Levels Of Water Deficit Stress Research Articles

Effect of sodium alginate-based superabsorbent hydrogel on tomato growth under different water deficit conditions

The main challenge facing agriculture today is water scarcity. At present, agriculture consumes around 70 % of the planet's freshwater, much of which is lost through evaporation, leaching and runoff. This wastage, combined with the increased frequency and severity of droughts linked to climate change, is having a considerable negative impact on crops. As a result, the food security of people living in regions with limited water resources is threatened. In this regard, efficient water management using water-saving materials and soil additives such as superabsorbent polymers (SAPs) are recognized as an effective strategy to boost water use efficiency by plants and improve agricultural productivity. The present study fits with this strategy and aims to investigate the effect of new sodium alginate-based hydrogel-treated sandy loam soil on seed emergence and growth of tomatoes as a crop model under different water-deficit stress levels. A set of pot experiments was conducted in a greenhouse chamber using sandy loam soil amended with two levels of hydrogel (0.1 % and 0.5 % by weight) along with untreated control, all under water-deficit stress at three levels: 30 % of the daily amount of required irrigation water (DARW) for different growing cycles (severe stress), 70 % DARW (mild stress), and 100 % DARW (normal irrigation conditions). The germination test showed the absence of phytotoxicity of the developed hydrogel and confirmed its suitability in protecting seedlings from drought stress. Greenhouse experiment results demonstrated that water stress and levels of applied hydrogel significantly (P < 0.05) affected plant growth parameters such as plant height, stem diameter, number of leaves, chlorophyll content, fresh weight, and dry weight compared with the treatments without SAPs. The developed sodium alginate-based SAPs showed relevant agronomical benefits under drought stress by retaining more water and nutrients, thus it had the potential to be used in agriculture for better water management along with significant environmental benefits.

Inoculating moldavian balm (Dracocephalum moldavica L.) with mycorrhizal fungi and bacteria may mitigate the adverse effects of water stress

Plant growth-promoting bacteria (PGPBs) play a crucial role in mitigating the oxidative damage caused by water stress in different plant species. The aim of this study was to determine the effects of PGPBs and mycorrhiza-like fungi (Piriformospora indica) on improving drought tolerance in moldavian balm (Dracocephalum moldavica L.), a medicinal and aromatic plant. For this purpose, a greenhouse study was conducted in a factorial experiment based on a randomized complete design with three replications. Results indicate that water stress reduces the membrane stability index (MSI), total chlorophyll content (Chlt), carotenoids, and maximum photochemical efficiency of photosystem II (Fv′/Fm′) in moldavian balm plants, while increasing superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and hydrogen peroxide (H2O2) content compared to the control (no water stress). Inoculation with PGPBs and Piriformospora indica helped alleviate the negative effects of water stress. The highest MSI (48%) and Fv′/Fm′ value (0.82) were observed when inoculated with Enterobacter and Piriformospora, respectively, under non-water-stressed conditions. Inoculation with Agrobacterium, Piriformospora, and Enterobacter improved the Chlt and leaf proline contents, as well as the SOD activity under high water stress, compared to the non-inoculated control values. Furthermore, inoculation with Pseudomonas under high water deficit stress levels increased the MDA content (0.51 mmol g−1 FW) and H2O2 levels (0.40 mmol g−1 FW). The highest yield of flowering branches (2.414 g pot−1) in moldavian balm was obtained with Enterobacter. Based on the enhanced physiological and biochemical responses, as well as increased antioxidant enzyme activity that improve water tolerance in this plant, it is recommended to use PGPBs and Piriformospora indica fertilization.

