Full Irrigation Conditions Research Articles

Long-term investigation of the irrigation intervals and supplementary irrigation strategies effects on winter wheat in the U.S. Central High Plains based on a combination of crop modeling and field studies

Implementing optimized irrigation strategies to achieve acceptable wheat yield while conserving groundwater resources is critical for extensively irrigated regions. Field experiments regarding winter wheat irrigation management were conducted for two growing seasons (2013–2014 and 2014–2015) to calibrate and validate the AquaCrop model. To determine proper parameterization of the AquaCrop model for various data availability conditions, the model performance was tested for calibration based on three different datasets, including a) calibration based on a full irrigation condition (CA 1), b) calibration based on a dryland condition (CA 2), and c) calibration based on diverse irrigation conditions, which included full irrigation, different deficit irrigation levels, and dryland (CA 3). The CA 3 calibration scenario resulted in the model's highest accuracy in simulating biomass, grain yield, total soil water, and seasonal evapotranspiration during the calibration and validation process. However, the model performance was also convenient when calibration based on full irrigation conditions was pursued. The calibrated and validated AquaCrop model based on the CA3 was used to analyze long-term (36-year) irrigation management scenarios for identifying the optimized water-conservative winter wheat irrigation strategies. The long-term analysis emphasized that increasing irrigation intervals from 7 to 15 or 20 days could reduce groundwater withdrawal by 52–64 % while expecting a 14–19 % reduction in grain yield. By implementing one 25 mm irrigation after planting and two 25 mm depth irrigation events at jointing or leaf growth stages, 91 % of Kansas's average winter wheat yield (2.88 tons/ha) could be achieved. During wet years, the 1.2 ton/ha reduction in biomass and 0.27–0.62 ton/ha reduction in grain yield is expected irrespective of irrigation management strategies. Considerable uncertainty was detected in grain yield production during dry years under dryland (rainfed) conditions. The maximum winter wheat production could be achieved under normal years, establishing a balance between precipitation and heat units. Our agro-hydrological analysis revealed that the highest irrigation water use efficiency could be attained by the application of two 25 mm irrigation events at jointing or flag leaf growth stages during normal years, the application of two irrigation events during jointing or heading during wet years, and two 25 mm irrigations at heading or flowering during dry years. The results of this research could be used as a baseline for producers of the U.S. Central High Plains and semi-arid regions with similar climate characteristics to cope with water scarcity in winter wheat production.

Elevated concentrations of soil carbon dioxide with partial root-zone drying enhance drought tolerance and agro-physiological characteristics by regulating the expression of genes related to aquaporin and stress response in cucumber plants

Water scarcity and soil carbon dioxide elevation in arid regions are considered the most serious factors affecting crop growth and productivity. This study aimed to investigate the impacts of elevated CO2 levels (eCO2 at rates of 700 and 1000 ppm) on agro-physiological attributes to induce drought tolerance in cucumbers by activating the expression of genes related to aquaporin and stress response, which improved the yield of cucumber under two levels of irrigation water conditions [75% and 100% crop evapotranspiration (ETc)]. Therefore, two field experiments were conducted in a greenhouse with controlled internal climate conditions, at the Mohamed Naguib sector of the national company for protected agriculture, during the winter seasons of 2021–2022 and 2022–2023. The treatments included eCO2 in soil under normal and partial root zoon drying (PRD, 100% ETc Full irrigations, and 75% ETc). All the applied treatments were organized as a randomized complete block design (RCBD) and each treatment was replicated six times. Untreated plants were designed as control treatment (CO2 concentration was 400 ppm). The results of this study showed that elevating CO2 at 700 and 1000 ppm in soil significantly increased plant growth parameters, photosynthesis measurements, and phytohormones [indole acetic acid (IAA) and gibberellic acid (GA3)], under partial root-zone drying (75% ETc) and full irrigation conditions (100% ETc). Under PRD condition, eCO2 at 700 ppm significantly improved plant height (13.68%), number of shoots (19.88%), Leaf greenness index (SPAD value, 16.60%), root length (24.88%), fresh weight (64.77%) and dry weight (61.25%) of cucumber plant, when compared to untreated plants. The pervious treatment also increased photosynthesis rate, stomatal conductance, and intercellular CO2 concentration by 50.65%, 15.30% and 12.18%; respectively, compared to the control treatment. Similar findings were observed in nutrient concentration, carbohydrate content, Proline, total antioxidants in the leaf, and nutrients. In contrast, eCO2 at 700 ppm in the soil reduced the values of transpiration rate (6.33%) and Abscisic acid (ABA, 34.03%) content in cucumber leaves compared to untreated plants under both water levels. Furthermore, the results revealed that the gene transcript levels of the aquaporin-related genes (CsPIP1-2 and CsTIP4) significantly increased compared with a well-watered condition. The transcript levels of CsPIP improved the contribution rate of cell water transportation (intermediated by aquaporin’s genes) and root or leaf hydraulic conductivity. The quantitative real-time PCR expression results revealed the upregulation of CsAGO1 stress-response genes in plants exposed to 700 ppm CO2. In conclusion, elevating CO2 at 700 ppm in the soil might be a promising technique to enhance the growth and productivity of cucumber plants in addition to alleviating the adverse effects of drought stresses.

