Drought-tolerant Cultivars Research Articles

Multivariate analyses of root phenotype and dynamic transcriptome underscore valuable root traits and water‐deficit responsive gene networks in maize

AbstractRoot system architecture (RSA) plays a vital role in plant adaptation and productivity under water‐deficit environments. In this study, we use two maize inbreeds to investigate root phenotypic and early transcriptional responses to water‐deficit stress. As evidenced by improved survival rate and photosynthetic efficiency at early seedling and late vegetative stage, CIMBL55 was characterized as a tolerant genotype versus sensitive SHEN5003. Image‐based root phenotyping revealed that drought tolerant cultivar had notably different RSA features from drought sensitive cultivar including larger root size, longer root length, and more number of lateral roots and seminal roots. Dynamic transcriptome investigations on primary and seminal root integrating differential gene expression, temporal gene co‐expression, and weighted gene co‐expression network analysis (WGCNA) revealed a high degree of genotype‐ and root type‐specificity in response to PEG‐induced water deficit. The higher drought tolerability of CIMBL55 versus SHEN5003 can be attributed to the enhanced expression of genes associated with antioxidant defense and a higher proportion of water‐deficit responsive genes. Upon water deficit, seminal roots exhibited more dramatic transcriptional changes than the primary root, and a more exclusive functional association with stress response. Genome‐wide WGCNA identified system‐level functionality of genes associated with specific root traits. Multiple root‐specific and root‐predominant hub genes were identified with functions involved in transcriptional regulation, root development, and drought response. Conclusively, integrated root phenotypic and transcriptomic analyses identified important root system architectures and water‐deficit responsive gene networks in maize. Findings will serve a valuable resource that merits in‐depth functional analyses toward a better understanding of RSA‐associated drought tolerance in maize.

Uni- and Multi-Variate Assessment of Drought Response Yield Indices in 10 Wheat Cultivars

Wheat (Triticum aestivum L.) is a major cereal with its productivity being highly affected by drought. In the current study, 10 wheat cultivars were evaluated for their grain yield under well-watered (Yp) and drought (Ys) conditions. Various drought response indices (mean productivity (MP), geometric productivity (GMP), tolerance index (TOL), stress susceptibility index (SSI), stress tolerance index (STI), harmonic mean of yield (HARM), yield stability index (YSI), relative drought index (RDI), two drought resistance indices (DRI1 and DRI2), yield reduction ratio (YRR) and yield index (YI)) were determined to identify high-yielding and drought tolerant cultivars. Spearman’s correlation coefficient among the estimated indices, hierarchical clustering of the concerned cultivars as well as principle component analysis (PCA) of both the indices and cultivars were employed. Wheat cultivars Sids 13 and Gemmeiza 11 were superior while Sakha 94 and Shandaweel 1 were inferior depending upon their Yp, Ys and drought response indices. Also, a non-significant positive correlation was recorded between Yp and Ys of the studied cultivars with GMP, STI and HARM being significantly correlated with both Yp and Ys. Based on PCA, Yp and Ys explained 61.6 and 38.1% of the total variation; respectively. Furthermore, cluster analysis sequestered the concerned cultivars into drought susceptible cultivars (Shandaweel 1, Giza 168 and Gemmeiza 11), drought moderate ones (Misr 2, Sakha 93 and Sakha 94) and drought tolerant ones (Misr 1, Sids 13, Gemmeiza 9 and Sids 12) based on the mean values of YSI, RDI, TOL, SSI and YRR within each group.

Assessment of pearl millet genotypes for drought stress tolerance at early and late seedling stages

Pearl millet is one of the most important C4 panicoid millet crops grown in dry and arid regions of India and West Africa. Drought is one of the major limitations to its growth potential. Therefore, selection of drought-tolerant cultivars through in vitro screening can be an important approach for crop improvement programmes. An experiment was conducted on six pearl millet genotypes with two different levels of osmotic stress treatments, i.e., control and 20% polyethylene glycol (PEG) 6000 at early seedling stage for eight seedling traits and proline content, while 30% PEG at late seedling stage for proline and malonaldehyde (MDA) content and gene expression analysis. Analysis of variance (ANOVA) showed significant treatment effects on all early seedling traits with respect to treatment x varietal interaction. Our results showed a relative decline for different seedling traits in individual genotypes with increased osmotic stress. TT-1 showed a maximum reduction in almost all traits while the minimum decline was noted in PRLT2/89-33. Further, proline and MDA accumulation in control and 30% PEG-6000-treated seedlings at late growth stages were in confirmation with the observations recorded at early seedling growth stages. Expression analysis using quantitative real-time (qRT)-PCR of three antioxidative genes namely, ascorbate peroxidase (APX), glutathione reductase (GlutR) and superoxide dismutase (SOD) also confirmed higher osmotic stress tolerance of PRLT2/89-33 seedlings. Overall results suggested that selection for any of the above traits at early or late-seedling growth stages may prove useful for crop improvement programs directed towards developing stress-tolerant cultivars.

