Salt-tolerant Genotypes Research Articles

In vitro plant regeneration, screening for salt and drought tolerance in sugarcane (Saccharum Spp.)

Soil salinity and drought are some of the major sugarcane production factors in Ethiopia. This investigation was conducted to develop, screen and select salt and drought tolerant genotypes under in vitro condition. Both direct and indirect pathways were employed in the development and selection of salt and drought tolerant lines from the commercial varieties. In all cultures, explants were inoculated to Murashige and Skoog (MS) medium supplemented with inhibitory levels of NaCl (0, 30, 100, 170 & 240 mM) and polyethylene glycol (0, 2.5, 5, 7.5 & 10%) concentrations. During callus induction, data for percent of explants induced callus and its morphological status were collected to evaluate varieties, and select healthy, salt and polyethylene glycol (PEG) tolerant calli. Moreover, shoot regeneration percentage, shoot Vigrousity and color were taken as major criteria to select stress (salt and PEG) tolerant shoot while data for plantlet root attributes were collected to screen stress tolerant plantlets. Results of the study indicated that health and salt tolerant calli and shoots were identified at MS medium supplemented with 170 Mm while 10% PEG was the best selection medium to select healthy and PEG tolerant calli and shoots. Our screening results suggested that the in vitro developed regenerants were more discriminated at 240 mM NaCl where S4SP-70-1284, S4 C0-501 and S2B-78-505 were selected as salt tolerant regenerants. Moreover, more variability was observed at MS medium induced with 10% polyethylene glycol where regenerants D4C-132-81, D5C-132-81, D3B52-298, D2B52-298 and D4B52-298 showed better degree of tolerance to drought. The dendrogram separated those regenerants developed through direct regeneration from those regenerants developed through indirect regeneration. It suggested the existence of somaclonal variation. Moreover, both dendrograms were capable of separating those regenerants exhibiting tolerance to the stresses in question thereby suggesting the existence of variability in relation to stress tolerance. We recommend these regenerants be used as a source of variability for future stress breeding studies. Moreover, these regenerants can be used as alternative varieties at salt affected and soil moisture limited fields of sugarcane production areas. However, it should be further evaluated for yield and yield quality before using for commercial purposes.

Discovery of microRNA-target modules of African rice (Oryza glaberrima) under salinity stress

Oryza glaberrima is the second edible rice in the genus Oryza. It is grown in the African countries. miRNAs are regulatory molecules that are involved in every domains of gene expression including salinity stress response. Although several miRNAs have been reported from various species of Oryza, yet none of them are from this species. Salt treated (200 mM NaCl for 48 h) and control smallRNA libraries of RAM-100, a salt tolerant genotype, each with 2 replications generated 150 conserve and 348 novel miRNAs. We also used smallRNAseq data of NCBI of O. glaberrima to discover additional 246 known miRNAs. Totally, 29 known and 32 novel miRNAs were differentially regulated under salinity stress. Gene ontology and KEGG analysis indicated several targets were involved in vital biological pathways of salinity stress tolerance. Expression of selected miRNAs as indicated by Illumina data were found to be coherent with real time-PCR analysis. However, target gene expression was inversely correlated with their corresponding miRNAs. Finally based upon present results as well as existing knowledge of literature, we proposed the miRNA-target modules that were induced by salinity stress. Therefore, the present findings provide valuable information about miRNA-target networks in salinity adaption of O. glaberrima.

