Effect of foliar applied zinc sulphate on phenotypic variability, association and heritability of yield and zinc biofortification related traits of wheat genotypes.

Wheat is an important food crop worldwide, providing substantial calories and nourishment. Genetic variability in wheat germplasm is crucial for the development of cultivars with desirable features. This two years study (2020-21 and 2021-22) was conducted to evaluate 13 diverse wheat genotypes factorially combined with foliar-applied zinc sulphate (0, 0.4, 0.6%) arranged in a triplicate randomized complete block design. Boxplot analysis revealed the significant (P < 0.01) phenotypic variation of wheat germplasm for all the studied traits, but maximum variation was observed for yield and Zn biofortification-related traits. Correlation and path analysis revealed a significant (P < 0.01) association among yield and biofortification-related traits. Zinc uptake showed maximum strength of association (r = 0.96, p < 0.01) with grain Zn concentration. The Biplot analysis showed the graphical representation of wheat accessions based on similar characteristics and then assort into distinct groups. Broadsense heritability (Hbs) was calculated to determine the proportion of variation transmitted to future generations. The high value of Hbs for yield and Zn biofortification-related traits indicates that these traits are governed by the additive type of gene action and can be fixed in early segregating generations. In crux, this study validated the genetic variability in existing wheat genotypes for yield and Zn biofortification-related traits and may be helpful to devise an efficient breeding program for wheat Zn biofortification.

Increased health risk assessment in different vegetables grown under untreated sewerage irrigation regime due to higher heavy metals accumulation.

Heavy metals are environmental pollutants and carcinogenic for human health if ingested. In developing countries, including Pakistan, untreated sewerage water is one of the major sources of irrigation for vegetable production in the vicinities of urban areas which might be toxic to human health due to heavy metals contamination. The present study was conducted to investigate the uptake of heavy metals by sewage water application and its impact on human health. The experiment consisted of five vegetable crops (Raphanus sativus L, Daucus carota, Brassica rapa, Spinacia oleracea, and Trigonella foenum-graecum L.) and two irrigation sources (clean water irrigation and sewage water irrigation). Each treatment was three time replicated for all five vegetables, and standard agronomic practices were applied. The results demonstrated that shoot and root growth in radish, carrot, turnip, spinach, and fenugreek was enhanced significantly with sewerage water, probably due to enhanced organic matter. However, pithiness was observed in the root of radish under sewerage water treatment. Very high concentrations of Cd, up to 7.08 ppm in turnip roots while up to 5.10 ppm in fenugreek shoot, were observed, and other vegetables also contained higher concentrations of Cd. Zn concentrations in the edible parts of carrot (control (C) = 129.17 ppm, sewerage (S) = 164.10 ppm), radish (C = 173.73 ppm, S = 253.03), turnip (C = 109.77 ppm, S = 149.67 ppm), and fenugreek (C = 131.87 ppm, S = 186.36 ppm) were increased by sewerage water treatment but a decrease in Zn concentration in spinach (C = 262.17 ppm, S = 226.97 ppm) was observed. Fe concentration in edible parts of carrot (C = 888.00 ppm, S = 524.80 ppm), radish (C = 139.69 ppm, S = 123.60 ppm), turnip (C = 195.00 ppm, S = 121.37 ppm), and fenugreek (C = 1054.93 ppm, S = 461.77 ppm) were also decreased by sewerage water treatment while spinach leaves had accumulated higher Fe (C = 1560.33 ppm, S = 1682.67 ppm) in sewerage water treatment. The highest bioaccumulation factor value was 4.17 for Cd in carrots irrigated with sewerage water. The maximum value of bioconcentration factor was 3.11 for Cd in turnip under control, and the highest value of translocation factor was 4.82 in fenugreek irrigated with sewerage water. Daily intake of metals and health risk index (HRI) calculation indicated that HRI for Cd was more than 1, suggesting toxicity in these vegetables while HRI for Fe and Zn is still under safe limit. Correlation analysis among different traits of all vegetables under both treatments revealed valuable information for selecting traits in the next crop breeding programs. It is concluded that untreated sewerage-irrigated vegetables, highly contaminated with Cd, are potentially toxic for human consumption and should be banned in Pakistan. Furthermore, it is suggested that the sewerage water should be treated to eliminate toxic compounds, particularly Cd, before irrigation usage and non-edible/phytoremediation crops might be grown in contaminated soils.