Melatonin-mediated alleviation of drought stress by modulation of physio-biochemical and metabolic status in Dracocephalum kotschyi Boiss. (Lamiaceae)

Dracocephalum kotschyi Boiss., a fragrant perennial plant belonging to the Lamiaceae family, contains many bioactive substances, including essential oil, terpenoids, phenolics, and flavonoids that possess a wide range of biological and pharmaceutical properties. Due to the importance of plant exploitation in dry and low-yield lands, the present study was conducted to explore the effect of the exogenous application of melatonin (0, 50, 100, 150, and 200 μM) on physiological, biochemical, and phytochemical traits of the plant subjected to different levels of water deficit stress (80 %, 60 %, and 40 % of field capacity). The results showed that the application of 150 μM melatonin caused the highest content in the relative growth rate (1.84 g/g d), chlorophyll content (14.55 mg/g FW), relative water content (93 %), and chlorophyll fluorescence (0.9) at different irrigation regimes. Reduced irrigation significantly reduced chlorophyll content and fluorescence, while exogenously applied melatonin enhanced their contents at all levels. Reduced irrigation caused a significant increase in the levels of malondialdehyde (7.47 µmol/g FW) and hydrogen peroxide (51.86 nmol/g). Total phenol content, antioxidant activity, and antioxidant power were increased by applying of melatonin up to 200 μM, while the irrigation rate decreased. The essential oil content was increased by reducing irrigation, so the highest content (3.0 % w/w) was observed at 40 % FC and 150 μM melatonin. Geranyl acetate (44.6–60.4 %), α-pinene (9.0–19.1 %), and geranial (6.2–16.2 %) were the major essential oil components of the treated plants. Reduced irrigation and application of melatonin up to 150 μM caused an increase in coumaric acid, rosmarinic acid, and rutin despite a decrease in the content of chicoric acid and apigenin. The highest oleanolic acid content (52.69 mg/g DW) was measured in the plants subjected to 40 % FC. The highest (132 mg/g DW) and lowest (43.58 mg/g DW) ursolic acid content was measured in 40 % FC with 200 μM melatonin and 80 % FC without melatonin treatment, respectively.

Cyclopia subternata growth, yield, proline and relative water content in response to water deficit stress

Cyclopia, generally known as honeybush, and belonging to the Fabaceae family, originates from the Cape Floristic Region of the Eastern Cape and Western Cape provinces of South Africa. Currently, 6 honeybush species are commercially cultivated but, to date, there have been limited trials attempting to study their agronomic water demand. A pot trial was conducted where Cyclopia subternata plants were cultivated on different soil types (Stellenbosch granite, Stellenbosch shale and Stellenbosch clovelly) and subjected to three different water-deficit stress levels (well-watered, semi-stressed and stressed). Remarkably, irrigation treatments and soil types did not significantly affect the growth of the plants. However, the well-watered treatment consistently had higher yields compared to the other two treatments. The water-stressed (semi-stressed and stressed) treatments had lower relative water contents (RWC) with higher concentrations of proline, which signify water stress, compared to the control treatment. Higher proline and lower RWC contents found in this study are indications of water stress.

The Effect of Inoculation Brant's Oak )Quercus brantii L.) Seed with Plant Growth-Promoting Bacteria on Some Physiological Traits of Seedling under Different Levels of Water-Deficit Stress

The Effect of Inoculation Brant's Oak )Quercus brantii L.) Seed with Plant Growth-Promoting Bacteria on Some Physiological Traits of Seedling under Different Levels of Water-Deficit Stress

Direct and Residual Effects of Water Deficit Stress, Different Sources of Silicon and Plant-Growth Promoting Bacteria on Silicon Fractions in the Soil

Silicon (Si) and plant growth promoting bacteria (PGPB) can effectively reduce the negative effects of water deficit stress and augment plant growth. Few studies have simultaneously investigated the effects of silicon nano-particles (Si-NPs) and plant growth-promoting bacteria (PGPB) on water deficit stress. Hence, the present study aimed to investigate the effects of different levels of water deficit stress (0.8, 0.6, and 0.4 FC), different resources of Si (Si: 100, and 200 mg kg−1 Si-NPs, and 200 mg kg−1 potassium silicate) and native PGPB (control, Pseudomonas19.sp, Bacillus76.sp, and a bacterial consortium of both) on Si fractions in the soil under canola-wheat cultivation. A factorial experiment was carried out in three replications. With increasing water deficit stress from 0.8FC to 0.4FC, the soluble and exchangeable silicon levels decreased significantly from 46.15 and 96.49 to 21.42 and 60.79 mg kg−1, respectively, while amorphous silicon increased from 233.53 to 356.00 mg kg−1. The results indicated that under water deficit stress conditions, both direct and residual effects of PGPB and Si-NPs positively affected the soluble, exchangeable, and amorphous fractions of Si. The highest levels of soluble (98.03 mg kg−1) and exchangeable (108.6 mg kg−1) Si in the soil in which canola was harvested were recorded for the treatment of 0.8 FC + 200 mg kg−1 Si-NPs + Pseudomonas19.sp. These were 78.78% and 57.73%, respectively, higher than those of the control treatment (0.8FC, without bacterial inoculation, and silicon). Moreover, after wheat harvesting, the highest levels of soluble (16.14 mg kg−1) and exchangeable (23.88 mg kg−1) Si in the soil were observed in the treatment of 0.8 FC + 200 mg kg−1 Si-NPs + Pseudomonas19.sp. These were 36.72 and 52.54%, respectively, higher than those of the control. Overall, the application of Si-NPs and PGPB significantly positively affected the absorbable components of Si in the soil, which was in favor of plant growth.

