Early Stages Of Seedling Growth Research Articles

Nanopriming with selenium doped carbon dots improved rapeseed germination and seedling salt tolerance

Soil salinity is a big environmental issue affecting crop production. Although seed nanopriming has been widely used to improve seed germination and seedling growth under salinity, our knowledge about the underlying mechanisms is still insufficient. Herein, we newly synthesized selenium-doped carbon dots nanoparticles coated with poly acrylic acid (poly acrylic acid coated selenium doped carbon dots, PAA@Se-CDs) and used it to prime seeds of rapeseeds. The TEM (transmission electron microscope) size and zeta potential of PAA@Se-CDs are 3.8 ± 0.2 nm and −30 mV, respectively. After 8 h priming, the PAA@Se-CDs nanoparticles were detected in the seed compartments (seed coat, cotyledon, and radicle), while no such signals were detected in the NNP (no nanoparticle control) group (SeO2 was used as the NNP). Nanopriming with PAA@Se-CDs nanoparticles increased rapeseeds germination (20%) and seedling fresh weight (161%) under saline conditions compared to NNP control. PAA@Se-CDs nanopriming significantly enhanced endo-β-mannanase activities (255% increase, 21.55 µmol h−1 g−1 vs. 6.06 µmol h−1 g−1, at DAS 1 (DAS, days after sowing)), total soluble sugar (33.63 mg g−1 FW (fresh weight) vs. 20.23 mg g−1 FW) and protein contents (1.96 µg g−1 FW vs. 1.0 µg g−1 FW) to support the growth of germinating seedlings of rapeseeds under salt stress, in comparison with NNP control. The respiration rate and ATP content were increased by 76% and 607%, respectively. The oxidative damage of salinity due to the over-accumulation of reactive oxygen species (ROS) was alleviated by PAA@Se-CDs nanopriming by increasing the antioxidant enzyme activities (SOD (superoxide dismutase), POD (peroxidase), and CAT (catalase)). Another mechanism behind PAA@Se-CDs nanopriming improving rapeseeds salt tolerance at seedling stage was reducing sodium (Na+) accumulation and improving potassium (K+) retention, hence increasing the K+/Na+ ratio under saline conditions. Overall, our results not only showed that seed nanopriming with PAA@Se-CDs could be a good approach to improve salt tolerance, but also add more knowledge to the mechanism behind nanopriming-improved plant salt tolerance at germination and early seedling growth stage.

Barnyardgrass (Echinochloa crus-galli) control and rice injury with labeled herbicides following exposure to sub-lethal concentrations of paraquat

Abstract Rice in Mississippi is often in early seedling growth stages when paraquat-based herbicide treatments are commonly applied to corn, cotton, and soybean; therefore, off-target movement onto adjacent rice fields may occur. After an off-target movement event has occurred, weed management in the rice crop is still necessary. Field studies were conducted from 2019 to 2021 in Stoneville, MS, to evaluate rice injury and barnyardgrass control with labeled herbicides after exposure to a sub-lethal paraquat concentration. Labeled herbicide treatments were recommended rates of imazethapyr, quinclorac, propanil, bispyribac-sodium, cyhalopfop, and florpyrauxifen-benzyl applied following rice exposure to a sub-lethal concentration of paraquat. Rice injury was detected 7 and 28 d after treatment (DAT) with injury ≥ 35 and 14%, respectively, following all labeled herbicides. Florpyrauxifen-benzyl and imazethapyr injured rice the greatest 28 DAT. Following paraquat exposure, barnyardgrass control was similar for all labeled herbicide treatments 7, 14, and 28 DAT except with florpyrauxifen-benzyl and no labeled herbicide (paraquat alone) 7 DAT. Across all evaluations, barnyardgrass control was at least 12% greater following paraquat exposure and labeled herbicide treatments than with no paraquat exposure. The current research demonstrates that labeled herbicides applied following exposure to a sub-lethal concentration of paraquat resulted in <36% injury and provided as great as 95% control of barnyardgrass, depending on the herbicide treatment. Therefore, the labeled herbicides choice following rice exposure to a sub-lethal concentration of paraquat should be based on weed spectrum.

