Mohammad Akmal

The transitional phase of climate change is becoming a threat worldwide. Fluctuations in temperature are frequently observed in the life cycles of field crops. The current study was intended to evaluate heat stress (HS) at sensitive stages on four wheat cultivars’ growth, grain yield, and quality traits during two consecutive seasons. The experiment included four spring wheat cultivars that were exposed to HS durations (i.e., 0, 48, 96 and 144 h) at booting and anthesis stages. Pots were kept in an open-air, and labeled pots were moved to the glasshouse at the respective growth stage. After HS treatments, pots were moved from the glasshouse to the original position in the open air. The results showed that the cultivars differed in yield and grain quality traits, but their collective mean effect was significantly expressed with HS and HS duration (HSd) on the measured traits. Spike length was significantly affected by HS at the anthesis in comparison to those obtained from the control. However, the increase in HSd did not cause a significant effect on spike length compared to other treatments. Spike weight was significantly decreased in plants exposed to HS at booting and anthesis as well as by increasing HSd. In addition, grain weight and numbers were decreased in plants exposed to HS at booting and anthesis stages with a similar pattern by increasing HSd. Moreover, a reduction in amylose content was observed in grains of plants exposed to HS at booting and anthesis stages or when plants as exposed to a longer period of HSd. Nonetheless, amylopectin, wet gluten (WG) and grain N (GN) showed an increase in plants exposed to HS at booting and anthesis stages and/or extending HSd. This study concludes that plants exposed to different HS treatments during the life cycle had lower values for spike length, grains weight, and grains number per spike including amylose content in comparison to those obtained from the control. The decrease was significantly noted in the yield and grain quality of wheat when plants were exposed to HS at the booting stage in comparison to those exposed to HS at anthesis.

Crop simulation models can be effective tools to assist with optimization of resources for a particular agroecological zone. The goal of this study was to determine the influence of N rates with different timing of application to wheat crop using prominent varieties using the CSM-CERES-Wheat model of the decision support system for agrotechnology transfer (DSSAT). Data were focused for yield traits, i.e., number of tillers, number of grains, grain weight, grain yield, biomass, and grain N content. To test the applicability of the CSM-CERES-Wheat version 4.7.5 model for agroclimatic conditions of Peshawar, Pakistan, experimental data from two years of experiments (2016–17 and 2017–18) were used for model calibration and evaluation. The simulation results of two years agreed well with field measured data for three commercial varieties. The model efficiency (R²) for wheat varieties was above 0.94 for variables tiller number per unit area (m⁻²), number of grains (m⁻²) and number of grains (spike⁻¹), 1000 grain weight (mg), biomass weight (kg ha⁻¹), grain yield (kg ha⁻¹), and harvest N content (kg ha⁻¹). Statistics of cultivars indicated that yield traits, yield, and N can be simulated efficiently for agroecological conditions of Peshawar. Moreover, different N rates and application timings suggested that the application of 140 kg N ha⁻¹ with triple splits timings, i.e., 25% at the sowing, 50% at the tillering, and 25% at the booting stage of the crop, resulted in the maximum yield and N recovery for different commercial wheat varieties. Simulated N losses, according to the model, were highly determined by leaching for experimental conditions where a single N application of 100% or existing double splits timing was applied. The study concluded that 140 kg N ha⁻¹ is most appropriate for wheat crop grown on clay loam soils under a flood irrigation system. However, the N fertilizer has to be given in triple splits of a 1:2:1 ratio at the sowing, tillering, and booting stages of the crop growth.

