Drought Susceptible Varieties Research Articles

Role of Trichoderma asperelloides and Trichoderma brevicompactum in improving drought tolerance in rice

Drought is considered as one of the major abiotic stresses affecting rice production under rainfed ecologies of Bangladesh hampering the country's self-sufficiency in rice production through reduced crop yield and quality. In the present study, we studied the effect of two species of plant growth promoting Trichoderma v iz; Trichoderma asperelloides and Trichoderma brevicompactum on rice plant development under drought stress and their role in inducing tolerance to drought at physiological and biochemical level. Results reveal that both species are capable of inducing plant tolerance to drought stress when tested on drought tolerant (BRRI dhan56) and drought susceptible (IR64) varieties. As the number of drought stress days increased, there was an increase in root length of both the varieties but increase in root length was more in BRRI dhan56 as compared to IR 64 when seeds of both varieties were primed with Trichoderma. There was significant change in proline, malondialdehyde (MDA), total Phenolic content (TFC), H2O2 content in Trichoderma treated versus non-treated plants for both varieties. These biochemical changes were verified with the expression of aquaporin (AQU), dehydrin (DHN) and DREB genes in both rice varieties treated with both Trichoderma species. Interaction studies of Trichoderma species with two rice genotypes suggested that AQU-2 expressed more in tolerant variety (BRRI dhan56) when primed with Trichoderma asperelloides whereas, both Trichoderma spp. up regulated the expression of DHN-4 and DREB genes in both rice genotypes under drought conditions. The present findings suggest that the both Trichoderma asperelloides and Trichoderma brevicompactum are most effective in improving drought tolerance in rice, and its prospective application will contribute to the advancement of rice genotypes to sustain crop productivity under drought stress.

Polyethylene glycol-induced drought stress screening of selected Philippine high-yielding sugarcane varieties

A greenhouse study was conducted to characterize the drought response of eight high-yielding sugarcane varieties at tillering stage using polyethylene glycol 6000 (PEG6000) induced drought conditions. Plant height, stalk diameter, dry matter accumulation, root characteristics, stomatal conductance, chlorophyll fluorescence, SPAD, normalized difference vegetation index (NDVI), and canopy temperature were evaluated at 2.5 months after planting after four weeks of induced drought conditions. The study aimed to determine whether 1.0% PEG treatment would be able to produce significant differences among test genotypes and use it as a basis to determine drought-tolerant and susceptible varieties. Significant differences were observed among genotypes in PEG stress treatments. PEG stress resulted in significant reductions relative to non-PEG treatment in plant height (32.1%), leaf dry matter (31.6%), and stalk dry matter (49.5%) while total root length (11.8%), root surface area (7.8%) and root volume (19.6%) have generally increased. Reduced plant height, stalk diameter, and dry matter accumulation were observed in susceptible genotypes, while potential tolerant lines maintained or exhibited less reduction in these traits. Moreover, principal component analysis suggests that stalk dry matter, stomatal conductance, chlorophyll fluorescence plant height, SPAD, canopy temperature, and NDVI, highly contributed to the overall variation in the data (41.5%). With this, vars. 2289, 1011, 2569, and 1899 were identified to be potential drought-tolerant varieties while vars. 1763 and 2155 were potential drought susceptible varieties. Screening for drought tolerance under controlled conditions using PEG-induced drought stress offers a promising approach for sugarcane breeding especially when focusing on specific drought responses during important formative stages such as tillering stage. Being able to select genotypes of interest as early as the tillering stage would significantly hasten breeding cycles and will highly benefit the efforts towards drought stress tolerance in sugarcane.

Development of a phenotyping protocol for combined drought and salinity stress at seedling stage in rice.