Evaluation of Upland Rice Response to Water Stress Using Polyethylene Glycol (PEG -6000) at Germination and Early Seedling Stage

Water stress is one of the most important crop growth limiting factors which leads to low crop productivity and yield instability. Water stress affects crop growth and development, especially during the germination and seedling period. The experiment was conducted in the growth chamber at the seed physiology laboratory of the Department of Seed, Crop and Horticultural Sciences, University of Eldoret to evaluate sixteen upland rice varieties to water stress tolerance at germination and early seedling growth stage. These varieties were tested against four levels of water stress imposed by Polyethylene glycol 6000 (PEG - 6000) at 0%, 5%,10% and 15% concentration. The lay out of the experiment was complete randomized design (CRD) with three replications. Osmotic stress induced by PEG levels significantly (P<.001) reduced plant growth parameters. The result showed that the germination percentage, germination index, Relative seedling height (%), seedling dry weight, Seedling fresh weight, Seedling length, seedling vigor index and mean germination time of all tested rice varieties were found decreasing trends with increasing the levels of PEG from 0 to 15% concentration levels. Among all the sixteen varieties, NERICA rice varieties followed by MWUR, White rice, Kpatawee, and Komboka had an outstanding performed in terms of germination percentage, germination index, seedling height, seedling dry weight, root length and relative dry weight under water induced stress by using PEG concentration levels compared to other varieties. Therefore, these varieties could be useful in breeding programs and can be cultivated in arid and semi-arid environment or where water shortage is a regular constraint.

The sensitivity of radish cultivars to high temperatures during germination and seedling growth stages

A laboratory experiment was conducted at constant temperatures of 20, 23, 26, 29, 32, 35, 38, and 41℃ to identify the response of six radish cultivars with different root sizes and colors to high-temperature stress during germination, emergence, and early seedling growth stage. Also, the optimal temperature was determined by calculating the relationship between seedling length and temperature via a polynomial regression model. The results showed that no seed germination was detected at 41℃, while emergence and seedling growth were not observed at 38℃ and above. Similar germination percentages, mean germination time, and germination index were obtained between 20℃ and 35℃. The root length reduced at 32℃ and it was more sensitive to high temperatures than shoots because the root/shoot length ratio showed a decreasing trend by increasing temperatures and longer root length was recorded at lower temperatures than 32℃. There were genotypic variations among radish cultivars for temperatures and ‘Kırmızı İnci’, ‘Beyaz İnci’, and ‘Siyah İnci’ produced a better performance than the others under high temperatures. The regression analysis predicted the optimal temperatures as 21.5℃ and 22.6℃ for root and shoot length, respectively. This study indicates that high temperatures inhibited seedling growth rather than seed germination performance of radishes.

AtTLP2, a Tubby-like protein, plays intricate roles in abiotic stress signalling.

The Arabidopsis Tubby-like protein (TLP) encoding gene, AtTLP2, plays intricate roles during ABA-dependent abiotic stress signalling, particularly salt and dehydration stress responses. TLPs (Tubby-like proteins) are a small group of eukaryotic proteins characterized by the presence of a Tubby domain. The plant TLPs have been widely shown to play important roles during abiotic stress signaling. In this study, we investigated the role of an Arabidopsis TLP, AtTLP2, in mediating abiotic stress responses. Both attlp2 null mutant and overexpression (OE) lines, in Arabidopsis, were studied which indicated the role of the gene also in development. The attlp2 mutant showed an overall dwarfism, while its overexpression caused enhanced growth. AtTLP2 localized to the plasma membrane (PM) and showed nuclear translocation in response to dehydration stress. The protein interacted with ASK1 and ASK2, but failed to show transactivation activity in yeast. AtTLP2 was transcriptionally induced by stress, caused by salt, dehydration and ABA. The attlp2 mutant was insensitive to ABA, but hypersensitive to oxidative stress at all stages of growth. ABA insensitivity conferred tolerance to salt and osmotic stresses at the germination and early seedling growth stages, but caused hypersensitivity to salt and drought stresses at advanced stages of growth. The OE lines were more sensitive to ABA, causing increased sensitivity to most stresses at the seed germination stage, but conferring tolerance to salt and osmotic stresses at more advanced stages of development. The stomata of the attlp2 mutant were less responsive to ABA and H2O2, while that of the OE lines exhibited greater sensitivity. Several ABA-regulated stress responsive marker genes were found to be downregulated in the mutant, but upregulated in the OE lines. The study establishes that AtTLP2 plays intricate roles in abiotic stress signaling, and the response may be largely ABA dependent.