ERF transcription factors involved in salt response in tomato

ERF transcription factors are important regulatory components of ethylene signaling, known to be involved in plant development and stress responses by regulating the expression of ethylene responsive genes. However, relatively less is known about the function of ERF gene family in wild tomato response to salt stress. Previously, we have carried out a microarray analysis on the salt-responsive genes in salt tolerant wild tomato Solanum pimpinellifolium ‘PI365967’. Five ERF genes (SpERFs) with induced expression upon salt treatment were subsequently selected for further characterization. Sequence analysis revealed that the seven amino acid residues in ERF proteins which are critical for their binding to the GCC-box in the promoter of ethylene responsive genes were conserved in five SpERFs. Two of five SpERFs (SpERF.B7 and SpERF.C11) belong to B3 sub-group as predicted by phylogenetic analysis. Expression analysis indicated that two SpERFs of B3 sub-group were more strongly induced in salt-tolerant genotypes than in salt-sensitive genotypes, in the order of PI365967 > LA2711 > Moneymaker, suggesting a positive role of B3 sub-group SpERFs in salt stress in tomato. To further confirm the function of B3 SpERFs in salt response, SpERF.B7 (one of two B3 SpERFs) was over-expressed in Arabidopsis. Consistent with our expectation, transgenic lines exhibited enhanced salt tolerance. These results will provide useful information for improving salt tolerance in tomato breeding in the future.

Screening of Sorghum genotypes for salt-tolerance based on seed germination and seedling stage

Screening of Sorghum genotypes for salt-tolerance based on seed germination and seedling stage

Expression pattern of salt tolerance-related genes in Aegilops cylindrica.

Aegilops cylindrica, a salt-tolerant gene pool of wheat, is a useful plant model for understanding mechanism of salt tolerance. A salt-tolerant USL26 and a salt-sensitive K44 genotypes of A. cylindrica, originating from Uremia Salt Lake shores in Northwest Iran and a non-saline Kurdestan province in West Iran, respectively, were identified based on screening evaluation and used for this work. The objective of the current study was to investigate the expression patterns of four genes related to ion homeostasis in this species. Under treatment of 400mM NaCl, USL26 showed significantly higher root and shoot dry matter levels and K+ concentrations, together with lower Na+ concentrations than K44 genotype. A. cylindrica HKT1;5 (AecHKT1;5), SOS1 (AecSOS1), NHX1 (AecNHX1) and VP1 (AecVP1) were partially sequenced to design each gene specific primer. Quantitative real-time PCR showed a differential expression pattern of these genes between the two genotypes and between the root and shoot tissues. Expressions of AecHKT1;5 and AecSOS1 was greater in the roots than in the shoots of USL26 while AecNHX1 and AecVP1 were equally expressed in both tissues of USL26 and K44. The higher transcripts of AecHKT1;5 in the roots versus the shoots could explain both the lower Na+ in the shoots and the much lower Na+ and higher K+ concentrations in the roots/shoots of USL26 compared to K44. Therefore, the involvement of AecHKT1;5 in shoot-to-root handover of Na+ in possible combination with the exclusion of excessive Na+ from the root in the salt-tolerant genotype are suggested.

Tolerance of melon cultivars to irrigation water salinity

ABSTRACT The use of saline water for irrigation causes severe restriction to nutritional balance, growth and production in many crops due to the effect of salts on plant and soil. The objective of this study was to investigate the response of melon (Cucumis melo L.) cultivars to various levels of irrigation water salinity on yield and fruit quality. A field experiment was conducted in a split-plot randomized block design with four replicates. The factors were five levels of irrigation water salinity (0.54, 1.48, 2.02, 3.03 and 3.90 dS m-1) in the plots and five melon cultivars (C1 - Sancho - Pele de sapo; C2 - Medellín - Pele de sapo; C3 - Mandacaru - Canary; C4 - Néctar - Galia; C5 - Sedna - Cantaloupe) in the sub-plots. According to the results, among the five genotypes studied, Sancho was the most salt-tolerant genotype, followed by Mandacaru, Medellín, Sedna and Néctar. Since irrigation water salinity did not influence the mean fruit weight, the reduction in the number of fruits was the main cause of yield reduction of the melon crop under high salinity water. The contents of total soluble solids increased under high salinity level.

