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High temperature stress during reproductive stages of wheat is a leading constraint in achieving food security. The objectives of study were to investigate heat sensitivity of terminal stages of wheat, to optimize foliar selenium dose, to boost nonenzymatic antioxidants and to determine correlation of these nonenzymatic antioxidants with yield and quality attributes of wheat crop. The field experiment was conducted for two consecutive years at agronomic research area, University of Agriculture Faisalabad, Pakistan. It was laid out in a randomized complete block design under split arrangement, and treatments were replicated thrice. Main plot factor comprised of heat imposition treatments; H0 = Control; H1 = Heat from spike to grain filling; H2 = Heat from flowering to grain filling while in subplots doses of foliar selenium were maintained; Se0 = Control (water spray); Se25 = 25 mg L−1; Se50 = 50 mg L−1; Se75 = 75 mg L−1 and Se100 = 100 mg L−1. Impact of H1 was more damaging compared to H2 and H0 for all response variables. Higher levels of proline, phenolics and leaf selenium were recorded with foliar spray of selenium either at 75 or at 100 mg L−1 under H0, whereas under H1 and H2, significantly higher responses were observed with 100 mg L−1 selenium for these traits. Increases in leaf chlorophyll and grain protein contents were statistically alike with 75 and 100 mg L−1 selenium; while in case of 1000-grain weight, harvest index and grain yield three levels of foliar selenium (50, 75 and 100 mg L−1) performed equally well under all the three heat stress treatments. Moreover, strong positive and significant associations of proline, phenolics, leaf selenium and chlorophyll were measured with yield of wheat. Conclusively, more harmful impacts were recorded under H1 compared to H2 and H0; while 75 mg L−1 Se proved more beneficial under H0 and 100 mg L−1 Se under H1 and H2. Strong associations of biochemical and agronomic traits were observed. [ABSTRACT FROM AUTHOR]

The tillering phase of wheat (Triticum aestivum) crops is extremely susceptible to drought. We explored the potential of silver nanoparticles (AgNPs) in protecting wheat genotypes from drought injury during this sensitive stage. After treating with AgNPs (60 ppm), the plants were submitted to different water levels; i.e. 100% field capacity (FC), 75% FC (mild drought), 50% FC (moderate drought) and 25% FC (severe drought) from 15 to 41 days after sowing (tillering phase). Leaf physiological data were collected at stress termination, while yield attributes were recorded at crop maturity. We found that increasing drought intensity significantly impaired leaf physiology and grain yield of both studied genotypes. Compared with control, moderately and severely drought-stressed plants produced 25% and 45% lesser grain yield per spike, respectively (averaged across genotypes and years of study). Likewise, moderate and severe drought reduced photosynthesis by 49% and 76%, respectively, compared with control. In contrast, AgNPs significantly restored leaf physiological functioning and grain yield formation at maturity. For example, under moderate and severe drought, AgNPs-treated plants produced 22% and 17% more grains per plant, respectively, than their respective water-treated plants. Our study suggests that exogenous AgNPs can protect wheat crops from drought during early development stages. Wheat (Triticum aestivum) crops suffer significant grain yield losses when water supplies are affected during the early developmental phases. This study shows varying levels of drought stress impaired carbon assimilation, tiller formation and final grain yield of wheat genotypes. In contrast, exogenously applied silver nanoparticles (AgNPs) restored plant growth and grain yield formation, suggesting their potential to protect wheat crops from drought-induced injury. [ABSTRACT FROM AUTHOR]

