Drought Resistant Genotypes Research Articles

Yield-related phenotypic traits of drought resistant maize genotypes

The aim of this study was to evaluate two maize genotypes with contrasting drought-resistant phenotypic traits and to characterize how the plastic phenotypic traits contribute to yield potential under drought. The maize genotypes DKB 390 and BRS 1010 present contrasting yield traits in relation to drought and were treated with two water regimes: well-watered plant (WW, ≈−2 kPa) and water deficit (WD, ≈−100 kPa). In WD conditions, DKB 390 had a greater capacity to accumulate biomass in shoots than BRS 1010, indicating that shoot traits are important in increasing yield gain in the DKB 390 drought tolerant genotype and therefore, an important phenotypic trait for breeding for high yield in drought conditions. However, neither the total root dry mass nor its ratio to the shoot was related to increased yield. A large reduction in gas exchange and increased water use efficiency was observed in BRS 1010 compared to DKB 390. These traits are likely related to yield loss mainly due to decreased transpiration rate and stomatal conductance, which led to low photosynthetic rates and reduced growth. The root angle between genotypes was a constitutive trait and can be primarily responsible for the differences in yield. However, this trait in the DKB 390 genotype was affected by WD, as indicated by narrowing of the root angle. Our work describes the relationship between the narrow root growth angle in DKB 390 and its association with an increased capacity for water uptake in deeper regions, which may result in higher yield under drought. Regarding leaf anatomy we hypothesized that both osmotic adjustment and cell wall properties can influence anisotropic cell expansion under WD conditions and result in leaf tissue with higher yield potential in DKB 390. The high plasticity of vascular tissues and wide vessels could indicate a greater propensity for embolism and a slower response to WD, leading to yield loss in BRS 1010. The results of the phenotypic plasticity of maize genotypes show a negative relationship between high plasticity and yield potential and suggest that high plasticity can result in higher yield potential only when are present in phenotypic traits responsible for higher water uptake and drought tolerance.

Using Carbon Isotope Discrimination to Assess Genotypic Differences in Drought Resistance of Parental Lines of Common Bean

Accurate assessment of crop water uptake (WU) and water use efficiency (WUE) is not easy under field conditions. Carbon isotope discrimination (Δ13C) has been used as a surrogate of WUE to examine crop yield responses to drought and its relationship with WU and WUE. A 2‐yr study was conducted (i) to characterize genotypic variation in Δ13C, grain yield, and other physiological parameters in common bean (Phaseolus vulgaris L.) parental lines, and (ii) to examine the relationships between grain Δ13C, shoot Δ13C, and grain yield under well‐watered and terminal drought stress conditions. All measured plant traits were strongly influenced by water availability, and genotypic differences in grain yield, shoot Δ13C, and grain Δ13C were found in both watered and terminal drought stress environments. The parental lines were classified into two drought adaptation groups, drought resistant and drought sensitive, based on a yield drought index. High yields under drought conditions were related to (i) greater water uptake, as indicated by high Δ13C in genotypes previously shown to have deeper roots (e.g., SEA 5 and BAT 477), and (ii) increased WUE, denoted by lower Δ13C and greater pod harvest index (PHI) (e.g., SER 16). Coupling of Δ13C measurements with measured yield and yield components analyses, such as PHI, provided an avenue to distinguish different physiological traits among drought resistant genotypes underlying adaptation to water deficit stress.

Drought Resistance Indices for Screening of Potato (Solanum tuberosum L.) Genotypes

