Soybean Seedlings Research Articles

SNP application improves drought tolerance in soybean

As an important bioactive molecule, nitric oxide (NO) can effectively alleviate the effects of drought stress on crops. However, it is still unclear whether it can increase the stress resistance of soybean. Therefore, in this study, our objective was to explore the effect of exogenous NO application on the physiological characteristics of soybean seedlings under drought stress. As test material, two soybean varieties, HN65 and HN44, were used, while sodium nitroprusside (SNP) of 100 μmol L−1, 200 μmol L−1, 500 μmol L−1, 1000 μmol L−1 served as an exogenous NO donor, and PEG-6000 as an osmotic regulator to simulate drought stress. The effects of irrigation with different SNP concentrations for different days on the physiological characteristics of the soybean seedlings under drought conditions were then investigated. The results obtained showed that the activities of antioxidant enzymes, osmotic regulator contents, as well as the abscisic acid and salicylic acid contents of the plant leaves increased with increasing SNP concentration and treatment time. However, we observed that excessively high SNP concentrations decreased the activities of key nitrogen metabolism enzymes significantly. This study provides a theoretical basis for determining a suitable exogenous NO concentration and application duration. It also highlights strategies for exploring the mechanism by which exogenous NO regulates crop drought resistance.

Exogenous melatonin mitigates saline-alkali stress by decreasing DNA oxidative damage and enhancing photosynthetic carbon metabolism in soybean (Glycine max [L.] Merr.) leaves.

Saline-alkali stress (SS) is a common abiotic stress affecting crop cultivation worldwide, seriously inhibiting plant growth and biomass accumulation. Melatonin has been proven to relieve the inhibition of multiple abiotic stresses on plant growth. Therefore, soybean cultivars Heihe 49 (HH49, SS-tolerant) and Henong 95 (HN95, SS-sensitive) were pot-cultured in SS soil and then treated with 300 μM melatonin at the V1 stage, when the first trifoliate leaves were fully unfolded, to investigate if melatonin has an effect on SS. SS increased reactive oxygen species (ROS) accumulation in soybean leaves and thereby induced DNA oxidative damage. In addition, SS retarded cell growth and decreased the mesophyll cell size, chloroplast number, photosynthetic pigment content, which further reduced the light energy capture and electron transport rate in soybean leaves, and affected carbohydrate accumulation and metabolism. However, melatonin treatment reduced SS-induced ROS accumulation in the soybean leaves by increasing antioxidant content and oxidase activity. Effective removal of ROS reduced SS-induced DNA oxidative damage in the soybean leaf genome, which was represented by decreased random-amplified polymorphic DNA polymorphism, 8-hydroxy-20-deoxyguanine content, and relative density of apurinic/apyrimidinic-sites. Melatonin treatment also increased the volume of mesophyll cells, the numbers of chloroplast and starch grains, the contents of chlorophyll a and b and carotenoids in soybean seedling leaves treated with SS, thereby increasing the efficiency of effective light capture and electron transfer and improving photosynthesis. Subsequently, carbohydrate accumulation and metabolism in soybean leaves under SS were improved by melatonin treatment, which contributes to providing basic substances and energy for cell growth and metabolism, ultimately improving soybean SS tolerance.

First report of Fusarium falciformecausing root rot of soybean (Glycine max L.) in Henan, China.