Seed Germination and Early Seedling Growth Responses to Drought Stress in Annual Medicago L. and Trifolium L. Forages

Climate change in the Mediterranean-like regions of South Africa has resulted in increased rainfall variability, a delayed start to the wet winter season, and increased occurrences of out-of-season summer rainfall events. These changes in bioclimatic conditions are predicted to become more pronounced and, therefore, could result in poor seedling establishment and false breaks from the soil seed bank, followed by seedling desiccation in annual medic and clover pastures. This study therefore aimed to quantify and compare the responses of three annual Medicago species and five annual Trifolium species to drought stress imposed at the seed germination, seedling establishment, and early seedling growth stages. Three separate controlled trials were conducted. Firstly, the seeds were germinated in seed germination chambers at constant temperatures ranging from 5 to 30 °C, in 5 °C increments, with five osmotic treatments within each temperature, and germination was recorded daily. For the second experiment, seeds were planted at 100, 70, 50, and 30% of the soil’s moisture-holding capacity without subsequent watering, and emergence was recorded daily. For the third experiment, one-month-old seedlings were subjected to two water-limitation periods (15 or 30 days), and their subsequent morphological responses were measured. The results from these experiments indicated that the species differed significantly in their responses to drought, and the best-performing species often differed when drought was imposed at different development stages. Five species—M. polymorpha L., M. truncatula Gaertn., T. alexandrinum L., T. vesiculosum Savi., and T. subterraneum L. ssp. subterraneum—were able to tolerate incidences of drought better than other species and, thus, should be prioritized for further research into the variation in drought tolerance between cultivars within these species.

Response of sugar metabolism in the cotyledons and roots of Ricinus communis subjected to salt stress.

Ricinus communis is an important oilseed crop worldwide and is also considered one of the best potential plants for salt-affected soil improvement in northeast China. However, little is known about photosynthesis and carbohydrate metabolism in this plant, nor the distribution of carbohydrates in cotyledons and roots under salinity stress. In the present study, seedling growth, gas exchange parameters (PN , E, gs and Ci ), carbohydrate (fructose, sucrose, glucose, soluble sugar and starch) metabolism and related enzymes and genes were measured in Ricinus plants. Under salt stress, PN of cotyledons decreased significantly (P< 0.05), resulting in weak photosynthetic capacity. Furthermore, salt stress increased sucrose and glucose content in cotyledons, but decreased soluble sugar and starch content. However, sucrose increased and starch decreased in roots. This may be correlated with the increasing sugar metabolism under salinity, including notable changes in sugar-related enzyme activities (SPS, SuSy, α-amylase and β-amylase) and gene expression of RcINV, RcSUS, RcAmY, RcBAM and RcGBE1. The results suggest that salinity reduces photosynthesis of cotyledons, alters carbohydrate allocation between cotyledons and roots and also promotes starch utilization in cotyledons and starch biosynthesis in roots, leading to a functional imbalance between cotyledons and roots. Together, these findings provide insights into the crucial role of sugar metabolism in improving salt-tolerance of Ricinus during the early seedling growth stage.

Improved drought tolerance of EMS mutagenized Alfalfa (Medicago sativa L.) mutants by in vitro screening at germination stage

The objectives of this study were to determine drought tolerant novel mutant of alfalfa (Medicago sativa L.) genotypes by screening EMS mutagenized 340675 M3 seeds at germination stages in the presence of osmotic stress of 35% PEG6000. Root growth assay provided several drought tolerant candidate mutants. Of those, 4 mutants were further evaluated at water deficit conditions applied for 24 days after the first cutting at flowering bud stage. The results revealed that mutants determined as drought tolerant at germination stage were also tolerant to water deficit conditions. Protein content and superoxide dismutase values were found to be higher in all mutants than controls. Ascorbate peroxides, glutton reductase and lipid peroxidase values varied based on the mutant genotype and duration of drought stress. Drought stress significantly changed transcriptional levels of MtP5CS, MtDehyd, MseIF-2, MtRD2 and MsNAC genes. These results indicated that in vitro screening of alfalfa mutant seeds for osmatic tolerance at germination and early seedling growth stages was successfully able to determine the drought tolerant alfalfa mutants which were also tolerant to water deficit conditions after the first cutting at flowering bud stage.