Effect of nitrogen fertilizer and zinc sulfate on growth, physiological, biochemical and nutrient use efficiency in fodder maize under irrigation regimes

To investigate the effect of nitrogen fertilizer and zinc (Zn) sulfate on growth, physiological, biochemical, and nutrient use efficiency in fodder maize under drought stress, an experiment was conducted during two cropping years 2019 and 2020. The experiment was performed as a split-factorial in the form of a randomized complete block design with four replications. The main factor was irrigation regimes in three levels: full irrigation (without stress or 100% of field capacity), irrigation based on 75% of field capacity, and irrigation based on 50% of field capacity. The first sub-factor included urea fertilizer at three levels of 0, 69, and 138 kg ha−1. The second sub-factor included foliar application of zinc sulfate at three levels of 0, 2, and 4 mg kg−1. The results showed that the highest fresh weight of maize fodder was obtained under conditions of full irrigation and the use of 138 kg ha−1 of N. The use of zinc at all irrigation levels increased the fresh weight of maize fodder. These results confirmed that if higher amounts of N are used, more zinc should be used to achieve a higher yield of maize forage. With the increase in the severity of drought stress, the concentration of nitrogen and phosphorus in the crop tissue, as well as the efficiency of using nitrogen and phosphorus, decreased. The highest value of nitrogen use efficiency was obtained in full irrigation conditions, using 69 kg ha−1 of N and 4 mg kg−1 of zinc. In addition, at all irrigation levels, the efficiency of using this element decreased with increasing zinc consumption.

Physiological adaptations of lucerne under a limited irrigation system

A field study was conducted to identify the physiological tolerance mechanism of lucerne to limited irrigations. Lucerne needs irrigation once in 10 days. So, limited irrigation treatment was imposed once every 25 days. In the initial part of the experiment, accessions collected from the western part of India were screened for biomass potential under limited irrigation in an augmented RBD design. Accessions that performed well under these conditions were grown under temporal isolation, and seeds were collected. In the second part, a field experiment was conducted at SRRS, ICAR-IGFRI, Dharwad, from December 2018 to March 2020 to screen lucerne accessions under limited irrigation to identify the physiological and morphological characters that are required to impart tolerance in lucerne under the cut and carry limited irrigation system. An RBD design was adopted to screen 12 lucerne accessions under limited and full irrigated conditions. Accessions that maintained good persistence under limited irrigation also performed significantly (Acc38/2010, Acc23/2010, A2) regarding yield. Persistence during the juvenile phase depended on conductance, osmotic adjustment and antioxidant capacity. Accessions showed a constant increase in the number of branches after each harvest under limited irrigation was promising in yield performance. Specific-leaf weight (SLW), crude protein, conductance, increased number of branches, and persistence were significantly and positively correlated with yield.

