Molecular characterization of salinity tolerance in wheat (Triticum aestivum L.)

Random amplified polymorphic DNA (RAPD) markers were used to estimate the genetical variability of three salt-resistant genotypes, SARC-1, SARC-5 and S-24, exposed to saline environment. High-yielding and salt-sensitive variety MH-97 was used as standard for comparison. The behavior of these genotypes under saline environment was analyzed by using the hydroponics screening methods at the seedling stage. One hundred and fifty primers were tested of which 52 primers revealed differences between SARC-1 and SARC-5, 54 revealed differences between SARC-1 and S-24 and 61 revealed differences between SARC-5 and S-24. Polymorphism differences between MH-97 and SARC-1, MH-97 and SARC-5 and MH-97 and S-24 were 53%, 64% and 42%, respectively. Four primer pairs amplified special fragments, which were located in all the three salt-resistant genotypes but none on the salt-sensitive genotype MH-97. Primer GLD-15 (5?-CCGTGGCATT-3?) generated a prominent fragment of length 1460 bp; primer GLF-18 (5?-ACCCGGAACC-3?) produced a fragment of length nearly 980 bp in the salt-resistant genotype; the primer pair GLE-5 (5?-TTCAAGCCCG-3?) located one polymorphic amplified band of 1290 bp and the primer GLH-9 (5?-ATCCAGGTCA-3?) performed as a weak polymorphic band of 640 bp, respectively.     

Physiological responses of irrigated wheat (Triticum aestivum L.) genotypes to water stress

The recent drought in South Africa has reduced the production of both dryland and irrigated wheat. This study evaluated physiological traits of irrigated wheat genotypes in response to water stress (WS) imposed at different growth stages. A 8?×?2?×?3 [(genotypes)?×?(water treatmets; stresses and non-stressed)?×?(growth stages; tillering, flowering and grain filling)] factorial experiment based on a randomised complete block design with three replicates was conducetd. In general, the rate of photosynthesis was unaffected by WS except for genotypes LM43 at tillering and LM98 at grain filling. Stomatal conductance (SC) and transpiration rate (Tr) followed the same treand except for genotype LM35 which reduced its SC and Tr significantly at grain filling. Instantaneous waster use efficiency (IWUE) of genotype LM35 and LM57 was unaffected (p?>?0.05) by WS at tillering but at flowering stage it was affected. However, at grain filling IWUE was affected (p?<?0.05) in genotypes LM35, ML57, LM79 and LM 98. The relative water content was unaffected at tillering except for LM35 and LM47 genotypes whereas at flowering LM57, ML79, LM83 and LM98 were affected. These results indicate some degree of drought tolerance of these genotypes at different growth stages.     

Screening for pre- and post-anthesis drought responses in selected bread wheat (Triticum aestivum L.) genotypes

ABSTRACT

Wheat genotypes with pre- and post-anthesis drought tolerance offer enhanced yield gains under water-limited environments. This study determined pre- and post-anthesis drought responses of selected bread wheat genotypes in order to identify and select candidate genotypes for breeding. Fifteen genetically differentiated wheat genotypes were evaluated under non-stressed (NS), pre-anthesis drought stress (PrADS) and post-anthesis drought stress (PoADS) in glasshouse (GH) and field (FLD) environments. Data were collected on agronomic and physiological traits including number of days to heading (DTH), days to maturity (DTM), plant height (PH), number of spikelet per spike (NSPS), number of kernels per spike (NKPS), thousand kernel weight (TKW), grain yield (GY) and canopy temperature (CT). Analysis of variance revealed significant effects of genotypes, environments and their interactions for studied traits. Weak and positive correlations were recorded between GY with PH (r?=?0.47 and 0.32), NSPS (r?=?0.37 and 0.52) and TKW (r?=?0.30 and r?=?0.20) under PrADS and PoADS conditions, respectively. Genotypes SMY-006, SMY-008, SMY-016, SMY-042 and SMY-044 were identified with pre- and post-anthesis drought tolerance and high yield potential and suitable yield-component traits. These are useful genetic stocks for breeding or cultivation in water-limited environments to improve yield gains.     