Comparative genetic, biochemical and physiological analysis of sodium and chlorine in wheat.

Plant with a great diversity shows several responses towards the biotic and abiotic stresses. Among these abiotic stresses, salinity is the main damaging factor as it reduces the yield of wheat plant with moderate salt tolerance. For its survival, plant undergoes through some genetic, biochemical and physiological changes to tackle the stress. This review mainly describes the conditions where various ions present in the soil, especially sodium and chlorine, enter into the plant and the genes or proteins involved with survival mechanism against the damage in plants. Salt stress causes alteration in enzymatic activity and Photosynthesis, oxidative stress, damage of cellular structure and components and ionic imbalance. Ion toxicity stress occur due to accumulation of excessive sodium ion and chloride ion. Transcriptional factors TaPIMP, TaSRG and TaMYBsdu 1 play key role in gene expression mechanism to overcome the stress. High affinity potassium transporter gene family is responsible for salt tolerance in wheat plant. HKT1;4 and HKT1;5 genes are responsible for Na exclusion in Triticum monococcum. Forty QTLs were found with the marker assisted selection in bread wheat for salinity tolerance and some morphological traits, 5 QTLs were related to sodium ion exclusion. In bread wheat, salt stress tolerance mechanism is mainly an exclusion of Na+ ions but also include K+ ion concentration. The salinity tolerant germplasm MW#293 provides an opportunity for the development of future salinity tolerant bread wheat.

Foliar application of zinc improves morpho-physiological and antioxidant defense mechanisms, and agronomic grain biofortification of wheat (Triticum aestivum L.) under water stress.

Agronomic biofortification with zinc (Zn) may be engaged to improve the nutritious value of food crops along-with tolerance to water deficit conditions. The Zn may increase plant resistance to water stress by boosting physiological and enzymatic antioxidants defense mechanisms. Major objective of this study was to investigate the effect of foliar applied Zn on grain zin biofortification and drought tolerance in wheat. Treatments include application of Zinc at terminal growth phases (BBCH growth stage 49 and BBCH growth stage 65) with five levels: 0 (control-ck), water spray, 5, 10 and 15 mM under two levels of water regimes; well-watered (where 80% water holding capacity (WHC) was maintained in the soil) and water stress, (where 40% WHC was maintained in the soil). Results revealed that water stress significantly reduced relative water contents, gas exchange attributes, plant height, yield and yield related attributes of wheat. In contrast, hydrogen peroxide, free proline levels, activities of malondialdehyde, and concentration of soluble protein were markedly increased under water stress condition. Application of various levels of Zn significantly improved the CAT, SOD, POD and ASP activities at 40% WHC compared with control treatment. Foliarly applied 10 and 15 mM Zn predominantly reduced the damaging impact of water stress by improving the plant status in the form of plant height, RWC and gas exchange attributes. Likewise, wheat plant treated with 10 mM Zn under water stress condition increased the grain yield by improving number of grains per spike, 100 grain weight and biological yield compared with control. Moreover, increasing Zn levels also increased Zn concentration in grains and leaves. Overall, this study suggests that optimum level of Zn (10 mM) might be promising for alleviating the adverse impacts of water stress and enhance the grain biofortification in wheat.

Morphological, physiological and molecular assessment of cotton for drought tolerance under field conditions.