Genetic analysis of yield and fiber quality traits in cotton (Gossypium hirsutum L.) under full and deficit irrigation conditions using full diallel method

The aim of the study was to assess the genetic structure and quantitative heritability of cotton yield, yield components and fiber quality parameters under well-watered (100%) and deficit (50%) irrigation conditions using a complete full diallel cross method with six cotton genotypes. The F1 and F2 generations were obtained to study the effect of irrigation conditions on genotypic variation and maternal effects on the traits studied. Parental, F1 and F2 generations were growed under full and deficit irrigation conditions and selected agronomic and fiber quality traits were measured. The data were analysed using various methods, including Griffing Method I, Model I analysis of variance, full diallel table analysis of variance, Jinks-Hayman diallel hybrid analysis. The Jinks-Hayman analysis of variance showed that dominant effects were more important in the inheritance of all traits, as indicated by the negative value of the difference between the additive variance and the dominance variance (D-H1). In addition, the average degree of dominance (H1/D)1/2 was greater than 1, indicating the predominance of dominant gene action in inheritance. The study concluded that starting selection in the F5–F6 generation is appropriate for drought resistant cotton breeding studies. It also emphasised the importance of conducting drought resistant cotton breeding under drought conditions due to the differences in gene movement between well-watered irrigation and drought stress conditions. The study highlighted the importance of population selection, environmental factors, data collection and analysis interpretation in breeding studies. It suggested that the Griffing diallel analysis method is suitable for hybrid breeding studies, while the Jinks-Hayman type analysis method is suitable for studying the genetic structures of populations.

Unveiling Drought-Resilient Latin American Popcorn Lines through Agronomic and Physiological Evaluation.

Water stress can lead to physiological and morphological damage, affecting the growth and development of popcorn. The objective of this study was to identify the yield potential of 43 popcorn lines derived from a Latin American germplasm collection, based on agronomic and physiological traits, under full irrigation (WW) and water deficit conditions (WS), aiming to select superior germplasm. The evaluated agronomic traits included the ear length and diameter, number of grains per row (NGR) and rows per ear (NRE), grain yield (GY), popping expansion (EC), volume of expanded popcorn per hectare (VP), grain length (GL), width, and thickness. The physiological traits included the chlorophyll, anthocyanin, and flavonoid content in the leaves. The genetic variability and distinct behavior among the lines for all the agronomic traits under WW and WS conditions were observed. When comparing the water conditions, line L292 had the highest mean for the GY, and line L688 had the highest mean for the EC, highlighting them as the most drought-tolerant lines. A water deficit reduced the leaf greenness but increased the anthocyanin content as an adaptive response. The GY trait showed positive correlations with the VP, NGR, and GL under both water conditions, making the latter useful for indirect selection and thus of great interest for plant breeding targeting the simultaneous improvement of these traits.

Improved water use efficiency and yield of drip-irrigated pepper under full and deficit irrigation conditions

Improved water use efficiency and yield of drip-irrigated pepper under full and deficit irrigation conditions

Glutathione‐induced hydrogen sulfide enhances drought tolerance in sweet pepper (Capsicum annuum L.)

AbstractGlutathione (GSH) has been studied for its potential to enhance stress tolerance in plant systems, but the role of hydrogen sulfide (H2S) in GSH‐induced water stress tolerance in sweet pepper (Capsicum annuum L.) is still under investigation. This study explores how H2S and GSH modulate water stress tolerance in pepper plants, addressing a research gap. The joint effect of sodium hydrosulfide (NaHS), a donor of H2S, and GSH on water stress tolerance was determined through pre‐treatment with the H2S scavenger 0.1 mM hypotaurine (HT). Pepper seedlings were sprayed with 1.0 mM GSH or GSH + 0.2 mM NaHS once a week, with soil moisture content set at 80% and 40% for full irrigation and water stress conditions for a duration of 2 weeks. The results showed that water stress significantly reduced total plant dry weight, chlorophyll a and b content, Fv/Fm, leaf water potential, and relative water content by 50%, 56%, 33%, 27%, 52%, and 34%, while increasing hydrogen peroxide (H2O2), proline, and H2S levels by 152%, 134%, and77%, respectively. Treatment with GSH and NaHS reduced water stress‐induced H2O2 production and improved plant growth, photosynthetic traits, proline, and the activity of L‐cysteine desulfhydrase (L‐DES), leading to the generation of H2S content. GSH reduced NADPH oxidase (NOX), superoxide dismutase (SOD), and H2O2 but increased glutathione peroxidase (GPX) activities. The interaction of NaHS and GSH led to further reductions in NOX, SOD, and H2O2 values but increased GPX activity. The combined GSH and NaHS treatment increased nitric oxide (NO) production but decreased the activity of S‐nitrosoglutathione reductase (GSNOR), potentially accelerating S‐nitrosylation. Hypotaurine negated the positive impacts of GSH on water stress tolerance by reducing H2S concentration in pepper plants, but this was corrected by the concurrent application of NaHS and GSH + HT. Therefore, water stress tolerance requires H2S.

