and tested using previously published data sets.ResultsWe demonstrate that the accuracy of PLSR to predict photosynthetic and related leaf traits in wheat can be improved with deep learning-based and ensemble models without overfitting. Additionally, these models can be flexibly applied across spectral ranges without significantly compromising accuracy.ConclusionThe method reported provides an improved prediction of wheat leaf and photosynthetic traits from leaf hyperspectral reflectance and do not require a full range, high cost leaf spectrometer. We provide a web service for deploying these algorithms to predict physiological traits in wheat from a variety of spectral data sets, with important implications for wheat yield prediction and crop breeding.

Variation in Growth, Physiology, Yield, and Quality of Wheat under the Application of Different Zinc Coated Formulations

Zinc (Zn) is critical for the activity of many enzymes including involved photosynthetic CO2 fixation and indirectly involved in the production of growth hormones and internode elongation in crop plants. In this regard, a field experiment was conducted to investigate the comparative effectiveness of the Zn blended, Zn coated and bio-activated Zn coated urea on the growth, physiological, yield, and quality of wheat. Three types of urea were prepared including bio-activated Zn coated, Zn coated and Zn blended urea. The bio-activated Zn coated urea was prepared by inoculating the powdered organic material with Zn solubilizing bacterium (Bacillus sp. AZ6) and then this material was mixed with ZnO. This bioactive Zn was coated on urea at the rate to formulate 1.5% bio-activated Zn coated urea. Moreover, Zn blended urea was prepared by mixing powder ZnO with urea while Zn coated urea with 1.5% Zn was prepared by mixing ZnO and urea under proper moisture conditions to ensure proper coating. In results, growth parameters were significantly increased with the application of bio-activated Zn coated urea as compared to other urea formulations and the control. The same treatment caused the maximum increase in quality parameters like oil contents (55%), protein (30%), and N concentration (30%) as compared to the control. In conclusion, the application of 1.5% bio-activated Zn coated urea was highly effective in enhancing the growth, physiological, yield, and quality parameters of wheat.

Advances in Wheat Physiology in Response to Drought and the Role of Plant Growth Promoting Rhizobacteria to Trigger Drought Tolerance.

In the coming century, climate change and the increasing human population are likely leading agriculture to face multiple challenges. Agricultural production has to increase while preserving natural resources and protecting the environment. Drought is one of the major abiotic problems, which limits the growth and productivity of crops and impacts 1–3% of all land.To cope with unfavorable water-deficit conditions, plants use through sophisticated and complex mechanisms that help to perceive the stress signal and enable optimal crop yield are required. Among crop production, wheat is estimated to feed about one-fifth of humanity, but faces more and more drought stress periods, partially due to climate change. Plant growth promoting rhizobacteria are a promising and interesting way to develop productive and sustainable agriculture despite environmental stress. The current review focuses on drought stress effects on wheat and how plant growth-promoting rhizobacteria trigger drought stress tolerance of wheat by highlighting several mechanisms. These bacteria can lead to better growth and higher yield through the production of phytohormones, osmolytes, antioxidants, volatile compounds, exopolysaccharides and 1-aminocyclopropane-1-carboxylate deaminase. Based on the available literature, we provide a comprehensive review of mechanisms involved in drought resilience and how bacteria may alleviate this constraint

Alleviatory effects of Silicon on the morphology, physiology, and antioxidative mechanisms of wheat (Triticum aestivum L.) roots under cadmium stress in acidic nutrient solutions

