Screening For Drought Tolerance Research Articles

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.

Screening drought tolerance of Vietnamese rice landraces in the laboratory and net house conditions

Screening drought tolerance of Vietnamese rice landraces in the laboratory and net house conditions

Character Selection and Tolerance Screening Efectivity on Static Hydroponic Method Under Drought Stress in Rice

This research was aimed to evaluate the efectivity of screening method and identification of tolerance screening selection character in statis hydroponic system towards drough stress. The research was carried out in Hydroponic Screenhouse Perdos Unhas, Tamalanrea, Makassar which throughout February-April 2020. This research was conducted in factorial design in nested patterns, where environment was the nested replication. Environments used were normal (0% PEG) and drought stress (10% PEG). Five rice varieties were used: Inpari 34, Ciherang, IR29 and Jeliteng. Research result showed that canopy height and fresh weight were the suitable selection character in drought tolerance screening through statis hydroponic cultivation. Grouping consistency was found between drought and salinity stress. Inpari 34, Ciherang, Jeliteng and Inpari 29 was considered to be have drought tolerance, whilst IR29 was examined to be responsive to drough stress in hydroponic culture. From the overall result, it can be concluded that hydroponic screening and PEG application was quite effective in rice drought stress tolerance screening

Role of Ascorbate and Ascorbate–Glutathione Cycle for Photosynthetic Protection in Selected Indigenous Rice Landraces Under Drought Stress

From precise drought tolerance screening of local rice landraces of Koraput, six rice landraces were identified as superior drought tolerant capacity in our earlier study. However, little information is available on their physiological response of redox regulation and photochemical activity under drought stress. The present work evaluates their redox regulations driven by ascorbate–glutathione cycle and photochemical activity of photosystem II under simulated drought stress by polyethylene glycol 6000. Leaf chlorophyll content, electron transport rate and effective quantum yield of PSII were significantly higher in studied indigenous rice genotypes in comparison with susceptible check variety under drought condition. Further, greater quantities of ascorbate and elevated levels of ascorbate–glutathione cycle enzyme activities were observed under drought treatment in studied indigenous rice genotypes in compared with susceptible IR64. The findings suggested that maintenance of better photochemical activity in studied rice genotypes under water-deficit condition may be due to improved redox regulation of ascorbate and efficient ascorbate regeneration pathways. This study thus shows a new light into drought stress response of indigenous rice of Koraput with global implications.

Root anatomy and nutrient uptake of the cattail Typha domingensis Pers. (Typhaceae) grown under drought condition

Typha domingensis is an invasive macrophyte which can be found even under low water levels. The objective of this study was to evaluate the root growth and anatomy as related to nutrient uptake and distribution of cattail under different water availabilities. Typha domingensis individuals were subjected to five water conditions: waterlogged, field capacity (FC), 75%FC and 50%FC. Nutrient contents of shoots and roots as well as the root growth and anatomy were evaluated. Lower water levels reduced root length (30%) and dry mass (90%) of cattail. Moderate drought increased aerenchyma development in root cortex but reduced the number and the diameter of xylem vessels in the vascular cylinder. Drought reduced the uptake of most nutrients; however, cattail promoted a higher translocation of macronutrients to shoot. Typha domingensis showed drought tolerance with modifications in root anatomy and higher nutrient translocation to shoots allowing its survival under mild water limitation.

Evaluation of blackgram (Vigna mungo) genotypes for drought tolerance under field and in vitro conditions