Evaluation of water management effects on potato yield and water productivity in northeast Iran using the SWAP model

ABSTRACT The agro-hydrological SWAP model was employed for simulation of evapotranspiration, yield, and water productivity of potato under six irrigation scenarios (100, 90, 80, 70, 60, and 50% potato water requirement (WR)) in Fariman, Ghoochan, and Golmakan in the northeast Iran. The results showed that the SWAP model well-simulated potato yield and water productivity. The model slightly overestimates the potato yield and underestimates the water productivity. The results revealed that irrigation scheduling is an important factor effecting on evapotranspiration, yield, and water productivity of potatoes. By decreasing irrigation water to 50% WR, potato evapotranspiration and yield decreased in all three study areas. However, potato water productivity increased in Fariman and Golmakan and decreased in Ghoochan, as irrigation volume decreased to 50% WR. In Fariman and Golmakan, irrigation at the rate of 80% WR led to the best irrigation management to have maximum water productivity (2.96 and 2.48 kg m−3, respectively) and acceptable potato yield (21,376.2 and 10,998.7 kg ha−1). In Ghoochan, by adopting the irrigation scenario at the level of 90% WR, the potato yield decreased by approximately 7.6% compared to the full irrigation conditions. However, the highest amount of water productivity (2.27 kg m−3) was achieved.

Comparing native and non-native seed-isolated strains for drought resilience in maize (Zea mays L.)

Maize, a vital crop for human nutrition, livestock, and industrial development, faces increasingly severe climatic conditions that hinder its production capacity along with other strategic crops. Novel treatments based on microorganisms have demonstrated efficiency in enhancing plant development and responding to stress. The use of bacteria isolated from seeds is a novel approach for biotreatment, as recent studies point to a co-evolution process for their presence in seeds. This approach hypothesize a pre-adaptation to its host, which may lead to increased efficiency. However, several aspects of this approach remain understudied. In this study, we aimed to evaluate the potential of native maize seed microbiota in comparison to that isolated from other species to mitigate drought stress. For this we characterized seedborne microbiota of a common productive maize variety in Portugal, to use it as biotreatment in other two varieties (sensitive and resistant to drought), selecting the strain Pseudomonas fulva MB as the most promising candidate. Stenotrophomonas maltophilia MS-M1 strain, isolated from wild alfalfa seeds and previously characterized as a drought-tolerant enhancer, served as a non-native control strain. According to the data, both varieties of maize demonstrated enhanced vegetative growth when treated with both individual strains, as well with the consortium, with an increase in plant height of 5–7 % in full and medium irrigation, and 50–55 % when not irrigated. This trend was also observed in plant weight, which increased by 13–23 %, even under no irrigation. In addition, production in both varieties was positively impacted by these treatments, based on the amount of grain produced (by weight). The drought-sensitive variety experienced a 17 % increase under full irrigation, while the most tolerant variety experienced a 25–40 % increase. Under medium irrigation level, the increase was about 15 % in both varieties, while a 100 % and 140 % increase was observed in each variety, respectively, when no irrigation was applied. The results suggest that native strain the P. fulva MB was slightly more efficient treatment, as it outperformed the non-native strain in terms of productivity in both varieties. However, the differences were not solid enough along all parameters to consistently asses such difference. The consortium treatment only showed better performance under full or medium irrigation conditions for some production traits. These findings support the use of seed microbiota as very efficient biotreatments, suggesting than even non-native strains have a remarkable beneficial impact (interspecific), expanding the possible of use of this kind of bioinoculants. Further test are required to optimize the use of seed-isolated strains as better adapted or tailor-made solutions for agriculture.