In breeding for drought tolerance, availability of precise, cheap and easy to apply selection tool is critical. The aim of the present study was to identify potential screening tools that are useful for selection of drought tolerant genotypes in potato and select drought resistant potato genotypes. The study assessed sixty clones arranged in a 10×6 alpha lattice design with two replicates in a managed stress experiment. Two irrigation treatments were applied: fully watered non-stress and terminal drought, where the irrigation water supply to the crop was withheld after 50 % flowering to induce post-flowering stress. Stress indices were calculated based on tuber yield of genotypes in both stressed and non-stressed conditions. Identification of drought tolerant genotypes based on a single index was less informative as different indices identified different genotypes as drought tolerant. Hence, to determine the most desirable drought tolerant clones rank sum of indices, correlation, and bi-plot display of the principal component analysis was employed. The indices modified stress tolerance index based on non-stressed yield, Men productivity, Geometric mean productivity, Stress tolerance index, Harmonic mean, modified stress tolerance index based on stressed yield and Yield index exhibited strong association with both yield under stressed and non-stressed yield. These indices discriminated drought tolerant genotypes with higher tuber yielding potential both under stress and non-stress conditions. Genotypes CIP-398180.612, CIP-397069.5, and CIP-304371.67 were identified as drought tolerant. These genotypes could be potentially grown both under drought prone and potential environments and these selection attributes could help to develop climate resilient potato varieties.

Application of thermal imaging and hyperspectral remote sensing for crop water deficit stress monitoring

Water deficit in crops induces a stress that may ultimately result in low production. Identification of response of genotypes towards water deficit stress is very crucial for plant phenotyping. The study was carried out with the objective to identify the response of different rice genotypes to water deficit stress. Ten rice genotypes were grown each under water deficit stress and well watered or nonstress conditions. Thermal images coupled with visible images were recorded to quantify the stress and response of genotypes towards stress, and relative water content (RWC) synchronized with image acquisition was also measured in the lab for rice leaves. Synced with thermal imaging, Canopy reflectance spectra from same genotype fields were also recorded. For quantification of water deficit stress, Crop Water Stress Index (CWSI) was computed and its mode values were extracted from processed thermal imageries. It was ascertained from observations that APO and Pusa Sugandha-5 genotypes exhibited the highest resistance to the water deficit stress or drought whereas CR-143, MTU-1010, and Pusa Basmati-1 genotypes ascertained the highest sensitiveness to the drought. The study reveals that there is an effectual relationship (R 2 = 0.63) between RWC and CWSI. The relationship between canopy reflectance spectra and CWSI was also established through partial least square regression technique. A very efficient relationship (calibration R 2 = 0.94 and cross-validation R 2 = 0.71) was ascertained and 10 most optimal wavebands related to water deficit stress were evoked from hyperspectral data resampled at 5 nm wavelength gap. The identified ten most optimum wavebands can contribute in the quick detection of water deficit stress in crops. This study positively contributes towards the identification of drought tolerant and drought resistant genotypes of rice and may provide valuable input for the development of drought-tolerant rice genotypes in future.

Bio-Physico-Chemical Response of Drought Tolerant Chickpeas to Nickel

Experiments were conducted to evaluate response of two genetically different drought tolerant varieties of Cicer arietinum L. namely PUSA 1103, Desi variety and PUSA 1105, Kabuli variety to the basal applications of nickel chloride doses viz; 0, 0.62, 3.12, 12.5, 62.5 and 125 µg g-1. Significant increase in the growth was observed at 0.62 and 3.12 µg g-1 nickel chloride doses. Addition of nickel dose above this level reduced the leaf area, plant growth, root length and yield of the plants. Fruiting stage showed more severe toxicity symptoms in comparison to the vegetative stages. Protein contents in seeds and chlorophyll contents along with nitrate reductase activity increased significantly in the leaves at the lower nickel doses. Peroxidase and superoxide-dismutase activities increased in a concomitant manner with increasing nickel concentrations. Increased concentrations of the soil applied nickel demonstrated an increase in the content of nickel higher in shoots also followed by roots. Accumulation of nickel and grain yield was higher in Desi chickpea variety PUSA 1103, indicating for its potential utilization in crop improvement strategies to breed new chickpea genotypes for nickel and drought resistance.

Next generation phenotyping for developing climate resilient rice varieties

Present paper deals with different components of next generation phenomics for characterizing rice genotypes for water deficit stress. Major sensors used in the study were non-imaging hyperspectal remote sensing, thermal imaging at ground platform and RGB and multispectral imaging sensors from drone platform. Different spectral indices were evaluated along with new proposed index and different multivariate models were studied for non-invasive estimation of relative water content (RWC) and sugar content in rice plant using spectral reflectance data collected in spectral range 350 to 2500 nm. Spectral data were further used for spectral discrimination of rice genotypes. Crop water stress index derived from thermal images acquired for rice genotypes could well characterize the drought resistant and sensitive genotypes. Initial study on field phenotyping through drone remote sensing using multispectral and RGB sensor was also explored to capture differential response of genotypes, trait and heat map mapping. All developed protocols as reliable alternative to conventional methods are fast, economic and non-invasive and in use in plant phenomics centre for high throughput plant phenotyhping for water deficit stress studies.

