Screening For Drought Tolerance Research Articles

Evaluation of UAV-derived multimodal remote sensing data for biomass prediction and drought tolerance assessment in bioenergy sorghum

Screening for drought tolerance is critical to ensure high biomass production of bioenergy sorghum in arid or semi-arid environments. The bottleneck in drought tolerance selection is the challenge of accurately predicting biomass for a large number of genotypes. Although biomass prediction by low-altitude remote sensing has been widely investigated on various crops, the performance of the predictions are not consistent, especially when applied in a breeding context with hundreds of genotypes. In some cases, biomass prediction of a large group of genotypes benefited from multimodal remote sensing data; while in other cases, the benefits were not obvious. In this study, we evaluated the performance of single and multimodal data (thermal, RGB, and multispectral) derived from an unmanned aerial vehicle (UAV) for biomass prediction for drought tolerance assessments within a context of bioenergy sorghum breeding. The biomass of 360 sorghum genotypes grown under well-watered and water-stressed regimes was predicted with a series of UAV-derived canopy features, including canopy structure, spectral reflectance, and thermal radiation features. Biomass predictions using canopy features derived from the multimodal data showed comparable performance with the best results obtained with the single modal data with coefficients of determination (R2) ranging from 0.40 to 0.53 under water-stressed environment and 0.11 to 0.35 under well-watered environment. The significance in biomass prediction was highest with multispectral followed by RGB and lowest with the thermal sensor. Finally, two well-recognized yield-based drought tolerance indices were calculated from ground truth biomass data and UAV predicted biomass, respectively. Results showed that the geometric mean productivity index outperformed the yield stability index in terms of the potential for reliable predictions by the remotely sensed data. Collectively, this study demonstrated a promising strategy for the use of different UAV-based imaging sensors to quantify yield-based drought tolerance.

Multilocational screening identifies new drought‐tolerant, warm‐season turfgrasses

AbstractDuring periods of drought, the irrigation needs of current warm‐season turfgrass cultivars and frequent municipal water use restrictions present a major challenge to the turfgrass industry. Turfgrass breeding programs have responded by placing more emphasis on improved drought response. During 2012–2013, 560 genotypes of four warm‐season turfgrass species developed by five southern breeding programs were evaluated for drought response in replicated field trials at seven locations. Breeders selected 35 genotypes as drought‐tolerant selections (DTS) for further evaluation. The objectives of this study were to verify superior drought response among DTS under short‐term drought conditions and to assess the effectiveness of this approach as a viable breeding strategy to improve drought response in warm‐season turfgrasses. Forty‐seven genotypes including standard commercial cultivars of zoysiagrass (Zoysia spp. Willd.), bermudagrass [Cynodon spp. (L.) Pers.], St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and seashore paspalum (Paspalum vaginatum Swartz) were exposed to dry‐downs in three consecutive years by withholding irrigation and excluding rainfall. Significant differences in drought performance were seen across genotypes over the multiyear study. Statistical contrasts found that DTS of zoysiagrass, St. Augustinegrass, and seashore paspalum generally performed better than the standard cultivars. Top‐performing DTS zoysiagrass and St. Augustinegrass genotypes maintained >50% green cover longer than the average of the standard cultivars. Based on this research, multilocational screening for drought tolerance was effective in selection of new genotypes with superior performance to standard cultivars and continued screening of turfgrass germplasm to identify new drought‐tolerant genotypes is warranted.

Physiological and Yield Responses of Selected Mungbean Genotypes to Terminal Drought