Soil water distribution and water productivity in red cabbage crop using superabsorbent polymeric hydrogels under different drip irrigation regimes

The water issue has emerged as a significant barrier to agricultural productivity, particularly in dry and semiarid agro-ecologies, particularly during the winter season. Superabsorbent hydrogels have been identified as effective tools for improving crop and water productivity in arid locations by enhancing moisture retention. The application of hydrogel to soil is commonly done as a basal application, and its effectiveness is heavily influenced by the moisture level present in the soil. Therefore, a two-year field study was carried out to study the effects of various hydrogels and their application techniques and to assess the efficacy of recently developed cross–linked hydrogels (SPG 1118 and Pusa hydrogel) on soil water distribution (both spatial and temporal), water productivity and profitability of red cabbage. The experiment consisted of two irrigation regimes [full irrigation (100% ETc) and limited irrigation (75% ETc)] assisted in main plots, with two type of hydrogels (Pusa Hydrogel and SPG 1118) and two methods of application [root dipping and soil application of hydrogels and Control with no application of hydrogel] assisted in sub plots. The field experiment was conducted using spilt plot design with three replications. The analysis of soil water distribution patterns reveals that the utilization of hydrogels has resulted in a notable increase of 3–6% in soil water content (SWC) under full irrigation conditions, as compared to plots subjected to limited water conditions. In comparison to plots without hydrogel application, the plots treated with SPG 1118 and Pusa hydrogel exhibited enhanced soil water content of 5–6% and 2–4%, respectively. Additionally, the application of hydrogels in the root dipping showed increased water availability in the crop's root zone compared to soil application in throughout the crop season. Thus, hydrogels with reduced irrigation application resulted in significantly higher crop water productivity (14%) and irrigation water productivity (8 – 14%) compared to full irrigation levels. Likewise, root dipping of SPG 1118 led in considerable improvement in CWP (12–14%) and IWP (11–12%) over no hydrogel applied plots. In relation to profitability, the adoption of full irrigation in conjunction with SPG 1118 hydrogel resulted in an 8% increase in the benefit cost ratio compared to the control plots. Hence, the use of the unique SPG 1118 hydrogel through direct application to the roots, whether under conditions of full or limited irrigation, presents an inventive approach to address the growing issues of water shortages and sustainability in countries experiencing water stress.

Do exogenous melatonin and nitric oxide mitigate the adverse effects of flooding stress in spinach?

Studies are being conducted to develop strategies to reduce the adverse effects of flooding stress in plants, including melatonin and nitric oxide (NO) applications. In the present study, we tried six different application subjects: full irrigation - control (FI), flooding stress (FS), FS + application of 50 µM melatonin, FS + application of 100 µM melatonin, FS + application of 50 µM nitric oxide (NO), and FS + application of 100 µM NO. The flooding subjects were subjected to stress 10 days before harvest, which was continued until harvest. Melatonin and nitric oxide were applied to plant leaves twice, with a 1-week interval, by spraying to cover the whole plant. We found that flooding stress reduced in certain agronomic parameters and exerted a negative effect on leaf relative water content (RWC), chlorophyll a, b, carotenoid, and protein content, actual photosynthetic efficiency (PSII), stomatal conductance (gs), and chlorophyll fluorescence (Fv/Fm). In addition to increasing the reactive oxygen species (ROS) production under stress conditions, Flooding stress significantly increased the content of proline, leaf temperature, and antioxidant enzyme activity. The melatonin and nitric oxide doses contributed to plant development as well as regulated the pigment content, thereby promoting the ROS-scavenging antioxidant defense system. The principal component analysis (PCA) performed to evaluate the data collectively revealed that full irrigation yielded the best results for agronomic and physiological parameters. The PCA results demonstrated that FS + application of 100 µM melatonin, located in the region closest to full irrigation conditions, was the most effective application under flooding stress conditions. Melatonin applications are crucial for sustainable agriculture, thereby reducing the yield and quality losses compared to nitric oxide applications in regions where spinach is cultivated, and there is a risk of floods.