Comparative phylogenetic analysis of aquaporins provides insight into the gene family expansion and evolution in plants and their role in drought tolerant and susceptible chickpea cultivars

Aquaporins (AQPs) are water channel proteins that play a significant role in drought stress. Although the AQPs identified in multiple plant species, there is no detailed evolutionary and comparative study of AQPs regarding chickpea plant. The current study involved evolutionary analyses coupled with promoter and expression analyses of chickpea AQPs (CaAQPs). A total of 924 non-redundant AQPs were studied in 24 plant species including algae, mosses, lycophytes, monocots and dicots. Phylogenetic analysis demonstrated a clear divergence of eight AQP subfamilies (LIPs, SIPs, GIPs, NIPs, XIPs, PIPs, HIPs and TIPs). The comparative phylogenetic trees of AQP subfamilies among Arabidopsis, soybean, common bean, maize and chickpea demonstrated that the AQPs were highly species-specific. Interestingly, the dual NPA motif was conserved in all species. However, the ar/R selectivity filter signatures [W/T/S/N/G/A]-[V/S/L/I/A]-[S/G/A]-R (in NIPs), F-H-T-R (in PIPs), [H/N/Q/S]-[A/I/L/S/V]-[A/G]-[A/C/L/M/R/V] (in TIPs) and [V/I/L/M]-[V/I/A/F/M]-[A/S/F/C]-[N/F/L/I/A/S (in SIPs) were found in five species. Moreover, the Froger's positions (P1-P5) were found as [F/L/Y]-[S/T]-A-Y-[L/I/M/V/F] (in NIPs), [Q/E/M]-S-A-F-W (in PIPs), [A/L/S/T/V]-[A/C/N/S/T/V]-[P/R/S]-[Y/N/F]-[W/Q] (in TIPs) and [I/M/F]-[A/V]-[A/V]-Y-W (in SIPs). The MEME motif analyses showed that most of the motifs were specific to subfamily and subgroups. Tissue-specific expression profiling of CaAQPs revealed that CaTIPs and CaPIPs are highly expressed in most of the tissues, while CaNIPs and CaSIPs have low expression. In promoter analysis of CaAQPs, multiple stress-related cis-acting elements e.g. MYB, MYC, ABRE, etc. were found. Semi-quantitative RT-PCR analysis showed that CaPIP2;3 and CaNIP3;1 are positive regulator, while CaSIP1;1 and CaPIP2;1 have a negative role in drought tolerance. The findings and implications of this study are discussed in detail.

Analysis of wheat gene expression related to the oxidative stress response and signal transduction under short-term osmotic stress

Water shortage is a major environmental stress that causes the generation of reactive oxygen species (ROS). The increase in ROS production induces molecular responses, which are key factors in determining the level of plant tolerance to stresses, including drought. The aim of this study was to determine the expression levels of genes encoding MAPKs (MAPK3 and MAPK6), antioxidant enzymes (CAT, APX and GPX) and enzymes involved in proline biosynthesis (P5CS and P5CR) in Triticum aestivum L. seedlings in response to short-term drought conditions. A series of wheat intervarietal substitution lines (ISCSLs) obtained by the substitution of single chromosomes from a drought-sensitive cultivar into the genetic background of a drought-tolerant cultivar was used. This source material allowed the chromosomal localization of the genetic elements involved in the response to the analyzed stress factor (drought). The results indicated that the initial plant response to drought stress resulted notably in changes in the expression of MAPK6 and CAT and both the P5CS and P5CR genes. Our results showed that the substitution of chromosomes 3B, 5A, 7B and 7D had the greatest impact on the expression level of all tested genes, which indicates that they contain genetic elements that have a significant function in controlling tolerance to water deficits in the wheat genome.