Next generation phenotyping for developing climate resilient rice varieties

Present paper deals with different components of next generation phenomics for characterizing rice genotypes for water deficit stress. Major sensors used in the study were non-imaging hyperspectal remote sensing, thermal imaging at ground platform and RGB and multispectral imaging sensors from drone platform. Different spectral indices were evaluated along with new proposed index and different multivariate models were studied for non-invasive estimation of relative water content (RWC) and sugar content in rice plant using spectral reflectance data collected in spectral range 350 to 2500 nm. Spectral data were further used for spectral discrimination of rice genotypes. Crop water stress index derived from thermal images acquired for rice genotypes could well characterize the drought resistant and sensitive genotypes. Initial study on field phenotyping through drone remote sensing using multispectral and RGB sensor was also explored to capture differential response of genotypes, trait and heat map mapping. All developed protocols as reliable alternative to conventional methods are fast, economic and non-invasive and in use in plant phenomics centre for high throughput plant phenotyhping for water deficit stress studies.

Analysis of transcriptional responses in root tissue of bread wheat landrace (Triticum aestivum L.) reveals drought avoidance mechanisms under water scarcity.

In this study, high-throughput sequencing (RNA-Seq) was utilized to evaluate differential expression of transcripts and their related genes involved in response to terminal drought in root tissues of bread wheat landrace (L-82) and drought-sensitive genotype (Marvdasht). Subsets of 460 differentially expressed genes (DEGs) in drought-tolerant genotype and 236 in drought-sensitive genotype were distinguished and functionally annotated with 105 gene ontology (GO) terms and 77 metabolic pathways. Transcriptome profiling of drought-resistant genotype “L-82” showed up-regulation of genes mostly involved in Oxidation-reduction process, secondary metabolite biosynthesis, abiotic stress response, transferase activity and heat shock proteins. On the other hand, down-regulated genes mostly involved in signaling, oxidation-reduction process, secondary metabolite biosynthesis, auxin-responsive protein and lipid metabolism. We hypothesized that the drought tolerance in “L-82” was a result of avoidance strategies. Up-regulation of genes related to the deeper root system and adequate hydraulic characteristics to allow water uptake under water scarcity confirms our hypothesis. The transcriptomic sequences generated in this study provide information about mechanisms of acclimation to drought in the selected bread wheat landrace, “L-82”, and will help us to unravel the mechanisms underlying the ability of crops to reproduce and keep its productivity even under drought stress.

Genotypic variability of Pinus sylvestris L. on the drought-resistance attribute

There was an increase and intensification of droughts in connection with global climate change in recent decades. Not all plant organisms are able to adapt to changing environmental conditions. Therefore, the question of stressresistant (drought-resistant) genotypes selection for breeding is quite urgent. This problem also concerns forest tree plants, including Scots pine, which is one of the main foresters in the Voronezh region. The results of vegetative and generative sphere analysis of individual Scotch pine trees with the help of biotechnology, molecular-genetic and cytogenetic method are given in this study. The possibility of applying the tissue culture method in vitro for testing initial plants for stress resistance, including drought resistance, is explained by the interconnection of cells, tissues and the whole plant properties. It is shown that the cytogenetic characteristics of the seed progeny and the indicators of callusogenic reactions do not always coincide in different genotypes: in some cases energy resources are spent on ontogeny protection, while, in other cases, to reproductive function maintain. There are trees, in which the state the generative sphere in arid years is at the level of optimal years, and their callus cultures reaction remains unchanged even under simulated conditions of drought. Based on the results obtained for the selection of Scots pine drought-resistant genotypes we suggest applying a system of criteria characterizing both the ability of the vegetative sphere to survive in drought conditions on the basis of the tissue culture method in vitro (callus tissue formation speed, its viability, frequency of callusogenesis), and the state of the generative sphere with the help of cytogenetic analysis of seed progeny (frequency of mitosis pathologies, the proportion of cells with micronuclei, mitotic activity). The expediency of applying the biotechnological approach was proved by analysis of the gene expression level of stress proteins: the level of AbaH gene expression correlates greatly with the indicator of the viability of callus cultures, including ones on a nutrient medium with an additional stress agent (NaCl). Trees that can be assigned to drought-resistant ones, according to the results of the analysis, should be recommended for use in breeding.