| Despite the genetic potential, the yield performance of a genotype is expressed in the prevailing environments. A high yielding genotype may not necessarily reflect its potential performance when subjected to a different Agro-Environment (AE). This study, therefore, aimed to assess the foremost developmental stages of the selected genotypes of wheat in three AE i.e . AEP (Peshawar), AEK (Kashmir) and AEC (Chitral). An experiment was conducted in a randomized complete block, having 3 replications. Four cultivars ( i.e . Pirsabak-2005, Pakhtunkhwa-2015, Pakistan-2013 and DN-84) along with three advanced lines (i.e. P-2, P-12 and P-18) were compared for the crop growth seasons (i.e. 2017-18 and 2018-19). Averaged across genotypes, days to emergence, heading, anthesis, and maturity did differ (p<0.05) in various AE, with highest in higher altitudes and lowest in the plains area. Genotypes differed in crop developmental stages with mild to marked effects on tiller height, spike length, spike weight and unit grain weight, which has resulted in significant changes (p<0.05) for biomass and grain yield. Harvest indices did differ for AE among genotypes. Based on the experimental results, it is concluded that a genotype may not necessarily perform similar in production with changing the AE. However, with a close association of the crop developmental stages, more than one genotype can be recommended to perform good within different AE to adress future food security. Moreover, expressing suitable traits, a genotype could be used as a source of well breeding material for ensuring food security in changing climate.

Uncertain heat shock by a rapid increase in temperature particularly at the critical growth stage affects plant productivity. The study aimed to assess qualitative changes in wheat grains when plant exposed to high temperature shock (HTS) at starting anthesis for limited durations (48, 72 and 96h). Selected wheat cultivars (Pirsabak-2005, Pakhtunkhwa-2015, Pakistan-2013, DN-84, P-2, P-12 and P-18) were exposed to extending HTS effective from anthesis in the field covering plants within plastic tents for a limited duration. The experiment was conducted in 2017-18 and 2018-19 at the Research Farm, the University of Agriculture Peshawar, Pakistan in a randomized complete block design, in three replications. Temperatures inside and outside plastic tents were manually noted. Two years mean data showed significant effects of HTS on the wheat grain quality. Imposed HTS for 48, 72 and 96h resulted in a reduction on grain amylose by 23, 39 and 48% and wet gluten by 16, 25 and 36%, respectively when compared with the control (i.e. no HTS). Contrary to this, as compared to the control treatment an increase noted in the grain amylopectin by 7, 11 & 17% and in the grain N-content by 13, 28 & 41% with imposing HTS extending to a duration of 48, 72 and 96h, respectively. The study concluded adverse effects of HTS at the anthesis stage on wheat grain quality disturbing amylose and amylopectin ratios, which latter on brought changes in floor structure and gluten elasticity. However, cultivar did differ to respond to the changes but have the option to choose the best one.

Drought stress is the most prominent limiting factor and abiotic stress that manipulates the physiological pathway, biochemical traits and hence negatively affects wheat crop productivity. The global nitrogen (N) recovery indicated that about two-fifths of N inputs are lost in the ecosystems through emission, denitrification, gaseous loss, leaching, surface runoff and volatilization etc. Farmers are using higher rates of N to harvest maximum yield but about 50–60% of applied N to crop field is not utilized by the plants and are lost to environment causing environmental pollution. These deleterious environmental consequences need to be reduced by efficient management of N and/or water. N-availability is often regulated by soil water; hence crop is experiencing N- and water-limitation simultaneously. There is great impetus to optimize their uptake through interconnectedness of water and N for yield determination of wheat because of the water scarcity and N losses. It is further advocate that there is need to investigate the intricate role of economizing N rate and water simultaneously for wheat crop growth, yield and backing quality may be beneficial to be investigate.

Drought stress, being the inevitable factor that exists in various environments without recognizing borders and no clear warning thereby hampering plant biomass production, quality, and energy. It is the key important environmental stress that occurs due to temperature dynamics, light intensity, and low rainfall. Despite this, its cumulative, not obvious impact and multidimensional nature severely affects the plant morphological, physiological, biochemical and molecular attributes with adverse impact on photosynthetic capacity. Coping with water scarcity, plants evolve various complex resistance and adaptation mechanisms including physiological and biochemical responses, which differ with species level. The sophisticated adaptation mechanisms and regularity network that improves the water stress tolerance and adaptation in plants are briefly discussed. Growth pattern and structural dynamics, reduction in transpiration loss through altering stomatal conductance and distribution, leaf rolling, root to shoot ratio dynamics, root length increment, accumulation of compatible solutes, enhancement in transpiration efficiency, osmotic and hormonal regulation, and delayed senescence are the strategies that are adopted by plants under water deficit. Approaches for drought stress alleviations are breeding strategies, molecular and genomics perspectives with special emphasis on the omics technology alteration i.e., metabolomics, proteomics, genomics, transcriptomics, glyomics and phenomics that improve the stress tolerance in plants. For drought stress induction, seed priming, growth hormones, osmoprotectants, silicon (Si), selenium (Se) and potassium application are worth using under drought stress conditions in plants. In addition, drought adaptation through microbes, hydrogel, nanoparticles applications and metabolic engineering techniques that regulate the antioxidant enzymes activity for adaptation to drought stress in plants, enhancing plant tolerance through maintenance in cell homeostasis and ameliorates the adverse effects of water stress are of great potential in agriculture.