The case of combined drought and salinity stress is increasingly becoming a constraint to rice production, especially in coastal areas and river deltas where low rainfall not only reduces soil moisture levels but also reduces the flow of river water, resulting in intrusion of saline sea-water. A standardized screening method is needed in order to systematically evaluate rice cultivars under combined drought+salinity at the same time because sequential stress of salinity followed by drought or vice-versa is not similar to simultaneous stress effects. Therefore, we aimed to develop a screening protocol for combined drought+salinity stress applied to soil-grown plants at seedling stage. The study system used 30-L soil-filled boxes, which allowed a comparison of plant growth under control conditions, individual drought and salinity stress, as well as combined drought+salinity. A set of salinity tolerant and drought tolerant cultivars were tested, together with several popular but salinity and drought-susceptible varieties that are grown in regions prone to combined drought+salinity. A range of treatments were tested including different timings of the drought and salinity application, and different severities of stress, in order to determine the most effective that resulted in visible distinction among cultivars. The challenges related to determining a protocol with repeatable seedling stage stress treatment effects while achieving a uniform plant stand are described here. The optimized protocol simultaneously applied both stresses by planting into saline soil at 75% of field capacity which was then allowed to undergo progressive drydown. Meanwhile, physiological characterization revealed that chlorophyll fluorescence at seedling stage correlated well with grain yield when drought stress was applied to vegetative stage only. The drought+salinity protocol developed here can be used for screening rice breeding populations as part of a pipeline to develop new rice varieties with improved adaptation to combined stresses.

Genetic analysis for detection of genes associated to drought tolerance in rice accessions belonging to north east India.

The North East (NE) India is rich in biodiversity and also considered as the secondary centre for origin of rice. The NE rice accessions was characterized previously using genetic markers and morphological traits. Simultaneously, genome-wide association studies (GWAS) reveal significant marker-trait associations for the drought tolerance traits. The genetic diversity and population structure of 296 NE rice accessions were studied using 96,712 single nucleotide polymorphism (SNP) markers distributed across 12 chromosomes. The accessions were clustered into two major sub-groups (SG). A total of 91 accessions were assembled as SG1 and 114 accessions as SG2, while the remaining 91 were admixture genotypes. A total of 200 genotypes belonging to different groups were phenotyped for yield component traits under drought and control conditions. The GWAS was performed to identify significant marker-trait associations (MTAs). Consequently, 47 MTAs were detected under drought, exhibiting 0.02-9.95% of phenotypic variance (P.V.). Whereas 58 MTAs were discovered under control conditions, showing a 0.01-9.74% contribution to the phenotype. Through in-silico mining of QTLs, 2999 genes were identified. Among these; only 22 genes were directly associated with stress response. These QTLs/genes may be deployed for marker-assisted pyramiding to improve drought tolerance in popular drought susceptible rice varieties.

Identification and characterization of genes for drought tolerance in upland rice cultivar 'Banglami' of North East India.

Rice is a major crop in Assam, North East (NE) India. The rice accessions belonging to NE India possess unique traits of breeder's interest, i.e., tolerant to biotic and abiotic stresses. In the present research programme, the stress responsive genes were identified within the QTLs associated with drought tolerance. The differential expression profiling of genes were performed under drought stress and control conditions. Thus, the 'candidate genes' associated with drought tolerance were recognised and may be deployed in a breeding programme. A drought-tolerant traditional rice cultivar, Banglami, was crossed with a high-yielding, drought-susceptible variety, Ranjit. The mapping population (F4) was raised through the single seed descent (SSD) method and used in QTL analysis. Under drought stress, a total of 4752 genes were identified through in-silico mining of QTLs. Among these, only 21 genes primarily associated with the stress response. The maximum of four stress-responsive genes were located within the QTLs, qNOG12.1 and qGY1.1. However, under control conditions, 2088 genes were identified, out of which, only 15 were categorised as the major stress responsive genes. The functional characterization of genes recognized 24 different types of proteins. Among these, peroxidase and heat shock proteins (Hsp) are the principal proteins encoded during stress. In addition to that, OsbZIP23, inorganic pyrophosphatase, universal stress protein, serine threonine kinase, NADPH oxidoreductase, and proteins belonging to the ABC1 family were also produced during stress condition. The differential expression profiling showed a profound expression pattern of three candidate genes under drought stress condition, i.e., OsI_32199 (Ascorbate peroxidase), OsI_37694 (Universal stress protein) and OsI_32167 (Heat shock protein 81 - 1). The novel candidate genes identified for drought tolerance, may be used in the breeding programme for the development of 'climate smart rice varieties'.