Climate change could be an existential threat to many crops. Drought and heat stress are becoming harder for cultivated crops. Cotton in Pakistan is grown under natural high temperature and low moisture, could be used as a source of heat and drought tolerance. Therefore, the study was conducted to morphological, physiological and molecular characterization of cotton genotypes under field conditions. A total of 25 cotton genotypes were selected from the gene pool of Pakistan based on tolerance to heat and drought stress. In field trail, the stress related traits like boll retention percentage, plant height, number of nodes and inter-nodal distance were recorded. In physiological assessment, traits such as photosynthesis rate, stomatal conductance, transpiration rate, leaf temperature, relative water content and excised leaf water loss were observed. At molecular level, a set of 19 important transcription factors, controlling drought/heat stress tolerance (HSPCB, GHSP26, HSFA2, HSP101, HSP3, DREB1A, DREB2A, TPS, GhNAC2, GbMYB5, GhWRKY41, GhMKK3, GhMPK17, GhMKK1, GhMPK2, APX1, HSC70, ANNAT8, and GhPP2A1) were analyzed from all genotypes. Data analyses depicted that boll retention percentage, photosynthesis, stomatal conductance, relative water content under the stress conditions were associated with the presence of important drought & heat TF/genes which depicts high genetic potential of Pakistani cotton varieties against abiotic stress. The variety MNH-886 appeared in medium plant height, high boll retention percentage, high relative water content, photosynthesis rate, stomatal conductance, transpiration rate and with maximum number transcription factors under study. The variety may be used as source material for heat and drought tolerant cotton breeding. The results of this study may be useful for the cotton breeders to develop genotype adoptable to environmental stresses under climate change scenario.

Genome-wide analysis of potassium transport genes in Gossypium raimondii suggest a role of GrHAK/KUP/KT8, GrAKT2.1 and GrAKT1.1 in response to abiotic stress.

Potassium (K+) is an important macro-nutrient for plants, which comprises almost 10% of plant's dry mass. It plays a crucial role in the growth of plants as well as other important processes related to metabolism and stress tolerance. Plants have a complex and well-organized potassium distribution system (channels and transporters). Cotton is the most important economic crop, which is the primary source of natural fiber. Soil deficiency in K+ can negatively affect yield and fiber quality of cotton. However, potassium transport system in cotton is poorly studied. Current study identified 43 Potassium Transport System (PTS) genes in Gossypium raimondii genome. Based on conserved domains, transmembrane domains, and motif structures, these genes were classified as K+ transporters (2 HKTs, 7 KEAs, and 16 KUP/HAK/KTs) and K+ channels (11 Shakers and 7 TPKs/KCO). The phylogenetic comparison of GrPTS genes from Arabidopsis thaliana, Glycine max, Oryza sativa, Medicago truncatula and Cicer arietinum revealed variations in PTS gene conservation. Evolutionary analysis predicted that most GrPTS genes were segmentally duplicated. Gene structure analysis showed that the intron/exon organization of these genes was conserved in specific-family. Chromosomal localization demonstrated a random distribution of PTS genes across all the thirteen chromosomes except chromosome six. Many stress responsive cis-regulatory elements were predicted in promoter regions of GrPTS genes. The RNA-seq data analysis followed by qRT-PCR validation demonstrated that PTS genes potentially work in groups against environmental factors. Moreover, a transporter gene (GrHAK/KUP/KT8) and two channel genes (GrAKT2.1 and GrAKT1.1) are important candidate genes for plant stress response. These results provide useful information for further functional characterization of PTS genes with the breeding aim of stress-resistant cultivars.

Conservation tillage improves productivity of sunflower (Helianthus annuus L.) under reduced irrigation on sandy loam soil.

Sunflower production is significantly lower in arid and semi-arid regions due to various crop management problem. Conservation of tillage provides the most excellent opportunity to reduce degradation of soil reserves and increase soil productivity. The main objective of this study was to investigate the combined effects of conservation tillage and drought stress on growth and productivity of different sunflower hybrids. Experimental treatments included two sunflower hybrids ('NK-Senji' and 'S-278'), two drought stress treatments (i.e., well-watered and drought stress at flowering and grain filling stages) and three tillage practices (i.e., conservation, minimum and deep tillage). The results indicated that morphological and physiological parameters, and yield-related traits were significantly (P≤0.05) affected by all individual factors; however, their interactive effects were non-significant. Among sunflower hybrids, 'NK-Senji' performed better for morphological, physiological, and yield-related traits than 'S-278'. Similarly, conservation tillage observed better traits compared to the rest of the tillage practices included in the study. Nonetheless, conservation tillage improved growth and yield-related traits of hybrid 'NK-Senji' under drought stress. Hence, it is concluded that conservation tillage can improve the productivity of sunflower under low moisture availability. Therefore, conservation tillage could be suggested in the areas of lower water ability to improve sunflower production. Nonetheless, sunflower hybrids or varieties need thorough testing for their adaptability to conservation tillage and low moisture availability before making recommendations.