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Wheat crops are highly sensitive to high temperatures during reproductive and grain filling phases. This study explored how hydrogen peroxide (H2O2) protects grain yield formation in wheat crops exposed to heat during different developmental phases. Two wheat genotypes, Ujala-16 and Anaj-17, of varying heat tolerances, were subjected to heat stress (32 °C/20 °C) at pre-anthesis, anthesis, and post-anthesis stages under glasshouse and field conditions. Before heat stress treatment, the plants were sprayed with 60-ppm hydrogen peroxide (H2O2). Post-stress changes in leaf physiology were studied to understand the heat recovery mechanism. Despite significant genotypic variations, high temperature damaged leaf physiology and grain yield of both studied wheat genotypes. On average, high temperatures during any developmental phase caused more damage to Anaj-17 than to Ujala-16. Compared with the control, the plants heated during pre-anthesis, anthesis, and post-anthesis produced 44%, 35%, and 25% lesser grains yield per spike (averaged across genotypes and experiments), respectively. In contrast, post-anthesis-stressed plants produced the smallest grains compared to those heated during pre-anthesis or at anthesis. Compared with the control, H2O2-treated plants sustained significantly higher leaf chlorophyll and net photosynthetic rate by protecting cellular membranes from heat injury. Under hot conditions, hydrogen peroxide-treated plants yielded 17% more grains (averaged across the developmental phases and genotypes) than control plants. Our study suggests wheat performance can be improved through exogenous H2O2 application, particularly during terminal heat stress. [ABSTRACT FROM AUTHOR]

Wheat crops are highly sensitive to high temperatures during their reproductive and grain-filling phases. We hypothesized that potassium could increase thermotolerance in wheat during grain filling by protecting cellular organelles, particularly chlorophyll, from heat injury. Two wheat genotypes, Ujala-16 (relatively heat tolerant) and Anaj-17 (relatively susceptible) were grown in pots and were submitted to 4 and 8 days of heat stress under polythene sheets 1 week after anthesis. One day before the onset of heat stress, 2% potassium (K) as K2SO4 was sprayed on all the plants. Flag leaves from both genotypes were collected after 4 and 8 days of heat stress. Leaf physiology changes were measured to quantify heat damage and to understand the K-induced recovery mechanism. The crop was harvested 125 days after sowing, and grain yield data were collected. Increasing duration of heat stress significantly impaired leaf physiology and grain yield of both studied wheat genotypes. Compared with control (under optimum temperature), 4 and 8 days heat-stressed plants produced 11 and 19% lesser grain yield per spike (averaged across genotypes and in the second years of study), respectively. Likewise, 4- and 8-days heat-stressed plants had 15 and 37% (averaged across genotypes and in the second years of study) lower flag leaf photosynthesis, respectively, compared with control plants. Across the genotypes, 8-days heat caused significantly more grain yield loss in Anaj-17 during the second year than in Ujala-16. Foliar K significantly restored leaf chlorophyll, Pn, Fv/Fm by reducing cellular membrane damage in the heat-stressed plants. This physiological recovery and activation of the plant defensive system by K under high-temperature stress protected the growth and grain development. For example, K'treated plants produced 19% higher 1,000 grain weight in 8 days of heat stress (across genotypes and in the second years of study) compared with water-treated plants under the hot environment of the respective thermal regime. Our study suggests that wheat performance under terminal heat stress can be improved through the exogenous application of K. [ABSTRACT FROM AUTHOR]

Drought stress is a major limitation in wheat production around the globe. Organic amendments could be the possible option in semi-arid climatic conditions to mitigate the adverse effects of drought at critical growth stages. Wheat straw biochar (BC0 = Control, BC1 = 3% biochar and BC2 = 5% biochar) was used to alleviate the drought stress at tillering (DTS), flowering (DFS), and grain filling (DGFS) stages. Drought stress significantly reduced the growth and yield of wheat at critical growth stages, with DGFS being the most susceptible stage, resulting in significant yield loss. Biochar application substantially reduced the detrimental effects of drought by improving plant height (15.74%), fertile tiller count (17.14%), spike length (16.61%), grains per spike (13.89%), thousand grain weight (10.4%), and biological yield (13.1%) when compared with the control treatment. Furthermore, physiological parameters such as water use efficiency (38.41%), stomatal conductance (42.76%), chlorophyll a (19.3%), chlorophyll b (22.24%), transpiration rate (39.17%), photosynthetic rate (24.86%), electrolyte leakage (-42.5%) hydrogen peroxide (-18.03%) superoxide dismutase (24.66%), catalase (24.11%) and peroxidase (-13.14%) were also improved by biochar application. The use of principal component analysis linked disparate scales of our findings to explain the changes occurred in wheat growth and yield in response to biochar application under drought circumstances. In essence, using biochar at 5% rate could be a successful strategy to promote wheat grain production by reducing the hazardous impacts of drought stress. [ABSTRACT FROM AUTHOR]