تأثیر تنش کمآبی بر صفات فیزیولوژیک و عملکرد دانه سویا تحت تأثیر تلقیح و عدم تلقیح با قارچ میکوریزا و باکتری ریزوبیوم

به‌منظور بررسی تأثیر تنش کم‌آبی و تلقیح با قارچ میکوریزا و باکتری ریزوبیوم بر صفات فیزیولوژیک و عملکرد دانه سویا، آزمایشی در سال زراعی 1396 در مزرعه هنرستان کشاورزی شهرستان ارومیه به‌صورت اسپلیت پلات فاکتوریل در قالب طرح بلوک‌های کامل تصادفی با سه تکرار اجرا شد. عامل تنش کم‌آبی در سه سطح شامل آبیاری مطلوب، تنش ملایم و تنش شدید کم‌آبی (به‌ترتیب آبیاری بعد از 70، 110 و 159 میلی‌متر تبخیر از تشتک تبخیر کلاس A)، عامل‌های فرعی قارچ میکوریزا در سه سطح شامل بدون میکوریزا، گونه Funneliformis mosseae و گونه Rhizophagus intraradices و باکتری ریزوبیوم در دو سطح شامل عدم تلقیح و Bradyrhizobium japonicum بود. در این بررسی دمای برگ، محتوای نسبی آب برگ، کلروفیل b، کلروفیل a، پرولین، نشت الکترولیت و عملکرد دانه مطالعه شد. تنش بیشتر کم‌آبی همراه با عدم تلقیح با میکوریزا دمای برگ را افزایش اما محتوی نسبی آب برگ و کلروفیل b را کاهش داد. افزایش تنش کم‌آبی همراه با عدم تلقیح با باکتری دمای برگ را افزایش اما کلروفیل b و عملکرد دانه را کاهش داد. تلقیح با باکتری با یا بدون تلقیح با قارچ دمای برگ را کاهش داد. این شرایط برای صفات محتوای نسبی آب برگ، محتوای کلروفیل b و a نیز وجود داشت. تلقیح با باکتری و میکوریزا بخصوص قارچ F. mosseae باعث شد حداکثر عملکرد دانه با 443.2 گرم در مترمربع به‌دست آید. میزان پرولین و درصد نشت الکترولیت در تیمار تنش کم‌آبی شدید و عدم تلقیح با میکوریزا و باکتری بیشتر از تیمارهای دیگر بود. حداقل میزان پرولین و درصد نشت الکترولیت نیز در تیمار آبیاری مطلوب همراه با تلقیح با باکتری و قارچ F. mosseae مشاهده شد. درمجموع، تنش کم‌آبی باعث ایجاد شرایط نامطلوب برای سویا شد که نتیجه آن کاهش عملکرد بود اما تلقیح با باکتری و قارچ باعث کاهش شرایط نامطلوب و رشد بهتر سویا شد.