EFFECTS OF MELATONIN ON PHYSIO-BIOCHEMICAL AND IONIC STRESS MARKERS IN MAIZE AT SEEDLING STAGE UNDER SALT STRESS

Oxidative stress due to salinity creates a challenging situation for seed germination and early seedling establishment in maize. Over than normal production of reactive oxygen species (ROS) leaves cataclysmic effects on the physiology of plants when subjected to saline environment. Melatonin is versatile stress mitigating organic molecule reported to have significant potential for scavenging ROS. The present study was conducted with the aim to study the effects of different concentrations of melatonin viz., control, 500, 1000 &amp; 1500 µM on the physiological and bio-chemical stress markers in the six maize genotypes viz., MMRI-Yellow, NCEV-1530-9, YH-1898, Composite, SB-9617 and FH-949.The study was planned in sand culture (pot study) using CRD with factorial arrangement. The results of the present study demonstrated that melatonin priming in all the concentrations viz., 500,1000 and 1500µM significantly enhanced the germination percentage (by 14.0 , 25.0 and 27 %), chlorophyll a (23.3, 43.3 &amp; 40.0 %), chlorophyll b contents (by 29.2, 50.0 &amp; 50.0 %), total soluble sugar-TSS (by 20.0, 31.5 &amp; 40.4 %), total soluble protein-TSP (by 10.0, 15.5 &amp; 20.5%), chlorophyll stability index-CSI (by 15.0, 20.3 &amp; 25.6%), membrane stability index-MSI (13.3, 25.7 &amp; 26.6%), relative water contents-RWC (13.7, 23.3 &amp; 24.0%), phenolic contents-TP (14.8, 24.3 &amp; 26.8 %), proline contents-Pro (23.0, 35.2 &amp; 37.7%), superoxide dismutase-SOD (by 25.5, 41.0 &amp; 45.0 %), per-oxidase-POD (by 17.8, 25.1 &amp; 24.7%), catalase-CAT (by 37.7, 51.5 &amp; 54.3%) and reduced concentrations of H2O2 (by19.3, 26.5 &amp; 30.1 %), malondialdehyde-MDA contents (by 15.1, 22.4 &amp; 22.3%) and electrolyte leakage-EL (by 12.4, 18.0 &amp; 16.5 %), compared to un-primed seed treatment. Interestingly the higher concentrations of melatonin were statistically produced the same effects. The genotype SB-9617outperformed, with respect to higher accumulation of photo-pigments, TSS, TSP and TP with improved of membrane stability, relative water contents and enhanced activities of the anti-oxidant enzymes (SOD, POD and CAT) showed reduced lipid per-oxidation and electrolyte. In PCA-bi-plot, PC1 and PC2 contributed maximally i.e. 90.9 and 3.7% to explain the total variations i.e 94.6 %. Additionally, SB-9617 with melatonin priming@ 1000µM proved the best to mitigate adverse effects of salt stress at germination and early seedling growth stage via cross taking with physiological and bio-chemical stress markers.