Extreme drought conditions have been a major limiting factor in legume production worldwide. The development of drought-resilient crops should help mitigate adverse effects of unfavorable environmental conditions such as drought; however, initial characterization is necessary to ensure that the germplasm has the essential genetic variation for drought tolerance. In this study, a field trial was conducted to characterize drought response and potential drought tolerance of 100 mungbean genotypes through the evaluation of several physiological parameters and seed yield. The genotypes were subjected to terminal drought stress before flowering (~ 30 d after planting), reducing soil moisture content (SMC) from 25.0–30.0% to 13.0–15.0% during treatment imposition. Significant differences were observed between mungbean genotypes for total chlorophyll content (Chl), total scavenging activity (SA), electrolyte leakage (EC), and chlorophyll fluorescence (Fv/Fm) during drought. Furthermore, by transforming each physiological parameter into principal components (PCs) via principal component analysis (PCA), five distinct clusters were generated. Based on their physiological response and seed yield, Clusters I and II were identified as potential drought susceptible group, Cluster III was moderately susceptible, and Clusters IV and V were identified as the potential drought-tolerant group. Correlation analysis and PCA also demonstrated the significant relationship among several key traits for drought tolerance such as chlorophyll content, electrolyte leakage, and antioxidant scavenging to chlorophyll fluorescence – suggesting the suitability of fluorescence parameter in mungbean mass screening for drought tolerance. Although weak correlation between physiological parameters to seed yield was present (0.3 <│r│< 0.5), correlations among each physiological parameter were moderately strong (0.5 <│r│< 0.7). The findings suggest that a physiological characterization during initial screening for drought tolerance was an effective approach in identifying possible sources of drought tolerance traits complementary with yield- related traits. The evaluation of chlorophyll fluorescence, scavenging activity, electrolyte leakage, and chlorophyll content was enough to differentiate and characterize the drought response of several mungbean genotypes and will be vital in the development of climate-resilient crops.

Drought tolerance screening of selected rice varieties by limited semi controlled field system

Drought tolerance is important trait for rice. Developing simple system for drought tolerance screening will increase efficiency and effectiveness of breeding for the certain purpose. This research aimed to screen selected variety for drought under limited semi controlled space system. The trial was conducted at the limited open space with controlled irrigation and drainage system in the area of Indonesian Centre of Rice Research green houses in Subang, West Java, from July to November 2019. Twenty varieties selected from previous drought screenings using concrete box method were transplanted at 21 days after sowing with planting space of 20 x 20 cm 1 – 3 seedling/hill in a single row of 10 plants followed randomized complete block design with two replications. The materials were watered for 4 weeks since transplanting. Re-watering was given until harvesting since IR 20 (drought sensitive check) was completely dry. The results showed variation level of drought tolerance among the tested genotypes. Based on leaf drying score at five weeks after treatment, Inpago 9 and Cisaat along with Salumpikit (drought tolerant check) were considered relatively tolerant. Inpago 9 (41.8 g) followed by Inpari 42 (34.7 g), and Inpago 8 (30.1 g) had the highest yield.

Screening for drought tolerance and diversity analysis of Bangladeshi rice germplasms using morphophysiology and molecular markers

Screening for drought tolerance and diversity analysis of Bangladeshi rice germplasms using morphophysiology and molecular markers

Screening for Drought Tolerance through Root Morphology and Yield Characters of Groundnut (Arachis hypogaea L.) Genotypes

Drought affects the rainfed groundnut (Arachis hypogaea L.) at different phases of development and it is the serious threats on groundnut productivity causing losses than any other abiotic factor under rainfed agriculture. In the world's semiarid regions, groundnut accounts for 90% of worldwide production. Drought mainly affects the pace and pattern of nutrient and water intake from the soil, affecting the architecture of the groundnut root system. Plant selections with desirable root trait have been a major focus in developing drought resistant Groundnut cultivars. In 2019, 60 groundnut genotypes were cultivated in root block design with two different soil water treatments, as well as in the field during the year under same circumstances. The purpose of this study was to see how different groundnut cultivars fared in terms of yield, yield contributing features, root characters, and their relationships with drought tolerance. Drought resistant genotypes had thicker roots, larger roots, and a deeper root system than susceptible genotypes. Recent series in groundnut genotypes of 60 numbers were sown during kharif 2019 (july-september) under rainfed condition (It includes life irrigation and rainfall received during cropping season). Groundnut genotypes were semi spreading with the duration of 110-120 days. Observation on root morphological character viz., roots length, root volume after 20 days of stress imposition of the crop and yield parameters were observed at the harvest. Among the 60 genotypes, 20 genotypes (VG 17008, VG 17046, VG 18005, VG 18102, VG 18077, VG 19572, VG 19709, VG 18111, VG19561, VG19576, VG 19620, VG 19681, VG 19688 etc.,) similarly, yield character were observed for 60 genotypes and all the genotypes given above recorded higher value in Total number of pods per plant, Number of double seeded pods per plant, Pod yield per plant, Harvest index and Total dry matter production. The methods used in this study identified correlation between yield character and root characters. Groundnut genotypes by assessing yield metrics and their relationship with root trait. These findings lay the groundwork for future study aimed at deciphering the molecular pathways underpinning Groundnut drought resistance.