Imbalance Water Deficit Improves the Seed Yield and Quality of Soybean

Water imbalance condition (WIC) in a maize-soybean relay intercropping system is the main abiotic stress limiting biomass production and seed yield and, consequently, seed-quality. This experiment was started to study the effects of WIC on soybean, in which two soybean genotypes ND12 and C103 were grown in pots with roots split equally between two soil column and six WIC treatments (%) T1 (100), T2, (100:50), T3 (100:20), T4 (50:50), T5 (50:20), and T6 (20:20) field capacity on both sides of soybean roots were used. Results showed that both genotypes responded significantly to WIC treatments for all the parameters; however, the level of response differed between genotypes. Maximum osmoprotectants (except proline), biomass, yield and yield-related traits and superior seed quality were observed with ND12. Among WIC treatments, T2 and T3 produced 94% and 85%, and 93% and 81% of T1 biomass and yield, respectively. Similarly, treatments T2 and T3 also improved the oil quality by maintaining the content of unsaturated fatty acids and isoflavone content, while opposite trends were observed for protein content. Overall, moderate water reduction (T2 and T3) can improve soybean seed-quality and by selecting drought-resistant genotypes we can increase the soybean yield under intercropping systems.

Adaptive capacity of winter wheat varieties and breeding material under the conditions of the South Steppe

Purpose. To study the adaptive signs of varieties and breeding material of winter wheat developed at the Institute of Irrigated Agriculture of the National Academy of Sciences of Ukraine. Methods. Field, laboratory (determination of the water-holding capacity of leaves at major phenological stages), structural analysis, drought tolerance estimation (the method is based on the seed ability to germinate in sugar solution with high osmotic pressure), qua­lity analy sis, and statistical analysis. Results. Having a high-yiel­­ ding potential, modern varieties of winter wheat realize only 45–50% of their yield potential as their adaptability is still insufficient to ensure guaranteed stable yield. Therefore, to create highly adaptive varieties and to search me­ thods of evaluating breeding material in terms of adaptability remains a challenge for modern practical breeding. Among the studied in rainfed conditions winter wheat varieties of the Institute of Irrigated Agriculture which are adaptable in terms of plant height and yield, there is a genetically determined difference between drought-resistant genotypes, which makes it possible to select the best of them. These genotypes are 80–90 cm tall, they ensure a yield potential of 10.5 t/ha and the following quality indicators of grain: protein content 14%, sedimentation 55–75 ml, kernel hardness 95%, gluten content 32%, gluten quality I–II group Conclusions. The research on the drought and heat resistance of winter wheat carried out in the most important ontogenetic periods against two backgrounds – irrigated and rainfed – in conditions of climate change of the steppe zone served a basis for new breeding material and varie­ties. The Institute of Irrigated Agriculture’s varieties that have complex adaptive capacity have passed state variety examination and recognized as suitable for introduction in the farms in the South of Ukraine.

Drought-tolerant and drought-sensitive genotypes of maize (Zea mays L.) differ in contents of endogenous brassinosteroids and their drought-induced changes.

The contents of endogenous brassinosteroids (BRs) together with various aspects of plant morphology, water management, photosynthesis and protection against cell damage were assessed in two maize genotypes that differed in their drought sensitivity. The presence of 28-norbrassinolide in rather high quantities (1–2 pg mg-1 fresh mass) in the leaves of monocot plants is reported for the first time. The intraspecific variability in the presence/content of the individual BRs in drought-stressed plants is also described for the first time. The drought-resistant genotype was characterised by a significantly higher content of total endogenous BRs (particularly typhasterol and 28-norbrassinolide) compared with the drought-sensitive genotype. On the other hand, the drought-sensitive genotype showed higher levels of 28-norcastasterone. Both genotypes also differed in the drought-induced reduction/elevation of the levels of 28-norbrassinolide, 28-norcastasterone, 28-homocastasterone and 28-homodolichosterone. The differences observed between both genotypes in the endogenous BR content are probably correlated with their different degrees of drought sensitivity, which was demonstrated at various levels of plant morphology, physiology and biochemistry.