Genome-Wide Identification and Characterization of Receptor-Like Protein Kinase 1 (RPK1) Gene Family in Triticum aestivum Under Drought Stress.

Receptor-like protein kinase 1 (RPK1) genes play crucial roles in plant growth and development processes, root architecture, and abiotic stress regulation. A comprehensive study of the RPK1 gene family has not been reported in bread wheat (Triticum aestivum). Here, we reported the genome-wide identification, characterization, and expression patterns of the RPK1 gene family in wheat. Results confirmed 15 TaRPK1 genes, classified mainly into three sub-clades based on a phylogenetic tree. The TaRPK1 genes were mapped on chromosomes 1–3 in the respective A, B, and D genomes. Gene structure, motif conservation, collinearity prediction, and synteny analysis were carried out systematically. A Gene ontology study revealed that TaRPK1 genes play a vital role during molecular and biological processes. We also identified 18 putative miRNAs targeting TaRPK1 genes, suggesting their roles in growth, development, and stress responses. Cis-Regulatory elements interpreted the presence of light-related elements, hormone responsiveness, and abiotic stress-related motifs in the promoter regions. The SWISS_MODEL predicted the successful models of TaRPK1 proteins with at least 30% identity to the template, a widely accepted threshold for successful modeling. In silico expression analysis in different tissues and stages suggested that TaRPK1 genes exhibited the highest expression in root tissues. Moreover, qRT-PCR further validated the higher expression of TaRPK1 genes in roots of drought-tolerant varieties compared to the drought-susceptible variety. Collectively, the present study renders valuable information on the functioning of TaRPK1 genes in wheat that will be useful in further functional validation of these genes in future studies.

Physiological and Transcription Analyses Reveal the Regulatory Mechanism in Oat (Avena sativa) Seedlings with Different Drought Resistance under PEG-Induced Drought Stress

Drought severely limits the growth and development of oat (Avena sativa) seedlings. As an osmotic regulator simulating a drought environment, Polyethylene glycol (PEG) has been widely linked in response to plant drought tolerance. However, the underlying mechanism of oats’ response to PEG stress is still largely unknown. Here, we investigated the physiological and transcriptome variables of the drought-resistant oat variety DA92-2F6, and the drought-susceptible variety Longyan 3 under 15% PEG-6000 drought stress to better understand the underlying drought tolerance molecular mechanisms. The physiological results showed that except for the cell membrane permeability, the antioxidant enzyme, osmotic adjustment substance, and photosynthetic efficiency were significantly higher in the DA92-2F6 after 7 d stress. Further, 12 cDNA libraries and 123,223 unigenes were obtained by RNA-seq. A total of 33,857 differentially expressed genes (DEGs) were detected, of which two co-upregulated and three co-downregulated in four comparisons. We highlighted an analysis of the DEGs in phytohormone signal transduction pathway. The auxin, cytokinin, and brassinosteroid signaling pathways, were suppressed in Longyan 3, while abscisic acid and jasmonic acid signaling pathways were mainly activated in DA92-2F6 under drought stress. The upregulated of PP2C, ABF, SNRK2, GID1, JAZ, and MYC2 genes may enhance the drought tolerance of DA92-2F6. Taken together, these results provided a new transcript resource for the drought tolerance improvement and a reference for oat drought resistance molecular breeding.

Generation Mean Analysis for Yield and Drought Tolerant Traits under Rainfed and Irrigated Conditions in Rice (Oryza sativa L.)