Growth-related changes in wheat (Triticum aestivum L.) genotypes grown under salinity stress

The sensitivity of crop genotypes determines the level of growth reduction by salinity. Effect of salinity levels (7.5 and 15 dihydrate m^?1) using completely randomized design (CRD) with four replications per treatment were compared on germination, chlorophyll content, water potential, ionic sodium and potassium (Na⁺, K⁺) balance, and other growth-related parameters of six wheat genotypes for varietal differences under long-term salinity stress. Chlorophyll contents at flowering stage and yield aspects at maturity of all the wheat genotypes decreased with increasing salinity. The maximum Na⁺ concentration was observed at 7.5 and 15 dS m^?1 in Bhakhar and Saher-2000, respectively, while minimum Na⁺ concentration was observed for 9476. However, the maximum K⁺ concentration and water potential was noticed in 9476 at 7.5 dS m^?1. Careful selection of salt-tolerant genotypes for field crops is an important perspective especially in the developing countries facing salinity problem. Our results revealed that the wheat genotype 9476 performed best regarding growth and physiological parameters compared to other wheat genotypes.     

Optimum rate of nitrogen application and seed rate for deteriorated wheat (Triticum aestivum L.)

In order to study the effect of seed quality (SQ), seed rate (SR), and nitrogen rate (NR) on yield and yield components of wheat, an experiment was conducted as a factorial-split plot based on the randomized complete block design with four replications in Golestan Province, Iran. Treatments included the combination of SR and NR (recommended rate, 15 and 30% higher than the recommended rate) as the main plots, and SQ (control, 15, 30 and 45?h of accelerated aging) as the subplots. The interaction of NR?×?SR was significant on 1000-seed weight, seed yield, plant height, the number of seeds, biological yield, and harvest index. There was a significant reduction in all traits with an increase in seed aging. Seed yield had a significant and positive correlation with yield components. Using higher density and applying higher nitrogen fertilizer than those of recommended could reduce the negative effects of seed aging in wheat.     

Improving of seed quality of black seed (Nigella sativa L.) by increasing seed phosphorus content in a calcareous soil

Phosphorus (P) sufficiency during seed formation and development can affect the quality of seeds production. For increasing P content of black seed (Nigella sativa) in a calcareous soil, series of experiments were conducted in completely randomized factorial design with 4 replications at the Faculty of Agriculture, Ferdowsi University of Mashhad, Iran, in 2012 and 2013. The combinations of vermicompost (V), sulfur (S), and Thiobacillus bacteria (T) were mixed with a calcareous soil fertilized with 0, 30 and 60 kg P ha^?1 in pots and incubated for 63 days. At the end of incubation period, black seeds were sown in the pots and plants were grown to maturity. Results showed that S+T and V treatments were significantly increased soil available P, emergence, plant P content, seed yield and vigor of the seeds production. There were positive relationship between soil and plant P concentration with the quality of seeds production.     

Effects of biofertilizers and cycocel on some physiological and biochemical traits of wheat (Triticum aestivum L.) under salinity stress

In order to study the effects of biofertilizers and cycocel on some physiological and biochemical characteristics of wheat (Triticum aestivum L.) under salinity condition, a factorial experiment was conducted based on randomized complete block design with three replications under greenhouse condition in 2015. Treatments were included salinity in four levels [no salt (control or S₀), salinity 30 (S₁), 60 (S₂) and 90 (S₃) mM NaCl equivalent of 2.76, 5.53 and 8.3 dS m^?1, respectively], four biofertilizers levels [no biofertilizer (F₀), seed inoculation by Azotobacter chrocoocum strain 5 (F₁), Pseudomonas putida strain 186 (F₂), both inoculation Azotobacter + Pseudomonas (F₃)] and three cycocel levels [without cycocel as control (C₀), application of 600 (C₁) and 1000 (C₂) mg L^?1]. Results showed that salinity severe stress (90 mM) decreased chlorophyll content, relative water content (RWC), total chlorophyll, photochemical efficiency of PSII and yield of wheat. Whereas, soluble sugars and proline content, electrical conductivity (EC), the activity of catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO) enzymes were increased. Similar results were observed in CAT, POD and PPO activities due to inoculation by biofertilizers and cycocel. Salinity at 30 mM increased the photochemical efficiency of PSII and chlorophyll content in plants grown under biofertilizer and cycocel treatment but with increasing salinity up to 90 mM mentioned parameters were decreased. The highest proline and soluble carbohydrate at all salinity levels were observed in plants treated in the highest cycocel level and Azotobacter+ Pseudomonas application. Generally, it was concluded that biofertilizers and cycocel can be used as a proper tool for increasing wheat yield under salinity condition.     