Direct somatic embryogenesis of drought resistance pistachio (Pistacia vera L.) and expression analysis of somatic embryogenesis-related genes

Pistachio (Pistacia vera) is one of the most important commercial nut crops worldwide. There is wild pistachio forest in Iran and is believed that all commercial genotypes originated from this forest. Climate change and its consequences like drought and salinity decreased the forests and orchards area. Vegetative propagation like somatic embryogenesis is necessary for the mass propagation of wild and elite genotypes to use in reforestation and revival orchards. Therefore, the focus of this study was to establish somatic embryogenesis protocol for wild, salt, and drought tolerant pistachio cultivars. Since molecular mechanisms involved in pistachio somatic embryogenesis pathway is largely unknown, expression of four notably embryogenesis-related genes (LEC, AGL15, BBM, and PKL) in embryonic explants were investigated. Explants were exposed to various combination and concentrations of plant growth regulators (PGRs) under light and dark conditions. In light condition, somatic embryos were directly established on explants in half strength MS medium supplemented with casein hydrolysate, and L-glutamine. Application of low concentration of auxins was increased the induction frequency of somatic embryos. Somatic embryos were matured and germinated on medium supplemented with 0.01 mg L−1 abscisic acid. The LEC, AGL15, and BBM genes exhibited high levels of expression in embryonic explants, which inferred that these genes played key roles during embryogenesis in pistachio. Successful establishment of a somatic embryo regeneration system for pistachio will produce a significant foundation for production and conservation of pistachio genotypes. This system is also provided an ideal model for investigating the role of embryogenesis-related genes.

Genesis of ultra-specialized histology with stable traits in mesophyll of drought tolerant apple cultivars

Even if some biological defense responses are activated instantaneously after stress occurrence, but other mechanisms of drought tolerance could be probed, detected and diagnosed as sable traits at mesophyll level. The present observations demonstrated multilateral modifications in different leaf parts, specialized parenchyma tissues and cribro-vascular bundles that facilitate vital activities in tolerant apple cultivars. In 2006, long deficit irrigation occurred in commercial apple collection containing 93 cultivars located in Karaj-Iran. Entire bearing 16-Year-old trees lost completely the crop except 16 CVs which were assessed for yield per tree since June drop to physiological maturity. Based on thehypothesis, stable traits were developed against drought stress through phenomenon of genesis. 19 different anatomical traits of mesophyll were accurately assessed in the selected resistant CVs compared with the susceptible "Golden Delicious" and native "Assali" as the controls. Microscopic studies computed on the transversal sections of mesophyll prepared by microtome ascertained ultra-specialized histological traits in the selected CVs. Morphologically, basal part of the main vein was completely spherical, outfitted, highly ordered and tidy tissues. Epidermis underlying layer was composed of well-organized tissues containing uniform cells by shape and size, inserted consistently next to one another in neat order with no intercellular space. Contrarily, controls showed opposite rhythm in all examined characters. Also, the mean number of epidermis layers at leaf margin resulted higher related to susceptible CVs. The mean number of vascular bundles and stomata decreased in tolerant CVs. These observations put in evidence some stable ultra-specialized histological traits of mesophyll, as a result of genesis route.

Identification and characterization of drought responsive miRNAs in a drought tolerant upland rice cultivar KMJ 1-12-3

Shortfall of rain that creates drought like situation in non-irrigated agriculture system often limits rice production, necessitating introduction of drought tolerance trait into the cultivar of interest. The mechanism governing drought tolerance is, however, largely unknown, particularly the involvement of miRNAs, the master regulators of biochemical events. In this regard, response study on a drought tolerant rice variety KMJ 1-12-3 to 20% PEG (osmolality- 315 mOsm/kg) as drought stress revealed significant changes in abundance of several conserved miRNAs targeting transcription factors like homeodomain-leucine zipper, MADS box family protein, C2H2 zinc finger protein and Myb, well known for their importance in drought tolerance in plants. The response study also revealed significant PEG-induced decrease in abundance of the miRNAs targeting cyclin A, cyclin-dependent kinase, guanine nucleotide exchange factor, GTPase-activating protein, 1-aminocyclopropane-1-carboxylic acid oxidase and indole-3-acetic beta-glucosyl transferase indicating miRNA-regulated role of the cell cycle regulators, G-protein signalling and the plant hormones ethylene and IAA in drought tolerance in plants. The study confirmed the existence of four novel miRNAs, including osa-miR12470, osa-miR12471, osa-miR12472 and osa-miR12473, and the targets of three of them could be successfully validated. The PEG-induced decrease in abundance of the novel miRNAs osa-miR12470 and osa-miR12473 targeting RNA dependent RNA polymerase and equilibrative nucleoside transporter, respectively suggested an overall increase in both degradation and synthesis of nucleic acids in plants challenged with drought stress. The drought-responsive miRNAs identified in the study may be proved useful in introducing the trait in the rice cultivars of choice by manipulation of their cellular abundance.