Generation mean analysis was carried out using two crosses, involving a high yielding drought susceptible variety NDR 359 and drought tolerant rainfed cultivars Nagina 22 and Vandana. Six generations namely P1, P2, F1, F2, BC1 and BC2 were grown under both rainfed and irrigated environment to study the gene action for various yield and drought tolerance traits. Scaling test revealed the presence of epistasis for most of the yield and drought tolerance traits in both the crosses. Hence, six parameter model was adopted for these traits and for few traits where epistasis was absent, three parameter model was used. The results revealed that dominance gene effect along with non-allelic interactions had profound effect on the genetic control of majority of the yield traits. Therefore, early generation selection will be misleading for these traits. However, the drought tolerance related traits like proline content and stomatal conductance were governed by additive component as well. Duplicate epistasis was observed for majority of the traits. Hence, present study indicates that, epistasis has a key role in the expression of almost all the traits in both the environment.

Genetic Retrospect of Seedcotton Yield and its Components from a 6-Parent Gossypium hirsutum Diallel Cross Under Water Stress Conditions

A six-by-six complete F1 Gossypium hirsutum, L. diallel cross of three pre-screened drought tolerant and three drought susceptible varieties (CRIS-134, CRIS-342, SINDH-1, NIAB-78, SADORI and BH-160) was evaluated for genetic parameters during 2009 at Sindh Agriculture University farm, Tandojam. The characters studied were number of bolls per plant, sympodial branches per plant, seedcotton yield per plant and lintcotton yield per plant. The objective of such study was to assess the effect of irrigation stress on the genetic inheritance pattern of above quantitative traits as to how far the genetic parameters are affected due to irrigation stress in the F1 diallel generation. Irrigation treatments were four; normal seven irrigations schedule, five irrigations, four irrigations (medium stress) and three irrigations up to 150 days of crop maturity (stress conditions). CRIS-134 in seven, Sadori in five and CRIS-342 in four and three irrigations treatments were the most recessive parents contributing increasing boll number into their progenies while BH-160 in seven, CRIS-342 in five and Sindh-1 in four and three irrigations treatments proved to be the most dominant parents responsible for contributing decreased boll number per plant into their progenies. Seedcotton per plant was partial dominant in seven irrigations treatment while it inherited as an overdominant trait in five, four and three irrigations respectively. BH-160 was the most recessive of all with increased sympodia contributing attributes in seven and four irrigations whereas Niab-78 in five and CRIS-342 in stress were the most recessive parents. Sindh-1 was the most dominant parent in seven, five and three irrigation treatments while CRIS-342 in four irrigations yielded decreased sympodia contributing attributes into their progenies. Sindh-1 in seven, BH-160 in five and three and CRIS-342 in four irrigations treatments proved to be the most recessive parents with increasing seedcotton yield attributes while CRIS-342 in seven and five and Sindh-1 in four and three irrigations were the most dominant parents contributing decreased seedcotton yield into their progenies. Inheritance trend of lintcotton per plant was similar to that of seedcotton yield per plant.

Effect of uniconazole to soybean seed priming treatment under drought stress at VC stage

Studying the mechanism of drought stress in soybean root at vegetative cotyledon (VC) stage by soaking seeds with uniconazole revealed new insights into soybean stress physiology. Therefore, a completely random pot experiments with different time gradients for water cut-off (24, 48, 72, 96 and 120 h, respectively) were carried out with uniconazole (0.4 mgL−1) with respect to morphological, microscopic, ultramicroscopic, physiological, and molecular studies on varieties Hefeng55 (H50, drought tolerant variety) and Kenfeng16 (K16, drought susceptible variety). Results revealed that uniconazole effectively alleviated the inhibition on root growth caused by drought stress, increased the number of root tips, significantly reduced lignification of vessels, alleviated the damage of mitochondria and nucleus caused by drought stress, further strengthened osmotic adjustment system and antioxidant system, especially when the soil moisture content was less than 14%, broke expression restriction of IAA due to drought stress, and inhibited GA3 generation; finally, we found that high-intensity drought stress significantly increased the expression levels of GmNAC003, GmNAC004, GmNAC015, GmNAC020, GmHK07, GmRR01, GmRR02 and GmRR16 genes relating to drought tolerance, while uniconazole had a significant inhibitory effect on GmNAC003, GmNAC004, GmNAC015, GmNAC020, GmRR01, GmRR02 and GmRR16 genes. Our results provided a reference for the mechanism of drought resistance in legume and the effect of uniconazole on alleviating drought stress.