Devolopment of Some Canola Genotypes to Salinity Tolerance Using Tissue Culture Technique

T HIS WORK was carried out during 2011- 2015 in the laboratories of Cell Research Department (CRD), Field Crops Research Institute (FCRI), Agricultural Research Center (ARC), Giza, as well as, in the greenhouse of Agronomy Department, Faculty of Agriculture, Ain Shams University, Egypt, to study the variation among canola varieties in response to salt tolerance through tissue culture propagation. This work was aimed to establish a regeneration protocol for canola genotypes, production of salt-tolerance plants through selection of salt-tolerance callus via somaclonal variation and subsequent regeneration of plantlets from such callus. Four genotypes of canola were used for establishment a regeneration protocol, Bingo and Torpe were uesed as highly salt tolerant genotypes while, Conny and Siberian as susceptible genotypes. The results indicated that MS medium supplemented with 2 mg/l 2,4-D was the successive medium for callus formation and shoot regeneration was obtained from MS medium supplemented with 5 mg/l BA + 0.05 NAA, while, 1mg/l IBA was the better growth regulator for rooting.For in vitro selection of salt tolerant calli, Torpe (genotype overcomes the others in calli survival percentages under 8000, 12000 and 16000 ppm NaCl concentrations. The results of shoot frequency from tolerant calli cleared that Torpe genotype recorded the highest value of shoot percentage followed by Bingo genotype, whereas, Conny followed by Siberian genotypes were recorded the lowest values. At 16000 ppm NaCl concentration, only tolerant calli of Torpe genotype was able to initiat shoot under this concentration. For acclamatization after regeneration from the tolerant calli, only five salt tolerant plantlets developed from Torpe genotype and eight salt tolerant plantlets developed from Siberian genotype that succeeded to complete their life cycle and reached maturity stage and produced seeds. These regenerated genotypes were referred as T1, T2, T3, T4 and T5, the five regenerated plants developed from Torpe genotype that tolerate NaCl concentration up to 16000 ppm, as well as, S1, S2, S3, S4, S5, S6, S7 and S8, the eight regenerated plants developed from Siberian genotype that tolerate NaCl concentration up to 12000 ppm.

Evaluation of some Bread Wheat Genotypes under Saline Soil Conditions Using Tolerance Indices and Multivariate Analysis

The present investigation was conducted in a field experiments at Sakha Agricultural Research Station Farm to evaluate 24 bread wheat genotypes during the two growing seasons 2014/2015 and 2015/2016 under normal and salinity stress conditions. The experimental design used was a randomized complete block design with three replicates. Eleven stress tolerance indices (STI's) were calculated based on average grain yield under normal and stress conditions across the two seasons. Moreover, cluster analysis was performed to identify the similarity/dissimilarity among the tested genotypes for grain yield and salinity tolerance. Results showed large values of broad-sense heritability (hb2) coupled with high values of genetic advance as a percent of mean (GA%) at 5% selection intensity for number of spikes/m2 and number of grains/spike in the adequate site. Concerning the salt stressed soil, the grain yield ratio, number of spikes/m2 and grain yield recorded the highest values of hb2 and GA%. However, there were crucial differences among tested genotypes in respect to grain yield under non-stress and salt stress sites, which demonstrates high genetic diversity among them that enabled us to screen salt tolerant genotypes. Already, the tested wheat genotypes exhibited different responses for salinity stress tolerance indices (STI's). Perfect and positive correlation coefficients (r = 1) were found between three pairs of indices (STI and GMP), (SSPI and TOL) and (CV and SSI) where each one of the previous three pairs occupied one dot on the biplot graph indicating that the three indices are identical for ranking genotypes for salinity tolerance and they could be interchangeably used as a substitute for each other. Therefore, using these pairs of (STI's) together in the same study is considered a waste of time and effort. The cluster analysis classified the tested genotypes into five main groups (clusters) where each group contained the genotypes that showed similar yield potential and salinity tolerance. The fifth cluster contained two promising genotypes namely; lines 2 and 17 that were characterized by moderate grain yield in each of the normal and salt soils recording the lowest grain yield reduction. Also, they occupied the first and second ranks among the tolerant genotypes for salinity stress. Accordingly, results would give a good chance to achieve genotypic improvement of wheat through the hybridization among genotypes taken from different clusters.