Salicylic acid effects on some physiochemical properties and secondary metabolite accumulation in Mentha piperita L. under water deficit stress

Salicylic acid (SA) play important roles in different physiological processes of plants such as plant growth, stress response, plant adaptation and secondary metabolite accumulation. This study was conducted to evaluate the effect of exogenous SA applications on the growthmeasurements such as fresh and dry weight of aerial part and lead dry weight, biochemical properties (membrane permeability, lipid peroxidation, Proline content and ROS scavenger enzymes) and secondary metabolite accumulation(total phenolic and the flavonoid and essential oil content) in peppermint (Mentha piperita L.) plants grown at different levels of water deficit stress (Field capacity: FC). For this aim, three different water deficit stress (no stress (100% FC), mild stress (75% FC) and moderate stress (50% FC)) and four different SA concentrations (0, 1, 2 and 2.5 mM) were applied to peppermint plants. Results showed that all of the measured parameters were affected by the water deficit stress and SA application. By elevating the level of water deficit stress, fresh and dry weights of aerial parts and dry leaf weight decreased. Increasing in the water deficit stress level from mild to moderate stress resulted to reduce the essential oil content while proline, lipid peroxidation, total phenolic contents, flavonoid content, and antioxidant enzyme activities increased depending on water deficit stress. Exogenous application of SA obstructed the negative effects of water deficit stress by decreasing the lipid peroxidation and membrane permeability and improving the antioxidant enzymes activities. Essential oil content increased significantly in plant treated with SA grown under water deficit stress conditions. Application of 2 or 2.5 mM of SA enhanced the plant growth and development without any toxic effects and increased significantly the total phenolic content, dry leaf weight, and the essential oil content in stressed and even in control (100% FC) peppermint plants.

Influence of PGPR-enriched liquid organic fertilizers on the growth and nutrients uptake of maize under drought condition in calcareous soil

In order to study the effect of water deficit stress (WDS), plant growth promoting rhizobacteria (PGPR)-enriched and non-enriched vermicompost tea(VT) and vermiwash(V) on the growth and nutrients uptakes of maize, a greenhouse experiment was conducted. The two-factor experiment was set up in a completely randomized design with three replications. The factors included: 1) liquid organic fertilizers (LOFs) with five levels (control, VT, V, vermicompost tea enriched with bacterium (VTB) and vermiwash enriched with bacterium (VB)) and 2) WDS with three levels (Field Capacity (FC), 80% FC and 60% FC(. At each irrigation interval, the volume of the used LOFs was equivalent to 60% of the volume of water required for 60% FC. At 60% FC, shoot dry matter (SDW), shoot N, P, Zn, Cu, and Fe uptake significantly decreased compared with those of FC and 80% FC, whereas shoot K uptake significantly increased. At all WDS levels, application of LOFs led to increase in SDW and shoot nutrients uptake. The highest amount of studied traits was obtained in VTB and VT treatments. Generally, VT treatments were more effective than V. Furthermore, PGPR-enriched LOFs were more effective than non-enriched ones. Application of LOFs may be considered as a practical approach for amplifying drought tolerance and reducing the risk of water scarcity in maize cultivation.

Effect of Irrigation Threshold on Crop Performances in Wet Seeded Rice

Decreasing availability and increasing costs of water and labour are driving researchers and farmers to find management strategies that increase input water productivity and reduce labour requirement in rice production. Wet seeding instead of transplanting greatly reduces the labour requirement for crop establishment, whereas use of alternate wetting and drying (AWD) instead of continuous flooding reduces irrigation input. However, the safe threshold for irrigating wet seeded rice (WSR), and how this varies with growth stage, has not been established. Therefore, a greenhouse experiment was conducted to determine the effects of different degrees of irrigation threshold during different crop growth stages on crop performance of WSR. This was done in greenhouse experiment in the 2011 wet season at the International Rice Research Institute, Los Baños, Philippines. In the experiments, water stresses were applied by withholding irrigation until soil water tension increased to 10, 20 or 40 kPa at 10 cm below the soil surface. Soil water tension was measured using 30 cm long gauge tensiometer installed with the center of the ceramic cup. The stresses were applied during three crop stages: 3-leaf (3L) to panicle initiation (PI), PI to flowering (FL), and FL to physiological maturity (PM). The experiment was also included a continuously flooded (CF) treatment. Stress during 3L to PI increased the time to PI (by 2 to 4 days) but reduced the duration of grain filling by 3 to 5 days, the larger values with 20 and 40 kPa thresholds. There was no effect of stress thresholds of 10 to 40 kPa during PI-FL on crop duration. Stress during grain filling reduced the duration of grain filling by 6 days for all thresholds. Stresses of 20 and 40 kPa during 3L to PI reduced green leaf and tiller density at PI, but this effect disappeared with the imposition of CF after PI. There were consistent trends for lower final biomass as the level of water deficit stress increased, and imposition of stresses of 20 and 40 kPa at any or all three stages significantly reduced biomass compared with CF. These results suggest that, for shortening the ripening period, water stress may be imposed as 10 to 20 kPa during FL to PM.&#x0D; Bangladesh Rice j. 2018, 22(1): 73-81