Exogenous application of silicon improves the performance of wheat under terminal heat stress by triggering physio-biochemical mechanisms.

Due to climate change, temperature in late February and early March raised up which cause heat stress at reproductive stage (terminal growth phase of wheat crop) which has become the major causative factor towards low wheat production in arid and semiarid regions. Therefore; strategies need to be adopted for improving terminal heat stress tolerance in wheat. In this study, we assessed whether foliar application of silicon (Si) (2 and 4 mM) at terminal growth phase i.e. heading stage of wheat imposed to heat stress (37 ± 2 °C) under polythene tunnel could improve the performance of wheat. Results of the study revealed that heat stress significantly reduced the photosynthetic pigments (chlorophyll a, b and a + b and carotenoids) leading to a lower grain yield. However, a 4 mM Si application (foliar applied) at heading stage prominently increased the chlorophyll a, b and a + b and carotenoids of flag leaf by improving the activities of enzymatic antioxidants (catalase, peroxidase and superoxide dismutase) and osmoprotectants (soluble sugar protein and proline) under terminal heat stress. Improvements in the performance of wheat (chlorophyll contents, carotenoids, soluble sugar and proteins and proline and yield) with foliar application of Si were also observed under control conditions. Correlation analysis revealed strong association (r > 0.90) of chlorophyll contents and carotenoids with grain and biological yield. Negative correlation (-0.81 < r > -0.63) of physio-biochemical components (antioxidants, proline, soluble sugars and proteins) with yield revealed that under heat stress these components produced in more quantities to alleviate the effects of heat, and Si application also improved these physio biochemical components. In crux, foliar application of Si alleviates the losses in the performance of wheat caused by terminal heat stress by improving the antioxidant mechanism and production of osmoprotectants.

Elevated carbon dioxide offers promise for wheat adaptation to heat stress by adjusting carbohydrate metabolism.

Carbohydrate metabolism in plants is influenced by thermodynamics. The amount of carbon dioxide (CO2) in the atmosphere is expected to rise in the future. As a result, understanding the effects of higher CO2 on carbohydrate metabolism and heat stress tolerance is necessary for anticipating plant responses to global warming and elevated CO2. In this study, five wheat cultivars were exposed to heat stress (40 °C) at the onset of anthesis for three continuous days. These cultivars were grown at two levels of CO2 i.e. ambient CO2 level (a[CO2], 380 mmol L-1) and elevated CO2 level (e[CO2], 780 mmol L-1), to determine the interactive effect of elevated CO2 and heat stress on carbohydrate metabolism and antioxidant enzyme activity in wheat. Heat stress reduced the photosynthetic rate (Pn) and grain yield in all five cultivars, but cultivars grown in e[CO2] sustained Pn and grain yield in contrast to cultivars grown in a[CO2]. Heat stress reduced the activity of ADP-glucose pyrophosphorylase, UDP-glucose pyrophosphorylase, invertases, Glutathione reductase (GR), Peroxidase (POX), and Superoxide dismutase (SOD) at a[CO2] but increased at e[CO2]. The concentration of sucrose, glucose, and fructose mainly increased in tolerant cultivars under heat stress at e[CO2]. This study confirms the interaction between the heat stress and e[CO2] to mitigate the effect of heat stress on wheat and suggests to have in-depth knowledge and precise understanding of carbohydrate metabolism in heat stressed plants in order to prevent the negative effects of high temperatures on productivity and other physiological attributes. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-01080-5.