The variation of relative water content, SPAD chlorophyll meter reading, stomatal conductance, leaf area, and specific leaf area of Jerusalem artichoke genotypes under different durations of terminal drought in tropical region

AbstractThis work assessed the responses of Jerusalem artichoke (JA) genotypes experienced to different durations of terminal drought for relative water content (RWC), SPAD chlorophyll meter reading (SCMR), stomatal conductance (SC), leaf area (LA) and specific leaf area (SLA), investigated the significant contributor of physiological traits to yield and yield reduction and diversity of physiological traits in terminal drought tolerance genotypes. Field research was conducted during the late‐rainy season for 2 years using a split‐plot design with four replications. The three irrigation treatments involved no‐drought (SD0), short (SD1) and long (SD2) durations of terminal drought were arranged as main plots, and sub‐plots were six genotypes of JA. The current study revealed that RWC, SC, LA, and SLA, were drastically reduced whilst SCMR values slightly increased under SD1 and SD2 compared to SD0. According to multiple linear regression indicated that SLA (SD0), and RWC (SD1 and SD2) had high contributions to tuber fresh weight (TFW), whereas SC had a high contribution to TFW reduction under terminal drought. Principal component analysis also confirmed that the diversity of LA, RWC, and SLA had maximized contributing traits, followed by HI, SCMR and SC in these breeding materials of JA under three irrigation treatments. Our finding emphasized that JA125 (low SLA), HEL256 and JA37 (high SLA) lead to the high performance of TFW under SD0, and they exhibited high TFW under SD1 by performing medium RWC. Likewise, JA4 and JA37 had high TFW under SD2 caused by medium RWC. HEL253 and JA60 were identified as terminal drought‐tolerant genotypes because of performed medium SC, which contributed to a low reduction in TFW. Our promising results are the basis for further studies, SLA, RWC and SC are an important keys for screening drought tolerance (low economic yield reduction) and these genotypes studied could be used for parental lines to improved drought tolerance progenies through breeding programs under different durations of terminal drought‐prone areas.

PLANT GROWTH PROMOTING ACTIVITIES OF RHIZOBACTERIA ISOLATED FROM RHIZOSPHERIC SOILS OF RURAL BANGALORE, INDIA

Soil is a dynamic ecosystem which provides support to plant life. Microorganisms inhabiting the rhizosphere region of soil play a key role in agriculture by promoting the exchange of plant nutrients and reducing the application of chemical fertilizers to a large extent. Engineering of rhizospheric region through exploitation of specific microorganisms leads to higher microbial diversity in the soil which in turn plays a significant role in maintaining the soil health. The present work envisages the isolation, screening and biochemical profiling of potent plant growth promoting rhizobacteria from various rhizospheric soils in and around Bangalore. Sixty isolates from rhizospheric region of fourteen different agricultural soils were screened for plant growth promoting traits such as phosphate solubilization, siderophore production, Ammonia, HCN & Phytohormone production. Twelve isolates that exhibited plant growth promotional traits were further subjected to screening for drought and salt tolerance. Among the twelve isolates, four potential isolates namely Serratia marcescens, Pseudomonas aeruginosa and Acinetobacter pittii were identified based on biochemical methods and 16SrRNA sequencing.