Silicon (Si), as a quasi-essential element, has a vital role in alleviating the damaging effects of various environmental stresses on plants. Cadmium (Cd) stress is severe abiotic stress, especially in acidic ecological conditions, and Si can demolish the toxicity induced by Cd as well as acidic pH on plants. Based on these hypotheses, we demonstrated 2-repeated experiments to unfold the effects of Si as silica gel on the root morphology and physiology of wheat seedling under Cd as well as acidic stresses. For this purpose, we used nine treatments with three levels of Si nanoparticles (0, 1, and 3 mmol L−1) derived from sodium silicate (Na2SiO3) against three concentrations of Cd (0, 50, and 200 µmol L−1) in the form of cadmium chloride (CdCl2) with three replications were arranged in a complete randomized design. The pH of the nutrient solution was adjusted at 5. The averages of three random replications showed that the mutual impacts of Si and Cd in acidic pH on wheat roots depend on the concentrations of Si and Cd. The collective or particular influence of low or high levels of Si (1 or 3 mM) and acidic pH (5) improved the development of wheat roots, and the collective influence was more significant than that of a single parallel treatment. The combined effects of low or high concentrations of Cd (50 or 200 µM) and acidic pH significantly reduced root growth and biomass while increased antioxidants, and reactive oxygen species (ROS) contents. The incorporation of Si (1 or 3 mmol L−1) in Cd-contaminated acidic nutrient solution promoted the wheat root growth, decreased ROS contents, and further increased the antioxidants in the wheat roots compared with Cd single treatments in acidic pH. The demolishing effects were better with a high level of Si (3 mM) than the low level of Si (1 Mm). In conclusion, we could suggest Si as an effective beneficial nutrient that could participate actively in several morphological and physiological activities of roots in wheat plants grown under Cd and acidic pH stresses.

Impact of Coating of Urea with Bacillus-Augmented Zinc Oxide on Wheat Grown under Salinity Stress.

Zinc (Zn) availability is limited in salt-affected soils due to high soil pH and calcium concentrations causing Zn fixation. The application of synthetic Zn fertilizer is usually discouraged due to the high cost and low Zn use efficiency. However, salt-tolerant Zn-solubilizing bacteria (ZSB) are capable of solubilizing fixed fractions of Zn and improving fertilizer use efficiency. In the current study, a product was formulated by coating urea with bioaugmented zinc oxide (ZnO) to improve wheat productivity under a saline environment. The promising ZSB strain Bacillus sp. AZ6 was used for bioaugmentation on ZnO powder and termed as Bacillus sp. AZ6-augmented ZnO (BAZ). The experiment was conducted in pots by applying urea granules after coating with BAZ, to evaluate its effects on wheat physiology, antioxidant activity, and productivity under saline (100 mM NaCl) and non-saline (0 mM NaCl) conditions. The results revealed that the application of BAZ-coated urea alleviated salt stress through improving the seed germination, plant height, root length, photosynthetic rate, transpiration rate, stomatal conductance, soil plant analysis development (SPAD) value, number of tillers and grains, spike length, spike weight, 1000-grain weight, antioxidant activity (APX, GPX, GST, GR, CAT, and SOD), and NPK contents in the straw and grains of the wheat plants. Moreover, it also enhanced the Zn contents in the shoots and grains of wheat by up to 29.1 and 16.5%, respectively, over absolute control, under saline conditions. The relationships and variation among all the studied morpho-physio and biochemical attributes of wheat were also studied by principal component (PC) and correlation analysis. Hence, the application of such potential products may enhance nutrient availability and Zn uptake in wheat under salt stress. Therefore, the current study suggests the application of BAZ-coated urea for enhancing wheat’s physiology, antioxidant system, nutrient efficiency, and productivity effectively and economically.

Dual-purpose wheat technology: a tool for ensuring food security and livestock sustainability in cereal-based cropping pattern