Assessment of safflower genotypes for individual and combined effects of drought and salinity stress at early seedling growth stages

Safflower is a highly valued oilseed crop. Safflower oil is a source of monounsaturated and polyunsaturated fatty acids which are important for a plurality of industries including the edible vegetable oil industry. Safflower is highly resistant to salinity and drought stress, which impede seed germination. Two safflower cultivars and 4 lines were screened against nine levels of osmotic stress treatments (using NaCl0 and PEG 60000 (control), NaCl-0.2, NaCl-0.4, PEG 6000-0.2, PEG 6000-0.4, PEG 6000-0.2+NaCl-0.2, PEG 6000-0.2+NaCl-0.4, PEG 6000-0.4+NaCl-0.2, PEG 6000-0.4+NaCl-0.4 MPa) for 8 days at seed germination stage. The osmotic stress was observed to induce a negative effect on the percentage of seed germination, shoot length, root length, root/shoot length ratio, fresh and dry weights of seedlings as well as on germination, and seedling vigor index. Lines and varieties significantly differed for respective and combined effects of stress treatments at early seedling growth stages. These results demonstrated that the respective effects of PEG 6000 and NaCl on safflower genotypes seedlings were less detrimental than the combined effects. Despite safflower varieties and lines were observed to be affected differently by individual and combined stresses, cv. Dinçer, lines G?8, and G?6 showed a tolerance response to the studied conditions. Significant positive correlations were identified between shoot length and germination percentage (r = 0.91*), and root length (r = 0.98**). A significant correlation was observed between seedling dry weight and root length (r = 0.94**), shoot length (r = 0.91*), and seedling fresh weight (r = 0.97**). Similarly, significant correlation coefficients were noted between seedling fresh weight and root length (r = 0.90*), and shoot length (r = 0.87*). Cv. Dinçer, lines G-8, and G-6 were determined to be significantly tolerant against salinity, drought, and combined stresses for the studied traits using principal component analysis. According to these findings, effects individually produced by salinity and drought on seedlings of safflower are less damaging to plant development when compared to the combined effects of said two stresses. This study emphasized the importance of monitoring the genotypes of safflower for salt and drought stress tolerances in breeding programs.

Contrasting effects of soil pH on seed germination and early seedling growth of Calobota sericea and Lessertia frutescens subs. frutescens

This study evaluated the impacts of pH on the germination and early seedling growth of Calobota sericea and Lessertia frutescens subsp. frutescens, two perennial legume species found in the semi-arid rangelands of South Africa. The results of this study revealed that L. frutescens had higher seed germination under more acidic conditions, while C. sericea had higher seed germination under alkaline conditions. Similarly, L. frutescens seedlings were found to be larger under more acidic conditions, while C. sericea seedlings were larger under more alkaline conditions. Both species were able to germinate under all of the pH treatments, suggesting that they are adapted to a wide range of pH conditions, at least at the germination and early seedling growth stage.

English

Salinity stress is one of the leading abiotic stresses seriously affecting the crop productivity across the world. Early growth stages are more affected by salinity stress than terminal growth stages. Therefore, maize genotypes were evaluated for their performance in three different studies (Experiment-1: irrigation of seeds with salt solutions (distilled water, 4 dS/m, 6 dS/m and 10 dS/m) for 5 days, Experiment-2: application of different salinity treatments (distilled water, 4 dS/m, 6 dS/m and 10 dS/m) for 20 days from sowing to seedling emergence stage, Experiment-3: application of salinity stresses in hydroponic culture under four above mentioned different salinity treatments. Time to start germination (TSG), time to 50% germination (TFG) and final germination percentage (FGP) of the maize genotypes was reduced by salinity stress. Radicle length, plumule length, root and shoot length and fresh weight and chlorophyll contents were also linearly reduced in maize genotypes by increasing salinity levels. Moreover, sodium (Na+) concentration was increased in seeds and seedlings of maize genotypes whereas; potassium (K+) concentration was reduced with gradual rise in salinity levels. Principal Component Analysis (PCA) biplots facilitated the efficient assortment of susceptible, moderately susceptible, moderately tolerant and tolerant maize genotypes for each of the three studies separately. Genotype „YS-2008‟ was susceptible for seed treatment and hydroponic studies whereas, genotype „T267-5‟ was susceptible for early seedling and hydroponic studies. Genotype „C864-284‟ was tolerant in early seedling and hydroponic studies. The GGE biplot analysis indicated that „YS-2008‟ genotype was susceptible for salinity stress. Under hydroponic conditions, genotypes could effectively be discriminated by the imposition of severe salt stress (10 dS/m); however, under seed treatments and early seedling growth stages, mild stress treatments (4 dS/m) were sufficient enough to discriminate the maize genotypes. Hydroponic evaluation of genotypes is suitable and preferable under high stress conditions at early growth stages. Identified tolerant and susceptible genotypes could be effectively used in different breeding programs to develop salt tolerant new cultivars for commercial purposes. © 2021 Friends Science Publishers

First Report of Sesame Mutants Tolerant to Severe Drought Stress during Germination and Early Seedling Growth Stages.