Physio-morphological traits and osmoregulation strategies of hybrid maize (Zea mays) at the seedling stage in response to water-deficit stress.

Drought has been identified as a major factor restricting maize productivity worldwide, especially in the rainfed areas. The objective of the present study was to investigate the physiological adaptation strategies and sugar-related gene expression levels in three maize (Zea mays L.) genotypes with different drought tolerance abilities (Suwan4452, drought tolerant as a positive check; S7328, drought susceptible as a negative check; Pac339, drought susceptible) at the seedling stage. Ten-day old seedlings of maize genotypes were subjected to (i) well-watered (WW) or control and (ii) water-deficit (WD) conditions. Leaf osmotic potential of cv. S7328 under WD was significantly decreased by 1.35-1.45 folds compared with cv. Pac339 under WW, whereas it was retained in cv. Suwan4452, which utilized total soluble sugars as the major osmolytes for maintaining leaf greenness, Fv/Fm, ΦPSII, and stomatal function (Pn, net photosynthetic rate; gs, stomatal conductance; and E, transpiration rate). Interestingly, sucrose degradation (65% over the control) in cv. Pac339 under WD was evident in relation to the downregulation of the ZmSPS1 level, whereas glucose enrichment (1.65 folds over the control) was observed in relation to the upregulation of ZmSPS1 and ZmSUS1. Moreover, CWSI (crop water stress index), calculated from leaf temperature of stressed plants, was negatively correlated with E, gs, and Pn. Overall, growth characteristics, aboveground and belowground parts, in the drought-susceptible cv. Pac339 and cv. S7328, were significantly decreased (> 25% over the control), whereas these parameters in the drought-tolerant cv. Suwan4452 were unaffected. The study validates the use of leaf temperature, CWSI, Pn, gs, and E as sensitive parameters and overall growth characters as effective indices for drought tolerance screening in maize genotypes at the seedling stage. However, further experiments are required to validate the results observed in this study under field conditions.

Screening for drought tolerance and molecular variability among some sugar beet cultivars

Drought is one of the significant abiotic stress factors that affect plant development and productivity. Screening and producing of more tolerant genotypes with higher yield capacity is the breeders' principal purpose. Therefore, this work was carried out to evaluate the performance of four sugar beet cultivars (Top, Hossam, Hercules and Kawamera) under water limitation. The drought stress experiment was applied based on three water regimes, 25%, 50% and 75% (severe, moderate and non-stress conditions, respectively) of relative water capacity (RWC). The study incorporated some productivity and quality traits. The results showed that drought stress has a significant effect on all studied traits. Whereas, increasing of water deficiency led to decrease of the productivity traits and increasing of quality parameters. Kawamera cultivar has superior performance in all the studied traits under all three different levels of water regime. Besides, the four cultivars were assessed by both SSR and ISSR molecular markers. SSR marker exhibited a higher polymorphism percentage (71.43%) than ISSR marker (44.26%). In addition, the mean polymorphism information content (PIC) value was higher for the SSR marker (0.25) than the ISSR marker (0.18) too. Moreover, the constructed dendrograms revealed that the SSR marker was able to separate the cultivars according to their drought-tolerance, where the highest drought-tolerant cultivar (Kawamera) was classified alone in the main cluster. However, the superiority of Kawamera cultivar under drought stress indicated that it could be utilized in breeding programs for developing more drought-tolerant sugar beet cultivars.

Characterization of Dynamic Regulatory Gene and Protein Networks in Wheat Roots Upon Perceiving Water Deficit Through Comparative Transcriptomics Survey.