Evaluation of CERES-Maize model for simulating maize phenology, grain yield, soil–water, evapotranspiration, and water productivity under different nitrogen levels and rainfed, limited, and full irrigation conditions

Evaluation of CERES-Maize model for simulating maize phenology, grain yield, soil–water, evapotranspiration, and water productivity under different nitrogen levels and rainfed, limited, and full irrigation conditions

Evaluating the impact of different UAV thermal sensors on evapotranspiration estimation

Accurate evapotranspiration (ET) estimation is vital for precise irrigation management. Remote sensing provides a unique method for obtaining spatial and temporal ET information. With technological advancements, several unmanned aerial vehicle (UAV) thermal sensors have been developed. However, the impact of thermal sensors on ET estimation is unclear. This study evaluated the impact of different UAV thermal sensors, including Micasense Altum and Flir Duo Pro-R (FDP-R), on ET estimation using the Two Source Energy Balance (TSEB) model. A field experiment was conducted during the 2021 sorghum growing period, with irrigation treatments consisting of four different regimes: full irrigation (S1), 70 % of S1 (S2), 40 % of S1 (S3), and rainfed (S4). The results revealed no statistically significant differences between the estimated ET values using Micasense Altum and FDP-R thermal sensors. The TSEB model's performance was entirely satisfactory for full irrigation, with RMSE values of 5.63 mm for Micasense Altum and 7.17 mm for FDP-R, in 10 days. However, the accuracy deteriorated with increasing water stress, reaching 29.02 mm for Micasense Altum and 25.12 mm for FDP-R, in 10 days in rainfed plots. The study results highlight the capability of both Micasense Altum and FDP-R thermal sensors to provide comparable ET estimates, particularly under full irrigation conditions. However, the decline in accuracy with increased water stress underlines a potential limitation of the TSEB model when applied to varying irrigation regimes. These insights emphasize the importance of adjustment of TSEB input parameters such as αPT coefficient, resistance terms etc. and sensor technologies, particularly in water-stressed environments, to ensure accurate ET estimation. This study demonstrated the potential of high-resolution UAV thermal sensors for precision irrigation management tasks. Further studies with different thermal sensors are needed to understand this technology's benefits fully. The impact of different climate conditions on ET estimation should also be explored for accurate results.

The E3 ligase TaGW2 mediates transcription factor TaARR12 degradation to promote drought resistance in wheat.

Drought stress limits crop yield, but the molecular modulators and their mechanisms underlying the trade-off between drought resistance and crop growth and development remain elusive. Here, a grain width and weight2 (GW2)-like really interesting new gene finger E3 ligase, TaGW2, was identified as a pivotal regulator of both kernel development and drought responses in wheat (Triticum aestivum). TaGW2 overexpression enhances drought resistance but leads to yield drag under full irrigation conditions. In contrast, TaGW2 knockdown or knockout attenuates drought resistance but remarkably increases kernel size and weight. Furthermore, TaGW2 directly interacts with and ubiquitinates the type-B Arabidopsis response regulator TaARR12, promoting its degradation via the 26S proteasome. Analysis of TaARR12 overexpression and knockdown lines indicated that TaARR12 represses the drought response but does not influence grain yield in wheat. Further DNA affinity purification sequencing combined with transcriptome analysis revealed that TaARR12 downregulates stress-responsive genes, especially group-A basic leucine zipper (bZIP) genes, resulting in impaired drought resistance. Notably, TaARR12 knockdown in the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-mediated tagw2 knockout mutant leads to significantly higher drought resistance and grain yield compared to wild-type plants. Collectively, these findings show that the TaGW2-TaARR12 regulatory module is essential for drought responses, providing a strategy for improving stress resistance in high-yield wheat varieties.