In the context of climate change and water scarcity, there is a need to develop and use drought-tolerant sesame cultivars. This study was conducted to evaluate the response of 13 sesame genotypes, including 11 mutants and their wild-types, to drought during germination and early seedling growth. Moderate and severe drought stress was simulated by applying polyethylene glycol (PEG) at two osmotic potentials, −0.6 MPa and −1.2 MPa, respectively, on seeds of two successive mutant generations, M2 and M3. The parameters measured or calculated were germination percentage (GP), germination rate (GR), mean germination time (MGT), root length (RL), shoot length (SL), root to shoot ratio (RSR), and the seedling vigor index (SVI). Results showed the significant effect of genotype, drought, and drought × genotype interaction on all parameters investigated. Under severe drought, seeds of seven genotypes, including wild types, were not able to germinate. There was a drastic decline of all parameters for the rest, except MGT and RSR, which markedly increased. Interestingly, two mutants, “ML2-5” and “ML2-10”, were identified as the most tolerant to severe drought and the most stable over both generations. The present work is the first report of sesame germplasm with such a high level of tolerance to drought during germination and early seedling growth stages.

Morphological, physiological and biochemical aspects of zinc seed priming-induced drought tolerance in faba bean

Faba bean (Vicia faba L.) productivity is limited by drought stress and is often associated with mineral nutrient deficiencies such as zinc (Zn). Three independent experiments were conducted to optimize Zn application and its role in tolerance against drought in faba bean. In the first experiment, faba bean seeds soaked in aerated 0.001, 0.01, 0.05, 0.1 and 0.5 M Zn solutions (osmopriming) or water (hydropriming) for 12 h were sown in Petri plates in a growth chamber. Based on the results, in the second and third experiments, faba bean seeds were subjected to osmopriming with 0.001 M Zn solution and hydropriming followed by surface drying and re-drying of seed to the original weight. In third experiment, treated faba bean seeds were planted in peat moss-filled pots maintained at 75 % water holding capacity (WHC) (well-watered) or 50 % WHC (drought stress). In the first study, seeds primed with high Zn concentration (≥ 0.01 M Zn) did not germinate. Drought stress suppressed the seedling emergence, growth with enhanced oxidative stress. However, seed priming with 0.001 M Zn solution followed by surface drying ameliorated the adverse effect of drought stress by increasing the biomass production (99.8 %), leaf area (23 %), α amylase activity (85 %), soluble sugar (54.7 %), Soil Plant Analysis Development (SPAD) value (48.7 %), leaf Zn concentration (79.8 %) with reduction in leaf malondialdehyde (42.7 %) content and total antioxidant activities (35.2 %) under drought stress compared to untreated control. Conclusively, adequate Zn supply through seed priming can help in ameliorating the adverse effect of drought stress in faba bean during the early seedling growth stage.

Changes in plant growth, leaf relative water content and physiological traits in response to salt stress in peanut (Arachis hypogaea L.) varieties