Blackgram a rainfed crop often experiences soil moisture deficit that reduces productivity to a large extent, could overcome by using a suitable drought resistant variety. Based on this, the present investigation was carried out during 2018 at Department of Genetics and Plant Breeding, Faculty of Agriculture, Annamalai University to study the drought tolerance in twenty-one blackgram genotypes. The selected genotypes (IC-343943, IC-343947, IC-343962, ABG-11013, KU-11680, TBG-104, VBG-10010, VBG-11011, VBG12005, VBG-12062, VBG-13017, ADT-5, RU-16-9, RU-16-13, RU-16-14, KGB-28, T-9, VBN(Bg)-4, VBN(Bg)-6, VBN(Bg)-7, MDU Local) were evaluated in the field condition for drought tolerance by imposing water stress during flowering and pod setting stages (4060 days after sowing) of the crop. The screening was also carried out in vitro by using PEG6000 at three concentrations viz., 0 bar, -3 bars and -6 bars to assess their seedling response under induced osmotic potential. Reduced growth was observed in all blackgram genotypes for all the characters except for the number of days to first flowering. Based on per se performance of genotypes under water-stressed field condition, the genotypes VBG12005, IC-343943 and IC-343947 were recommended as drought-tolerant genotypes for seed yield. In vitro condition, reduction in germination percentage, plumule and radicle length and biomass yield observed under increasing polyethylene glycol (PEG) induced water stress. In vitro screening of blackgram genotypes using PEG 6000 found that the genotypes VBG-11011, RU-16-9 and VBG-13017 expressed tolerance to drought at seed germination level. Thus, seedling stage screening for drought tolerance alone is not reliable as the tolerance mechanism may vary at different growth stages.

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The study was conducted to characterize early maturing sorghum genotypes under moisture stress and non-stress environments based on root angle. Phenotyping of 23 early maturing sorghum genotypes was carried out under post-flowering moisture stress and non-stressed environment using randomized complete block design (RCBD) in two replications at Werer Agricultural Research Center in 2018 off season. The genotypes were selected based on root angle data that varied from 13.0 to 26.75°. The analysis of variance revealed significant variation among genotypes for most of the traits. Post-flowering drought reduced grain yield by 21% and all the traits showed a reduction in value except flag leaf area. Grain yield showed positive correlations with seedling vigor, grain filling rate, thousand grain weight and panicle weight while negative correlations with number of fertile tiller and panicle exertion for both environments. Root angle revealed positive correlation with grain yield, grain filling rate and thousand grain weight while there was negative phenotypic correlation with panicle exertion in the stressed environment. Therefore, selection for high correlated traits could aid breeding program to develop genotypes with superior yield under both environments flag leaf area, chlorophyll content, harvest index and root angle traits could be used as morphological marker for drought tolerance screening in sorghum since there was positive correlation with yield observed for stressed environment only. The result revealed the importance of intermediate to slightly wider root angle for drought tolerance of early maturing sorghum genotypes by enhancing lateral water absorption of the roots under silty clay soil. Key words: Correlation, early maturing sorghum, morphological marker, post-flowering drought, root architecture, root traits.

Screening of Worldwide Barley Collection for Drought Tolerance: The Assessment of Various Physiological Measures as the Selection Criteria.

Drought is a devastating environmental constraint affecting the agronomic production of barley. To facilitate the breeding process, abundant germplasm resources and reliable evaluation systems to identify the true drought-tolerant barley genotypes are needed. In this study, 237 cultivated and 190 wild barley genotypes, originating from 28 countries, were screened for drought tolerance under the conditions of both water deficit and polyethylene glycol (PEG)-simulated drought at seedling stage. Drought stress significantly reduced the plant growth of all barley genotypes, but no significant difference in drought-induced reduction in the performance of barley seedlings was observed under these two drought conditions. Both cultivated and wild barley subspecies displayed considerable genotypic variability in drought tolerance, which underpinned the identification of 18 genotypes contrasting in drought tolerance. A comparative analysis of drought effects on biomass, water relation, photosynthesis, and osmotic adjustment was undertaken using these contrasting barley genotypes, in order to verify the reliability of the screening and to obtain the credible traits as screening criteria of drought tolerance in barley. As expected, the selected drought-tolerant genotypes showed much less reduction in shoot biomass than drought-sensitive ones under water deficit, which was significantly positively correlated with the results of large-scale screening, confirming the reliability of the screening for drought tolerance under two drought conditions in this study. Likewise, the traits of water relation, photosynthetic activity, and osmotic adjustment differed greatly between the contrasting genotypes under water deficit stress, and they were highly correlated to the growth of barley seedlings, suggesting the potential of them to be the selection criteria for drought tolerance. The analysis of the variable importance of these traits in drought tolerance indicated that sap osmolality and relative water content in the youngest fully-expanded leaf are the suitable selection criteria of screening for drought tolerance in barley at seedling stage.