Combined application of zinc and silicon alleviates terminal drought stress in wheat by triggering morpho-physiological and antioxidants defense mechanisms.

Wheat is an important global staple food crop; however, its productivity is severely hampered by changing climate. Erratic rain patterns cause terminal drought stress, which affect reproductive development and crop yield. This study investigates the potential and zinc (Zn) and silicon (Si) to ameliorate terminal drought stress in wheat and associated mechanisms. Two different drought stress levels, i.e., control [80% water holding capacity (WHC) was maintained] and terminal drought stress (40% WHC maintained from BBCH growth stage 49 to 83) combined with five foliar-applied Zn-Si combinations (i.e., control, water spray, 4 mM Zn, 40 mM Si, 4 mM Zn + 40 mM Si applied 7 days after the initiation of drought stress). Results revealed that application of Zn and Si improved chlorophyll and relative water contents under well-watered conditions and terminal drought stress. Foliar application of Si and Zn had significant effect on antioxidant defense mechanism, proline and soluble protein, which showed that application of Si and Zn ameliorated the effects of terminal drought stress mainly by regulating antioxidant defense mechanism, and production of proline and soluble proteins. Combined application of Zn and Si resulted in the highest improvement in growth and antioxidant defense. The application of Zn and Si improved yield and related traits, both under well-watered conditions and terminal drought stress. The highest yield and related traits were recorded for combined application of Zn and Si. For grain and biological yield differences among sole and combined Zn-Si application were statistically non-significant (p>0.05). In conclusion, combined application of Zn-Si ameliorated the adverse effects of terminal drought stress by improving yield through regulating antioxidant mechanism and production of proline and soluble proteins. Results provide valuable insights for further cross talk between Zn-Si regulatory pathways to enhance grain biofortification.

Expression studies of stress responsive genes in cotton Gossypium hirsutum L.

BACKGROUND: Cotton is the world's richest source of natural fiber. Meanwhile cotton plant is top ranked stress sensitive plant thereby affecting its yield and fiber quality. But, in climate change scenario, fiber yield and quality are being affected due to environmental stresses, especially heat, drought and salinity. Present study is aimed to identify cotton genotype harboring prominently expressed stress responsive genes. METHODS: Four cotton genotypes (IUB-13, IUB-222, IUB-09 and MM-58) were evaluated under drought and salinity stress for yield traits and expression of different stress responsive genes (GhWRKY3, GhDREB2 and GhRDR6). RESULTS: Pronounced expression of GhWRKY3, GhDREB2and GhRDR6 was observed in cotton variety IUB-13 in stress condition (drought and salinity) as compared to control followed by IUB-222 which revealed that these genotypes might possess substantial potential to cope with environmental hazards encountered in growing season CONCLUSION: Utilization of cotton genotypes i.e., IUB-13 and IUB-222 in cotton breeding program can be very much fruitful for developing cotton genotypes adoptable to climate change.

Phenotypic characterization of exotic tomato germplasm: An excellent breeding resource.

Tomato production in Pakistan faces significant problems of low yields due to various biotic and abiotic stresses primarily because of a narrow genetic base of the cultivars being used. Therefore, Introduction and evaluation of the exotic tomato germplasm has become necessary to acquire elite material to develop future breeding programs. To this end, the present study was conducted for the phenotypic characterization of twenty exotic tomato genotypes along with two locally grown cultivars in semi-arid subtropical climate. Data were collected for morphological, fruit quality and fruit yield traits. A significant (p<0.05) phenotypic variation was observed for all the studied traits. Maximum yield was obtained from "Rober" i.e., 1508.31 g per plant. The maximum shelf life was observed in the Cromco, with the least weight loss (2.45%) and loss in the firmness of fruit (22.61%) in 4 days. Correlation analyses revealed a strong genetic association among morphological and yield related traits. High estimates of the heritability (ranged from 79.77% to 95.01% for different traits), along with a high genetic advance (up to 34%) showed the potential usefulness of these traits and genotypes to develop breeding programs to improve the tomato yield and fruit quality.