Evaluation of advanced back cross lines for drought tolerance in rice (Oryza sativa L.)

Drought is the largest abiotic constraint to rice production which cause significant yield loss depending upon the severity. Development of rice varieties with tolerance to drought and high use water use efficiency is the need of the hour. Despite the importance of drought as major abiotic constraint, the efforts to develop drought tolerant rice varieties are very low. Breeding efforts until recent past were focused on understanding and improvement of secondary traits that are putatively associated with drought tolerance. However, the genetic gain in yield by improvement of secondary traits is very low. Hence, improvement of yield per se under drought conditions will be better solution. Introgression of yield QTLs under drought in the genetic background of high yielding varieties will be helpful to overcome the problem to a certain extent. In the present study, 31 advanced back cross lines (BILs) derived from drought susceptible mega variety Samba Mahsuri (BT 5204) and a drought tolerant tolerant land race Azucena were evaluated under drought. Thirty one advanced back cross inbred lines (BC2F4) lines having yield QTLs viz., qDTY3.1 on chromosome 3 and qDTY2.1 on chromosome 2 were phenotyped under drought conditions. The results suggested that wide range of variation was observed for yield and its component traits in the BILs generated in the background of BPT 5204 and direct selection for yield under water stress coupled with marker assisted screening would help in development of drought tolerant version of mega varieties with improved yield under stress. Thermo tolerance studies indicated that high variability was observed for the BILs in terms of % seedling survival, % reduction in root and shoot growth under stress.

Unraveling regulatory divergence, heterotic malleability, and allelic imbalance switching in rice due to drought stress

The indica ecotypes, IR64, an elite drought-susceptible variety adapted to irrigated ecosystem, and Apo (IR55423-01 or NSIC RC9), a moderate drought-tolerant upland genotype together with their hybrid (IR64 × Apo) were exposed to non- and water-stress conditions. By sequencing (RNA-seq) these genotypes, we were able to map genes diverging in cis and/or trans factors. Under non-stress condition, cis dominantly explains (11.2%) regulatory differences, followed by trans (8.9%). Further analysis showed that water-limiting condition largely affects trans and cis + trans factors. On the molecular level, cis and/or trans regulatory divergence explains their genotypic differences and differential drought response. Between the two parental genotypes, Apo appears to exhibit more photosynthetic efficiency even under water-limiting condition and is ascribed to trans. Statistical analyses showed that regulatory divergence is significantly influenced by environmental conditions. Likewise, the mode of parental expression inheritance which drives heterosis (HET) is significantly affected by environmental conditions indicating the malleability of heterosis to external factors. Further analysis revealed that the HET class, dominance, was significantly enriched under water-stress condition. We also identified allelic imbalance switching in which several genes prefer IR64- (or Apo-) specific allele under non-stress condition but switched to Apo- (or IR64-) specific allele when exposed to water-stress condition.

High-throughput miRNA deep sequencing in response to drought stress in sugarcane.

The online version contains supplementary material available at 10.1007/s13205-021-02857-x.