Assessment of watermelon accessions for salt tolerance using stress tolerance indices

ABSTRACT Salt stress is the most significant constraint for agricultural production in arid and semi-arid regions. Thus, genetically improved stress-tolerant varieties are needed for the future. The identification of salt-tolerant genotypes is the starting point for such breeding studies. This study was conducted to determine and assess the tolerance of different watermelon genotypes under saline conditions. Twenty-two watermelon genotypes and accessions were grown in pots with 3 kg of soil in four saline stress conditions (0 mmol kg-1 as the control, 25, 50 and 100 mmol kg-1 NaCl). The detrimental effects of salt stress on the plants were evident with increasing doses of NaCl. Stress indices calculated over the plant dry weights under the 100 mmol kg-1 salinity level were used to assess the salt tolerance of the genotypes. Stress intensity was calculated as 0.76. Such a value indicated that the highest dose of salt exerted severe stress on the plants. The G04, G14 and G21 genotypes were considered to be salt tolerant, since these genotypes showed the highest values of K/Na and Ca/Na ratios in the plant tissue. The losses in dry mass at severe salt stress reached 75.48%. In principal component analyses, the genotypes had positive correlations with stress tolerance indices of MP (mean productivity), GMP (geometric mean productivity) and STI (stress tolerance index). The GMP and STI indices indicated that G04 (a member of Citrullus colocynthis), G14 and G21 could be prominent sources to develop salt tolerance.

Leaf photosynthesis, chlorophyll fluorescence and ion content of barley (Hordeum vulgare) in response to salinity

ABSTRACTEight barley genotypes contrasting in their salinity tolerance were assessed for their chlorophyll fluorescence, photosynthetic performance, lipid peroxidation level and ionic content. A pot experiment was conducted in Borj-Cedria (Tunisia), in a wire house with a glass roof to avoid rainfall. The assay consisted of three treatments (0, 100 and 200 mM NaCl) with eight barley genotypes following a completely randomized design. Each pot was considered as one replicate and nine replicates were used for each genotype and treatment. The salt-tolerant genotypes Kerkna and Tichedrett recorded the highest tolerance for photosynthesis and potassium accumulation, whereas the susceptible genotypes were mostly affected at severe salinity. Contrasting behavior was noted for fluorescence attributes, while PSII yield was unchanged reflecting good protection against photodamage. Photosynthetic performance, enhanced water use efficiency, maintained leaf K+ and oxidative defense remain the key components for tolerance mechanisms. Salt-tolerant barley could be suitable for management of salt-affected soils.

Interactive effects of saline irrigation water and genotypes on nutrient composition of chamomile (Matricaria Recutita L.)

ABSTRACTThis study was conducted to elucidate the effect of salinity (2, 6, 9, and 12 dS m−1 sodium chloride (NaCl)) on three Iranian German chamomile genotypes (Shiraz, Ahvaz, and Isfahan). The Shiraz and Ahvaz genotypes, respectively, had the highest productivity and tolerance level, while the Isfahan was the less salt-tolerant genotype. In contrast to quantitative traits, the Isfahan genotype exhibited superior qualitative traits in terms of essential oil and chamazulene percentage. The differential responses to productivity and salt-resistance were attributed to the genetic variation, higher root to shoot ratios, and compartmentalization of sodium in roots of the Shiraz and Ahvaz genotypes, leading to better nutrient uptake and balance. While the nutrient composition was relatively in the same range for all genotypes, the higher accumulation of phosphorus in root and anthodia of the Shiraz genotype was evident. In addition, anthodia of the Ahvaz and root of the Shiraz genotype stored more nitrogen nutrient element.