Zinc biofortification potential of diverse mungbean [Vigna radiata (L.) Wilczek] genotypes under field conditions.

Zinc (Zn) is an important micronutrient for crop plants and essential for human health. The Zn-deficiency is an important malnutrition problem known globally. Biofortified foods could overcome Zn deficiency in humans. Mungbean [Vigna radiata (L.) Wilczek] is an important, pulse crop frequently grown in arid and semi-arid regions of the world. Mungbean could provide essential micronutrients, including Zn to humans. Therefore, it is very important to investigate the impact of Zn fertilization on the yield and grain biofortification of mungbean. Twelve mungbean genotypes (i.e., NM-28, NM-2011, NM-13-1, NM-2006, NM-51, NM-54, NM-19-19, NM-92, NM-121-25, NM-20-21, 7006, 7008) were assessed for their genetic diversity followed by Zn-biofortification, growth and yield under control (0 kg ha-1) and Zn-fertilized (10 kg ha-1) conditions. Data relating to allometric traits, yield components, grain yield and grain Zn contents were recorded. Zinc fertilization improved entire allometric and yield-related traits. Grain yield of different genotypes ranged from 439 to 904 kg ha-1 under control and 536 to 1462 kg ha-1 under Zn-fertilization. Zinc concentration in the grains varied from 15.50 to 45.60 mg kg-1 under control and 18.53 to 64.23 mg kg-1 under Zn-fertilized conditions. The tested genotypes differed in their Zn-biofortification potential. The highest and the lowest grain Zn contents were noted for genotypes NM-28 and NM-121-25, respectively. Significant variation in yield and Zn-biofortification indicated the potential for improvement in mungbean yield and grain Zn-biofortification. The genotypes NM-28 and NM-2006 could be used in breeding programs for improvement in grain Zn concentration due to their high Zn uptake potential. Nonetheless, all available genotypes in the country should be screened for their Zn-biofortification potential.

Optimizing sowing date for peanut genotypes in arid and semi-arid subtropical regions.

Peanut (Arachis hypogea L.) is an important nut crop extensively grown in rainfed regions of Pakistan. The crop requires low inputs; thus, could grow successfully under diverse environmental conditions. Due to pegging ability, peanut grows aggressively in sandy and sandy-loam soils. However, it has not introduced to Thal region of southern Punjab, Pakistan. A two-year field experiment was conducted to optimize sowing dates for two peanut genotypes ('BARI-2016' and 'NO-334') in Thal region (Layyah). Similarly, a yield trial was conducted at Chakwal where both genotypes are extensively grown. Five sowing dates (10th April, 1st May, 20th May, 10th June and 30th June) were included in the study. The highest seed yield was obtained with early sown crop (10th April) during both years. Pod formation reduced with increasing atmospheric temperature and no pods were formed on the plants sown on 30th June. Decreased pod formation seemed a major reason for low yield in late-sown crop. The highest yield was observed for the crop sown on 10th April, which was decreased by 40% for the crop sown on 1st May. Genotype 'BARI-2016' performed better for seed yield at both locations compared with 'NO-334'. The results suggested that genotype 'BARI-2016' is more adaptive to arid and semi-arid condition under rainfed or irrigated conditions. Sowing peanut at optimum time would increase seed yield in arid and semi-arid regions. Nonetheless, 'BARI-2016' can be grown under rainfed and irrigated conditions successfully.

Impact of heat stress responsive factors on growth and physiology of cotton (Gossypium hirsutum L.).