Soybean (Glycine max L.) is an important crop in China owing to its high oil and protein content, with approximately 9.88 million ha of production in 2020. In September 2021, soybean plants showing wilting, root necrosis, and brown discoloration were observed, with an average incidence of approximately 36% in seven fields in Yongcheng City and Shangqiu City, Henan, China. Fungi were isolated from small pieces of symptomatic root tissues after being surface-sterilized (70% ethanol for 50 s followed by 3% NaClO for 1.0 min), rinsed three times in sterile distilled water, and then placed on PDA and incubated at 25℃ for 5 days in the dark. Single-spore cultures of twenty isolates were obtained by dilution plating(Leslie and Summerell 2006), and then were cultured on carnation leaf agar at 25℃ for 14 days. Macroconidia were mostly 3-septate, hyaline, falcate, with slightly curved apexes, with well-developed foot cells and blunt apical cells, and measured 29.3 to 45.0 (average 34.7) μm × 4.6 to 8.0 (average 6.0) μm. Microconidia were one to two celled, hyaline, and measured 11.9 to 29.0 (average 20.1) μm × 3.9 to 7.6 (average 5.7) μm. These morphological characteristics were consistent with previous descriptions ofthe Fusarium solani species complex (FSSC)(Leslie and Summerell 2006; Summerell et al. 2003). Partial sequences of translation elongation factor-1α (TEF) and RNA polymerase II subunit (RPB2) gene were PCR amplified using region specific primers as described by O'Donnell et al. (2008). The nucleotide sequences obtained from twenty isolates were deposited in GenBank with accession numbers of ON375405-ON375423, ON697187 (TEF) and ON331917-ON331936 (RPB2). Phylogenetic analysis revealed the isolates were nested within F. falciforme based on the DNA sequences of the above two genes (Chitrampalam and Nelson 2016). Pathogenicity tests of two representative isolates (21BeanYC3-3 and 21BeanYC7-5) were performed on two-week-old healthy soybean seedlings (cv. Shengdou 101) by injecting and cutting root method with a conidial suspension (1×106 conidia per mL) of F. falciforme(2 mL to one seedling). Control seedlings were inoculated with 2 mL distilled water. After 40 days under 25℃, 16h light/8h dark, the root system of all inoculated soybean plants exhibited dark brown lesions over the entire taproot, while control plants remained healthy. The fungus was reisolated from inoculated plants and identified asF. falciformebased on morphological characteristics and molecular methods described above. To our knowledge, this is the first report of root rot in soybean (Glycine max L.) caused by F. falciforme in Henan, China. The results are important for soybean production and breeding programs.

Comparative study of the toxicity mechanisms of quinolone antibiotics on soybean seedlings: Insights from molecular docking and transcriptomic analysis

The ecological effects of quinolone antibiotics (QNs) on non-target organisms have received widespread attention. The toxicological mechanisms of three common QNs, that is, enrofloxacin, levofloxacin, and ciprofloxacin, on soybean seedlings were investigated in this study. Enrofloxacin and levofloxacin caused significant growth inhibition, ultrastructural alterations, photosynthetic suppression, and stimulation of the antioxidant system, with levofloxacin exhibiting the strongest toxic effects. Ciprofloxacin (<1 mg·L−1) did not have a significant effect on the soybean seedlings. As the concentrations of enrofloxacin and levofloxacin increased, antioxidant enzyme activities, malondialdehyde content, and hydrogen peroxide levels also increased. Meanwhile, the chlorophyll content and chlorophyll fluorescence parameters decreased, indicating that the plants underwent oxidative stress and photosynthesis was suppressed. The cellular ultrastructure was also disrupted, which was manifested by swollen chloroplasts, increased starch granules, disintegration of plastoglobules, and mitochondrial degradation. The molecular docking results suggested that the QNs have an affinity for soybean target protein receptors (4TOP, 2IUJ, and 1FHF), with levofloxacin having the highest binding energy (−4.97, −3.08, −3.8, respectively). Transcriptomic analysis has shown that genes were upregulated under the enrofloxacin and levofloxacin treatments were mainly involved in ribosome metabolism and processes to synthesize oxidative stress-related proteins. Downregulated genes in the levofloxacin treatment were primarily enriched in photosynthesis-related pathways, indicating that levofloxacin significantly inhibited gene expression for photosynthesis. Genes expression level by quantitative real-time PCR analysis was consistent with the transcriptomic results. This study confirmed the toxic effect of QNs on soybean seedlings, and provided new insights into the environmental risks of antibiotics.

The Effect of Biochar Applications at Different Doses on Soybean Seedlings Grown in Salty Conditions

In this research, the effects of biochar application at different doses on the mineral element content of soybean seedlings under salt stress were investigated under greenhouse circumstances. In the study, leaf and root some mineral contents were investigated. According to the data obtained from the study, it was stated that while the leaf and root plant nutrient content of soybean seedlings decreased in salty conditions in general, the applied biochar increased the leaf and root plant nutrient content. This positive effect of biochar treatments on enhancing mineral element content was dose dependent. In conclude, biochar can be used as an amendment for increasing plant nutrient use efficiency of plants under saline conditions.

Susceptibility of the Most Popular Soybean Cultivars in South-East Europe to Macrophomina phaseolina (Tassi) Goid.