Ethylene triggers salt tolerance in maize genotypes by modulating polyamine catabolism enzymes associated with H2O2 production

The current study was undertaken to investigate if there is a relationship between metabolisms of ethylene and polyamines in the processes of salinity acclimation of salt-tolerant and salt-sensitive maize genotypes. Biphasic ethylene production (at 5.5 and 12.5h) was registered only in salt-sensitive plants during NaCl exposure. In the salt-tolerant genotype, the unique ethylene peak at 5.5h was closely related to increased polyamine accumulation (a polyamine-dependent H2O2 signalling process), whereas the same did not occur in the salt-sensitive genotype. The absence of H2O2 signalling at 5.5h in the salt-sensitive genotype was related to a burst in ethylene production at 12.5h, known as ‘stress ethylene’, as well as a concomitant decrease in total polyamine content by salinity. The lack of stress ethylene synthesis in the salt-tolerant genotype was attributed to down-regulation of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) activity and ZmACO5b gene expression. Our findings suggest that ethylene is intimately involved in salt stress acclimation through activation of a complex pathway of signalling by H2O2 that is polyamine catabolism-dependent.

Comprehensive physiological analyses and reactive oxygen species profiling in drought tolerant rice genotypes under salinity stress.

Rice being a staple cereal is extremely susceptible towards abiotic stresses. Drought and salinity are two vital factors limiting rice cultivation in Eastern Indo-Gangetic Plains (EIGP). Present study has intended to evaluate the consequences of salinity stress on selected drought tolerant rice genotypes at the most susceptible seedling stage with an aim to identify the potential multi-stress (drought and salt) tolerant rice genotype of this region. Genotypic variation was obvious in all traits related to drought and salt susceptibility. IR84895-B-127-CRA-5-1-1, one of the rice genotypes studied, exhibited exceptional drought and salinity tolerance. IR83373-B-B-25-3-B-B-25-3 also displayed enhanced drought and salt tolerance following IR84895-B-127-CRA-5-1-1. Variations were perceptible in different factors involving photosynthetic performance, proline content, lipid peroxidation, K+/Na+ ratio. Accumulation of reactive oxygen species (ROS) disintegrated cellular and sub-cellular membrane leading to decreased photosynthetic activities. Therefore, accumulation and detoxification of reactive oxygen species was also considered as a major determinant of salt tolerance. IR84895-B-127-CRA-5-1-1 showed improved ROS detoxification mediated by antioxidant enzymes. IR84895-B-127-CRA-5-1-1 seedlings also displayed significant recovery after removal of salt stress. The results established a direct association of ROS scavenging with improved physiological activities and salt tolerance. The study also recommended IR84895-B-127-CRA-5-1-1 for improved crop performance in both drought and saline environments of EIGP. These contrasting rice genotypes may assist in understanding the multiple stress associated factors in concurrent drought and salt tolerant rice genotypes.

Salinity induced changes in water relations, oxidative damage and morpho-physiological adaptations of pistachio genotypes in soilless culture

Selecting salt tolerant rootstocks is a sustainable approach for developing fruit trees in salinity prone areas. 60-day-old seedlings of Pistacia vera ‘Akbari’ and ‘Ghazvini’, and P. vera ‘Ghazvini’ × P. atlantica (G×A) were subjected to 0, 50, 100 and 150 mM NaCl in half strength Hoagland’s nutrient solution. After 45 days, the growth, water relations, and oxidative damage parameters were investigated. Salt stress reduced plant biomass, height, crown diameter and leaf number, but increased specific leaf area (SLA) of the seedlings. Under salt stress, the growth of ‘Akbari’ seedlings was higher than the other genotypes. Accumulation of malondialdehyde (MDA) and proline was observed in the leaves of salt affected seedlings. ‘Ghazvini’ seedlings had the highest MDA concentration and the lowest cell membrane stability in their leaves. Degredation of photosynthetic pigments under salt stress was lower in the leaves of ‘Akbari’ seedlings than that in other genotypes. Increase in leaf succulence was observed in ‘Akbari’ and G×A seedlings in response to salt stress. Relative water content and concentration of anthocyanins in the leaves of pistachio genotypes remained unchanged under salt stress. The results revealed that monitoring leaf abscission, SLA, leaf succulence, MDA concentration, and photosynthetic pigments provide suitable contrast for screening salt tolerance in pistachio. Furthuremore, ‘Akbari’ was found to be the most salt tolerant genotype.