Salt stress and mungbean [Vigna radiata (L.) Wilczek]: effects,physiological perspective and management practices for alleviating salinity

Mungbean is an important food grain legume with high economic status. It has an excellent source of dietary protein and nutritional health benefits, particularly for the vegetarians. It increases soil fertility and also plays an imperative role in major cropping systems due to its short life span. Production of mungbean is still decreasing due to its susceptibility towards various environmental stress factors. Salt stress is one of the most prevailing abiotic stress imposing threats for agriculture food crops along with increasing world population and limited natural resources. Fewer efforts have been made to develop an improved variety of mungbean. The present review summarizes the adverse effects of salt stress and mungbean response at the physiological and molecular level. It covers recent studies on introgression of useful traits in mungbean for its better adaptability and survival under stressed conditions. Modern biotechnological approaches and traditional breeding methods may assist the development of salt-tolerant cultivars of mungbean for salinity-affected area in arid and semi-arid regions. Researchers involved in this area should keep this goal on priority for sustainable mungbean production. Availability of protein-rich food may help to reduce the problem of malnutrition in poor families and national food security issue for a continuous rising population.     

Application of biochar in mitigation of negative effects of salinity stress in wheat (Triticum aestivum L.)

Salinity is a major abiotic stress that affects crop production throughout the world. Biochar is an activated carbon soil conditioner that can alleviate the negative impacts of salinity. The research was conducted to evaluate the ameliorative effect of 1% and 2% of biochar application on wheat seed germination and growth attributes under salinity. Both levels of biochar improved the germination and growth conditions under salinity; however, 2% biochar level was more effective compared to 1% level. Root and shoot length increased up to 23% and11% with 2% biochar, respectively. The maximum increase of 16% and 10% in leaf water potential and osmotic potential was noted with 2% biochar at 150 mM salt. The decrease in proline content and soluble sugar at 2% biochar was 51% and 27%, respectively. Decrease in superoxide dismutase activity was 15.3% at 2% level of biochar under stress biochar mitigates the negative effects of salinity and improved wheat productivity.     

Changes in bacterial populations along roots of wheat (Triticum aestivum L.) seedlings

Summary In this study the bacterial populations on root tips (1–2 days old) of wheat (Triticum aestivum L.) were compared with the populations on root segments about 1 week older (root base). The isolates were characterized with a set of physiological tests and the test results were used to group the bacteria by means of cluster analysis. Some clusters contained bacteria that occurred mainly on the root tips and were characterized by the ability to produce acid from different sugars and by the presence of the enzymes nitrate reductase, lipase, and oxidase; they were sensitive to high salt concentrations in the media. Another cluster included significantly more isolates from the root-base segments; these bacteria were characterized by a negative reaction to most of the physiological tests; the colonies formed by these bacteria had yellow pigmentation. Possiblemechanisms for the changes in the bacterial populations are discussed.     

