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.     

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.     

Auxin production by rhizobacteria was associated with improved yield of wheat (Triticum aestivum L.) under drought stress

Drought tolerant rhizobacteria of the genus Bacillus, Enterobacter, Moraxella and Pseudomonas colonizing the root system of Acacia arabica were isolated to mitigate the drought stress of wheat (Triticum aestivum L.). In vitro auxin production by rhizobacteria was quantified by Ultra High Performance Liquid Chromatography (UPLC). Analysis of the crude extracts detected the indole-3-acetic acid (IAA), indole-3-carboxylic acid (ICA) and indole-3-lactic acid (ILA). Highest IAA production of 25.9 µg ml^?1 was observed for Bacillus amyloliquefaciens S-134. Pot trials were conducted to evaluate the role of rhizobacteria to enhance the growth of wheat at different water regimes. At highest water stress i.e. 10% field capacity (FC), significant improvement of shoot length was observed with B. amyloliquefaciens S-134. For yield parameters, B. muralis D-5 and E. aerogenes S-10 recorded 34% and 1 fold increases for spike length and seed weight, over respective control at 10% FC. Mixed culture combinations of M-2 (B. thuringiensis S-26, D-2, B. amyloliquefaciens S-134, B. simplex D-11) and M-3 (M. pluranimalium S-29, B. simplex D-1, B. muralis D-5, P. stutzeri S-80) showed significant improvement for tillers and number of spikelets. In conclusion, application of the drought tolerant rhizobacteria can help to overcome productivity losses in drought prone areas.     

Growth,morphological and yield responses of irrigated wheat (Triticum aestivum L.) genotypes to water stress

Water shortages is a major constraint in wheat production in South Africa. It is important therefore to assist irrigated wheat farmers to identify water stress tolerant growth stages in irrigated wheat genotypes. This study evaluated new wheat genotypes for water stress at different growth stages. An 8 (genotypes) × 2 (water treatments) × 3 (growth stages) factorial experiment was laid out in a randomised complete block design with three replicates. The results indicated that plant height was not affected (p > .05) by water stress at tillering and grain filling. Water stress imposed at the tillering stage reduced the number of fertile tillers (p < .05) in susceptible genotypes while at the flowering and grain filling stages all genotypes were tolerant (p > .05). Aboveground biomass was only affected (p < .05) by water stress imposed at the tillering stage. Water stress reduced grain yield on the genotypes where stress was imposed at the tillering stage (p < .05); whereas when stress was imposed at flowering and grain filling the grain yield was not reduced (p > .05). This study provided evidence to suggest that most genotypes were tolerant to water stress at the flowering and grain filling stages.     

Water stress effects on biochemical traits and antioxidant activities of wheat (Triticum aestivum L.) under In vitro conditions

Water stress is one of the major environmental stresses that affect agricultural production worldwide, especially in arid and semi-arid regions. This research investigated the effect of water deficit, induced by PEG-6000 on wheat genotypes (GA-2002, Chakwal-97, Uqab-2000, Chakwal-50 and Wafaq-2001) grown in modified MS medium solution. Osmotic stress caused a more pronounced inhibition in leaf relative water content and leaf membrane stability more sensitive (index in Wafaq-2001 and Uqab-2000) genotypes compared with the tolerant (Chakwal-50, GA-2002 and Chakwal-97) genotypes. Upon dehydration, an incline in proline, total soluble sugar, total soluble protein, superoxide dismutase, peroxidase, catalase and malondialdehyde activity content were evident in all genotypes, especially at osmotic stress of ?8 bars. The observed data showed that status of biochemical attributes and antioxidant enzymes could provide a meaningful tool for depicting drought tolerance of wheat genotypes. The present study shows that genotypic differences in drought tolerance could be likely attributed to the ability of wheat plants to induce antioxidant defense under drought conditions. In order to develop genotypes with stable, higher yields in dry farming conditions, it is necessary to characterise genetic resources based on drought adaptation, determine suitable genotypes, and then use them in breeding programmes.     