A well-developed root system benefits host plants by optimizing water absorption and nutrient uptake and thereby increases plant productivity. In this study we have characterized the root transcriptome using RNA-seq and subsequential functional analysis in a set of drought tolerant and susceptible genotypes. The goal of the study was to elucidate and characterize water deficit-responsive genes in wheat landraces that had been through long-term field and biochemical screening for drought tolerance. The results confirm genotype differences in water-deficit tolerance in line with earlier results from field trials. The transcriptomics survey highlighted a total of 14,187 differentially expressed genes (DEGs) that responded to water deficit. The characterization of these genes shows that all chromosomes contribute to water-deficit tolerance, but to different degrees, and the B genome showed higher involvement than the A and D genomes. The DEGs were mainly mapped to flavonoid, phenylpropanoid, and diterpenoid biosynthesis pathways, as well as glutathione metabolism and hormone signaling. Furthermore, extracellular region, apoplast, cell periphery, and external encapsulating structure were the main water deficit-responsive cellular components in roots. A total of 1,377 DEGs were also predicted to function as transcription factors (TFs) from different families regulating downstream cascades. TFs from the AP2/ERF-ERF, MYB-related, B3, WRKY, Tify, and NAC families were the main genotype-specific regulatory factors. To further characterize the dynamic biosynthetic pathways, protein-protein interaction (PPI) networks were constructed using significant KEGG proteins and putative TFs. In PPIs, enzymes from the CYP450, TaABA8OH2, PAL, and GST families play important roles in water-deficit tolerance in connection with MYB13-1, MADS-box, and NAC transcription factors.

Identification for surrogate drought tolerance in maize inbred lines utilizing high-throughput phenomics approach.

Screening for drought tolerance requires precise techniques like phonemics, which is an emerging science aimed at non-destructive methods allowing large-scale screening of genotypes. Large-scale screening complements genomic efforts to identify genes relevant for crop improvement. Thirty maize inbred lines from various sources (exotic and indigenous) maintained at Dryland Agriculture Research Station were used in the current study. In the automated plant transport and imaging systems (LemnaTec Scanalyzer system for large plants), top and side view images were taken of the VIS (visible) and NIR (near infrared) range of the light spectrum to capture phenes. All images were obtained with a thermal imager. All sensors were used to collect images one day after shifting the pots from the greenhouse for 11 days. Image processing was done using pre-processing, segmentation and flowered by features’ extraction. Different surrogate traits such as pixel area, plant aspect ratio, convex hull ratio and calliper length were estimated. A strong association was found between canopy temperature and above ground biomass under stress conditions. Promising lines in different surrogates will be utilized in breeding programmes to develop mapping populations for traits of interest related to drought resilience, in terms of improved tissue water status and mapping of genes/QTLs for drought traits.

High-throughput field phenotyping reveals genetic variation in photosynthetic traits in durum wheat under drought.

Chlorophyll fluorescence (ChlF) is a powerful non-invasive technique for probing photosynthesis. Although proposed as a method for drought tolerance screening, ChlF has not yet been fully adopted in physiological breeding, mainly due to limitations in high-throughput field phenotyping capabilities. The light-induced fluorescence transient (LIFT) sensor has recently been shown to reliably provide active ChlF data for rapid and remote characterisation of plant photosynthetic performance. We used the LIFT sensor to quantify photosynthesis traits across time in a large panel of durum wheat genotypes subjected to a progressive drought in replicated field trials over two growing seasons. The photosynthetic performance was measured at the canopy level by means of the operating efficiency of Photosystem II ( ) and the kinetics of electron transport measured by reoxidation rates ( and ). Short- and long-term changes in ChlF traits were found in response to soil water availability and due to interactions with weather fluctuations. In mild drought, and were little affected, while was consistently accelerated in water-limited compared to well-watered plants, increasingly so with rising vapour pressure deficit. This high-throughput approach allowed assessment of the native genetic diversity in ChlF traits while considering the diurnal dynamics of photosynthesis.

Root and canopy traits and adaptability genes explain drought tolerance responses in winter wheat.