Oxidative stress in soybean seedlings and the length of the soybean stem lesions infected with the fungus Macrophomina phaseolina (Tassi) Goid were evaluated to determine the most tolerant soybean cultivar to this pathogen. The level of superoxide anion radical (O2•-) production, the activity of the antioxidant enzyme superoxide-dismutase (SOD), and the intensity of lipid peroxidation (LP) were measured in four soybean cultivars: Favorit, Atlas, Victoria, and Rubin. Results showed that O2•- radical production and SOD activity were the most elevated in the cv. Favorit inoculated with M. phaseolina, while the level of lipid peroxidation intensity was the lowest compared to the control. This indicates that the soybean cv. Favorit has managed to prevent infection with M. phaseolina. Furthermore, higher O2•- radical production and lower SOD enzyme activity were measured in cv. Victoria, with enhanced lipid peroxidation. This means that the cv. Victoria was infected with M. phaseolina, and was the most sensitive. None of the tested oxidative stress parameters showed a significant difference in the cvs. Atlas and Rubin compared to the control. Furthermore, the highest lesion length was measured in the cv. Victoria, followed by cv. Favorit, while the lowest lesion length was measured in the cv. Atlas followed by the cv. Rubin; and thus, the cv. Atlas followed by the cv. Rubin, were the most tolerant soybean cultivars to this pathogen.

Comparison and Evaluation of Low-Temperature Tolerance of Different Soybean Cultivars during the Early-Growth Stage

Low temperatures have seriously affected crop growth owing to climate change and frequent extreme weather. Low-temperature disasters easily affect the early-growth stages of planted soybeans in Northeast China. In the present study, the comprehensive evaluation method using low-temperature (4 °C) simulation at soybean germination and seedling stages was used to compare soybean cultivars. The results revealed that low temperatures inhibited the germination ability of soybean seeds and prolonged the average germination time (about 7–13 days under low temperatures). Simultaneously, low-temperature stress at the seedling stage decreased plant height and dry weight, but accumulated proline and soluble sugar. The soluble protein content of most cultivars decreased at low temperatures. Peroxidase activity was significantly decreased in henong70, suinong82, and heinong83, and opposite in the other cultivars. Additionally, MDA content increased in cultivars heinong69, dongnong42, and dongnong55. The final comprehensive evaluation showed that Suinong42 had better low-temperature tolerance, whereas Kendou40 was more sensitive to low temperatures. The grey correlation analysis also showed that dry weight and proline can be used as the target traits for cultivar improvement.

P1 of turnip mosaic virus interacts with NOD19 for vigorous infection.

P1 protein, the most divergent protein of virus members in the genus Potyvirus of the family Potyviridae, is required for robust infection and host adaptation. However, how P1 affects viral proliferation is still largely elusive. In this work, a total number of eight potential P1-interacting Arabidopsis proteins were identified by the yeast-two-hybrid screening using the turnip mosaic virus (TuMV)-encoded P1 protein as the bait. Among which, the stress upregulated NODULIN 19 (NOD19) was selected for further characterization. The bimolecular fluorescent complementation assay confirmed the interaction between TuMV P1 and NOD19. Expression profile, structure, and subcellular localization analyses showed that NOD19 is a membrane-associated protein expressed mainly in plant aerial parts. Viral infectivity assay showed that the infection of turnip mosaic virus and soybean mosaic virus was attenuated in the null mutant of Arabidopsis NOD19 and NOD19-knockdown soybean seedlings, respectively. Together, these data indicate that NOD19 is a P1-interacting host factor required for robust infection.

Photosynthetic Acclimation of Shade-Grown Soybean Seedlings to a High-Light Environment.