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.     

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.     

Ferulic acid from aleurone determines the antioxidant potency of wheat grain (Triticum aestivum L.)

Grain is an important source of phytochemicals, which have potent antioxidant capacity. They have been implicated in the beneficial health effect of whole grains in reducing cardiovascular disease and type 2 diabetes. The aim of the present study was to identify the most important antioxidant fractions of wheat grain. It was found that the aleurone content of these fractions was highly correlated with the antioxidant capacity of the fractions (r = 0.96, p < 0.0001). Ferulic acid appeared to be the major contributor to the antioxidant capacity in fractions with higher antioxidant capacity. The contribution of protein was rather limited. It was concluded that the antioxidant potency of wheat grain fractions is predominantly determined by aleurone content, which can be attributed to the presence of relatively large amounts of phenolic compounds, primarily ferulic acid.     

Comparison of protein quality and mineral element concentrations in grain of spelt (Triticum spelta L.) and common wheat (Triticum aestivum L.)

The cultivation of Triticum spelta (spelt) has no tradition in Hungary. In recent years the interest towards this old species renewed in many countries. This high‐nutritional cereal, which has a high ash and fibre content, can be used in many health‐oriented grain‐based food products. Therefore, field experiments have been conducted for some years to test the performance of this species under home growing conditions. Here we report the results of analyses for some important quality parameters of grain samples from the 1996/97 season in comparison with those of older and new home‐grown bread wheat cultivars. Three common wheat cultivars and one advanced spelt line were grown on small plots fertilised with an NPK dose necessary to reach the highest yield and quality. Spikes were sampled weekly from the time of 70–77% grain moisture to full ripening. The grains were analysed for ash, N, P and K content and amino acid composition. Concentrations of 16 other macro + micro elements and in the ripe grains, baking quality parameters were also assessed. The grain development of spelt showed a remarkable time‐lag compared to that of the common wheat cultivars. However, the highest thousand‐grain‐masses, ash, N, and P concentrations were measured in this cultivar after milk ripening. The grains of spelt contained the macro‐nutrient Mg and four micro‐nutrients (Zn, Mn, Fe, Cu) in higher concentrations compared to those of the common wheat varieties. The total and essential amino acid concentrations measured in the ripe grains of spelt were also remarkably higher.

Although its wet gluten content (47.5%) was considerably higher than that of the bread wheat cultivars, its breadmaking quality was poor.     

Effects of tropospheric ozone on the yield and grain protein content of spring wheat (Triticum aestivum L.) in the Nordic countries

Eight Nordic open‐top chamber experiments with field‐grown spring wheat were combined to obtain relationships between ozone exposure and yield loss. Two exposure indices, AOT30 and AOT40 (AOT = accumulated exposure over threshold), were tested. Strongly significant linear regressions between relative yield and exposure were obtained with both indices. The coefficient of determination (r²) was higher and the model assumptions of linear regression were satisfied to a larger extent with AOT30 than with AOT40. The exclusion of charcoal‐filtered treatments from the analysis made little difference to the regressions. The AOT30 regression model predicted larger yield loss than the AOT40 regression model, especially for the range of exposures, which is likely to occur in the Nordic countries. The protein content of the grain increased with increasing ozone exposure in all eight experiments, but to a varying degree.     

Mitigation of salinity stress in wheat (Triticum aestivum L.) seedlings through physiological seed enhancements

Salinity stress can be mitigated by using the physiological seed enhancements. Kharchia 65 (salt tolerant) and PI.94341 (salt sensitive) genotypes were evaluated under salt stress (20 dS/m) by various priming treatments, that is hydropriming and halopriming (50?mmol, KCl and NaCl) in a pot study. Experiment was conducted in completely randomized design under factorial arrangements with three replications. Priming agents improved the final emergence percentage (FEP), emergence index (EI) and reduced the mean emergence time of both wheat genotypes under normal and saline conditions as compared to non-primed seed. Priming treatments elicited the efficiency of wheat seedlings by increasing both Fv/Fm and Ft under both normal and salt stress conditions which were strongly linked with low Na⁺ and high K⁺. In conclusion, all three priming agents effectively nullified the deleterious effects of salt stress by improving seed emergence and triggering the physiological attributes of wheat.     