Drought and salinity affect leaf and root anatomical structures in three maize genotypes

Salt and drought stresses are being quite similar considered as two major constraints in maize production. To explore the anatomical bases of resistance to salt and drought stresses, 14 days old seedlings of three maize hybrid genotypes were subjected to salt (100 mM NaCl) and drought stress (equiosmotic PEG-6000) under hydroponic conditions. The experiment was laid out following a completely randomized design having four replicates. Root protoxylem and metaxylem thickness and root diameter were found to be unaffected in both of the drought resistant genotypes in response to salt and drought stresses whereas root protoxylem thickness increased (33.8 and 112.8% by salt and drought stress, respectively) in sensitive genotype (BARI hybrid maize-7). Bundle sheath thickness was found to increase in response to stresses (58.4 and 59.3% by salt and drought stress, respectively) in BARI hybrid maize-12. BARI hybrid maize-12 showed unaffected response in leaf epidermal thickness, phloem area, xylem area and total leaf thickness under both salt and drought stressesJ. Bangladesh Agril. Univ. 16(1): 47-55, April 2018

Integrated omics data of two annual ryegrass (Lolium multiflorum L.) genotypes reveals core metabolic processes under drought stress

BackgroundAnnual ryegrass (Lolium multiflorum L.) is a commercially important, widely distributed forage crop that is used in the production of hay and silage worldwide. Drought has been a severe environmental constraint in its production. Nevertheless, only a handful of studies have examined the impact of short-term drought stress on annual ryegrass. The aim of this study was to explore how stress-induced core metabolic processes enhance drought tolerance, or adaptation to drought, in annual ryegrass.ResultsWe profiled the transcriptomes, proteomes, and metabolomes of two annual ryegrass genotypes: the drought-resistant genotype “Abundant 10” and drought-susceptible genotype “Adrenalin 11.” We identified differentially expressed metabolites and their corresponding proteins and transcripts that are involved in 23 core metabolic processes, in response to short-term drought stress. Protein–gene–metabolite correlation networks were built to reveal the relationships between the expression of transcripts, proteins, and metabolites in drought-resistant annual ryegrass. Furthermore, integrated metabolic pathways were used to observe changes in enzymes corresponding with levels of amino acids, lipids, carbohydrate conjugates, nucleosides, alkaloids and their derivatives, and pyridines and their derivatives. The resulting omics data underscored the significance of 23 core metabolic processes on the enhancement of drought tolerance or adaptation to drought in annual ryegrass.ConclusionsThe regulatory networks were inferred using MCoA and correlation analysis to reveal the relationships among the expression of transcripts, proteins, and metabolites that highlight the corresponding elements of these core metabolic pathways. Our results provide valuable insight into the molecular mechanisms of drought resistance, and represent a promising strategy toward the improvement of drought tolerance in annual ryegrass.

Effect of salinity and drought stress on germination and early seedlings growth of bread wheat (Triticum aestivum L.)

Salinity is one of the most important environmental stresses that limits soil fertility and has adverse effects on plant growth. In order to increase wheat production under saline conditions, it is necessary to better understand genotypic difference, the physiological and biochemical processes of salt tolerance in wheat. The aim of this study was to determine the most tolerant winter wheat varieties against salinity and osmotic stress at germination stage and early seedlings growth. The salinity and osmotic stress were simulated in controlled environmental conditions by adding different concentrations of NaCl and mannitol solution to the growing media of five winter wheat variety. In all studied varieties the benchmark water potential in which they had germinated and had a good seedlings growth was of -0.3MPa. Under the stronger stress, -0.6 MPa, all varieties showed reduction in the all examined parameters. The variety Bosanka, had the highest final germination and germination energy under both mannitol and salt stress treatments. The parameters defining the development or percentage of strong seeds, coleoptile and root length, fresh and dry weight of root and coleoptile of a seed were more affected by water deficit stress and salt stress than germination and germination energy. Biplot analysis showed that wheat cultivars grown under -0.6MPa osmotic had higher values of root/coleoptile ratio in relation to control and -0.3MPa treatment which is the most reliable for screening properties of the genotypes for drought resistance in seedling stage.