Soybean in relay intercropping is initially exposed to a shade environment, followed by exposure to full sunlight after the harvesting of primary crops, e.g., maize. Therefore, soybean's ability to acclimate to this changing light environment determines its growth and yield formation. However, the changes in soybean photosynthesis under such light alternations in relay intercropping are poorly understood. This study compared the photosynthetic acclimation of two soybean varieties with contrasting shade tolerance, i.e., Gongxuan1 (shade-tolerant) and C103 (shade-intolerant). The two soybean genotypes were grown in a greenhouse under full sunlight (HL) and 40% full sunlight (LL) conditions. Subsequently, after the fifth compound leaf expanded, half of the LL plants were transferred to a high-sunlight environment (LL-HL). Morphological traits were measured at 0 and 10 days, while chlorophyll content, gas exchange characteristics and chlorophyll fluorescence were assayed at 0, 2, 4, 7 and 10 days after transfer to an HL environment (LL-HL). Shade-intolerant C103 showed photoinhibition 10 days after transfer, and the net photosynthetic rate (Pn) did not completely recover to that under a high light level. On the day of transfer, the shade-intolerant variety, C103, exhibited a decrease in net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (E) in the low-light (LL) and low-light-to-high-light (LL-HL) treatments. Additionally, intercellular CO2 concentration (Ci) increased in low light, suggesting that non-stomatal factors were the primary limitations to photosynthesis in C103 following the transfer. In contrast, the shade-tolerant variety, Gongxuan1, displayed a greater increase in Pn 7 days after transfer, with no difference observed between the HL and LL-HL treatments. Ten days after transfer, the shade-tolerant Gongxuan1 exhibited 24.1%, 10.9% and 20.9% higher biomass, leaf area and stem diameter than the intolerant C103. These findings suggest that Gongxuan1 possesses a higher capacity to adapt to variations in light conditions, making it a potential candidate for variety selection in intercropping systems.

Long-Term Tillage and Crop Rotation Regimes Reshape Soil-Borne Oomycete Communities in Soybean, Corn, and Wheat Production Systems.

Soil-borne oomycetes include devastating plant pathogens that cause substantial losses in the agricultural sector. To better manage this important group of pathogens, it is critical to understand how they respond to common agricultural practices, such as tillage and crop rotation. Here, a long-term field experiment was established using a split-plot design with tillage as the main plot factor (conventional tillage (CT) vs. no till (NT), two levels) and rotation as the subplot factor (monocultures of soybean, corn, or wheat, and corn-soybean-wheat rotation, four levels). Post-harvest soil oomycete communities were characterized over three consecutive years (2016-2018) by metabarcoding the Internal Transcribed Spacer 1 (ITS1) region. The community contained 292 amplicon sequence variants (ASVs) and was dominated by Globisporangium spp. (85.1% in abundance, 203 ASV) and Pythium spp. (10.4%, 51 ASV). NT decreased diversity and community compositional structure heterogeneity, while crop rotation only affected the community structure under CT. The interaction effects of tillage and rotation on most oomycetes species accentuated the complexity of managing these pathogens. Soil and crop health represented by soybean seedling vitality was lowest in soils under CT cultivating soybean or corn, while the grain yield of the three crops responded differently to tillage and crop rotation regimes.

Effect of Exogenous Tryptophan on Primary Metabolism and Oxidative Stress and Their Relationship with Seedling Germination and Vigor of Glycine Max L.

Treatments that increase the germination potential and vigor of Glycine max seedlings are continuously being stimulated, with the aim of achieving a higher percentage of emergence and better performance in the field. Considering the relationship of tryptophan with germination-associated phytohormones, this study tested the hypothesis that exogenous supply of tryptophan to soybean seeds can affect germination, physiological vigor, and the accumulation of primary and oxidative metabolism molecules in seedlings. Soybean seeds were exposed to soaking solutions containing different concentrations of the amino acid (0, 25, 50, 100, and 200 µM), and the seedlings were evaluated at three time periods, at 8 h after sowing (HAS), and 5 and 14 days after sowing (DAS). Treated seeds showed better germination fitness and seedlings showed greater vigor, and these parameters increased with increasing concentrations of tryptophan. In the initial hours and days of germination process evaluation (14 HAS and 5 DAS), the activities of starch metabolism enzymes (α- and β-amylase) tended to be higher, resulting in increased contents of sucrose, reducing sugars, and total soluble solids at 8 DAS, constituting an important metabolic effect for seedling growth. On the other hand, the induction of germination and vigor promoted by exogenous tryptophan in soybean seedlings occurred by stimulating the metabolic pathways of oxidative stress, resulting in increased concentrations of H2O2, malondialdehyde, and proline in the tissues. Additionally, it led to increased activities of the antioxidant enzymes superoxide dismutase and ascorbate peroxidase. These parameters were responsive to increasing supplied concentrations of tryptophan. Thus, the metabolic stress in soybean seeds induced by auxin seems to be an important inductive pathway for germination and vigor of G. max seeds.