Assessment of Cotton Leaf and Yield Responses to Water-Deficit Stress During Flowering and Boll Development

Rainfall future events are predicted to decline to 30 to 127 mm in the majority of counties of the Texas High Plains and Rolling Plains because of climate change. Cotton (Gossypium hirsutum L.) is the major crop grown on the High Plains of Texas, and the lower humidity associated with the predicted reduction in rain raises the possibility of increased vegetative water-deficit stress and reproductive dehydration stress. This study assesses the vegetative and reproductive developmental processes of commercial cotton cultivar-response following water-deficit stress, specifically during flowering and boll development. Cultivars showed a significant relationship between the leaf water-deficit stress levels during boll development and final seed cotton yields. However, the cultivar Phytogen 72 (PHY72) was an exception to this observation. PHY72 exhibited excellent leaf water-deficit stress tolerance yet had reduced seed cotton yields compared with the other cultivars evaluated. Genetic analysis of the sensitivity of the PHY 72 pollen suggested a maternal deficiency in the tapetum development of the PHY 72 pollen coat resulting in increased dehydration sensitivity. Structural differences in pollen coat development in two cultivars (PHY 72 and NM67) were observed under both scanning electron and transmission electron microscopy. Predicted reduced rainfall and higher temperatures in the future, may necessitate approaches to improve not only vegetation tolerance to stress but also reproductive tolerance both of which may be important for breeding the new generation of crops.

Is time important in response of morpho-physiological parameters in Withania coagulans L. landraces to water deficit stress?

Withania coagulans is one of the most important medicinal species of the Solanaceae which has pharmacological properties for future research in drug development. Photosynthesis and morphological parameters in response to drought of this species have not been investigated as yet, though the issue is of interest. The factorial combination of four water deficit stress (20% (un-stressed control), 30%, 40% and 50% of FC depletion) and four landraces of W. coagulans (Fanuj, Khash, Saravan and Sarbaz) were laid out in a randomized complete design in a phytotron over the course of 180 days. The first, second, third and fourth samplings were performed every 45 day after imposing the treatments (DAT). The results demonstrated that increase in the water deficit stress levels, decreased minimal fluorescence (F0), leaf greenness, photosynthesis rate, plant height, leaf area, dry weight and quantum yield of PSII photochemistry )ФPSII(in all landraces and maximum photochemical efficiency of PSII (Fv/Fm) in Fanuj, but increased non-photochemical quenching)NPQ(and Fv/Fm in Saravan and Sarbaz landraces. The W. coagulans landraces such as Fanuj with the highest vector loadings of ФPSII at 135 and 180 DAT and Fv/Fm at 45 DAT and Sarbaz with the highest vector loading of F0 at 45 DAT were found suitable for unstressed and severe stress conditions, respectively. Among the chlorophyll fluorescence and morphological parameters, total dry weight had the significant positive correlations with plant height, leaf area and F0 at 45 DAT. Thus, this study indicated chlorophyll florescence should be measured at different phases and future studies should focus on the sensitivity of these parameters to detect potential times among subjects of different stresses. These parameters are easy, cheap, efficient and reliable physiological characteristics which can be used to guide the breeding of new resistant genotypes. According to results, W. coagulans can be called "Xerophytes Camel".