Responses of Mungbean to Water Deficit, Water use Efficiency and Drought Resistance

Backround: Legumes are the second important agricultural crop of great prominence to humans. Among 20000 legume species the mungbean is one of the most important grain cultivated in India. Drought is a major environmental stress that affects mungbean in the sub-humid, dry and intermediate zones of India. The present study records the response of mung bean varieties to water stress during its growth stage.Methods: The impact of drought stress imposed on the crop was evaluated by measuring the water relation parameters and the biochemical progresses like osmolyte accumulation, nitrate assimilation and antioxidant system in Mung bean during 2017-2018 in Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore.Result: Drought stress altered the water status of the crop by reducing the RWC, which was enhanced in drought susceptible varieties. Increased amount of proline denotes the osmoregulatory mechanism in the crop to bring about resistance and the elevated levels of antioxidant enzymes shows the protective mechanism in the crop at cellular level.

Evaluation of Oxidant and Antioxidant Systems in Drought Response of Cowpea Varieties

Plant in their natural environment are exposed to several stresses such as the drought that affect their growth and productivity. Exposure of plant to drought leads to oxidative stresses as a result of increase in ROS, however plant counteract this effect by its antioxidant system. H 2 O 2 , malondialdehyde, membrane stability index, catalase and ascorbate peroxidase activities where evaluated in leaves of two cowpea varieties drought tolerant (Dan’ila) and drought susceptible (TVU 7778) during 2 weeks water deficit and 5days recovery. The result indicates significant increase in the H 2 O 2, MDA, CAT and APX activities in both varieties during the stress period and significant decrease during recovery in drought tolerant variety compared to the drought susceptible variety. The membrane stability index decreases significantly during stress period in both varieties. Drought tolerant variety has the higher ability to counteract oxidant activity during the drought stress and recover faster than the drought susceptible variety. Keywords : Drought, antioxidant, cowpea DOI: 10.7176/JNSR/12-8-03 Publication date: April 30 th 2021

Drought susceptibility index and correlation of soybean based on yield and yield component

The objectives of this study were to know drought susceptible and resistant varieties of soybean-based on the average value of drought susceptibility index and correlation of yield and yield components traits under drought stress condition. This study was conducted using an experimental method and was laid out using Factorial Completely Randomized Design (CRD), two factors with three replicates of each experimental unit. Factor 1 soybean variety consists of 7 genotypes: Lawit, Sibayak, Kaba, Pangrango, Seulawah, Nanti, and Burangrang, and factor 2 drought stress condition: no drought stress (reasonable condition), drought stress during the vegetative phase, drought stress during the generative phase, and drought stress during vegetative and generative phases. Yield component traits observed were the number of pod per plant, number of empty pod per plant, number of filled pod per plant, number of seeds per plant, the weight of 100 dry seeds, and seed weight per plant. Based on the results of the study, it can be concluded that: 1). Variety of Sibayak and Nanti, were classified as resistance to drought stress either during the vegetative phase, generative phase, or continuous drought. 2). The highly significant positive correlation of among yield and yield components of soybean under drought stress were: seed weight per plant - number of pods, seed weight per plant - number of filled pods, and seed weight per plant - number of seed per plant, while highly significant negative correlation occurred in the character of flowering date - 100 seed weight.

Comparison of tolerance related proteomic profiles of two drought tolerant tomato mutants improved by gamma radiation

Lycopersicon esculentum L., also known as tomato, is an important industrial plant due to its products which worth billions of dollars annually, besides its nutritional value and health benefits. In this study, we investigated the two-dimensional protein expression profiles in drought tolerant mutant plants derived from industrial 5MX12956 tomato variety by Cs-137 gamma radiation source induced mutations. Drought tolerance of mutants were evaluated and confirmed by in vivo and in vitro methods. Eleven drought responsive protein spots were identified by two-dimensional electrophoresis and MALDI-TOF-MS. Identified proteins which presented differential expression under drought conditions were clustered under six distinct groups based on their cellular functions. These clusters are ATP and carbohydrate metabolism, mRNA processing and protein phosphorylation, oxidation reduction and stress response, signaling and supporting cytoskeleton. Our results contributed proteomic data to drought tolerance of our tomato mutants which were originated from drought susceptible 5MX12956 variety. They may also facilitate basis for future investigations into the genetic and physiological aspects of this tolerance.