Ectopic Expression of OsPYL/RCAR7, an ABA Receptor Having Low Signaling Activity, Improves Drought Tolerance without Growth Defects in Rice.

Overexpression of abscisic acid (ABA) receptors has been reported to enhance drought tolerance, but also to cause stunted growth and decreased crop yield. Here, we constructed transgenic rice for all monomeric ABA receptors and observed that only transgenic rice over-expressing OsPYL/RCAR7 showed similar phenotype with wild type, without total yield loss when grown under normal growth condition in a paddy field. Even though transgenic rice over-expressing OsPYL/RCAR7 showed neither an ABA-sensitivity nor an osmotic stress tolerance in plate assay, it showed drought tolerance. We investigated the ABA-dependent interaction with OsPP2CAs and ABA signaling induction by OsPYL/RCAR7. In yeast two hybrid assay, OsPYL/RCAR7 required critically higher ABA concentrations to interact with OsPP2CAs than other ABA receptors, and co-immunoprecipitation assay showed strong interaction under ABA treatment. When ABA-responsive signaling activity was monitored using a transient expression system in rice protoplasts, OsPYL/RCAR7 had the lowest ABA-responsive signaling activity as compared with other ABA receptors. OsPYL/RCAR7 also showed weak suppression of phosphatase activity as compared with other ABA receptors in vitro. Transcriptome analysis of transgenic rice over-expressing OsPYL/RCAR7 suggested that only a few genes were induced similar to control under without exogenous ABA, but a large number of genes was induced under ABA treatment compared with control. We conclude that OsPYL/RCAR7 is a novel functional ABA receptor that has low ABA signaling activity and exhibits high ABA dependence. These results lay the foundation for a new strategy to improve drought stress tolerance without compromising crop growth.

Study of Some Physiological Responses of Different Pomegranate (Punica Granatum L.) Cultivars under Drought Stress to Screen for Drought Tolerance

ABSTRACT Pomegranate (Punica granatum L.) is one of the most important Iranian horticultural products, which is usually cultivated in arid and semi-arid regions. Climate change has led to drought stress and it’s a threat to the agricultural products as well as pomegranate. This experiment was conducted on two-year-old rooted pomegranates of eight commercial cultivars namely ‘Malase Saveh’ (‘M-Saveh’), ‘Malase Isfahan’ (‘M-Isfahan’), ‘Robabe Ghermeze Shiraz’ (‘Robab’), ‘Gabrie Yazd’ (‘G-Yazd’), Gabrie Torshe Yazd’ (‘GT-Yazd’), ‘Zaghe Sefide Yazd’ (‘ZS-Yazd’), ‘Zaghe Torshe Yazd’ (‘ZT-Yazd’) and ‘Malase Torshe Pishva’ (‘M-Pishva’). Irrigation treatments were 50% of maximum allowable deficiency (without stress) and 80% of maximum allowable deficiency (stress). This research carried out as a factorial experiment based on randomized complete block design. Increased proline content was variable in pomegranate cultivars exposed to stress, so that, the highest increase was observed in the ‘M-Saveh’ with a 20.27% increase compared to the control treatment. ‘Robab’ showed the lowest increase in proline content. The highest increase in superoxide dismutase and peroxidase activity was 8.49 and 16.84%, respectively, in ‘ZS-Yazd’. The activity of superoxide dismutase in ‘Robab’, which was exposed to drought stress, decreased. This cultivar showed the highest electrolyte leakage with an average of 83.58%. The lowest electrolyte leakage was belonged to ‘ZS-Yazd’ (24.1%), and then ‘GT-Yazd’ (18.66%). Cluster analysis divided the genotypes into four main groups. ‘ZS-Yazd’ and ‘M-Saveh’ were in the same group. These two cultivars were more tolerant to drought stress than other cultivars in the physiological aspects.