Pakistan ranked highest with reference to average temperatures in cotton growing areas of the world. The heat waves are becoming more intense and unpredictable due to climate change. Identification of heat tolerant genotypes requires comprehensive screening using molecular, physiological and morphological analysis. Heat shock proteins play an important role in tolerance against heat stress. In the current study, eight heat stress responsive factors, proteins and genes (HSFA2, GHSP26, GHPP2A, HSP101, HSC70-1, HSP3, APX1 and ANNAT8) were evaluated morphologically and physiologically for their role in heat stress tolerance. For this purpose, cotton crop was grown at two temperature conditions i.e. normal weather and heat stress at 45 °C. For molecular analysis, genotypes were screened for the presence or absence of heat shock protein genes. Physiological analysis of genotypes was conducted to assess net photosynthesis, stomatal conductance, transpiration rate, leaf-air temperature and cell membrane stability under control as well as high temperature. The traits photosynthesis, cell membrane stability, leaf-air temperature and number of heat stress responsive factors in each genotypes showed a strong correlation with boll retention percentage under heat stress. The genotypes with maximum heat shock protein genes such as Cyto-177, MNH-886, VH-305 and Cyto-515 showed increased photosynthesis, stomatal conductance, negative leaf-air temperature and high boll retention percentage under heat stress condition. These varieties may be used as heat tolerant breeding material.

The fingerprints of climate warming on cereal crops phenology and adaptation options.

Growth and development of cereal crops are linked to weather, day length and growing degree-days (GDDs) which make them responsive to the specific environments in specific seasons. Global temperature is rising due to human activities such as burning of fossil fuels and clearance of woodlands for building construction. The rise in temperature disrupts crop growth and development. Disturbance mainly causes a shift in phenological development of crops and affects their economic yield. Scientists and farmers adapt to these phenological shifts, in part, by changing sowing time and cultivar shifts which may increase or decrease crop growth duration. Nonetheless, climate warming is a global phenomenon and cannot be avoided. In this scenario, food security can be ensured by improving cereal production through agronomic management, breeding of climate-adapted genotypes and increasing genetic biodiversity. In this review, climate warming, its impact and consequences are discussed with reference to their influences on phenological shifts. Furthermore, how different cereal crops adapt to climate warming by regulating their phenological development is elaborated. Based on the above mentioned discussion, different management strategies to cope with climate warming are suggested.

Terminal drought and heat stress alter physiological and biochemical attributes in flag leaf of bread wheat.

Heat stress along with low water availability at reproductive stage (terminal growth phase of wheat crop) is major contributing factor towards less wheat production in tropics and sub-tropics. Flag leaf plays a pivotal role in assimilate partitioning and stress tolerance of wheat during terminal growth phase. However, limited is known about biochemical response of flag leaf to combined and individual heat and drought stress during terminal growth phase. Therefore, current study investigated combined and individual effect of terminal drought and heat stress on water relations, photosynthetic pigments, osmolytes accumulation and antioxidants defense mechanism in flag leaf of bread wheat. Experimental treatments comprised of control, terminal drought stress alone (50% field capacity during reproductive phase), terminal heat stress alone (wheat grown inside plastic tunnel during reproductive phase) and terminal drought stress + terminal heat stress. Individual and combined imposition of drought and heat stresses significantly (p≤0.05) altered water relations, osmolyte contents, soluble proteins and sugars along with activated antioxidant defensive system in terms of superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX). Turgor potential, POD and APX activities were lowest under individual heat stress; however, these were improved when drought stress was combined with heat stress. It is concluded that combined effect of drought and heat stress was more detrimental than individual stresses. The interactive effect of both stresses was hypo-additive in nature, but for some traits (like turgor potential and APX) effect of one stress neutralized the other. To best of our knowledge, this is the first report on physiological and biochemical response of flag leaf of wheat to combine heat and drought stress. These results will help future studies dealing with improved stress tolerance in wheat. However, detailed studies are needed to fully understand the genetic mechanisms behind these physiological and biochemical changes in flag leaf in response to combined heat and drought stress.

Efficacy of fertilizing method for different potash sources in cotton (Gossypium hirsutum L.) nutrition under arid climatic conditions.