Bread wheat (Triticum aestivum L) is one of the three main staple crops worldwide contributing 20% calories in the human diet. Drought stress is the main factor limiting yields and threatening food security, with climate change resulting in more frequent and intense drought. Developing drought-tolerant wheat cultivars is a promising way forward. The use of holistic approaches that include high-throughput phenotyping and genetic markers in selection could help in accelerating genetic gains. Fifty advanced breeding lines were selected from the CIMMYT Turkey winter wheat breeding program and studied under irrigated and semiarid conditions in two years. High-throughput phenotyping was done for wheat crown root traits and canopy senescence dynamics using vegetation indices (green area using RGB images and Normalized Difference Vegetation Index using spectral reflectance). In addition, genotyping by KASP markers for adaptability genes was done. Overall, under semiarid conditions yield reduced by 3.09 t ha-1 (-46.8%) compared to irrigated conditions. Genotypes responded differently under drought stress and genotypes 39 (VORONA/HD24-12//GUN/7/VEE#8//…/8/ALTAY), 18 (BiII98) and 29 (NIKIFOR//KROSHKA) were the most drought tolerant. Root traits including shallow nodal root angle under irrigated conditions and root number per shoot under semiarid conditions were correlated with increased grain yield. RGB based vegetation index measuring canopy green area at anthesis was better correlated with GY than NDVI was with GY under drought. The markers for five established functional genes (PRR73.A1 –flowering time, TEF-7A –grain size and weight, TaCwi.4A - yield under drought, Dreb1- drought tolerance, and ISBW11.GY.QTL.CANDIDATE- grain yield) were associated with different drought-tolerance traits in this experiment. We conclude that–genotypes 39, 18 and 29 could be used for drought tolerance breeding. The trait combinations of canopy green area at anthesis, and root number per shoot along with key drought adaptability makers (TaCwi.4A and Dreb1) could be used in screening drought tolerance wheat breeding lines.

Ameliorative Effects of Calcium Sprays on Yield and Grain Nutritional Composition of Maize (Zea mays L.) Cultivars under Drought Stress

Drought stress is seriously affecting maize production. To investigate the influence of calcium (Ca) foliar application on maize production and chemical composition of grains under drought stress, two experiments were carried out at Cairo University Research Station, Giza, Egypt, during the summer seasons of 2018 and 2019. The experimental design was split-split plot design with a completely randomized blocks arrangement with three replications. Water regimes were assigned to the main plots [100 (control), 75, and 50% of estimated evapotranspiration]. Calcium levels (zero and 50 mg/L) were assigned to the sub plots. Maize cultivars (SC-P3444, Sammaz-35 and EVDT) were assigned to the sub-sub plots. Three maize cultivars were sprayed with Ca solution concentration (50 mg/L) under normal and drought conditions. The control treatment (0 mg/L) was sprayed with an equal amount of distilled water for comparison. Results indicated a significant decrease in total yield and grain characteristics [protein, ash, total sugars, nitrogen (N), phosphorus (P), potassium (K), and iron (Fe) contents] as a response of drought. Calcium foliar application significantly increased maize yield, protein, ash, carbohydrates, starch, total sugars, and ionic contents of grains, except for manganese (Mn), under all irrigation levels. Based on the drought tolerance index (DTI), only cultivar SC-P3444 showed drought tolerance while cultivars Sammaz-35 and EVDT were sensitive to drought stress. Foliar application of Ca on SC-P3444 cultivar achieved the highest grain yield per hectare (8061 kg) under the water regime of 100% of the total evapotranspiration, followed by Sammaz-35 (7570 kg), and EVDT (7191 kg) cultivars. At the water regime of 75% of estimated evapotranspiration (75% irrigation), Ca foliar application increased grain yield by 16, 13 and 14% in SC-P3444, Sammaz-35, and EVDT, respectively. At the water regime of 50% of the estimated evapotranspiration (50% irrigation), Ca foliar application increased grain yield by 17, 16, and 13% in SC-P3444, Sammaz-35, and EVDT, respectively. In brief, Ca had a clear impact on productivity and grain quality with important implications for maize yield under normal and water stress conditions. Our findings demonstrate that foliar application of Ca enabled drought stressed maize plants to survive better under stress. The most water stress tolerant cultivar was SC-P3444 followed by Sammaz-35 and EVDT under drought stress.

Cell Suspension Culture and In Vitro Screening for Drought Tolerance in Soybean Using Poly-Ethylene Glycol.