Drought-tolerant sesame mutant lines assessed by physiological traits and stress indices under water deficit conditions

Climate change and water scarcity are the most important factors that affect crop production in dry areas. Sesame (Sesamum indicum L.) is a very ancient oilseed crop cultivated in arid and semi-arid regions and therefore its productivity is limited under drought conditions, which makes the selection and development of drought-tolerant cultivars imperative. This study aims to evaluate the responses to drought stress of eleven M4 sesame mutants, in addition to their two wild-type parents, cultivated in two contrasting environments. Drought stress was applied, under field conditions, by reducing the amount of irrigation water supplied by half, compared to the control. Physiological traits and various drought indices were measured/calculated. All data were subjected to analysis of variance and unweighted pair group method with arithmetic mean (UPGMA) to classify genotypes as drought sensitive or drought tolerant. Significant variations among genotypes were observed in their reactions to water regimes and environments. Overall, under water stress, proline content and stomatal resistance significantly increased, while chlorophyll content, seed yield, and relative water content significantly decreased in stressed plants. Drought indices revealed substantial differences among genotypes, with tolerant ones showing the best scores. Furthermore, correlation analysis demonstrated significant associations between physiological traits and drought indices. In light of all the traits/indices investigated, the mutant ‘US1-2’ was found to be very drought-sensitive, although it performed best under full-irrigation conditions. In contrast, the mutant lines ‘ML2-37’ and ‘ML2-37’ proved to be highly drought-tolerant and, therefore, they can be handled as an elite germplasm for the development of resilient cultivars adapted to arid and semi-arid regions where irrigation water is a limiting factor. This work constitutes a significant contribution to research on sesame drought tolerance and offers promising prospects for this crop in the context of global climate change.

Drought resistance of nine maize cultivars released from the 1970s through the 2010s in China

ProblemWater scarcity has become a limiting factor for increasing crop production. Yield losses due to drought stress can best be resolved by breeding new, drought-tolerant cultivars, however, the genetic gains in drought resistance of different maize cultivars especially under precise water control conditions were not systematically studied.The objectives of this study were to assess 1) the change in yield and WUE of different cultivars from the 1970s through the 2010s under precise water control conditions and 2) find out the main factors affecting the yield and WUE change of different cultivars. MethodsWe selected nine hybrids from different eras for a detailed field study under three different water treatments (full irrigation, moderate drought, and intense drought) in a rainout shelter at Hengshui (115°40′E, 37°44′N) in southern Hebei province in 2018 and 2019. We compared the grain yield and water use efficiency (WUE) of different cultivars from the 1970s through the 2010s under drought-stress (moderate drought and intense drought) and fully-irrigated conditions. ResultsThe maize yield and WUE showed a significant linear increase with the year of release. The average yield gains were 111, 113.4 and 121.3 kg ha−1yr−1 under fully-irrigated, moderate and intense drought conditions while the WUE gains were 0.31, 0.38 and 0.72 kg ha−1 mm−1 yr−1 respectively. The yield reduction ratio showed a significant linear decrease from the 1970 s through the 2010s under both moderate water deficit and intense water deficit which were 0.51 % and 0.99 % yr−1, indicating that modern cultivars had better drought resistance than older ones. With increased water stress, the yield gap and yield reduction ratio between full irrigation and drought treatments (moderate drought and intense drought) increased significantly. The significant increase in the number of ears per hectare and the number of kernels per ear was the main reason for maize yield increase with the year of release from 1970s to 2010s under drought treatments. Under drought stress, the uniformity of yield component decreased significantly compared to the fully-irrigated treatment. In addition, an overly large leaf area was not conducive to drought resistance. ConclusionsModern cultivars had better drought resistance than older ones. Selecting hybrids with higher uniformity and smaller leaf area was beneficial to improve the maize drought resistance. ImplicationsThe results of this study will be beneficial for the breeding and selecting drought-resistant cultivars.

Influences of calcium silicate fertilization to physiological and bio-active responses of maize under drought and well-watered conditions

A pot experiment was conducted to investigate the effects of silicon (Si) on morpho-physiological and bio-chemical traits of maize under different irrigation regimes. Experimental treatments comprised of irrigations [60% and 100% of field capacity (FC)], treatments (0, 50, 100, 150, 200 mg kg−1 CaO4Si) and growing stages (GS) [7th (first) and 14th (second) days of water restriction]. 150 mg kg−1 Si increased the growth of maize by inducing transpiration rate (67.56%), water use efficiency (138.36%) and seedling length (19.83%) at first GS whilst enhanced carotenoids (10.95%), total phenolic compounds (45.04%) and decreased proline (7.87%) at the second GS of 60% treatment. In addition, 200 mg kg−1 Si elevated photosynthesis rate (40.54%), total antioxidant activity (12.69%) and decreased proline (52.77%) at the first GS while increased total anthocyanin content (14.99%) during the second GS of 60% application. Silicon had positive impacts on maize under full irrigation conditions too such that 150 mg kg−1 Si reduced transpiration rate (48.43%) and induced total antioxidant activity (39.95%) at first GS while 200 mg kg−1 Si increased water use efficiency by 144.30% at the second GS. In conclusion Si increased drought resistance due to increasing application doses, and on contrary of the literature, Si positively affected many characters at well-watered environment.