MORPHOLOGICAL AND PHYSIOLOGICAL TRAITS OF UPLAND RICE CULTIVARS AFFECTED BY WATER DEFICIT

The use of drought-tolerant cultivars is a promising strategy to minimize the effects of water deficits on upland rice productivity. Therefore, it is important to establish an adequate methodology to evaluate the performance of upland rice cultivars under water deficit. In this study, one evaluated the effects of water deficit on morphological and physiological traits of two upland rice cultivars, in a greenhouse, in soil columns, using a phenotyping platform named SITIS. The experiment occurred in a complete randomized block design, in a split plot scheme with four replications. The main plots consisted of a well-irrigated treatment with daily replacement of 100% evapotranspired water and four water restriction regimes (daily replacement of 20%, 40%, 60% and 80% evapotranspired water at the well-irrigated treatment) and, the subplots, of the Douradão and BRS Soberana cultivars, which are tolerant and sensitive to water stress, respectively. It is feasible to use the SITIS platform and the proposed protocol (water regimes) to evaluate upland rice cultivars for tolerance to water stress. Under water deficit, the Douradão cultivar restricted its transpiration and showed harvest index, grain yield and water use efficiency higher than the BRS Soberana cultivar.

Drought tolerance indices for selection of drought tolerant, high yielding upland rice genotypes

The purposes of this study were (1) to assess the effectiveness of drought tolerance indices for selection of drought tolerance in upland rice, and (2) to identify the most suitable drought tolerance indices to select for drought tolerant, high yielding upland rice genotypes. This study employed a Split Plot design consisting of irrigation levels as the main plots, and rice genotype as the sub-plot treatments. There were three main plots: 100% field capacity (FC); 75% FC; and 50% FC level. The subplot treatments consisted of 40 upland rice genotypes. Grain yields under no-stress and stressed conditions were used to calculate drought tolerance indices. There were significant variations in grain yields and drought tolerance indices between different rice genotype treatments. The indices from the literature found to be most suitable for the selection of drought tolerant upland rice cultivars were STI, GMP, MRP, HARM, REI, ATI, YI, SNPI. Ten genotypes from among the 40 tested - namely HK-07, ADN-04, PMK-01, ADN-05, NGR-022, ALR-02, HK-06, and KMD-01 - were selected as combining drought tolerance with high yield potential.

Chl a fluorescence and proteomics reveal protection of the photosynthetic apparatus to dehydration in tolerant but not in susceptible wheat cultivars

Seedlings of spring wheat (Triticum aestivum L.) cultivars, Ethos and Zebra, differing in drought tolerance were dehydrated to reach a water saturation deficit (WSD) in leaves ~15, 30, and 50 %. Ethos, the drought tolerant cultivar, dried slower in comparison with Zebra and regrew in 70 % upon rehydration. The effect of dehydration on photosystem II was evaluated by Chl a fluorescence (OJIP transients). The inflection point of double normalized curves (ΔWOJ) calculated for Ethos was negative for seedlings with 15 % WSD, nearly zero for those with 30 % WSD, and about +0.05 for those with 50 % WSD. In case of Zebra, the 15 % WSD already induced a positive ΔWOJ (+0.05) and 50 % WSD maximized it to +0.10, which is a sign of drought susceptibility. The proteomic studies revealed, that among identified 850 spots, 80 protein spots were differentially expressed during dehydration. The differentially expressed proteins of the drought tolerant cultivar indicated the protection of the photosynthetic apparatus and proteome rebuilding in response to drought. In the drought susceptible cultivar, protection of proteins and membranes and partial scavenging reactive oxygen species appeared.