Two dimensional in-vitro phenotyping of root system architecture using Poly Ethylene Glycol in backcross inbred lines harboring drought tolerant QTLs of rice (Oryza sativa L.)

The present investigation was made to validate the effect and expression of multiple drought QTLs from Apo in the background of high yielding drought susceptible variety IR 64 under two dimensional in-vitro root architecture studies. The genotype CB 229 (DTY2.2, DTY3.1 and DTY8.1) recorded a higher network bushiness, network width, specific root length and network distribution of roots under PEG treatment (stress) and in network area CB 193-3 outperformed than CB 229. This clearly shows that introgression of multiple drought QTLs in various combination in the same genetic background enhances different level of expression of QTLs and tolerance to varied intensity of drought. Under field screening for drought, CB 229 out performed in both spikelet fertility percentage and yield than the remaining BILs. The traits viz., major ellipse axis, maximum number of roots, network bushiness, specific root length, network convex area and network width are positively correlated with spikelet fertility percentage and single plant yield under drought experiment. Principal component analysis accounted for 78.47 per cent of variability among root traits in PC1 and was loaded with all the traits observed under in-vitro condition. Hence, an understanding on complex nature of QTL expression associated with root system architecture under in-vitro stress in rice may help the breeder to develop new cultivars with enhanced level of tolerance against water limited situations in near future.

Introgression of drought tolerance QTLs through marker assisted backcross breeding in wheat (Triticum aestivum L.)

The present study reports the introgression of the genomic regions linked with drought tolerance traits viz., NDVI, staygreen, chlorophyll content/chlorophyll fluorescence and yield from a drought tolerant parent HI1500 in to a popular high yielding but drought susceptible wheat variety GW322 following the marker assisted backcross breeding. Background selection with 109 polymorphic SSR markers accelerated genome recovery of recurrent parent which ranged from 72.14 to 86.9% in BC1F1, 90.33 to 92.02% in BC2F1 and 91.6 to 94.95% with an average of 93.5% in BC2F2 generation. Eighteen homozygous BC2F3 progenies were found to be phenotypically superior for morpho-physiological and agronomic traits over the recurrent parent GW322.

Physiological and Molecular Osmotic Stress Responses in Three Durum Wheat (Triticum Turgidum ssp Durum) Genotypes

This study aims to investigate the activities and expression of enzymes of primary metabolism and relate these data with the growth performance of three different durum wheat genotypes (Maali; YT13; and ON66) under osmotic stress. Growth traits—including plant height, dry weight (DW) and relative water content (RWC)—were measured to classify genotypes depending on their tolerance to stress. Several enzymes were investigated: Ascorbate peroxidase (APX), Glutamine Synthetase (GS), Glutamine dehydrogenase (GDH), Glutamate synthase (GOGAT), Glucose 6-phosphate dehydrogenase (G6PDH), and Phosphoenolpyruvate Carboxylase (PEPC). The expression of the cytosolic and plastidic glutamine synthetase (TaGS1 and TaGS2), high affinity nitrate transporters (TaNRT2.3) and Glutamate dehydrogenase (TaGDH) were also detected by qRT-PCR. The results indicated different growth performances among genotypes, indicating Maali and YT13 as tolerant genotypes and ON66 as a drought-susceptible variety. Data showed a decrease in PEPC and increase in APX activities under osmotic stress; a slight decrease in GS activity was observed, together with an increase in G6PDH in all genotypes; GS and NRT2 expressions changed in a similar pattern in the different genotypes. Interestingly, Maali and YT13 showed higher transcript abundance for GDH under stress compared to ON66, suggesting the implication of GDH in protective phenomena upon osmotic stress.