New Sunflower Genotypes with Resistance to Drought, Main Pathogens and Broomrape (Orobanche cumana), Created at NARDI Fundulea

The development of human society in general depends and is conditioned by the presence of fresh water resources. Certainly, the main cause, which has led to the ascending curve of current needs and consumption, is determined by the demographic explosion and the rapid urbanization process. Therefore, industry and agriculture are among the biggest consumers of water. The real problem is not lack of resources but effective distribution and overall management it is. In the context of the aforementioned, at NARDI Fundulea was developed in 2010 a program to improve drought resistance and obtain new genotypes through introgression of resistance genes from Helianthus argophyllus species in cultivated specie (Helianthus annuus L.) (Project MAKIS, Financed by the World Bank). Helianthus argopyllus is the most interesting species with very pubescent leaves, moderate transpiration and good photosynthetic activity. These characters provide superior water use efficiency compared to cultivated species. For these reasons, it has been used in our research to achieve the above-mentioned goal. In this project, at NARDI Fundulea has successfully used interspecific immature embryo culture to obtain drought-resistant genotypes and shortening the breeding process by getting two to three generations/year. Starting with the BC6 generation of self-pollination, the resulted fertile lines (B, maintainer lines) were cross polinated with an androsterility source in order to produce the sterile analogues of these lines (all being B, maintenance, fertile) were performed. After 4-5 generations of sterile plant selection, sterile analogue lines for each of the new creations were obtained. After this, new sunflower hybrids were obtained using certain fertility restoration lines from the NARDI Fundulea collection. The new hybrids were tested in three very different locations and years in terms of rainfall and temperatures during sunflower vegetation (2014-2015-2016). Based on the results we can conclude that interspecific hybridization may be an additional technique in the breeding of the sunflower and can be successfully used to create new sources of genetic variability to improve germplasm for drought and pathogens resistance. The newly created genotypes have responded positively to testing under different climatic and soil conditions and can be included in the approval list for both classical and ecological culture conditions.

Comprehensive Screening of Some West and Central African Sesame Genotypes for Drought Resistance Probing by Agromorphological, Physiological, Biochemical and Seed Quality Traits

Sesame is an important crop in West and Central Africa playing a role of an alternative cash crop for smallholders. However, sesame productivity is highly impaired by drought. This study aimed at identifying some drought-resistant genotypes and efficient screening traits in large sesame germplasm. Ten genotypes were examined based on 21 biochemical, physiological, agromorphological and seed quality traits under three weeks of water stress. A high variability for drought resistance was observed among the genotypes. The genotypes WC17, WC18 and WC14 were drought resistant, WC12, WC13, WC06 and WC03 were moderately drought resistant while, WC02, WC10 and WC08 were drought sensitive, based on principal component analysis. The resistant genotypes exhibited both avoidance and tolerance features including increase of the root system, reduced water loss, highest activity of antioxidative enzymes and accumulation of proline. They produced higher biomass and had higher ability to maintain seed quality under drought stress compared with the sensitive genotypes. Strong accumulation (~200% ratio stress/control) of biochemical markers including superoxide dismutase, ascorbate peroxidase, catalase and proline could be regarded as an important indicator for selecting drought resistant genotypes. This study represents a reference for future research towards developing new varieties with improved drought resistance in West and Central Africa.

Growth and developmental responses of crop plants under drought stress: a review

Water deficit conditions are a bearing on plant growth and development leading to diminished crop productivity. However, improving the crop productivity is need of the time to sustain the food security under ever increasing world population. Drought episodes are increasing with varying intensity and duration. Drought stress imposes alterations in crucial plant growth and developmental processes, including germination, plant height, stem diameter, number of leaves, leaf size and area, dry matter production and partitioning, flower and fruit production, and maturity. Nonetheless, plants show some morphological changes to cope with drought stress by lowering water loss, enhanced water uptake and maintenance of tissue water status. Some plants complete their life cycle early before the onset of drought to escape water deficit conditions. Identification of effects of drought stress on morphological attributes and morphological changes in response to drought can be promising for selection and breeding of drought resistant genotypes.