Yield determination in winter wheat under different water regimes

Wheat (Triticum aestivum) is grown in a wide range of water regimes and produces both grain and forage in the U.S. Southern Great Plains (SGP). Despite being relatively adapted to water stress, decreased water supply has become the main abiotic factor limiting wheat yield in the region. A 5-yr field study was conducted to investigate the yield determination in winter wheat under a center pivot irrigation system. Twenty elite wheat cultivars were grown at four water regimes, I100, I75, I65, and I50 to meet 100%, 75%, 65%, and 50% evapotranspiration (ET) requirement, respectively. The 2011 and 2013 seasons had all irrigation levels, while there were only two irrigation levels in 2012 (I50 and I65) and 2014 (I75 and I100), and three irrigation levels in 2015 (I50, I75, and I100). In most seasons, ET, biomass, and grain yield decreased consistently from higher to lower water regime, but water use efficiency (WUE) and harvest index (HI) were the highest at I75. Averaged across all years and genotypes, grain yield was reduced by only 5% from I100 to I75 indicating that reducing irrigation to meet 75% of ET requirement can still achieve similar yield to I100 and maximize HI and WUE. Newer cultivars including Duster, Endurance, Winterhawk, TAM 112, and TAM 113 had greater yield at I50 compared to other cultivars. Grain yield showed a strong relationship with biomass, HI, and ET. At lower water regimes (I50, I65), all three yield components (spikes per square meter, seeds per spike, and kernel weight) were correlated to grain yield. At higher water regimes (I75 and I100) grain yield was consistently related to kernel weight. This study demonstrated that high yield can be achieved at an irrigation level of I75. In addition, planting newer drought tolerant cultivars may provide yield benefits under water-limited conditions in the SGP.

Overexpression of ß-Ketoacyl Co-A Synthase1 Gene Improves Tolerance of Drought Susceptible Groundnut (Arachis hypogaea L.) Cultivar K-6 by Increased Leaf Epicuticular Wax Accumulation.

Drought is one of the major environmental constraints affecting the crop productivity worldwide. One of the agricultural challenges today is to develop plants with minimized water utilization and reduced water loss in adverse environmental conditions. Epicuticular waxes play a major role in minimizing water loss. Epicuticular wax covers aerial plant parts and also prevents non-stomatal water loss by forming the outermost barrier from the surfaces. Epicuticular wax content (EWC) variation was found to be affiliated with drought tolerance of groundnut cultivars. In the current study, a fatty acid elongase gene, KCS1, which catalyzes a rate limiting step in the epicuticular wax biosynthesis was isolated from drought tolerant cultivar K-9 and overexpressed in drought sensitive groundnut cultivar (K-6) under the control of CaMV35S constitutive promoter. Transgenic groundnut plants overexpressing AhKCS1 exhibited normal growth and displaying greenish dark shiny appearance. Environmental scanning electron microscopy (ESEM) revealed the excess of epicuticular wax crystal depositions on the transgenic plant leaves compared to non-transgenic wild type plants. The findings were further supported by gas chromotography–mass spectroscopic analysis (GC-MS) that revealed enhanced levels of fatty acids, secondary alcohols, primary alcohols, aldehydes, alkanes, and ketones in transgenics compared to wild types. The AhKCS1 overexpressing transgenic groundnut plants exhibited increase in the cuticular wax content, reduction of water loss, lower membrane damage, decreased MDA content, and high proline content compared to that of non-transgenic groundnut plants. Our findings suggest that the AhKCS1 gene plays a major role in combating drought stress by preventing non-stomatal water loss in drought sensitive groundnut cultivar (K-6).

Evaluation of Drought Tolerant Rice Cultivars Using Drought Tolerant Indices under Water Stress and Irrigated Condition

Drought is the most critical abiotic factor reducing rice yield in rainfed and drought prone areas. Majority of rice cultivated area in south Asia are under rainfed, where water stress at any of the critical growth stage causes sharp decline in yield. Research was conducted in western Nepal at farmers field around the close vicinity of Regional Agriculture Research Center (RARS) Nepalgunj. Ten different rice cultivars were evaluated under drought stress and non-stress condition during the year 2017 to identify superior stress tolerant cultivars. Different drought tolerance indices like stress tolerance (TOL), Stress tolerance index (STI), Stress susceptibility index (SSI), were tested in screening superior rice cultivars. Significant reduction in mean grain yield was observed under drought stress in all rice cultivars under the study. The rice cultivars with high STI values and low TOL and SSI were identified as superior drought tolerant cultivars. Based on results of different tolerance indices, Sukha series of rice, Sukha Dhan 1-6 and Radha-4 showed low TOL and SSI and high STI values and were identified as drought tolerant cultivars. The present study reveals that selection based on drought tolerance indices can be an efficient tool in identification of superior drought tolerant cultivars with higher yield and stability.