Soybean (Glycine max (L) Merrill) is used in India mostly as a substantial fund of protein and oil, which makes the crop significantly important. Somaclonal variation has been researched as a base of additional variability for drought in soybean. In the present experiment calli/cell clumps/embryoids rose from immature and mature embryonic axis and cotyledons explants were exposed to different concentrations of polyethylene glycol (PEG6000). A discontinuous method proved to be superior as it permitted the calli/embryoids/cell clumps to regain their regeneration competence. A total of 64 (12.21%) plantlets of genotype JS335 and 78 (13.13%) of genotype JS93-05 were regenerated after four consequent subcultures on the selection medium with an effective lethal concentration of 20% PEG6000, and proliferated calli/embryoids/cell clumps were further subcultured on Murashige and Skoog regeneration medium supplemented with 0.5 mgL−1 each of α-napthalene acetic acid (NAA), 6-benzyladenine (BA) and Kinetin (Kn), 20.0 gL−1 sucrose and 7.5 gL−1 agar. Putative drought-tolerant plantlets were acquired from genotype JS93-05 (38) in more numbers compared to genotype JS335 (26). Random decamer primers confirmed the presence of variability between mother plants and regenerated plants from both the genotypes. Since these plantlets recovered from tolerant calli/embryoids/cell clumps selected from the medium supplemented with PEG6000, the possibility exists that these plants may prove to be tolerant against drought stress.

Seed inoculation of desert-plant growth-promoting rhizobacteria induce biochemical alterations and develop resistance against water stress in wheat.

Water shortage limits agricultural productivity, so strategies to get higher yields in dry agricultural systems is vital to circumvent the effect of climate change and land-shortage. The plant rhizosphere harbors beneficial bacteria able to confer biotic/abiotic tolerance along with a positive impact on plant growth. Herein, three bacterial strains, Proteus mirabilis R2, Pseudomonas balearica RF-2 and Cronobacter sakazakii RF-4 (accessions: LS975374, LS975373, LS975370, respectively) isolated from native desert-weeds were investigated for their response to improve wheat growth under drought stress. The bacteria showed drought tolerance up to 20% polyethylene glycol (PEG; -0.6MPa), and salt (65-97 g l-1 ), 1-aminocyclopropane-1-carboxylate (ACC)-deaminase activity, P/Zn/K-solubilization, calcite degradation, IAA, and siderophore production. The plant growth-promoting rhizobacteria (PGPR) were evaluated on wheat under water stress. The P. balearica strain RF-2 primed seeds showed a maximum promptness index and germination index under PEG-stress, that is, 68% and 100%, respectively. Inoculation significantly improved plant growth, leaf area, and biomass under water stress. P. mirabilis R2 inoculated plant leaves showed the highest water contents as compared to the plants inoculated with other strains. C. sakazakii RF-4 inoculated plants showed minimum cell injury, electrolyte leakage, and maximum cell membrane stability at PEG stress. After 13 days exposure to drought, C. sakazakii RF-4 treated plants showed an overall higher expression of cytosolic ascorbate peroxidase (cAPX) and ribulose-bisphosphate carboxylase (rbcL) genes. The activity of stress-induced catalase and polyphenol oxidase was reduced, while that of peroxidase and superoxide dismutase increased after inoculation but the response was temporal. Taken together, this data explains that different PGPR (especially C. sakazakii RF-4) modulate differential responses in wheat that eventually leads towards drought tolerance, hence, it has the potential to enhance crop production in arid regions.

Photosynthetic activity of Triticum dicoccum × Triticum aestivum alloplasmic lines during vegetation in connection with productivity traits under varying moister conditions

Drought is a key stressor under global climate change conditions around the world. Triticum dicoccum Shuebl is a species with high potential drought tolerance. Photosynthesis is the primary physiological process affected by water deficit. Rapid light curves (RLCs), recorded using PAM-fluorometers, appear suitable for drought tolerance determination in breeding material. Chlorophyll fluorescence parameters at different vegetation stages, morphophysiological traits, and their relationship with the productivity were analyzed in nine alloplasmic lines (allolines) of T. dicoccum Shuebl × T. aestivum L. partially exposed to drought conditions. Quantum yield parameters at the beginning of RLC at the early vegetation stages correlated with the productivity of investigated lines. Parameters related to photosynthetic capacity had a stronger correlation with the productivity at the stages of subflag and flag formation. For drought tolerance screening, quantum yield of nonorganized energy passive dissipation is particularly promising. Chlorophyll fluorescence and productivity data confirm the potential of the presented breeding strategy in allolines D-d-05 and D-d-05b.