Salinity is the main environmental factor accountable for decreasing crop productivity worldwide. The effects of NaCl salinity on plant growth (leaf relative water content (RWC), leaf dry weight (LDW), shoot length (SL), number of leaves (NL), number of branches (NB) and total leaf area (TLA) and physiological characteristics (stomatal conductance (gs), transpiration rate (TR), net photosynthetic (Pn), yield of photosystem II (ΦPsII) and the intercellular CO2 concentration (CO2int) in peanut (Arachis hypogaea L.) varieties (‘Vanda’, ‘P244601’ and ‘Pl184948’, widely used in Cameroon, Tanzania and Ghana, respectively, were investigated under hydroponic condition. Plants were subjected to four levels of NaCl (0, 40, 80 and 120 mM) at early seedling growth stage of plant development. Application of NaCl treatment led to a significant decrease in LDW, SL, NL, TLA, Pn, gs, TR and CO2int concentration of ‘Vanda’ and ‘P244601’ compared to untreated plants while the plant growth inhibition was notably noted at 120 mM NaCl in ‘P1184948’ for LDW, SL and NB. The highest depressive effect was detected in gs of salt-sensitive ‘Vanda’ while the lowest were recorded in gs of salt-tolerant ‘P1184948’ at high salinity level. Enhanced NaCl concentrations led to a significant increase in ΦPSII of ‘P1184948’ compared to ‘Vanda’, ‘P244601’ and untreated plants. Leaf CHL content was significantly increased in moderately-tolerant ‘‘P244601’ and salt-tolerant ‘P1184948’ at 80 mM NaCl compared to salt sensitive ‘Vanda’ and untreated plants. The depressive effect of salt on RWC was recorded at 120 mM NaCl in peanut leaves of all varieties. Under salt stress ‘P1184948’ was observed to have relatively higher tolerance on average of all growth and physiological traits than ‘Vanda’ and P244601’ suggesting that it could be grown in salt-affected soils.

A Gnotobiotic Model to Examine Plant and Microbiome Contributions to Survival under Arsenic Stress.

So far, the relative importance of the plant and its microbiome in the development of early stages of plant seedling growth under arsenic stress has not been studied. To test the role of endophytic bacteria in increasing plant success under arsenic stress, gnotobiotic seeds of J. montana were inoculated with two endophytic bacteria: Pantoea conspicua MC-K1 (PGPB and As resistant bacteria) and Arthrobacter sp. MC-D3A (non-helper and non-As resistant bacteria) and an endobacteria mixture. In holobiotic seedlings (with seed-vectored microbes intact), neither the capacity of germination nor development of roots and lateral hairs was affected at 125 μM As(V). However, in gnotobiotic seedlings, the plants are negatively impacted by absence of a microbiome and presence of arsenic, resulting in reduced growth of roots and root hairs. The inoculation of a single PGPB (P. conspicua-MCK1) shows a tendency to the recovery of the plant, both in arsenic enriched and arsenic-free media, while the inoculation with Arthrobacter sp. does not help in the recovery of the plants. Inoculation with a bacterial mixture allows recovery of plants in arsenic free media; however, plants did not recover under arsenic stress, probably because of a bacterial interaction in the mixture.

Assessment of Barley Genotypes Response to Salinity Stress at Early Seedling Growth Stage

This study was performed to assess several indices for identifying barley genotypes at early growth stage with the best performance in salinity conditions. The effect of salinity treatments was studied through an analysis of the dry matter production, results showed significant differences among genotypes. The majority of used tolerance indices indicated that ESBYTM8910, 4 Shori and MBS8715 were the best barley genotypes showing the highest stress resistance for the greatest NaCl concentration. It is based on used stability parameters that the genotypes MBS8712 and Jo torsh were the most phenotypically stable. In general, the tolerant genotypes showed the least stability based on mostly of stability parameters&#x0D;

Seed germination and early seedling growth of six wetland plant species in saline-alkaline environment

This study focused on the effect of saline and alkaline stress on six typical wetland plant species during seed germination and early seedling growth stages. Based on the indicators of germination, seedling growth and ionic absorption in seedlings, relatively saline and alkaline tolerant plant species were selected and tolerance mechanism was discussed. Results showed that the existence of saline and alkaline stress inhibited the capacity of germination and early seedling growth of most tested plant species to varying degrees, therein effects of saline-alkaline stress were greater than saline stress. Based on the results of principal component analysis (PCA), germination percentage, K+ content, plant height, Na+ content and Na+/K+ ratios can be selected as representative indicators for saline and alkaline tolerance evaluation during seed germination and early seedling growth stages. Among tested species, Juncus effusus and Vetiveria zizanioides exhibited relatively higher saline and alkaline tolerant capacity during their seed germination and early seedling growth. Additionally, both species increase K+ accumulation and retain lower Na+/K+ ratios, which might be their tolerance mechanisms at ion level. In conclusion, V. zizaniodes and J. effusus were recommended as potential plant species for restoring degraded saline-alkaline wetlands and/or establishing constructed wetlands for treating saline wastewater.