In silico Mining of EST-SSRs from the Drought Tolerant ESTs in Safflower

Drought stress is a major abiotic factor causing yield loss in safflower and limited studies have been carried out to dissect the molecular mechanism at EST-SSR level. In this study, a possible relationship between simple sequence repeats (SSRs) distribution and drought stress was studied using three EST libraries of safflower, Ct-D-EST, Ct-NEST and Co-EST. The Ct-D-EST was generated from drought tolerant safflower cultivar A-1; Ct-N-EST and Co-EST were the EST datasets of safflower and its wild progenitor C. oxycanthus, respectively. In total, 156 (45%), 1194 (5%) and 1550 (9%) EST-SSRs were mined from Ct-D-EST, Ct-N-EST and Co-EST libraries, respectively. Comparison of EST-SSRs from Ct-D-EST with that of SSRs from other two libraries showed reasonable differences for each class of repeats. Large variations were observed for dinucleotide repeats in all the libraries. In drought EST-SSRs, only one kind of amino acid was produced by repeat (ATG)14 which encodes met indicating the loci and repeat observed to be 100%. Since three ESTs with SSRs from Ct-D-EST, annotated to putative candidate genes, S-adenosylmethionine synthetase, one-helix protein and myo-inositol 1-phosphate synthetase, did not express with SSRs in the Ct-N-EST, these can be considered as potential candidate genes for drought tolerance. A trinuceotinde SSR, encoding met, was also found in the EST annotated to putative s-adenosylmethionine synthetase, hence, both can be considered as indices for drought tolerance. The genomic resources and the information generated in this study may be useful for the safflower breeders particularly for the development of drought tolerant cultivar.

Heterologous expression of rice RNA-binding glycine-rich (RBG) gene OsRBGD3 in transgenic Arabidopsis thaliana confers cold stress tolerance.

Imparting cold stress tolerance to crops is a major challenge in subtropical agriculture. New genes conferring cold tolerance needs to be identified and characterised for sustainable crop production in low-temperature stress affected areas. Here we report functional characterisation of OsRBGD3, classified previously as a class D glycine-rich RNA recognition motif (RRM) containing proteins from a drought-tolerant Indica rice cultivar N22. The gene was isolated by screening yeast one-hybrid library using the minimal promoter region of the OsMYB38 that is necessary for cold stress-responsive expression. OsRBGD3 exhibited cold, drought and salt stress inductive expression in a drought tolerant N22 rice cultivar as compared with susceptible variety IR64. OsRBGD3 was found to be localised to both nuclear and cytoplasmic subcellular destinations. Constitutive overexpression of the OsRBGD3 in transgenic Arabidopsis conferred tolerance to cold stress. ABA sensitivity was also observed in transgenic lines suggesting the regulatory role of this gene in the ABA signalling pathway. OsRBGD3 overexpression also attributed to significant root development and early flowering in transgenics. Hence, OsRBGD3 could be an important target for developing cold tolerant early flowering rice and other crops' genotypes for increasing production in low temperature affected areas.

Biochemical Responses of Wheat Cultivars to PEG-Induced Drought Stress

Aim of the present study was to study the biochemical responses of wheat cultivars (Platinum Lok 1, Eagle 135, Prerna Amber, Kisan Farmer 2189 and Ankur Kedar) to polyethylene glycol (PEG-6000—0, 5, 10 and 15%) induced drought stress. Lipid peroxidation, H2O2, proline, glycine betaine (GB) and activities of the antioxidant enzymes were evaluated at seedling stage. As the concentration of PEG increased, an increase in free proline and GB accumulation was observed in all the wheat cultivars to different extent. However, the magnitude of reduction of these parameters was more in Prerna Amber and Eagle 135. Platinum Lok 1 showed an increase in free proline and GB contents with low levels of MDA and H2O2 contents as compared to rest of the cultivars. The activities of catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) enzymes showed increasing trend with respect to increasing PEG concentration. However, no specific trend was observed for the activity of ascorbate peroxidase (APX). Activities of POX and SOD were significantly high in Plantinum Lok 1. Overall results indicated that Platinum Lok 1 can be considered as drought tolerant which can be associated with higher proline and GB accumulation and lower MDA and H2O2 contents. Biochemical parameters such as osmolytes and antioxidant enzymes could provide useful tools for identification of drought tolerant wheat cultivars at seedling stage.