ABSTRACT Wheat cultivation under a dual-purpose (DP) system holds great potential to provide additional fodder for livestock with marginal grain reduction. This study explores the potential of wheat as a DP crop for improving both, forage and grain cropping system by finding out optimal sowing dates and cultivars suitable for DP cropping. Field experiments with four cultivars (Saleem-2000, Bathoor-2007, Fakhre Sarhad-99 (FS-99) and Siran-2008), three sowing dates (October 15, October 30 and November 15) and two cutting treatments (cut and no-cut) determines the effects on yield and physiology of wheat. Wheat sown either in mid or end of October resulted in 11 and 8% increase in grain yield while 13 and 9% in biological yield over mid November sowing, respectively. This increase in yield was due to higher grain spike−1, chlorophyll content, transpiration rate and relative water content. The cultivars Siran-2008 and Saleem-2000 had higher biological and grain yields than other cultivars across cutting and sowing dates treatments. Biological and grain yields were reduced by 4% and 3%, respectively under the DP wheat compared with no-cut treatment, but grains N content was unaffected. Conclusively, DP wheat system (cut treatment) had higher profitability (11.2%) than wheat crop sown only for grain purposes.

Interactive effects of Ag-nanoparticles, salicylic acid, and plant growth promoting rhizobacteria on the physiology of wheat infected with yellow rust

The present investigation deals with the comparative study of plant growth promoting rhizobacteria (PGPR), salicylic acid (SA), and Ag-nanoparticle (AgNPs) on the physiology, sugar metabolism and yield of two varieties of wheat V-1 (GA 2002) and V-2 (Inqalab-91), differing in sensitivity to yellow rust. The study was based on the hypothesis that bacteria from stressed habitat may have better biocontrol potential than that of the normal condition. Three PGPR strains Bacillus cereus, Bacillus spp., and Burkholderia sp. were used as bioinoculant. The former two were isolated from the rhizosphere of wheat previously infected with rust and powdery mildew respectively and Burkholderia sp. was isolated from the rhizosphere of uninfected wheat. The seeds were soaked for 2 h prior to sowing in the broth culture of PGPR strains and SA. The AgNPs were applied as foliar spray (60 days after sowing). Yellow rust was induced 68 days after sowing. The treatments with Bacillus cereus, AgNPs, and SA effectively reduced the yellow rust in wheat as measured by AUDPC (area under production curve). Bacillus cereus significantly stimulated phenylalanine ammonia lyase activity. The abscisic acid (ABA), SA, indole acetic acid (IAA), and gibberellin (GA), the chlorophyll, and carotenoids contents were also increased in the sensitive variety (infected with yellow rust) following PGPR application. PGPR further augmented the activities of antioxidant enzymes and proline content. The biological yield was significantly higher in plants inoculated with Bacillus cereus. Bacillus cereus appears to act synergistically with SA to increase grain size. The tolerance to yellow rust is mediated by increase in the activity of phenylalanine ammonia lyase (PAL) and superoxide dismutase (SOD) and ABA content. AgNPs delay maturity and have a greater impact on the accumulation of photosynthates. Bacillus cereus can act synergistically with SA to improve total sugar content of flag leaves + grain. The AgNPs can be supplemented with Bacillus cereus for enhanced sugar production and sugar translocation to grains. AgNps and Bacillus cereus exhibit similar biocontrol potential against yellow rust as evidenced by AUDPC and PAL activity, but the Bacillus cereus superseded on AgNPs with respect to production of phytohormones, effect being more pronounced in the sensitive variety Inqalab-91.

Image-Based, Organ-Level Plant Phenotyping for Wheat Improvement

Wheat was one of the first grain crops domesticated by humans and remains among the major contributors to the global calorie and protein budget. The rapidly expanding world population demands further enhancement of yield and performance of wheat. Phenotypic information has historically been instrumental in wheat breeding for improved traits. In the last two decades, a steadily growing collection of tools and imaging software have given us the ability to quantify shoot, root, and seed traits with progressively increasing accuracy and throughput. This review discusses challenges and advancements in image analysis platforms for wheat phenotyping at the organ level. Perspectives on how these collective phenotypes can inform basic research on understanding wheat physiology and breeding for wheat improvement are also provided.