Identification of main-effect quantitative trait loci (QTLs) for low-temperature stress tolerance germination- and early seedling vigor-related traits in rice (Oryza sativa L.)

An attempt was made in the current study to identify the main-effect and co-localized quantitative trait loci (QTLs) for germination and early seedling growth traits under low-temperature stress (LTS) conditions in rice. The plant material used in this study was an early backcross population of 230 introgression lines (ILs) in BCIF7 generation derived from the Weed Tolerant Rice-1 (WTR-1) (as the recipient) and Haoannong (HNG) (as the donor). Genetic analyses of LTS tolerance revealed a total of 27 main-effect quantitative trait loci (M-QTLs) mapped on 12 chromosomes. These QTLs explained more than 10% of phenotypic variance (PV), and average PV of 12.71% while employing 704 high-quality SNP markers. Of these 27 QTLs distributed on 12 chromosomes, 11 were associated with low-temperature germination (LTG), nine with low-temperature germination stress index (LTGS), five with root length stress index (RLSI), and two with biomass stress index (BMSI) QTLs, shoot length stress index (SLSI) and root length stress index (RLSI), seven with seed vigor index (SVI), and single QTL with root length (RL). Among them, five significant major QTLs (qLTG(I)1, qLTGS(I)1–2, qLTG(I)5, qLTGS(I)5, and qLTG(I)7) mapped on chromosomes 1, 5, and 7 were associated with LTG and LTGS traits and the PV explained ranged from 16 to 23.3%. The genomic regions of these QTLs were co-localized with two to six QTLs. Most of the QTLs were growth stage-specific and found to harbor QTLs governing multiple traits. Eight chromosomes had more than four QTLs and were clustered together and designated as promising LTS tolerance QTLs (qLTTs), as qLTT1, qLTT2, qLTT3, qLTT5, qLTT6, qLTT8, qLTT9, and qLTT11. A total of 16 putative candidate genes were identified in the major M-QTLs and co-localized QTL regions distributed on different chromosomes. Overall, these significant genomic regions of M-QTLs are responsible for multiple traits and this suggested that these could serve as the best predictors of LTS tolerance at germination and early seedling growth stages. Furthermore, it is necessary to fine-map these regions and to find functional markers for marker-assisted selection in rice breeding programs for cold tolerance.

Maize WRKY114 gene negatively regulates salt-stress tolerance in transgenic rice.

Overexpression in rice of the isolated salt-responsive WRKY114 gene from maize resulted in decreases in both salt-stress tolerance and abscisic acid sensitivity by regulating stress- and abscisic acid-related gene expression. WRKYs are an important family of transcription factors that widely participate in plant development, defense regulation and stress responses. In this research, WRKY114 encoding a WRKY transcription factor was cloned from maize (Zea mays L.). ZmWRKY114 expression was down-regulated by salt stress but up-regulated by abscisic acid (ABA) treatments. ZmWRKY114 is a nuclear protein with no transcriptional activation ability in yeast. A yeast one-hybrid experiment confirmed that ZmWRKY114 possesses an ability to specifically bind to W-boxes. The heterologous overexpression of ZmWRKY114 in rice enhanced the salt-stress sensitivity as indicated by the transgenic plants having reduced heights, root lengths and survival rates under salt-stress conditions. In addition, transgenic plants also retained lower proline contents, but greater malondialdehyde contents and relative electrical leakage levels. Additionally, ZmWRKY114-overexpressing plants showed less sensitivity to ABA during the early seedling growth stage. Further analyses indicated that transgenic rice accumulated higher levels of ABA than wild-type plants under salt-stress conditions. Transcriptome and quantitative real-time PCR analyses indicated that a few regulatory genes, which play vital roles in controlling plant stress responses and/or the ABA signaling pathway, were affected by ZmWRKY114 overexpression when rice was treated with NaCl. Thus, ZmWRKY114 may function as a negative factor that participates in salt-stress responses through an ABA-mediated pathway.