The influence of different methods and norms of application of the herbicide Pivot on weed vegetation and productivity of soybean varieties Kasatka

Relevance. The growth of acreage under soybeans caused an increased demand of agricultural producers for drugs for the control of harmful objects. Herbicides are one of the most popular classes of pesticides used in many types of crop production.Methods. The effect of the water-soluble herbicide Pivot with consumption rates of 0.5 l/ha and 0.8 l/ha was studied in the experiment. A model variety of soy Killer whale was taken for research. Experience options: spraying the soil before sowing with sealing; spraying the soil before soybean seedlings; spraying plants in the phase of two triple leaves; control (without treatment). The studies were carried out by field and laboratory methods using appropriate techniques.Results. It was found that with a high mixed type of contamination of soybean crops (74–88 pieces of weeds / m2 in control), the use of different methods and norms of the herbicide Pivot, VC proved to be highly effective and safe for culture: reduction of the number of weeds, % to control at a rate of 0.5 l/ha — 86.4–88.1%, at a rate of 0.8 l/ha — 89.2–92.9%. The reaction of soybeans to a decrease in clogging, in comparison with the control, was manifested in an increase in: the number of branches — by 30.0–41.7%, the number of beans — by 40.7–53.0%, the number of seeds from one plant — by 32.2–55.0%, the mass of seeds from one plant — by 52.2–60.4%, the mass of 1000 seeds — by 27.3–30.7%. The average yield of soybeans in the control was 1.36–1.38 t/ha. In the variants with the use of herbicides, reliable crop yield increases of 30.7–52.9% were obtained. When conducting a comparative analysis of the rates of herbicide application on structural indicators and soybean yield, the advantage of a dosage of 0.8 l/ha was revealed, and when comparing the methods of application — spraying the soil before soybean seedlings.

Classification of soybean genotypes during the seedling stage in controlled drought and salt stress environments using the decision tree algorithm

AbstractSoybean is one of the most important oilseed crops grown worldwide. However, abiotic stresses such as drought and salinity can seriously affect soybean production, especially in tropical climate conditions. To evaluate the adaptability and stability of soybean genotypes under abiotic stress conditions, some studies have proposed a multitrait tool to select stress‐tolerant soybean genotypes through a multitrait stability index (MTSI). This index can be used under stressful environmental conditions to quantify the genotypic stability of soybean cultivars. Our study is based on an unprecedented approach, where we propose to use a machine learning algorithm called ‘Random Forest’ to obtain a classification model based on a decision tree algorithm. The decision tree data structure can be used even by nonexperts facilitating the decision‐making process for genotype selection. The proposed model evaluated the importance of six shoot and root morphological variables and predicted from which controlled growth environment the soybean plants originated. Using this model more than 73% of the genotypic patterns were learned correctly. Besides that, this model can also predict and rank the most critical variables in the development of soybean genotypes, having obtained results very similar to recent field research. The research is important for plant breeders who seek an early selection of soybean seedlings for drought and saline stresses.

Physiological mechanism of melatonin attenuating to osmotic stress tolerance in soybean seedlings.

Drought is one of the most significant abiotic stress threatening to crop production worldwide. Soybean is a major legume crop with immense economic significance, but its production is highly dependent on optimum rainfall or abundant irrigation. As the global climate changes, it is more important to find solutions to make plants more resilient to drought. The prime aimed of the study is to investigate the effect of melatonin on drought tolerance in soybean and its potential mechanisms. Soybean seedlings were treated with 20% polyethylene glycol 6000 (PEG 6000) and subjected to osmotic stress (14 days) with or without 100 μM melatonin treatment. Our results revealed that melatonin supplementation significantly mitigated PEG-induced growth retardation and increased water absorption ability. Foliar application of melatonin also increased gas exchange and the chlorophyll fluorescence attributes by the mitigation of the osmotic-induced reduction of the reaction activity of photosystems I and II, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), electron transport activity, and photosynthetic efficiency. In addition, PEG-induced elevated production of reactive oxygen species (ROS) and malondialdehyde (MDA) content were significantly reversed by melatonin treatment. Equally important, melatonin boosted the antioxidant activities of soybean plants. Moreover, osmotic stress substantially increased abscisic acid (ABA) accumulation in roots and leaves, while melatonin-received plant leaves accumulated less ABA but roots content higher ABA. Similarly, melatonin significantly suppressed ABA biosynthesis and signaling gene expression in soybean exposed to drought stress. Furthermore, osmotic stress significantly suppressed plasmalemma (GmPIPs) and tonoplast aquaporin (GmTIPs) genes expression, and their transcript abundance was up-regulated by melatonin co-addition. Taken together, our results indicated that melatonin potentially improves drought tolerance of soybean through the regulation of ABA and aquaporin gene expression, increasing photosynthetic efficiency as well as enhancing water uptake efficiency.