Development of SSR Markers Based on Transcriptome Sequencing and Association Analysis with Drought Tolerance in Perennial Grass Miscanthus from China.

Drought has become a critical environmental stress affecting on plant in temperate area. As one of the promising bio-energy crops to sustainable biomass production, the genus Miscanthus has been widely studied around the world. However, the most widely used hybrid cultivar among this genus, Miscanthus × giganteus is proved poor drought tolerance compared to some parental species. Here we mainly focused on Miscanthus sinensis, which is one of the progenitors of M. × giganteus providing a comparable yield and well abiotic stress tolerance in some places. The main objectives were to characterize the physiological and photosynthetic respond to drought stress and to develop simple sequence repeats (SSRs) markers associated with drought tolerance by transcriptome sequencing within an originally collection of 44 Miscanthus genotypes from southwest China. Significant phenotypic differences were observed among genotypes, and the average of leaf relative water content (RWC) were severely affected by drought stress decreasing from 88.27 to 43.21%, which could well contribute to separating the drought resistant and drought sensitive genotype of Miscanthus. Furthermore, a total of 16,566 gene-associated SSRs markers were identified based on Illumina RNA sequencing under drought conditions, and 93 of them were randomly selected to validate. In total, 70 (75.3%) SSRs were successfully amplified and the generated loci from 30 polymorphic SSRs were used to estimate the genetic differentiation and population structure. Finally, two optimum subgroups of the population were determined by structure analysis and based on association analysis, seven significant associations were identified including two markers with leaf RWC and five markers with photosynthetic traits. With the rich sequencing resources annotation, such associations would serve an efficient tool for Miscanthus drought response mechanism study and facilitate genetic improvement of drought resistant for this species.

Half-sibling loblolly pine clones exhibited intraspecific variation, a G × E interaction, and differences in stable isotope composition in response to soil moisture availability

We examined the response of three loblolly pine half-sibling clones (hereafter referred to as Clone 1, 2, and 3) to soil moisture availability in a greenhouse study. Three soil moisture treatments were imposed. Two were constant soil moisture treatments at either high (−0.3MPa) or low (−1.5MPa) soil water potential. The third was an alternating wet-dry treatment that alternated between one week at high (−0.3MPa) and three weeks at low (−1.5MPa) soil water potential, which simulated several natural wetting-drying cycles. At intervals throughout the experiment we measured biomass accumulation (via sequential harvesting), change in height, pre-dawn needle water potential, afternoon needle water potential, dark respiration, and morning and afternoon gas exchange (photosynthesis, stomatal conductance, intercellular CO2, and transpiration). Carbon allocation to root and shoot biomass, stomatal density, and carbon isotope composition were measured at the end of the experiment.All clones accumulated more biomass in the high soil moisture treatment than in the low soil moisture treatment, but there was a genetic by environment (G×E) interaction: Clone 1 accumulated more biomass than the other clones in the low soil moisture treatment and less than the others in the high soil moisture treatment. Stable carbon isotope composition, which we interpreted as a time-integrated index of water use efficiency, was significantly higher (indicating greater water use efficiency) in Clone 2, compared to Clones 1 and 3 across all soil moisture treatments except in the wet-dry treatment, where Clone 1 and 3 were not significantly different. A strong negative correlation was found between stable carbon isotope composition and biomass accumulation. Gas exchange parameters and needle water potential were higher in the high soil moisture treatment compared to the other treatments across all clones. Morning measurements of gas exchange were higher in Clones 2 and 3 than in Clone 1 across all treatments. Stomatal density varied significantly among clones but not among treatments. These results demonstrated that closely related clones differed in their growth and physiological responses to moisture availability, suggesting that clonal variation could be used to breed for increased drought resistance or to identify drought resistant genotypes for selective deployment.