Bacterial Root Endophytes: Characterization of Their Competence and Plant Growth Promotion in Soybean (Glycine max (L.) Merr.) under Drought Stress.

Recently, the application of endophytes in the alleviation of different types of stresses has received considerable attention, but their role in drought stress alleviation and growth promotion in soybean is not well-stated. In this study, twenty bacterial endophytes were isolated from soybean root tissues and screened for plant growth-promoting (PGP) traits, biocontrol potential, and drought stress alleviation. Out of them, 80% showed PGP traits, and 20% showed antagonistic activity against Fusarium oxysporum (ITCC 2389), Macrophomina phaseolina (ITCC 1800), and Alternaria alternata (ITCC 3467), and only three of them showed drought tolerance up to 15% (−0.3 MPa). Results indicated that drought-tolerant PGP endophytic bacteria enhanced soybean seedling growth under drought stress conditions. Morphological, biochemical, and molecular characterization (16S rRNA) revealed that these three bacterial isolates, AKAD A1-1, AKAD A1-2, and AKAD A1-16, closely resemble Bacillus cereus (GenBank accession No. MN079048), Pseudomonas otitidis (MW301101), and Pseudomonas sp. (MN079074), respectively. We observed that the soybean seedlings were grown in well-watered and drought-stressed soil showed the adverse effect of drought stress on morphological (stem length, root length, plant fresh and dry weight) as well as on biochemical parameters (a decline of photosynthetic pigments, membrane damage, etc.). However, soybean seedlings inoculated with these endophytes have improved the biomass significantly (p ≤ 0.05) under normal as well as in drought stress conditions over control treatments by influencing several biochemical changes. Among these three endophytes, AKAD A1-16 performed better than AKAD A1-2 and AKAD A1-1, which was further validated by the ability to produce the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase in the following order: AKAD A1-16 > AKAD A1-2 > AKAD A1-1. Scanning electron microscopy images also showed a bacterial presence inside the roots of soybean seedlings. These findings supported the application of bacterial root endophytes as a potential tool to mitigate the effect of drought as well as of fungal diseases on the early seedling growth of soybean.

Drought Tolerance Screening for Rice Genotypes Using Various Drought Indices in Lamjung, Nepal

A field experiment was conducted during rainy reason of 2018 to rectify stable and high yielding rice varieties at moisture stress condition at Lamjung, Nepal. 13 rice genotypes were evaluated at randomized complete block design (RCBD) with three replications. About 5 cm stagnant water was maintain in irrigated field until one month before harvesting whereas in rainfed field no extra irrigation was provided and drainage of excess rainfall water. Drought indices such as tolerance index (TOL), stress susceptibility index (SSI), yield stability index (YSI), Stress tolerance index (STI), mean productivity index (MP), geometric mean productivity index (GM) were computed. Results showed significantly different for all drought indices Average yield reduction was 27% . Ys was positive and significant association with Yp. The MP, GM and STI were positive correlation with grain yield under both environments whereas SSI and YSI was negative non-significant association with both stress and normal condition yield. In principle component analysis (PCA) two component explained more than 99% variation. Combined analysis showed that Radha 11, Radha 13, DRR 44, NR 119, Sukhadhan 5 and Ghaiya 2 were top performer in stress condition whereas NR 119 reported the lowest yield reduction in stress condition. Sawa Mansuli Sub-1 most susceptible under stress condition exhibiting 54 % yield reduction in stress condition. Manabahu was stable but lower yielding varieties.