Water deficit reduces crop productivity. Cytokinin (CK) is a growth regulator which is a potent coordinator between physiological traits and senescence. A study was carried out to investigate the drought ameliorating effects of exogenous applied cytokinin in wheat. Experiment was comprised of seven treatments(C= Control, DT= Drought at tillering, DT+CK= Drought at tillering + CK, DA= Drought at anthesis, DA+CK= Drought at anthesis + CK, DG= Drought at grain filling, DG+CK= Drought at grain filling + CK).Cytokinin was applied foliarly@ 25 mg L-1 solution of cytokinins. CK application under drought stress significantly increased growth and yield characteristics (P< 0.05). An increase of 4.36%, 7.21% and 5.55% in grain yield was recorded with CK application when drought was applied at tillering, anthesis and grain filling stage, respectively. Other physiological parameters increased by CK included photosynthesis rate, leaf area index, chlorophyll content, activities of ascorbate peroxidase, catalase, peroxidase, superoxide dismutase and endogenous hormonal level of kernels. It was concluded that CK improved plant growth, minimized ill impacts of reactive oxygen species and increase transfer of assimilates to grains under drought. [ABSTRACT FROM AUTHOR]

Drought is a major constraint for agricultural productivity worldwide, and it is likely to further increase. Different strategies are required to mitigate drought stress in plants. In a two-year study that conducted at agronomic research area of the Islamia University of Bahawalpur, we investigated the role of rhizobacteria (RB) and cytokinins (Ck) on drought tolerance, nutrient uptake, yield, and physiological parameters in wheat under drought stress at different developmental stages (tillering, anthesis, and grain filling). Thirteen treatments used were well-watered control plants without RB or Ck, drought at tillering, anthesis, or grain filling without or with RB alone, Ck alone, or combination of both (RB+Ck). In both years, and at the different stages, measured parameters were highest in the well-watered plants but lowest in drought-stressed plants. Application of RB and Ck to drought-stressed plants increased these parameters in the order RB+Ck > RB > Ck. In some cases, under drought stress, there was no difference between inoculation with RB and application of Ck. It was concluded that the combined application of RB and Ck could play a significant role in improving wheat yield and also alleviation of stress under drought condition. [ABSTRACT FROM AUTHOR]

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: T0 – 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. [ABSTRACT FROM AUTHOR]

The ability to identify the vulnerable regions within the crop fields assist the farmers in executing the counter plans precisely. In this regard, the unmanned aerial vehicles (UAVs) equipped with red-green-blue and multispectral sensors have added a new dimension in precision agriculture for a broad range of applications. In this study, we present the transformation of an off-the-shelf quadrotor platform into an aerial-crop-observer by adding customized payload capable of delivering high-resolution multispectral imagery. The main objective of the study was to aerially quantify the response of wheat crop under the influence of different elements critical to crop health, i.e. nitrogen (N), phosphorus, zinc, irrigation levels (I), and agro-climatological conditions. Two different experimental plots with different varieties of wheat crop were selected for the study. The vegetation indices were derived after all the necessary radiometric and geometrical corrections. The linear estimation models were developed to assess the grain yield, aboveground biomass, and leaf area index. Our results indicate that high-resolution multispectral imagery acquired through lightweight UAVs offers a standing potential for quantifying aerial observations of wheat crop under a variety of field-inputs. The study is characterized through respective soil analysis, applied field inputs, calibration of aerial image sensors, the agro-climatological observations, and derivations of vegetation indices. [ABSTRACT FROM AUTHOR]