Wheat growth, applied water use efficiency and flag leaf metabolome under continuous and pulsed deficit irrigation

The intensity and frequency of precipitation events are predicted to change over the coming decades. For many areas, longer periods without rainfall are expected. We investigated the importance of irrigation frequency under water deficit conditions for growth, physiology and chemistry of wheat (Triticum aestivum). Drought-stressed plants received 40% of the water provided for control plants and were either watered every other day (continuous drought, cd) or every eight days (pulsed drought, pd). Maximum quantum yield of photosystem II (Fv/Fm), aboveground biomass, applied water use efficiency (WUEapl) and the flag leaf metabolome were assessed twice during development. Fv/Fm was not affected by irrigation. Drought-exposed plants produced less biomass, but had higher WUEapl than control plants. More metabolic features responded to the pd compared to the cd treatment and more features were increased than decreased in pool size in flag leaves. Salicylic acid glucoside was generally decreased under drought. In pd plants, two benzoxazinoid glucosides were enhanced at the first time point and concentrations of several flavonoid glycosides were modulated. This study extends our knowledge about drought effects on wheat; it highlights that the frequency of watering determines how plant growth, physiology and metabolism are affected by drought.

Physiology and defense responses of wheat to the infestation of different cereal aphids

Cereal aphids are major insect pests of wheat, which cause significant damages to wheat production. Previous studies mainly focused on the resistance of different wheat varieties to one specific aphid species. However, reports on the physiology and defense responses of wheat to different cereal aphids are basically lacking. In this work, we studied the feeding behavior of three cereal aphids: the grain aphid, Sitobion avenae (Fabricius), the greenbugs, Schizaphis graminum (Rondani), and the bird cherry-oat aphid, Rhopalosiphum padi (Linnaeus) on winter wheat, and the physiology and defense responses of wheat to the infestation of these cereal aphids with focus on how these cereal aphids utilize divergent strategies to optimize their nutrition requirement from wheat leaves. Our results indicated that S. graminum and R. padi were better adapted to penetrating phloem tissue and to collect more nutrition than S. avenae. The harm on wheat physiology committed by S. graminum and R. padi was severer than that by S. avenae, through reducing chlorophyll concentration and interfering metabolism genes. Furthermore, cereal aphids manipulated the plant nutrition metabolism by increasing the relative concentration of major amino acids and percentage of essential amino acids. In addition, different cereal aphids triggered specific defense response in wheat. All of these results suggested that different cereal aphids utilize divergent strategies to change the physiological and defense responses of their host plants in order to optimize their nutrition absorption and requirement. These findings not only extend our current knowledge on the insect–plant interactions but also provide useful clues to develop novel biotechnological strategies for enhancing the resistance and tolerance of crop plants against phloem-feeding insects.

Appraisal of nitric oxide priming to improve the physiology of bread wheat – CORRIGENDUM

Appraisal of nitric oxide priming to improve the physiology of bread wheat – CORRIGENDUM

Appraisal of nitric oxide priming to improve the physiology of bread wheat

AbstractSeed priming is a pre-sown treatment and it is often used to improve the performance of plants in any environment, especially germination. In the current study, various concentrations of nitric oxide (NO) were used to evaluate its role for the induction of physiological variations within seven different wheat (Triticum aestivum L.) genotypes. Two experiments were conducted during 2013 and 2014 and the data were statistically analysed for significance. All these genotypes after treatment with sodium nitroprusside (SNP) as NO donor at 10−4 and 10−5 M concentrations were sown following randomized complete block design with triplicates in the fields of District Muzaffarabad, Pakistan. The concentration of NO at 10−4 M showed promising results and most of the studied characters were found improved compared to control. Wheat varieties primed with 10−4 M SNP showed highest germination speed and germination percentage. NARC-2011 and Uqab-2002 showed much improvement in physiological attributes at both concentrations of NO priming. However, Uqab-2002 and Punjab-2011 showed a significant increase in chlorophyll contents and leaf moisture content with 10−4 and 10−5 M SNP priming compared to control. Highest relative water content was observed within unprimed Lasani, whereas the relative injury was found to be decreased at 10−4 M SNP primed Faisalabad-2008. Wheat varieties Punjab-2011 and Faisalabad-2008 showed the highest increase in grain yield and biological yield by 10−4 M SNP. Hence, it is concluded that sowing of crops after priming at 10−4 M NO concentration can improve the germination, biochemistry and physiology that ultimately lead to an increase in crop yield.