Precise choice of potassium (K) source and application method does matter for its cost-effectiveness. This study was aimed to evaluate the best source and method of K fertilizer application to improve cotton productivity and profitability under an arid climate. Three different K sources (KNO3, K2SO4 and KCl) were applied at 100 kg ha-1 by four methods, i.e. a) basal application, b) side dressing, c) fertigation and d) foliar application of 2% K2SO4. The highest productivity and profitability were recorded with K2SO4 applied as foliar application. Total boll weight per plant was similar in foliar applied K2SO4 and basal application of KNO3. Better boll opening in foliar applied K2SO4, perhaps, played decisive role for increased seed-cotton yield. For basal application and side dressing, KNO3 produced the highest seed-cotton yield, but the benefit cost ratio was better for foliar applied K2SO4. In crux, foliar application of K2SO4 might be opted to improve the seed cotton yield, fiber quality and net returns under the arid climate. However, soil K application through K2SO4 and/or KNO3 is essential to balance the K removal from soil.

Potassium Application Improves Grain Yield and Alleviates Drought Susceptibility in Diverse Maize Hybrids.

Maize (Zea mays L.) is an important component of global food security but its production is threatened by abiotic stresses in climate change scenarios, especially drought stress. Many multinational companies have introduced maize hybrids worldwide which have variable performance under diverse environmental conditions. The maize production is likely to be affected by a future water crisis. Potassium (K) is a well-known macronutrient which improves the performance of cereals under abiotic stresses. In this field experiment, we assessed the influence of soil applied K on the productivity of diverse maize hybrids grown under well-watered and drought stress conditions. The study consisted of three K levels viz., control (no KCl), KCl at 50 kg ha-1, and KCI at 75 kg ha-1 factorally combined with two irrigation levels (i.e., normal recommended irrigation, well-watered condition, and half of the recommended irrigation, drought stress condition) and eight maize hybrids. Irrigation was kept in main plots, potassium in subplot, and maize hybrids in sub-subplots. The results revealed that performance of the maize hybrids was significantly influenced by all three factors, and the interaction of irrigation with potassium and irrigation with hybrids was significant; results being non-significant for all other interactions. Potassium application improved yield traits and water productivity under both normal and water stress conditions but effect was more prominent under water stress conditions than normal conditions. Potassium application also alleviated drought susceptibility of all maize hybrids. In all cases, the performance of maize hybrids was maximum under potassium application at 75 kg ha-1.

Sewage waste water application improves the productivity of diverse wheat (Triticum aestivum L.) cultivars on a sandy loam soil.

Water stress due to climate change is an emerging threat to wheat (Triticum aestivum L.) productivity in the arid regions of the world which will impact the future food security. In this scenario, the investigations are needed to check the feasibility of alternate sources of irrigation water to fulfill the irrigation demands of the crops in the arid regions. This 2-year study was aimed to investigate the influence of three irrigation sources (sewage water, canal water, and underground water) on the productivity of 10 wheat cultivars under an arid climate of Layyah, Pakistan. The results indicated that the number of fertile tillers, grains per spike, 1000-grain weight, and grain yield varied from 114 to 168 m-2, 34.8 to 53.3, 33.4 to 38.4 g, and 2.68 to 4.05 Mg ha-1, respectively in various wheat cultivars. The highest fertile tillers (168 m-2) were recorded in cultivar Gold-2016 followed by Aas-2011 (155 cm), AARI-2011 (153 m-2), and Ujala-2016 (150 m-2). The highest 1000-grain weight of 38.4 g was recorded in cultivar NARC-2016. The grains per spike (53.3) were the highest in cultivar Ujala-2016. The grain yields were the highest in cultivars Ujala-2016 (4.05 Mg ha-1) and Gold-2016 (3.91 Mg ha-1). The highest grain yield of 3.71 Mg ha-1 was recorded with sewage water irrigation against the grain yield of 3.18 and 2.91 Mg ha-1 in canal and underground water irrigation, respectively. There existed a strong co-relation of fertile tillers and grains per spike with the grain yield of wheat. Application of sewage water also enhanced the total nitrogen, extractable potassium, and available phosphorous in soil. In crux, the cultivation of recently bread wheat cultivars (viz. Ujala-2016, Gold-2016) and the irrigation of field with sewage water in the absence of canal water might be a viable option to boost wheat productivity under arid regions. A range of genetic variability existed for different traits in the cultivars; therefore, these can be used to breed wheat cultivars to be used for sewage water cultivation.