RPA-CRISPR/Cas12a mediated isothermal amplification for visual detection of Phytophthora sojae.

Phytophthora sojae is among the most devastating pathogens of soybean (Glycine max) and severely impacts soybean production in several countries. The resulting disease can be difficult to diagnose and other Phytophthora species can also infect soybean. Accurate diagnosis is important for management of the disease caused by P. sojae. In this study, recombinase polymerase amplification (RPA) in combination with the CRISPR/Cas12a system were used for detection of P. sojae. The assay was highly specific to P. sojae. The test results were positive for 29 isolates of P. sojae, but negative for 64 isolates of 29 Phytophthora species, 7 Phytopythium and Pythium species, 32 fungal species, and 2 Bursaphelenchus species. The method was highly sensitive, detecting as little as 10 pg.µL-1 of P. sojae genomic DNA at 37°C in 20 min. The test results were visible under UV light and readout coming from fluorophores. In addition, P. sojae was detected from natural inoculated hypocotyls of soybean seedlings using this novel assay. The rapidity and accuracy of the method were verified using 30 soybean rhizosphere samples. In conclusion, the RPA-CRISPR/Cas12a detection assay developed here is sensitive, efficient, and convenient, and has potential for further development as a kit for monitoring root rot of soybean in the field.

Stimulating Role of Calcium and Cyclic GMP in Mediating the Effect of Magnetopriming for Alleviation of Salt Stress in Soybean Seedlings

This current study examined the role of calcium (Ca) and Cyclic GMP (cGMP) in mitigating the adverse effect of salt stress through magnetopriming of soybean cultivar JS-335 seeds with a static magnetic field (SMF, 200 mT for 1 h). The salt stress (50 mMNaCl) extensively reduced the early seedling growth (64%), vigour Index-I (71%), vigour Index-II (39%), total amylase (59%), protease (63%), and nitrate reductase (NR, 19%) activities in un-primed soybean seedlings. However, magnetopriming and Ca treatment enhanced all of these measured parameters along with remarkable increase in reactive oxygen species (ROS) and nitric oxide (NO) content. The exogenous application of Ca2+, cGMP and ROS regulators such as nifedipine (Ca2+ channel blocker), EGTA, ethylene glycol-β-amino ethyl ether tetra acetic acid (Ca2+chelators), genistein (cGMP blocker), and dimethyl thiourea (DMTU, H2O2 inhibitor) negatively affects the SMF-induced seedling length, seedling vigour, ROS, NO, and enzyme activities such as protease, total amylase, and NR in soybean seedlings. Results presented by using specific various biochemical inhibitors of Ca, cGMP, or ROS signalling in vivo indicated that Ca and cGMP are also involved with ROS and NO in the signal transduction of magnetic field enthused soybean seed germination and seedling growth under salt stress.

EFFECT OF MOISTURE ON SEEDLING STAGE OF SOYBEAN (GLYCINE MAX)

The research was conducted at Rampur Campus, Khairahani, Nepal to analyze the effect of moisture on different soybean (Glycine max) genotypes under a partially controlled environment. The experiment was carried out in a Completely Randomized Design (CRD) with 16 distinct genotypes and 3 water levels (waterlogged, control and drought) as treatment and replicated with 3 times. Various parameters including germination percentage, plant mortality, plant height, number of leaves, and number of branches were measured at different stages of growth. The results showed that genotypes SBO122 and TGX1891116FN exhibited early germination with the highest germination percentage recorded at 5 days after sowing (DAS). TGX1891116FN showed the highest germination percentage of 100% at 15 DAS. However, the germination percentages were lower in other genotypes, which could be attributed to the lower temperatures during the research period. The mortality rate of soybean seedlings varied among genotypes and moisture treatments. Genotype CM9125 showed the highest mortality rate of 100%, followed by Puja and GC8234GC-13 with a mortality rate of 88.87%. Plant height was significantly affected by different genotypes and moisture treatments. Under normal conditions, genotype Puja exhibited the highest plant height at 20 DAS, while under waterlogging conditions, TGX1989-19F had the highest height. Drought conditions also affected plant height, with genotype GC8234GC13 showing the highest height at 30 DAS. These findings can contribute to the development of soybean varieties that are resistant to moisture stress and improve soybean production in Nepal.