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.     

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.     

Effects of sulphur application on grain yield and quality,and assessment of sulphur status in winter wheat (Triticum aestivum L.)

Abstract

Winter wheat was grown in 26 field trials in Norway during the period 2004–2006. The main aim was to determine the effect of various sulphur (S) fertilization strategies at two different nitrogen (N) levels on grain yield and quality of winter wheat. With the exception of four trials in central Norway, all the trials were located in the south-eastern part of the country.

Increasing the N fertilization from 170 to 210 kg N ha^?1 resulted in significantly higher grain protein content (GPC) and sodium dodecyl sulphate (SDS) sedimentation volume. On clayey soils in southeast Norway, increased N-fertilization also resulted in higher grain yield and lower test weight and thousand grain weight (tgw).

Omitting S fertilization significantly reduced grain yields on sandy soils in southeast Norway and on loam and silt loam in central Norway, whereas no yield reduction was found on clay soils. SDS sedimentation volume and specific SDS (sSDS = SDS/GPC) were significantly reduced when S-fertilization was omitted. GPC was reduced by S fertilization in central Norway. Generally there were no significant responses at application rates higher than 12 kg S ha^?1.

The malate:sulphate method is a field-based diagnostic test used to determine whether S deficiency is likely to occur. The results did not indicate that this test is reliable under Norwegian conditions. On the other hand, the use of a chlorophyll meter measurements to assess S status gave promising results.     

Evaluation of wheat (Triticum aestivum L.) phenolic acids during grain development and their contribution to Fusarium resistance

The phenolic acid profiles of six cultivars of wheat with known tolerance to Fusarium head blight were evaluated during plant development from anthesis through maturity. Analysis by HPLC of grain at anthesis revealed that p-coumaric and ferulic acid were the two principal phenolic compounds present. The effect of these two phenolic acids on Fusarium species was evaluated in vitro. Both phenolic acids demonstrated significant reductions (p < 0.05) of Fusarium species growth at all concentrations tested. Ferulic acid is the primary phenolic acid in grain at all stages of development, and its concentration increased steadily during grain development prior to a 50% decrease during grain ripening. The accumulation of ferulic acid synthesis from anthesis until approximately 20 days after anthesis appears related with cultivar resistance to Fusarium. Concentrations of ferulic acid in the grain were similar at maturity, implying that the end-use quality would be similar for both resistant and susceptible cultivars.     

Determining critical limit of boron in soil for wheat (Triticum aestivum L.)

Abstract

Critical values of boron (B) for wheat nutrition in soil and plant were determined through a pot experiment with twenty-one surface soils of Alluvial flood plain and Red-latertic belt comprising three major soil orders (Entisols, Alfisols, Inceptisols) with four levels of boron. Application of boron significantly increased the dry matter yield as well as uptake of B by plants. Critical concentration of hot calcium chloride (CaCl₂) extractable B in soil for wheat was found to be 0.53?mg?kg^?1. The critical plant B concentration varied with growth stages and values were 7.4?mg?kg^?1 at panicle initiation and 4.18?mg?kg^?1 at maturity, respectively. The findings of this investigation also recommend the application of 2?kg?B^?1?ha^?1 for ensuring B sufficiency to wheat in Indo-gangetic alluvial and Red-Lateritic soils.     