Screening drought-tolerant genotypes in bread wheat (Triticum aestivum L.) using different multivariate methods

Wheat (Triticum aestivum L.) is one of the most widely cultivated crops in rainfed areas of Iran, where drought is the main limiting factor on yield. The object of this study was the identification of drought-tolerant genotypes in bread wheat. Forty bread wheat genotypes were tested in separate experiments under drought stress and normal conditions in two years (2009–2010 and 2010–2011). Nine drought-tolerance/susceptibility indices including stress susceptibility index (SSI), mean productivity (MP), tolerance (TOL), stress tolerance index (STI), geometric mean productivity (GMP), yield index (YI), yield stability index (YSI), linear regression coefficient (β) and drought response index (DRI) were determined. Simultanously applied factor analysis used two factors instead of nine indices in this study. Mahdavi was recognized as the most drought-tolerant genotype in both years based on factor analysis. In this study an equation was developed for estimating the Stress Tolerance Score (STS). The results of the equation were identical to those of factor analysis in both years. The equation was much easier to use than factor analysis and is suggested as a screening tool for the identification of drought-tolerant genotypes. In this study, Mahdavi was the most drought-tolerant genotype also corresponding to this equation.     

Response of selected drought tolerant wheat (Triticum aestivum L.) genotypes for agronomic traits and biochemical markers under drought-stressed and non-stressed conditions

ABSTRACT

Genetic improvement of wheat for drought tolerance can be achieved by developing suitable ideotypes with enhanced yield-response associated with agronomic traits and biochemical markers. The objective of this study was to determine drought response of elite drought tolerant wheat genotypes using agronomic and biochemical traits to select promising lines for breeding. Fourteen wheat genotypes selected from the International Maize and Wheat Improvement Center’s heat and drought tolerance nursery and one standard check variety were evaluated under drought-stressed (DS) and non-stressed (NS) conditions using a randomised complete block design in three replications. Significant (P?<?0.05) genotype, drought condition and genotype?×?drought condition interaction effect were detected for the tested traits suggesting differential response of genotype for selection. Grain yield positively correlated with sucrose (r?=?0.58; P?<?0.05), fructose (r?=?0.52; P?<?0.05) and total sugar (r?=?0.52; P?<?0.05) contents under NS condition and with sucrose (r?=?0.80; P?<?0.001), total sugar (r?=?0.84; P?<?0.001) content, proline content (r?=?0.74; P?<?0.001) and number of grains per spike (r?=?0.58; P?<?0.05) under DS condition. Genetically unrelated wheat genotypes such as SM04, SM19, SM29, SM32, SM45 and SM97 possessing key agronomic and biochemical traits were selected for cultivar development for drought-stressed environments.     

Assessment of terminal drought tolerance among elite wheat (Triticum aestivum L.) genotypes using selected agronomic and physiological traits

ABSTRACT

The selection response of wheat (Triticum aestivum L.) under water-limited condition can be enhanced through breeding novel genotypes possessing drought-adaptive and yield-related agronomic and physiological traits. The objective of this study was to evaluate terminal drought tolerance among bread wheat genotypes and select superior parents for breeding. Agronomic and physiological responses of 28 wheat lines were assessed under well-watered (WW) and terminal drought (TD) treatments using a 7?×?4 alpha-lattice design under rainout shelter (RS) and glasshouse (GH) environments. Significant (p?≤?0.05) genotype?×?environment interaction effects were observed for number of days to heading (DTH), number of days to maturity (DTM), number of productive tillers per plant (TN), grain yield (GY), thousand kernel weight (TKW), stomatal conductance (SC), leaf canopy temperature (LCT) and chlorophyll content index (CCI) suggesting varied genotypic response under WW and TD treatments. Correlation analysis revealed significant associations TN and GY (r?=?0.67; p?≤?0.001), TKW and GY (r?=?0.72; p?≤?0.001), CCI and GY (r?=?0.39; p?≤?0.05) under TD treatment. Drought tolerant wheat genotypes such as LM100, LM72, LM22 and LM95 are useful for direct cultivation and for developing breeding populations with enhanced yield performance.     