Comparison of various modelling approaches for water deficit stress monitoring in rice crop through hyperspectral remote sensing

This study was conducted to understand the behaviour of ten rice genotypes for different water deficit stress levels. The spectroscopic hyperspectral reflectance data in the range of 350–2500 nm was recorded and relative water content (RWC) of plants was measured at different stress levels. The optimal wavebands were identified through spectral indices, multivariate techniques and neural network technique, and prediction models were developed. The new water sensitive spectral indices were developed and existing water band spectral indices were also evaluated with respect to RWC. These indices based models were efficient in predicting RWC with R2 values ranging from 0.73 to 0.94. The contour plotting using the ratio spectral indices (RSI) and normalized difference spectral indices (NDSI) was done in all possible combinations within 350–2500 nm and their correlations with RWC were quantified to identify the best index. Spectral reflectance data was also used to develop partial least squares regression (PLSR) followed by multiple linear regression (MLR) and Artificial Neural Networks (ANN), support vector machine regression (SVR) and random forest (RF) models to calculate plant RWC. Among these multivariate models, PLSR-MLR was found to be the best model for prediction of RWC with R2 as 0.98 and 0.97 for calibration and validation respectively and Root mean square error of prediction (RMSEP) as 5.06. The results indicate that PLSR is a robust technique for identification of water deficit stress in the crop. Although the PLSR is robust technique, if PLSR extracted optimum wavebands are fed into MLR, the results are found to be improved significantly. The ANN model was developed with all spectral reflectance bands. The 43 developed model didn’t produce satisfactory results. Therefore, the model was developed 44 with PLSR selected optimum wavebands as independent x variables and PLSR-ANN model 45 was found better than the ANN model alone. The study successfully conducts a comparative 46 analysis among various modelling approaches to quantify water deficit stress. The methodology developed would help to identify water deficit stress more accurately by predicting RWC in the crops.

Effect of Water Deficit Stress on Yield Performances in Wet Seeded Rice

Worldwide fresh water scarcity and labour unavailability in agriculture are driving researchers and farmers to find management strategies that will increase water productivity and reduce labour requirement. Wet seeding instead of transplanting rice greatly reduces the labour requirement for crop establishment, while use of alternate wetting and drying (AWD) instead of continuous flooding reduces irrigation input. However, the safe threshold for irrigating wet seeded rice (WSR) at different crop stages has not been investigated. Therefore, experiment was conducted to determine the effects of different degrees of water stress during different crop growth stages on yield performance of WSR. This was done in greenhouse experiment in the 2011 wet season 2011 at the International Rice Research Institute, Los Baños, Philippines. In the experiment, water stresses were applied by withholding irrigation until soil water tension increased to 10, 20 or 40 kPa (kilo pascal) at 10 cm below the soil surface. Soil water tension was measured using 30 cm long guage tensiometer installed with the center of the ceramic cup. The stresses were applied during three crop stages: 3-leaf (3L) to panicle initiation (PI), PI to flowering (FL), and FL to physiological maturity (PM). The experiment also included a continuously flooded (CF) treatment. The number of drying events ranged from 8-12 during 3L-PI, 6-10 during PI-FL and 6-10 during FL-PM. There was a consistent trend for a decline in the number of irrigations and irrigation input with increasing irrigation threshold, and thresholds of 20 and 40 kPa resulted in significantly lower input than with CF. There were consistent trends for lower grain yield as the level of water deficit stress increased, and imposition of stresses of 20 and 40 kPa at any or all three stages significantly reduced grain yield compared with CF. There was a trend for the reduction in grain yield to be greater when the stresses were imposed at all three stages compared with a single stage, but the differences were not significant. There was a consistent trend for irrigation water productivity (WPi) to decrease as the irrigation threshold increased, with significantly lower values for a 40 kPa threshold at any stage, in comparison with CF. This was because the decline in water input to the pots was less than the decline in yield as the threshold increased. The results suggest that the optimum threshold for irrigation of WSR is 10 kPa during the vegetative and grain filling stages, and that the soil should be kept at close to saturation during PI-FLBangladesh Rice j. 2017, 21(1): 1-12

Effect of endophytic fungus Piriformospora indica on yield and some physiological traits of millet (Panicum miliaceum) under water stress