The Influence of Tillage and Cover Cropping on Soil Microbial Parameters and Spring Wheat Physiology

The soil tillage system and the distribution of stubble catch crops increase the content of organic carbon, thus increasing the biochemical activity of soil. The aim of the study was to assess the impact of leguminous cover crops and different tillage soil systems before spring wheat sowing on the count of soil microorganisms, biochemical activity, microbiological diversity and the physiological state of the plants in correlation with yield. The study compared and analysed the following systems: (1) conventional tillage (CT) to a depth of 22 cm, followed by spring wheat sowing using four simplified cultivation technologies called conservation tillage. The following simplified tillage systems were evaluated: (2) skimming before sowing the cover crop and spring wheat sowing after ploughing tillage (CT), (3) skimming before sowing of the cover crop (sowing wheat with no-till technology (NT)), (4) direct sowing of ground cover plants (NT) and spring wheat sowing after ploughing cultivation (CT) and (5) direct sowing of cover crop (NT) and sowing wheat directly into cover crop (NT). The results showed that applying the cover crop and soil tillage method before sowing wheat improved all tested parameters. The highest values of the analysed parameters were observed in the treatment with soil skimming before sowing of the cover plant, and then with sowing the wheat directly into the mulch. The activity of dehydrogenase was 90% higher, while the activity of phosphatase was 32% higher, in comparison to the control group. Both the activity of catalase and the biological index of fertility were 200% higher, in comparison to the control group. Metagenomic analysis showed that soil bacterial communities collected during treatment ‘zero’ and after different cultivations differed in the structure and percentage of individual taxa at the phylum level.

Effects of silicon nanoparticles on growth and physiology of wheat in cadmium contaminated soil under different soil moisture levels.

Soil degradation with different stress conditions like accumulation of cadmium (Cd) contents in soil and drought stress has become one of the most dangerous issues that obstruct the sustainable agriculture production. Silicon nanoparticles (Si NPs) play beneficial roles in combating various biotic and abiotic stresses but their role under combined metal and drought stress is not studied. A pot study was designed to determine the effect of Si NPs on wheat (Triticum aestivum L.) growth and uptake of Cd grown in Cd contaminated soil with different water levels under ambient conditions. Four different levels of Si NPs (0, 25, 50, and 100 mg/kg) were applied in the soil before 1 week of wheat sowing and two water levels (70% and 35% soil water-holding capacity) were introduced after 50 days of seed sowing for the remaining growth period. The lowest biomass, yield, and photosynthesis were observed in the control plants while oxidative stress and the highest Cd concentrations in shoots, roots, and grains were observed in the control plants, and the drought stress further enhanced this effect on the plants. The Si NPs treatments improved the plant growth indicators and photosynthesis, and reduced the Cd concentrations in wheat tissues, especially in grains either without or with drought stress. The Si NPs reduced the oxidative stress in leaves as was indicated by the reduced production of hydrogen peroxide, electrolyte leakage, and malondialdehyde contents, and increase in superoxide dismutase and peroxidase activities. The improvement in wheat growth and a reduction in oxidative stress and Cd concentration in tissues were dependent on the levels of Si NPs and the effect was the highest with the highest level of NPs used.