Screening of winter triticale genotypes for resistance to salinity in the shoot apical meristem culture

Purpose. To conduct in vitro screening of different genotypes of winter triticale for resistance to salinity in the shoot apical meristem culture. Methods. Plant tissue culture in vitro, in vitro breeding, statistical analysis. Results. It was found that the increase of sodium chloride concentration from 0.6 to 1.5% resulted in inhibition of the callus culture growth in all genotypes that was indicative of the toxic effect of the stress factor. It turns out that 1.2% sodium chloride concentration allowed to differentiate triticale genotypes for salt tolerance. The line ‘38/1296’ appeared to be the most resistant to salinity stress because under breeding conditions calli of this genotype were characterized by higher morphogenetic potential, had the highest crude mass increase, and plants-regenerants were obtained only from explants of this line after cultivation on the medium containing 1.5% sodium chloride. The ‘ADM 11’ variety was the most sensitive to saline stress as mass necrosis and lack of regenerative ability in its calli were observed under breeding conditions. In the studied forms, genotypic dependence of morphogenesis processes in vitro culture was registered. From the induced calli, plants-regenerants were obtained, and their completion of growing, root development and transfer to in vivo conditions were optimized. Conclusions. Genotypic response to salinity stress in the culture of shoot apical meristems of winter triticale was expressed by various crude mass increase and different morphogenetic potential on exposure to a stress factor. The line ‘38/1296’ can be used as a valuable material for further breeding of winter triticale. The culture of shoot apical meristems is recommended to apply as a test system for screening of triticale genotypes for resistance to salinity stress

Different statistical procedures for selection of salt tolerant barley genotypes at germination stage

Growing of salt tolerant crops is a good option to obtain economical yields from saline areas and screening salt tolerant plants, particularly in early growth stages as one of the most important determinants of high yield, is important. So a laboratory experiment was performed to assess several indices for identifying barley genotypes with better performance under saline conditions. The effect of salinity stress was studied through an analysis of the dry matter production, that yielding results showed significant differences among genotypes. The multiple statistical procedures which have been used in this study showed that mean productivity and geometric mean productivity indices could be a useful indicator of desirable genotypes in both stress and non-stress conditions at this stage especially in high level of salinity. The majority of used tolerance indices indicated that MBS8715 was the best barley genotype showing the highest stress resistance for the most salt concentration.

RESPONSE OF SOME FORAGE PEA GENOTYPES TO SALT STRESS DURING THE SEEDLING STAGE

Salinity stress is a common problem under dry climatic condition all over the world. The determination of salt tolerant genotypes has a crucial importance to alleviate this problem. Pea known as the most salt tolerant plant among legumes and seedling stage is the most sensitive to salt stress than the other growth stages. The experiment was carried out in the growth chamber to observe tolerance of the examined genotypes to different salt doses. Therefore germination rates, mean germination time (mgt), root/shoot lengths and fresh/dry seedling weights of some forage pea genotypes (Local population, Crackerjack, Golyazi, Ozkaynak, Rose, Taskent, Tore, Ulubatli) under different salt concentrations (Control, 5, 10, 15 and 20 dS m-1) were determined. The results showed that salinity x genotype interaction was significant among genotypes with respect to all investigated parameters. Crackerjack had the highest germination rate and root length with the increasing salt levels and it was followed by Ozkaynak, Rose, Taskent and Tore. Ozkaynak was the fastest germinated genotype with respect to mgt with 1,92 days and the genotype had the longest shoot length. Fresh seedling weight of Crackerjack was the higher than all other genotypes but there was not a significant difference between Rose and Crackerjack. Results indicated that Taskent, Tore, Ozkaynak, cultivars could be recommended upto moderate saline areas while Crackerjack and Rose could be recommended for slightly saline areas. Article DOI: https://dx.doi.org/10.20319/lijhls.2017.32.2437 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

The Proteome Response of \u201cHordeum marinum\u201d to Long-term Salinity Stress