Comparative Contribution of СО2/Н2О Exchange Components to the Process of Adaptation to Drought in Xero-Halophytes from the Family Chenopodiaceae with Different Types of Photosynthesis

Components of СО2/Н2О exchange (rates of apparent photosynthesis, transpiration, and dark respiration), as well as efficiency of photosystem I, growth rate, and proline content, were investigated in plants of the С3 species (Atriplex verrucifera M. Bieb), two populations of the С4 species (A. tatarica L.), and two populations of the intermediate С3–С4 species (Sedobassia sedoides (Pall.) Freitag & G. Kadereit), family Chenopodiaceae, in the course of adaptation to PEG-induced moderate osmotic stress (–0.4…–0.5 MPa). Two taken СО2 concentrations (400 and 200 ppm) enabled the examination of stomatal and metabolic contribution to the formation of the mechanisms of drought tolerance and estimate sensitivity of stomata. Under moderate water deficit, the С3 species showed drought tolerance and succulence and was notable for insensitive stomata. Examination of growth characteristics made it possible to reveal differences in productivity and tolerance between populations of the С4 and С3–С4 species. In spite of a different nature of carbon-concentrating mechanism (aspartate in С4 and photorespiratory in С3–С4), populations tolerant to water deficiency shared common features: less sensitive stomata and operation of the mechanism stabilizing water balance of the leaf cells probably due to proline and cyclic transport of electrons. Realization of such a strategy maintains coordination among parameters of СО2/Н2О exchange, which ensures a lower variability of dark respiration and a greater tolerance of plants to moderate osmotic stress. In nontolerant populations, adaptation mainly depends on stomatal closure, which probably results in upsetting the balance among parameters of СО2/Н2О exchange.

Screening for Drought Tolerance in Maize (Zea mays L.) Germplasm Using Germination and Seedling Traits under Simulated Drought Conditions.

Maize is known to be susceptible to drought stress, which negatively affects vegetative growth and biomass production, as well as the formation of reproductive organs and yield parameters. In this study, 27 responsive traits of germination (G) and seedlings growth were evaluated for 40 accessions of the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) germplasm collection, under no stress and simulated drought stress treatments by 10%, 15%, and 20% of polyethylene glycol (PEG). The three treatments significantly reduced G% and retarded seedlings growth, particularly the 15% and 20% PEG treatments; these two treatments also resulted in a significant increase of abnormal seedlings (AS). The heritability (H2) and correlations of the traits were estimated, and drought tolerance indices (DTIs) were calculated for traits and accessions. The H2 of G% values were reduced, and H2 for AS% increased as the PEG stress increased. Positive correlations were found between most trait pairs, particularly shoot and root traits, with 48 highly significant correlations under no stress and 25 highly significant correlations under the 10% PEG treatments, particularly for shoot and root traits. The medium to high heritability of shoot and root seedling traits provides a sound basis for further genetic analyses. PCA analysis clearly grouped accessions with high DTIs together and the accessions with low DTIs together, indicating that the DTI indicates the stress tolerance level of maize germplasm. However, the resemblance in DTI values does not clearly reflect the origin or taxonomic assignments to subspecies and varieties of the examined accessions.

Rapid method of screening for drought stress tolerance in maize (Zea mays L.)