Piriformospora indica is one of the cultivable root-colonising endophytic fungi of the order Sebacinales, which efficiently promote plant growth, uptake of nutrients, and resistance to biotic and abiotic stresses. The aim of this study was to evaluate the effect of P. indica on millet (Panicum miliaceum L.) under water-stress conditions. Two field experiments were carried out in a factorial arrangement at Bu-Ali Sina University of Hamedan, Iran, during 2014 and 2015. The first factor was three levels of water-deficit stress, with irrigation after 60 mm (well-watered), 90 mm (mild stress) and 120 mm (severe stress) evaporation from pan class A. The second factor was two levels of fungus P. indica: inoculated and uninoculated. Results showed that water-deficit stress significantly decreased grain yield and yield components. Colonisation by P. indica significantly increased number of panicles per plant, number of grains per panicle and 1000-grain weight, regardless of water supply. Inoculation with P. indica increased grain yield by 11.4% (year 1) and 19.72% (year 2) in well-watered conditions and by 35.34% (year 1) and 32.59% (year 2) under drought stress, compared with uninoculated plants. Maximum flag-leaf area (21.71 cm2) was achieved with well-watered conditions. Severe water stress decreased flag-leaf area by 53.36%. Flag-leaf area was increased by 18.64% by fungus inoculation compared with the uninoculated control. Under drought conditions, inoculation with P. indica increased plant height by 27.07% and panicle length by 9.61%. Severe water stress caused a significant decrease in grain phosphorus concentration, by 42.42%, compared with the well-watered treatment. By contrast, grain nitrogen and protein contents were increased about 30.23% and 30.18%, respectively, with severe water stress. Inoculation with P. indica increased grain phosphorus by 24.22%, nitrogen by 7.47% and protein content by 7.54% compared with control. Water stress reduced leaf chlorophyll and carotenoid concentrations, whereas P. indica inoculation enhanced chlorophyll concentrations by 27.18% under severe water stress. The results indicated the positive effect of P. indica on yield and physiological traits of millet in both well-watered and water-stressed conditions.

CPPU (N-(2-chloro-4-pyridinyl)-N’-phenylurea) Enhancement of Cotton Yields

The gradual depletion of the Ogallala Aquifer under the Southern High Plains of Texas during the past fifty years has resulted in reduced well capacities for cotton irrigation. Water table declines have already led some to shift from irrigated to dryland farming, and many of the remaining wells cannot provide enough water for full irrigation. The present study evaluated the effectiveness of the synthetic cytokinin CPPU (N-(2-chloro-4-pyridinyl)-N’-phenylurea) on the stimulation of lateral root production and enhancement of cotton yields under dryland conditions. Seed treatments of 250 µmol/mol or seedling sprays of 5 µmol/mol at the cotyledon stage, increased lateral root production. Cotton yield increases associated with the increased rooting ranged from 8 to 20% in three years of field studies under dryland conditions. The greatest yield increases were associated with dry shallow soils. Evaluation of water-deficit stress levels in untreated and CPPU-treated cotton showed reduced water-deficit stress levels throughout the growing season in the CPPU-treated cotton. This study showed that application of CPPU to cotton, early in development, has the potential to reduce water stress and increase yields.

CORRELATION AND HERITABILITY ESTIMATION OF VARIOUS SEEDLING TRAITS IN BRASSICA NAPUS L. UNDER WATER DEFICIT CONDITIONS

Brassica napus L. contains edible oil ensuring safe limits for human health. But farmers prefer to use their fertile land for main crops and only marginal lands for oilseed. Those marginal lands usually face water scarcity and other a-biotic stresses that affect the normal growth and development of plant. Here we tested three levels of water deficit stress (control, medium and high) under controlled conditions. Seedlings were analyzed for various seedling traits to measure the relative effect of different levels water deficit stress. Graphical trends depicts that increasing level of water deficit stress causes declines in leaf area, root length, shoot length, fresh and dry weight of roots and shoots. Correlation coefficients exposed positive significant correlation of fresh shoot weight with chlorophyll contents, relative water contents, leaf area and shoot length at both genotypic and phenotypic level. Path coefficient analysis displayed high direct effects on fresh shoot weight were due to relative water content, root to shoot ratio. Chlorophyll contents, relative water content, leaf area, root length and shoot length showed high broad sense heritability (h2BS) coupled with high genetic advance (GA). These traits could be focused while breeding for water deficit conditions.