Salinity is a major constraint to crop productivity and mechanisms of plant responses to salinity stress are extremely complex. “Hordeum marinum” is a salt tolerant barley species, which could be a good source to evaluate salt-tolerance patterns. Proteomics is a powerful technique to identify proteins involved in plant adaptation to stresses. We applied a proteomic approach to better understanding the mechanism of plant responses to salinity in a salt-tolerant genotype of barley. At the 4-leaf stage, plants were exposed to 0 (control treatment) or 300 mM NaCl (salt treatment). Salt treatment was maintained for 3 weeks. Total proteins of leaf 4 were extracted and separated by two-dimensional gel electrophoresis. More than 290 protein spots were reproducibly detected. Of these, 20 spots showed significant changes to salt treatment compared to the control: 19 spots were upregulated and 1 spot was absent. Using MALDI-TOF/TOF MS, we identified 20 cellular proteins which represented 11 different proteins and were classified into five categories. These proteins were involved in various cellular functions. Upregulation of proteins which involved in protein processing (ribosomal protein, cullin family, cp31AHv protein and RNA recognition motif (RRM) superfamily), photosynthesis (Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) and Ribulose bisphosphate carboxylase/oxygenase activase (rubisco activase)), energy metabolism (cytosolic malate dehydrogenase (cyMDH) and fructokinase), oxygen species scavenging and defense (cystatin and thioredoxin) may increase plant adaptation to salt stress.

Genome-wide analysis of DUF221 domain-containing gene family in Oryza species and identification of its salinity stress-responsive members in rice.

DUF221 domain-containing genes (DDP genes) play important roles in developmental biology, hormone signalling transduction, and responses to abiotic stress. Therefore to understand their structural and evolutionary relationship, we did a genome-wide analysis of this important gene family in rice. Further, through comparative genomics, DDP genes from Oryza sativa subsp. (indica), nine different wild species of rice and Arabidopsis were also identified. We also found an expansion of the DDP gene families in rice and Arabidopsis which is due to the segmental duplication events in some of the gene family members. In general, a highly purifying selection was found acting on all the deduced paralogous and orthologous DDP gene pairs. The data from microarray and subsequent qRT-PCR analysis revealed that although several OsDDPs were differentially regulated under salinity stress, yet OsDDP6 was upregulated at all the developmental stages in salt tolerant rice genotype, FL478. Interestingly, OsDDP6 was found to be involved in proline metabolism pathway as indicated by protein network analysis. The diverse gene structures, varied transmembrane topologies and the differential expression patterns implied the functional diversity in DDP genes. Therefore, the comprehensive evolutionary analysis of DDP genes from different Oryza species and Arabidopsis performed in this study will provide the basis for further functional validation studies vis-à-vis DDP genes of rice and other plant species.

Identification of mega-environments and rice genotypes for general and specific adaptation to saline and alkaline stresses in India

In the present study, a total of 53 promising salt-tolerant genotypes were tested across 18 salt-affected diverse locations for three years. An attempt was made to identify ideal test locations and mega-environments using GGE biplot analysis. The CSSRI sodic environment was the most discriminating location in individual years as well as over the years and could be used to screen out unstable and salt-sensitive genotypes. Genotypes CSR36, CSR-2K-219, and CSR-2K-262 were found ideal across years. Overall, Genotypes CSR-2K-219, CSR-2K-262, and CSR-2K-242 were found superior and stable among all genotypes with higher mean yields. Different sets of genotypes emerged as winners in saline soils but not in sodic soils; however, Genotype CSR-2K-262 was the only genotype that was best under both saline and alkaline environments over the years. The lack of repeatable associations among locations and repeatable mega-environment groupings indicated the complexity of soil salinity. Hence, a multi-location and multi-year evaluation is indispensable for evaluating the test sites as well as identifying genotypes with consistently specific and wider adaptation to particular agro-climatic zones. The genotypes identified in the present study could be used for commercial cultivation across edaphically challenged areas for sustainable production.