Comparative growth and physiological responses of two wheat (Triticum aestivum L.) cultivars differing in salt tolerance to salinity and cyclic drought stress

Two cultivars of wheat (Triticum aestivum L.) with differential salinity tolerance were compared by evaluating the growth attributes, pigment composition and accumulation of Na⁺, K⁺, Zn²⁺, Fe ²⁺, Mn ²⁺ and proline. Wheat cultivars Al-Moiaya (AM) (salt tolerant) and Habbe-Druma (HD) (salt sensitive) were subjected to four levels of salinity (1.21 dS m^?1, 4.4 dS m^?1, 8.8 dS m^?1 and 13.2 dS m^?1) in factorial combinations with three drought stress (FC 30%, FC 60% and FC 90%) treatments in a randomized complete block design. Plant dry weight, leaf area ratio (LAR), soluble protein and total chlorophyll (Chl) content were higher in AM than HD. Salt-tolerant AM maintains a higher K⁺/ Na⁺ ratio and thereby is able to grow better than the salt-sensitive HD under both the stresses. The lower foliar Na⁺ in AM resulted in retention of higher Chl content, reflected in the strong positive correlations between plant ion status and Chl contents (Na⁺-Chl r² = 0.83; Chl- Fe²⁺ r² = 0.76; Zn²⁺ r² = 0.93 and Mn²⁺ r² = 0.88). In conclusion, our results suggested that the K⁺/Na⁺ ratio, exclusion of Na⁺ and ion homeostasis play much more important roles in the tolerance to salinity and drought stress than the compatible osmolyte, proline.     

Influence of additional amino acids in growth of different wheat (Triticum aestivum L) genotypes

Abstract

Wheat is the main source of carbohydrates and amino acids consumed in the world. Amino acids and other physiological characters were determined in six wheat genotypes viz. IBWSN-1010, IBWSN -1025, TD-1, ESW-9525, Khirman and Chakwal-86 for pot experiment, to evaluate the response of genotypes under water stress at Nuclear Institute of Agriculture (NIA), Tandojam, Sindh, Pakistan, during 2018. Eight different physiological indices (Proline content, glycine-betaine, total sugars, total chlorophyll, nitrate reductase activity (NRA), potassium (K⁺) content, osmotic potential (OP) and relative water content (RWC)) were determined. The variance of analysis shows two-way interaction one with water stress [Control (normal four irrigations) and the other with terminal drought (Soaking dose) having significance at p?≤?0.05. It was observed that, ESW9525, IBWSN-1010 and IBWSN-1025 exhibited the tolerance followed by, Khirman and Chakwal-86 by maintaining their OP and accumulation of higher proline and glycine-betaine content. Whereas, moderate total soluble sugars were found in these genotypes. However, NRA increased in IBWSN-1010 enhancing tolerance under water stress.     

Evaluation of bread wheat (Triticum aestivum L.) genotypes for yield and related traits under drought stress conditions

ABSTRACT

Drought is a major factor threatening crop production worldwide. Developing wheat varieties that are adapted to drought prone environments is a sustainable strategy to improve wheat production and productivity. The aim of this study was to evaluate and select bread wheat genotypes for yield and yield components, and for stability under drought stress and non-stress conditions. One hundred and twenty genotypes were evaluated at five test sites in the 2018/19 cropping season using a 10 x 12 alpha lattice design with two replicates. The level of drought stress was imposed using different sowing dates (early planting representing non-stressed, while late planting as drought stressed conditions) following the onset of the main rain at each site. Grain yield and yield components were recorded, and drought indices were calculated for each genotype. Among the drought tolerance indices, GMP, MP, HM, STI and YI were found to be the most suitable for predicting drought tolerance because they had significant and positive correlations with yield under drought stress and non-stress conditions. Rank sum analysis identified the most drought tolerant genotypes as ‘YS-34', ‘YS-85' and ‘YS-82’. The selected wheat genotypes are useful genetic resources for future drought tolerance breeding programmes in Ethiopia or similar agro-ecologies.     

cDNA-AFLP technique discloses differential gene expression in response to salinity in wheat (Triticum aestivum L.)

Genetic Resources and Crop Evolution - Salinity is one of the well-known abiotic stresses resulting in loss of wheat yield. The identification of differentially induced genes and then becoming...     