Drought stress is the major production constraint in rainfed maize. Screening for drought tolerance is severely affected by the lack of a simple and reliable phenotyping technique. The objective of this study was to standardize a simple hydroponic based drought screening technique in maize. In this context, one week old uniform seedlings of 55 inbreds and 5 hybrids were transferred to hydroponic solution in the glass house. The seedlings were allowed to acclimatize for next one week in hydroponic solution. The drought stress was imposed by removing seedlings from nutrient solution and exposed to air for 6 and 4 hours daily for a period of 5 and 4 consecutive days in hybrids and inbreds, respectively. Data were recorded on all shoot and root parameters, and based on stress symptoms, a drought tolerance score was given to each genotype. The percent deductions in shoot and root fresh weight from non-stress to stress ranged from 11.7 to 84.4 and 2.1 to 77.5, respectively. Six inbred lines, namely, DQL790-4, CML334, CM140, CML422, CM125 and HKI488 and three hybrids namely DMRH1306, DMRH1410 and PMH4 were found drought tolerant. The effectiveness of this screening technique was compared and confirmed using pots screening as well as by expression profiling of key antioxidant genes (Sod2, Sod4, Sod9 and Apx1) playing role in drought stress tolerance. This phenotyping technique is very short, low cost and simple which can be utilized in preliminary drought screening for large set of maize germplasm and mapping populations.

Screening for drought tolerance in wheat genotypes by morphological and SSR markers

Drought stress has become a significant abiotic stress for wheat in Bangladesh. This study aimed to explore drought tolerance in Bangladeshi wheat based on morpho-physiological and molecular traits. Ten wheat genotypes selected based on the previous research were grown in pots under control (100% field capacity) and drought stress (30% field capacity), applied from third leaf stage till maturity. Drought stress affected the yield contributing characters and significantly reduced grain yield. Drought susceptibility index and drought tolerance efficiency were used as criteria for selection. Sonalika, Sourav, and BARI gom-28 were least affected and emerged as drought tolerant. Durum, Pavon-76, BARI gom-25, and BARI gom-33 were moderately tolerant, while BARI gom-24, BINA gom-1, and BARI gom-20 were susceptible as they were severely affected. Thirteen SSR markers linked to drought tolerance were used to characterize 26 wheat genotypes. A total of 73 alleles were detected with an average of 5.62 alleles per locus. Polymorphism information content (PIC) and Nei’s (Proc Natl Acad Sci USA 70:3321–3323; 1973) gene diversity were 0.69 and 0.73, respectively. The coefficient of genetic similarity matrix for all 325 pairs of genotypes ranged from 0.15 to 1.00 with an average of 0.57. Similarity indices-based cluster analysis separated 26 genotypes into different groups. Two tolerant genotypes, Sourav and Sonalika, and two moderately tolerant genotypes, Durum and Pavon-76, as identified by morphological study were grouped in cluster 1. These four genotypes, therefore, passed the screening for drought tolerance in molecular and morphological studies and are promising for cultivation in the drought-prone areas of Bangladesh.

Wilting index and root morphological characteristics used as drought-tolerance variety selection at the seedling stage in soybean (Glycine max L.)

Drought stress is a common issue that affects agriculture production. The soybean plant is one of the drought-sensitive crops that could lose the yield of up to 40% under severe drought years. Improvements in drought tolerance have been one of the main objectives of breeding programs in soybean. In this study, 62 soybeans [Glycine max (L.) Merri.] germplasms including landraces and elite cultivars were evaluated by analyzing canopy and root morphological characteristics at seedling stage under polyethylene glycol (2.5 M PEG 8000, − 0.54 MPa) simulated drought stress. The results showed that the wilting index of sixty-two soybean germplasms showed significant polymorphism differences after 4 days PEG treatment. The lowest wilting index was 2.75 in Tiefeng 31, while the largest reached 9 in Fengdou 93 and Songzidou. The wilting index was positively correlated with plant height, electrolyte leakage, and negatively correlated with a dry weight of the above-ground part, stomatal conductance, and transpiration rate by regression analysis. The root system architecture (RSA) study showed root-canopy ratio, root length, number of the lateral roots, root surface area, and root volume were significantly negatively correlated with the wilting index and positively correlated with the root volume. Based on these results, sixty-two soybean germplasms were comprehensively evaluated for drought-tolerant cultivar by the principal component analysis (PCA). The results showed that Tiefeng 31 was the most drought-tolerant elite cultivar. However, Fengdou 93 was the most drought-sensitive elite variety. The drought tolerance screening results were consistent with the wilting index and RSA analysis, especially the root length. Both droughts tolerant and sensitive elite cultivar could be further used to breed drought-tolerant germplasms and to clarify the drought tolerance mechanism in soybean.