| This study was focused on N split application timing effect on wheat performance as sole or intercrop with other selected species. The study was conducted at Agronomy Research Farm, the University of Agriculture, Peshawar, during winter 2015-16. Treatments included cropping pattern viz. sole and intercrop of lines with 1:1 ratio i.e. one wheat row followed by one other crop species and 2:1 ratio i.e. two wheat rows followed by one other crops rows of Brassica ( Brassica juncea ), Fababean ( Vicia faba ) and Sunflower ( Helianthus annuus ), hereafter, referred as IC-I and IC-II. The N splits were applied of the total recommended 120 kg ha -1 N in splits, i.e. N splits application (NS) viz. NS 1 (50% sowing and 50% tillering), NS 2 (25% sowing: 50% tillering and 25% anthesis) and NS 3 (25% sowing, 25% tillering and 50% anthesis). Experimental design was a randomized complete block, replicated three times. Results showed a delay in maturity with taller plants at the split N application of NAT 2 and NS 3 as compared to the NS 1 . Likewise, better traits of wheat plant and hence the yield including grain wet gluten content were reported for the treatment NS 3 as sole wheat crop, followed by the intercropped with fababean. Among the intercropping, IC-I with fababean showed better future scope of wheat crop production under the changing climate to produce higher production per unit area with sustainable soil use under cereal cropping system. Among the tested species sunflower and flax were not suitable choices as IC with wheat. The study concluded with the expected increase in rainfall of the changing climate in KP which is expected at the time of the wheat crop at anthesis, three N splits application i.e. NS 2 and NS 3 are the best options over NS 1 for wheat crop in KP. Further, to adding that it minimized lodging resistant of intercrop over sole wheat and that wheat intercrop with fababean has a potential to harvest quality grains with sustainable soil management at wheat – maize cropping system.

Soil organic carbon (SOC) sequestration is one of the major agronomic measures to mitigate green house gas emission, enhance food security, and improve agriculture sustainability. The study, therefore, aimed to evaluate crop growth (CG) and radiation use efficiency in spring wheat (Triticum aestivum L.) treated soil with residue type (RT), that is, cowpea (Vigna unguiculata) as legume (LR), maize (Zea mays L.) as cereal (CR) and no residue (NR) treatment applied (5 t ha⁻¹) on dry matter basis. The CR was subsequently incorporated with tillage depths (TD), that is, deep (DT = 35 cm) and shallow (ST = 15 cm) as main plot treatments. The N was applied in two splits starting from 0 to 160 kg ha⁻¹ as sub plot treatments. Experiment was conducted in two CG seasons 2009–11 at Agronomy Research Farm, the University of Agriculture Peshawar, Pakistan. Results showed the highest CG and RUE with LR incorporated than CR and/or NR with DT. Increasing N-rate resulted an increase in CG, RUE and biomass of wheat. Residue of LR or CR deeply incorporate into the soil has resulted healthy traits (i.e., tillers- and spikes number), which resulted higher biomass. Nitrogen applied 120 kg ha⁻¹ resulted in higher CG, RUE and grain yield for treatment LR, followed by CR and the lowest for the NR. Crop of second year showed higher grain yield, which was due to healthy traits including better CG and RUE. The study suggests that CR of LR or CR nature incorporated deep into the soil can optimize crop N-fertilizer demand for optimum production, which protects environment from the excessive use of N application.