Stability of Solanum aethiopicum Shum accessions under varied water deficit stress levels and identification of pertinent breeding traits for resistance to water shortage

Drought is a major constraint to productivity of Solanum aethiopicum ‘Shum’ group due to loss in market and nutrient value of stressed plants. This study evaluated S. aethiopicum Shum group accessions to identify genotypes (G) that excel across moisture deficit stress levels (WLs). A split-plot arrangement composed of four WLs and twenty accessions of S. aethiopicum as main plot and sub-plot factors, respectively, was implemented in a screenhouse, and repeated for two experiments. In each experiment, there was a highly significant effect of at least two WLs on mean performance among at least two accessions for most of the traits at p PH > LPP. Consequently, based on LRWC, the most superiorly stable accessions were identified as accession 160 followed by accessions 145, 137, 108P and 184G while the least stable ones were identified as accessions 163G, 141, 163 and 108. The broad sense heritability (H 2) for each of the three recommended traits for drought resistance breeding was above 0.9 thus supportive for a good response to selection. Drought stress negatively affected the performance of S. aethiopicum Shum group but the exhibited variation allowed for selection of superiorly stable genotypes.

Impact of water-deficit stress on tritrophic interactions in a wheat-aphid-parasitoid system.

Increasing temperature and CO2 concentrations can alter tritrophic interactions in ecosystems, but the impact of increasingly severe drought on such interactions is not well understood. We examined the response of a wheat-aphid-parasitoid system to variation in water-deficit stress levels. Our results showed that arid area clones of the aphid, Sitobion avenae (Fabricius), tended to have longer developmental times compared to semiarid and moist area clones, and the development of S. avenae clones tended to be slower with increasing levels of water-deficit. Body sizes of S. avenae clones from all areas decreased with increasing water-deficit levels, indicating their declining adaptation potential under drought. Compared to arid area clones, moist area clones of S. avenae had a higher frequency of backing under severe water stress only, but a higher frequency of kicking under well-watered conditions only, suggesting a water-deficit level dependent pattern of resistance against the parasitoid, Aphidius gifuensis (Ashmead). The number of S. avenae individuals attacked by the parasitoid in 10 min showed a tendency to decrease with increasing water-deficit levels. Clones of S. avenae tended to have lower parasitism rates under treatments with higher water-deficit levels. The development of the parasitoid tended to be slower under higher levels of water-deficit stress. Thus, the bottom-up effects of water-deficit stressed plants were negative on S. avenae. However, the top-down effects via parasitoids were compromised by water-deficit, which could favor the growth of aphid populations. Overall, the first trophic level under water-deficit stress was shown to have an indirect and negative impact on the third trophic level parasitoid, suggesting that parasitoids could be increasingly vulnerable in future warming scenarios.

Comparison of different uni- and multi-variate techniques for monitoring leaf water status as an indicator of water-deficit stress in wheat through spectroscopy

Ten different wheat genotypes were studied for understanding their differential behaviour to different water-deficit stress levels. Hyperspectral data (350–2500 nm) and relative water content (RWC) of plants were measured at different stress level for identifying optimal spectral bands, indices and multivariate models to develop non-invasive phenotyping protocols. Evaluation of water sensitive existing spectral indices, proposed indices and band depth analysis at selected wavelengths was done with respect to RWC and prediction models were developed. The prediction models developed were efficient in predicting RWC with the R2 values ranging from 0.73 to 0.88 for spectral indices and 0.74–0.85 with continuum depth. Then, the ratio spectral indices (RSI) and normalised difference spectral indices (NDSI) were obtained in all possible combinations within 350–2500 nm and their correlations with RWC were quantified to identify the best indices. The best spectral indices for estimating RWC in wheat were RSI (R1391, R1830) and NDSI (R1391, R1830) with R2 of 0.86 and 0.81, respectively. Spectral reflectance data were also used to develop partial least squares regression (PLSR) followed by multiple linear regression (MLR), support vector machine regression (SVR), multivariate adaptive regression spline (MARS) and random forest (RF) model to calculate plant RWC. Among these multivariate models, PLSR was the best model for prediction of RWC (R2 and RMSE of 0.96 and 3.88%; 0.91 and 6.52% for calibration and validation, respectively). The methodology developed would help for its further use in high-throughput phenomics of different crops for drought stress.