Germination and growth inhibitors from wheat (Triticum aestivum L.) husks

On the basis of our findings that the germination of intact wheat seeds (with husks) belonging to dormancy varieties was restrained as compared with that of the dehusked seeds (grains), the germination inhibitors in the husks were explored. The water-soluble extracts from the husks were separated by the aid of inhibition assay experiments, resulting in the characterization of 2-phenylethyl alcohol 1, 4-vinylphenol 2 and its 2-methoxy derivative 3, and dihydroactinidiolide 4, all of which showed clear inhibition of germination at 500 ppm in aqueous solution. The related compounds 1-phenylethyl alcohol 5 and tetrahydroactinidiolide 6 were as active as 1 and 4, while no noticeable difference in activity was detected among both enantiomers and the DL-form of compounds 4-6. Clear synergistic relations were observed between 4 and 1 and also 4 and 3. Since the present inhibitors have been isolated from various kinds of seed plants, they may be responsible for the general germination inhibition in the seed plants.     

Biochemical factors in wheat (Triticum aestivum L.) involved in the tetany syndrome

Nitrogen in winter wheat (Triticum aestivum L.) forage was fractionated into water‐soluble protein N (WSPN) and non‐protein N (NPN). Both WSPN and NPN can be rapidly converted to ammonia in the rumen which may increase pH of rumen fluid and decrease solubility of Mg compounds and lead to increased incidence of grass tetany. In plant samples taken after spring growth initiation, WSPN represented approximately 50% of total N and NPN represented approximately 25% of total N. Total N concentration and relative percentages of WSPN and NPN decreased with advancing plant maturity in 1974, but during 1975 the relative WSPN and NPN percentages remained relatively constant at 43 to 55% and 18 to 30% of total N, respectively. Total N, WSPN, and NPN concentrations decreased as plants matured.

Total water‐soluble carbohydrates (TWSC) were determined and N/TWSC ratios were calculated in wheat forage. TWSC concentrations increased from the initial sampling date to a peak concentration and then declined during the latter part of the sampling period. N/TWSC ratios were widest at the initial sampling date and decreased markedly in subsequent samplings.

Organic acid concentrations were determined in 1975 wheat forage samples by gas‐liquid chromatography. Citric and trans‐aconitic acids have been implicated in the etiology of grass tetany as chelating agents for Mg and Ca. Chelation in the rumen fluid may reduce Mg and Ca absorption or chelation in the blood serum may reduce biological activity. Malic and aconitic acids accumulated in wheat. Malic acid concentration increased with advancing plant maturity to a maximum of 1.70% (dry weight basis). Aconitic acid concentrations were highest at the mid‐point in the sampling period, a maximum of 1.24% being determined.     

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.     

Investigating the effect of Azospirillum brasilense and Rhizobium pisi on agronomic traits of wheat (Triticum aestivum L.)

ABSTRACT

Plant growth-promoting rhizobacteria (PGPR) play an important role in improving crop growth but have not been studied sufficiently. A wire house experiment was conducted in Pakistan to determine the combined effect of inoculating wheat seeds with PGPR on the subsequent growth and yield of the wheat. The experiment included four treatments: T_{0 –} no-inoculation (control), T₁ – Azospirillum brasilense inoculation, T₂ – Rhizobium pisi inoculation and T₃ – co-inoculation with A. brasilense and R. pisi. Development and growth attributes, as well as final yield of wheat, were studied. Co-inoculation of seeds with both strains increased significantly wheat grain yield, the number of grains per plant and 1000-grain weight by 36%, 11% and 17%, respectively, compared to non-inoculated control. While crop growth rate increased for, respectively, 5.5% and 33% at tillering and flag leaf stages, corresponding values for T₃ were about 9% and 14% higher than values for sole inoculations in T₁ and T₂. Co-inoculation also significantly increased leaf epicuticular wax and relative water content as compared to the control treatment. Thus, inoculation of wheat seeds with A. brasilense and R. pisi and their combination is a promising method to improve growth, yield and quality of wheat.