Effects of polyamines on agronomic traits and photosynthetic physiology of wheat under high temperature stress

Two spring wheat varieties were used to study alleviating effects of exogenous spermine (Spm) and spermidine (Spd) on agronomic traits and photosynthesis under high temperature treatment (HT). Our results showed that HT significantly decreased grain mass per panicle of heat-resistant variety (XC 6) by 25% and heat-sensitive variety (XC 31) by 32%. After HT, i.e., at 13 d after flowering, the decrease in net photosynthetic rate of XC 6 (38%) was lower than that of XC 31 (53%); the reason for this was related to XC 6, which could maintain correspondingly normal chlorophyll content (Chl), stomatal conductance (gs), transpiration rate (E), and intercellular CO2 concentration. Exogenous Spm and Spd could increase relative water content, Chl, gs, E, the maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, antenna conversion efficiency, and photochemical quenching coefficient of flag leaves under HT. Our results indicated that the heat resistance of XC 6 is better than that of XC 31 and exogenous Spm and Spd could alleviate the heat injury of photosynthesis of wheat flag leaves.

Effects of Microplastics on the Growth, Physiology, and Biochemical Characteristics of Wheat (Triticum aestivum)

The toxicological effects of microplastics in the soil environment have gradually attracted widespread attention, while less is known about the influence of microplastics on plants. The growth of wheat, photosynthetic pigment content, soluble protein content, and the antioxidant enzyme activities of leaves were investigated to explore the toxic effects of microplastics on wheat (Triticum aestivum). In this study, 100 nm and 5 μm polystyrene microplastics (PS-MPs) were used for soil culture treatment combined with hydroponic growth. The results showed that in hydroponic experiment, high concentrations (200 mg·L-1) of PS-MPs significantly inhibited the elongation of wheat roots and stems, and 5 μm PS-MPs showed a greater toxicity effect than 100 nm PS-MPs. Roots and stem length inhibition rates were 67.15% and 56.45%, respectively. In the soil culture tests, 10 mg·kg-1 PS-MPs had the most significant effect on wheat growth. Within the test content range (0-100 mg·kg-1), with an increase in PS-MPs exposure, the content of photosynthetic pigment and soluble protein in wheat leaves increased first and then decreased. This indicated that PS-MPs damaged the photosynthetic pathway of wheat leaves and inhibited protein synthesis. SOD activity decreased, and CAT decreased first and then increased, indicating that the possible mechanism of toxicity to wheat involves oxidative stress. The results provide a basis for the ecological risk assessment of microplastics in the soil environment.

The Coupling Effects of Plant Growth Promoting Rhizobacteria and Salicylic Acid on Physiological Modifications, Yield Traits, and Productivity of Wheat under Water Deficient Conditions

Water deficit and soil infertility negatively influence the growth, nutrient uptake, and productivity of wheat. Plant growth promoting rhizobacteria (PGPR) and salicylic acid (SA) were evaluated as possible solutions to mitigate the impacts of water deficit on growth, physiology, productivity, and nutrient uptake of wheat (Triticum aestivum L. cv. Sakha 95). Over two growing seasons (2016/2017 and 2017/2018) field experiments were conducted to examine eight combinations of two water treatments (water deficit and well-watered) with four soil and foliar treatments (control, PGPR, SA, and combination of PGPR + SA). The application of PGPR increased soil microbial activity resulting in increased field capacity and available soil water. Likewise, the application of the combined treatment of PGPR and SA significantly increased chlorophyll content, relative water content, stomatal conductance, soil microbial population, and showed inhibitory impacts on proline content, thus improving yield-related traits, productivity, and nutrient uptake (N, P, K) under water deficit compared to the control treatment. The results show that the integrative use of PGPR in association with SA may achieve an efficacious strategy to attenuate the harmful effects of water deficit as well as the amelioration of productivity and nutrient uptake of wheat under water-deficient conditions.

Elevated CO2 alleviates the negative impact of heat stress on wheat physiology but not on grain yield.