A field experiment was conducted with the objectives to improve nitrogen use efficiency, reduce the cost of production and improve the wheat yield and quality on sustained basis. Trial was conducted following randomized complete block design with split plot arrangement having three replications. In three main plots, randomization of manure was done as no poultry manure application, 1 t ha-1 layer poultry manure (N=3.96%, P=1.92%, K=1.5%) and 1 t ha-1 broiler poultry manure (N=3.12%, P=1.84%, K=1.5%). In five sub plots, randomization of nitrogen from urea source was done at 0, 25, 50, 75 and 100 kg ha-1. Application of poultry manure (layer or broiler) increased yield components and grain yield significantly. Grain yield, grain crude protein contents, number of fertile tillers, spike length, flag leaf area, fresh weight, dry weight, plant height and number of grains increased with each increasing rate of applied nitrogen however, maximum agronomic nitrogen use efficiency (27.39 kg kg-1), physiological nitrogen use efficiency (41.03 kg kg-1) and 1000-grain weight (37.50 g) were observed in treatment where nitrogen was applied at the rate of 75 kg ha-1. Maximum grain yield and benefit cost ratio were observed where layer poultry manure was applied in integration with 100 kg ha-1 nitrogen. However, economic analysis showed that farmers can get maximum benefits (BCR= 2.6) by applying layer poultry manure in integration with 100 kg N ha-1, or by broiler poultry manure application along with 75 kg N ha-1 (BCR= 2.5). [ABSTRACT FROM AUTHOR]

Global warming is posing threat to agriculture through increasing incidence of abiotic stresses particularly drought stress. Water stress at grain filling stage of wheat crop is detrimental to crop mineral nutrition because it reduces soil moisture and inhibits the optimal crop growth and development by decreasing the availability of nutrients uptake. Glycine betaine and potassium production is accelerated in plants particularly under drought stress conditions for regulation of cell homeostasis (protective mechanism). For the reason, a pot and two field trials were conducted to evaluate the impact of foliar application of glycine betaine and potassium alone and in combination, when water was withheld at grain filling stage. Different doses of glycine betaine (0, 50, 100 and 150 mM) and potassium (0, 0.5, 1.0 and 1.5%) and all possible combinations were used. After harvesting, plant mineral content (N, P, K, Na, and Ca) was assessed. The results indicated that the application of K at 1.5% in combination with glycine betaine at 100 mM was most beneficial in diluting the impact of water stress at grain filling stage. Further it was suggested that the responses of wheat crop to these osmolytes should be studies at molecular level under drought to identify the mechanisms which are tangled for variable plant responses. [ABSTRACT FROM AUTHOR]

Drought is the major abiotic limiting factor for healthy crop growth. Glycinebetaine applied under drought mitigates the adverse effect of drought and improved the plant's tolerance. The present investigation was conducted to find out the response of wheat (Triticum aestivum L.) cultivars (Lasani-2008, Auqab-2000) under water deficit conditions to exogenous application of 100 mM glycinebetaine at different growth stages, Zadoks GS 22, GS 60 and GS 73, representing tillering, flower initiation and grain filling stages, respectively. The objective was to find out the best glycinebetaine (GB) application stage for mitigating the negative effect of drought stress on wheat plants. During investigation various growth traits (plant height, spike length, number of spikelets per spike, number of grains per spike, 1000-grain weight and grain yield per plant) and physiological parameters (water potential, osmotic potential and turgor potential) of crop were recorded using standard procedures. Drought stress at all three critical growth stages adversely affected (P<0.05) all the growth, yield and physiological components of wheat plant. The exogenous application of GB at all three critical growth stages improved the drought tolerance of plants and improved the growth, yield and physiological performance of wheat, however, grain filling stage was found more responsive. [ABSTRACT FROM AUTHOR]

Study to find out the response of wheat (Triticum aestivum L.) cultivars to exogenous application of 100 mM glycinebetaine (GB) at different growth stages (vegetative, flowering and grain filling) was carried out under water limited environment, at the Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad during 2008-09, to find out the best GB application stage for improvement in drought tolerance potential. The wire house experiment was laid out in completely randomized design. Data regarding various physiological and biochemical parameters of crop were recorded using standard procedures. The data so collected were analyzed statistically by using the Fisher's analysis of variance technique and LSD at 5% probability was used to compare the differences among treatment means. Drought stress at all three critical growth stages adversely affected plant's nutrient uptake and it also reduced the net photosynthesis rate (Pn) and transpiration rate (E) of wheat plant. Exogenous application of GB under drought at all three critical growth stages improved tolerance of wheat by reducing toxic nutrient's uptake however, grain filling stage was found more responsive. [ABSTRACT FROM AUTHOR]