Use of IR thermography in screening wheat (Triticum aestivum L.) cultivars for salt tolerance

Thermography is proposed to be an alternative non-destructive and rapid technique for the study and diagnosing of salt tolerance in plants. In a pot experiment, 30 cultivars of wheat (Triticum aestivum L.) were evaluated in terms of their leaf temperature and shoot growth and their ion distribution responses to NaCl salinity at two concentration levels: the control with electrical conductivity (EC) of 1 dS m^?1 and salinity treatment with EC of 16 dS m^?1 (150 mM). A completely randomized block design with factorial treatments was employed with three replications. The results indicated that thermography may accurately reflect the physiological status of salt-stressed wheat plants. The salt stress-based increase in leaf temperature of wheat cultivars grown at 150 mM NaCl reached 1.34°C compared to the control. According to the results obtained, it appears that thermography has the capability of discerning differences of salinity tolerance between the cultivars. Three salt-tolerant wheat cultivars, namely Roshan, Kharchia and Sholeh, had higher mean shoot dry matter (0.039 g plant^?1) and higher mean ratio of leaf K⁺/Na⁺ (14.06) and showed lower increase in the mean leaf temperature (0.37°C) by thermography compared to the control. This was while nine salt-sensitive cultivars, namely Kavir, Ghods, Atrak, Parsi, Bahar, Pishtaz, Falat, Gaspard and Tajan, had lower mean plant dry matter production (0.027 g plant^?1), lower mean ratio of K⁺/Na⁺ (9.49) and higher mean increases in leaf temperature (1.24°C).     

纳米氧化铜对小麦根系生理生化行为的影响

为阐明纳米金属材料暴露对植物生长的影响及其作用机制,采用模拟土壤的琼脂培养方法研究了纳米氧化铜(CuO NPs)对小麦(Triticum aestivum L.)根伸长及相关生理生化行为的影响。结果表明:小麦根伸长与CuO NPs暴露浓度之间存在指数相关关系,在低浓度CuO NPs(10 mg/L)暴露下得到一定程度促进,而在高浓度(100 mg/L)下受到强烈抑制。小麦根内超氧化物歧化酶(SOD)活性随CuO NPs暴露浓度的变化趋势与小麦根伸长具有一致性。另外,在1~100 mg/L范围内,随着CuO NPs暴露浓度的升高,小麦根内丙二醛(MDA)含量不断增加,但植物蛋白含量急剧降低。以上结果说明CuO NPs对根伸长抑制主要是由于纳米材料暴露造成植物细胞膜氧化损伤,小麦能通过提高根系活力对CuO NPs暴露作出适应性应激响应以减少纳米材料毒性的伤害。     

Drought stress-induced oxidative stress and antioxidative responses in four wheat (Triticum aestivum L.) varieties

Drought stress was imposed on four varieties of wheat (Triticum aestivum L.), Mohan Wonder (MW), Kedar (K), Gayetri (GY) and Gandhari (GN), for 3, 6 and 9 days. The activities of all five tested antioxidative enzymes, peroxidase, ascorbate peroxidase, catalase, glutathione reductase and superoxide dismutase, were enhanced initially in varieties K and GN, whereas in MW and GY, catalase and superoxide dismutase showed a decrease in activity at all periods of drought stress. Peroxidase and glutathione reductase activities increased even on the ninth day of stress in K and GN, but all other activities showed a decrease after 3 days of stress. H₂O₂ accumulation increased with drought stress, but in K and GN there was decrease during prolonged drought stress. Lipid peroxidation increased significantly due to drought stress, which was higher in the case of MW and GY. Proline, phenol and ascorbate content increased with period of drought stress. Carotenoid accumulation also increased initially. Total chlorophylls showed a general decrease during drought stress. The results of this study indicate that two of the varieties, MW and GY, are susceptible to drought stress, whereas the other two, K and GN, are tolerant, with peroxidase and glutathione reductase being most important in conferring tolerance.