Selection and screening of drought tolerant high yielding chickpea genotypes based on physio-biochemical indices and multi-environmental yield trials

BackgroundChickpea is one of the major legume crops being cultivated in the arid and semi-arid regions of Pakistan. It is mainly grown on the marginal areas where, terminal drought stress is one of the serious threats to its productivity. For defining the appropriate selection criteria for screening drought tolerant chickpea genotypes, present study was conducted. Distinct chickpea germplasm was collected from different pulses breeding institutes of Pakistan and evaluated for drought tolerance at germination and early seedling stages, furthermore, at late vegetative growth stages physiochemical traits and multi-environment yield performance were also tested.ResultsChickpea genotypes under different environments, were significantly varied for different seedling traits, physio-chemical attributes and seed yield. Genotypes showing drought tolerance by performing better at an early seedling stages were not correspondingly high yielding. Screening for drought tolerance on seed yield basis is the most appropriate trait to develop the drought tolerant as well as high yielding chickpea genotypes. Results confirmed that traits of early growth stages were not reflecting the drought tolerance at terminal growth stages and also did not confer high yielding. NIAB-rain fed environment proved ideal in nature to screen the chickpea genotypes whereas, NIAB-lysimeter and Kalur Kot was least effective for selecting genotypes with high seed yield. Genotypes D0091–10, K010–10, D0085–10, K005–10, D0078–10, 08AG016, 08AG004, D0080–10, 09AG002, K002–10 and D0099–10 were high yielding and drought tolerant based on their performance across multiple hotspot environments.ConclusionsThe selected genotypes are intended for further evaluation for varietal approval to recommend for general cultivation on farmer fields in drought hit areas of Pakistan. Among physio-biochemical traits, higher proline, glycine betain, RWC and CMS were reflecting the higher capability to tolerate the drought stress in chickpea. Drought sensitive genotypes (K0037–10, 2204, K0052–10, 09AG015, K0042–10, CM709/06, K0068–10, K004–10, K0026–10 and K0063–10) were also identified in present study which were resourceful asset for using as contrasting parents in hybridization programs. To our knowledge, this is first report using an integrated approach involving, physio-biochemical indices, and multi-environmental yield trials, for comparison, screening and selection of chickpea genotypes for drought tolerance.

Improved production of echinenone and canthaxanthin in transgenic Nostoc sp. PCC 7120 overexpressing a heterologous crtO gene from Nostoc flagelliforme

Echinenone and canthaxanthin are important carotenoid pigments with food and industrial applications. Biosynthesis of echinenone and/or canthaxanthin is catalyzed by β-carotene ketolase (CrtO), with β-carotene as the substrate. In this study, we generated transgenic Nostoc sp. PCC 7120 overexpressing a heterologous crtO gene from Nostoc flagelliforme and evaluated the productivity of both pigments. Normal (BG11 medium, 30 °C) and osmotic stress (BG11 medium supplemented with 0.4 M mannitol, 30 °C) conditions were used for cultivation. As compared to control strain, production of echinenone and canthaxanthin in transgenic strain were respectively increased by more than 16 % and 80 %, under either normal or osmotic stress conditions. Especially upon the stress condition, higher proportion of echinenone and canthaxanthin in total pigments was achieved, which should be beneficial for downstream separation and purification. In addition, transgenic strain showed drought tolerance and could revive from desiccation treatment after rewetting. Thus, this study provided technical clues for production of both pigments in engineered cyanobacteria as well as for cyanobacterial anhydrobiotic engineering.