Hot days are becoming hotter and more frequent, threatening wheat yields worldwide. Developing wheat varieties ready for future climates calls for improved understanding of how elevated CO2 (eCO2) and heat stress (HS) interactively impact wheat yields. We grew a modern, high-yielding wheat cultivar (Scout) at ambient CO2 (aCO2, 419 μl l -1) or eCO2 (654 μl l-1) in a glasshouse maintained at 22/15 °C (day/night). Half of the plants were exposed to HS (40/24 °C) for 5 d at anthesis. In non-HS plants, eCO2 enhanced (+36%) CO2 assimilation rates (Asat) measured at growth CO2 despite down-regulation of photosynthetic capacity. HS reduced Asat (-42%) in aCO2- but not in eCO2-grown plants because eCO2 protected photosynthesis by increasing ribulose bisphosphate regeneration capacity and reducing photochemical damage under HS. eCO2 stimulated biomass (+35%) of all plants and grain yield (+30%) of non-HS plants only. Plant biomass initially decreased following HS but recovered at maturity due to late tillering. HS equally reduced grain yield (-40%) in aCO2- and eCO2-grown plants due to grain abortion and reduced grain filling. While eCO2 mitigated the negative impacts of HS at anthesis on wheat photosynthesis and biomass, grain yield was reduced by HS in both CO2 treatments.

Insights into transcriptional characteristics and homoeolog expression bias of embryo and de-embryonated kernels in developing grain through RNA-Seq and Iso-Seq.

Bread wheat (Triticum aestivum L.) is an allohexaploid, and the transcriptional characteristics of the wheat embryo and endosperm during grain development remain unclear. To analyze the transcriptome, we performed isoform sequencing (Iso-Seq) for wheat grain and RNA sequencing (RNA-Seq) for the embryo and de-embryonated kernels. The differential regulation between the embryo and de-embryonated kernels was found to be greater than the difference between the two time points for each tissue. Exactly 2264 and 4790 tissue-specific genes were found at 14days post-anthesis (DPA), while 5166 and 3784 genes were found at 25DPA in the embryo and de-embryonated kernels, respectively. Genes expressed in the embryo were more likely to be related to nucleic acid and enzyme regulation. In de-embryonated kernels, genes were rich in substance metabolism and enzyme activity functions. Moreover, 4351, 4641, 4516, and 4453 genes with the A, B, and D homoeoloci were detected for each of the four tissues. Expression characteristics suggested that the D genome may be the largest contributor to the transcriptome in developing grain. Among these, 48, 66, and 38 silenced genes emerged in the A, B, and D genomes, respectively. Gene ontology analysis showed that silenced genes could be inclined to different functions in different genomes. Our study provided specific gene pools of the embryo and de-embryonated kernels and a homoeolog expression bias model on a large scale. This is helpful for providing new insights into the molecular physiology of wheat.

Effects of Pre-Anthesis Drought, Heat and Their Combination on the Growth, Yield and Physiology of diverse Wheat (Triticum aestivum L.) Genotypes Varying in Sensitivity to Heat and drought stress

Independent and combined drought and heat stress negatively affect wheat yield and physiology. The present study was aimed to quantify effects of Drought [D], heat [H] and combined heat and drought [HD] during reproductive stage on wheat yield and to identify physio-biochemical traits which were strongly associated with improved yield and tolerance of wheat under stressful conditions. One hundred and eight elite diverse wheat genotypes were exposed to [H], [D] and [HD] treatments from heading till maturity. Grain yield was reduced by 56.47%, 53.05% and 44.66% under [HD], [H] and [D] treatment, respectively. The [HD] treatment affects the grain yield by reducing metabolism and mobilization of reserves to developing grains and leaves. Disintegration of membrane structure, chlorophyll and protein molecules was higher under [H] stress than [D] stress while water status of genotypes and sink strength was more affected by [D] than [H] stress. Multivariate analysis showed a strong correlation of chlorophyll content before and after anthesis, water-soluble carbohydrates (WSC), proline content (PC) and all other studies agronomic and physiological traits with grain yield while days to anthesis (DTA) and days to maturity (DTM) were negatively associated with grain yield under stress showing advantage of early maturity during stress. Traits having a major contribution in the first two principal components under different stress treatments may lead to improved varieties with heat and drought stress tolerance. To best of over knowledge, the present study is the first detailed study which used physiological and biochemical traits to explain the variation in grain yield and related traits in diverse wheat germplasm.