Quinoa plant architecture: A key factor determining plant productivity and seed quality under long-term drought

Chenopodium quinoa (quinoa) is an underutilized crop proposed as key to achieving food security within the current climatic context, where water scarcity in rainfed areas is becoming more frequent and severe, especially in Mediterranean regions. Thus, aiming at deepening our knowledge regarding the impact of water limitation on the quinoa seed nutritional quality, seeds obtained from primary and secondary panicles of four different European-adapted cultivars (F14, F15, F16, and Titicaca) growing under full irrigation and water-limiting conditions, were here analyzed. A set of parameters were evaluated in this work, including agronomical (such as yield, seed weight, seed area, and seed germination and viability rates) and nutritional (including the seed proximate composition, mineral content, and antioxidants) traits. Our results indicate that the morphological changes associated with drought stress affect secondary panicles’ seed yield. This phenomenon was generally associated with an improvement in the nutritional quality of those seeds. However, cultivars such as F16, despite keeping total seed yield under low water availability, showed drought's detrimental effect on the seed nutritional quality. In contrast, cultivars like F15 and Titicaca reduced their seed yield under water-limiting conditions but increased their protein, iron, copper, calcium, manganese, and zinc contents, especially in secondary panicles. Therefore, the dichotomy between seed quantity and quality has to be considered in this crop under water stress scenarios, highlighting differences in sink strength along the plant panicles determining seed nutritional quality.

Physiological, Biochemical, Anatomical, and Agronomic Responses of Sesame to Exogenously Applied Polyamines under Different Irrigation Regimes

Polyamines (PAs) are plant growth regulators that attenuate the destructive impacts of water deficit on sesame plants, particularly in arid regions under abrupt climate change. Limited information is available on the physiological, biochemical, anatomical, and agronomic responses of sesame to exogenous application of PAs under water deficit under field conditions. Thus, a two-season field trial was carried out to assess the impact of exogenously sprayed spermine (Spm), spermidine (Spd), and putrescine (Put) on physio-biochemical and anatomical parameters and their influences on agronomic performance and crop water productivity of sesame plants. The sesame plants were assessed under three irrigation regimes; full irrigation (100% ETc), mild drought (75% ETc), and severe drought (50% ETc) conditions. Drought stress displayed negative impacts on all evaluated parameters. However, exogenously applied Pas, especially Put, restricted the destructive effects of water deficit. The application of PAs exhibited highly significant enhancement in photosynthetic pigments (chlorophyll a, b, and carotenoids), gas exchange (net photosynthetic rate, stomatal conductance, and rate of transpiration), water relations (relative water content, membrane stability index, excised leaf water retention), and plant nutrient content (N, P, and K) compared to untreated plants, particularly under severe drought stress. Moreover, PA application displayed highly significant amelioration in osmoprotectants (free proline, soluble sugars, α-Tocopherol, ascorbate, and glutathione), and antioxidant enzyme activities (catalase, peroxidase, superoxide dismutase, ascorbate peroxidase, and glutathione reductase). In addition, foliar nourishing with PAs exhibited a highly significant reduction in oxidative stress markers (malondialdehyde, electrolyte leakage, superoxide, and hydrogen peroxide). These positive impacts of PA application under drought stress were reflected in highly significant improvement in anatomical characteristics (midrib length and width, vascular bundle length and width, thickness of phloem, xylem and collenchyma, vessel diameter, and number of xylem rows in midvein bundle), and yield-related traits (plant height, leaf area, number of capsules per plant, 1000-seed weight, seed yield, and oil content). Consequently, exogenous application of PAs (in particular, Put) could be exploited to enhance the crop water productivity and yield traits of sesame plants under low water availability in arid regions.