Drought Screening and Supplemental Irrigation Management for some Rice Cultivars in Drought Prone Area of Bangladesh

Water stress is one of the limiting factors for rice production. Under rainfed condition with erratic rainfall, water stress becomes a serious threat for sustainable rice production. Drought tolerant cultivars along with appropriate management practices can solve the problem. Field and control condition studies were carried out to study the response of some rice cultivars to water-stress, and to develop appropriate on-farm management strategy for sustainable yield under drought condition. The results revealed that most of the cultivars produced good yield under drought condition compared to normal irrigated condition (under control condition and field study). Levee management strategy (of height of 20 cm) seems a viable option to alleviate the effect of drought under field condition. Levee management and life-support supplemental irrigation (when necessary) can facilitate good yield of most of the cultivars. These cultivars seemed to be appropriate for cultivation in drought-prone areas.

Canopy Temperature and Chlorophyll Content are Effective Measures of Drought Stress Tolerance in Durum Wheat

Durum wheat (Triticum durum L.) is used for the preparation of multiple food products, including pasta and bread. Its production is restricted due to diverse environmental stresses i.e. drought and heat stress. Here, comparative analysis of durum wheat varieties was done by studying canopy temperature depression (CTD) and chlorophyll content (CHL), yield and yield contributing traits to evaluate their performance under stress and low stress conditions. Twelve durum wheat genotypes were studied under stressful and low-stress conditions in Gachsaran region of Iran. CTD and CHL were measured at two stages, from the emergence of fifty percent of inflorescence (ZGS 54) to watery ripe stage (ZGS 71). According to stress tolerance index (STI), mean productivity (MP) and geometric mean productivity (GMP) indices, genotype G10 exhibited the most, while genotype G6, the least relative tolerance, respectively. Based on MP and GMP, genotype G10 was found to be drought tolerant, while genotype G2 displayed the lowest amount of MP and GMP. Therefore these genotypes are recommended to be used as genitors in artificial hybridization for improvement of drought tolerance in other cultivars. All indices had high correlation with grain yield under stress and non-stress condition, indicating more suitability of these indices for selection of resistant genotype. Results of the present study showed that among drought tolerance indices, harmonic mean (HM), GMP, CTD and modified STI index (K2STI) can be used as the most suitable indicators for screening drought tolerant cultivars.

YIELD FORMATION CAPACITY, SOIL WATER CONSUMPTION PROPERTY, AND PLANT WATER USE EFFICIENCY OF WHEAT UNDER WATER-SAVING CONDITIONS IN NORTH CHINA PLAIN

The drastically reduced underground water and shortage of the water resource have caused limitation for the winter wheat (T. aestivum) production in North China Plain. In this study, using a drought-tolerant wheat cultivar Shimai 18 as material, we investigated the yield formation capacity, soil water consumption property, and the plant water use efficiency (WUE) of wheat under various irrigation treatments. Our results indicated that the yield capacities of wheat varied largely across irrigation treatments in three growth seasons with contrasting precipitation patterns. The wheat yields showed constant in growth season with more rainfall and lowered to some extent in seasons with regular or less rainfall under I1 (water-saving condition with one time of irrigation) compared with I3 (regular irrigation with three times of irrigation). Along with increase of the irrigation times, plant WUE lowered drastically in all of three growth seasons examined, together with significantly increased evapotranspiration (ET) amount and relative constant of soil water deposits. These results suggested that the water-saving management is feasible in the winter wheat production in North China Plain. Additionally, the plant leaf area index (LAI), dry matter accumulation, and biomass partitioning rate of vegetative tissues during late growth stage (from flowering to maturity) were consistent with the yield formation capacities of the wheat cultivar. Our investigation indicates that the water-saving management using drought tolerant cultivars is effective in production of winter wheat in North China Plain, which can drastically improve the plant WUE and maintain the sustainable wheat productivity under reduced irrigation conditions.