Mitigation of Salinity Stress on Soybean Seedlings Using Indole Acetic Acid-Producing Acinetobacter pittii YNA40

Soybean is an important oil crop with multiple uses. Soybeans can grow in various soil types and climates; however, salt stress reduces their yield. Plant growth-promoting microorganisms are an environmentally benign way to combat stress and boost plant tolerance. In the present study, we have identified plant growth-promoting bacteria that can produce indole acetic acid (IAA) and induce distinct growth characteristics in soybean plants under salt stress. The YNA40 isolate was identified as Acinetobacter pittii through 16S rRNA sequencing and phylogenetic analysis. A pure culture of Acinetobacter pittii YNA40 was subjected to chromatographic and mass spectrometry selected-ion monitoring (GC-MS/SIM) for IAA quantification. The results revealed that the YNA40 bacterial strain showed a significantly higher IAA concentration (473.88 ng/mL) at 4% sodium chloride (NaCl). Moreover, in a salt-stress condition, inoculation with Acinetobacter pittii YNA40 was able to induce increased shoot length (23.48%), shoot weight (24%), root length (2.47%), and root weight (44.82%) compared to the uninoculated control. Therefore, soybean seedlings were inoculated with YNA40 to examine their potential for promoting growth and reprogramming after salt stress. Inoculation with YNA40 isolates mitigated the salt stress and significantly improved the growth of the plant, enhanced the chlorophyll contents, and improved the quantum efficiency of chlorophyll fluorescence, total phenolic content, flavonoid content, the diphenyl-1-picrylhydrazyl (DPPH) activity, and antioxidant activities of soybean plants during and after salt stress. The present research demonstrated that the application of the YNA40 isolate is promising for reducing salt stress in soybean plants and helps plants grow better in a salt-stressed environment.

Arbuscular mycorrhizal fungus Rhizophagus irregularis alleviates drought stress in soybean with overexpressing the GmSPL9d gene by promoting photosynthetic apparatus and regulating the antioxidant system

Drought is the most destructive abiotic stress and negatively affects crop growth and productivity. Modern breeding efforts have produced numerous cultivars with distinct genetic traits that improve crop growth and drought stress tolerance. Arbuscular mycorrhizal fungi (AMF) can enhance drought tolerance in soybean plants by directly providing nutrients to plants, promoting photosynthesis, or influencing interspecific plant interactions in natural communities. However, the interactions between AMF and wild and transgenic soybean genotypes remain unclear. Therefore, in the present study, we evaluated the effect of arbuscular mycorrhizal fungi on the growth performance of drought-stressed transgenic soybean lines (ZXOE-11 and ZXOE-13) overexpressing GmSPL9d gene and their wild soybean Tianlong 1 (TL1) at the seedling stage (45 d after sowing). The results showed that colonization of wild and transgenic soybean with Rhizophagus irregularis significantly decreased the adverse effects of drought on plant growth. AMF inoculation significantly increased plant biomass, root activity, chlorophyll metabolism, photosynthesis, and chlorophyll fluorescence in wild-type and transgenic plants under both control and drought stress conditions. Drought causes the production of ROS, such as hydrogen peroxide, which enhances MDA, thereby decreasing the membrane stability index (MSI). However, AMF-inoculated plants exhibited decreased ROS accumulation and increased MSI. Moreover, AMF treatment significantly improved osmolyte, nitrogen, and nitrate reductase activity under control and drought conditions, which increased the relative water content. Furthermore, AMF treatment enhanced the antioxidant systems of drought-stressed plants by increasing the activities of peroxidase, superoxide dismutase, catalase, and ascorbate peroxidase. AMF improved the growth performance, photosynthesis, and antioxidant activity of transgenic plants under drought stress conditions. The present findings indicate that the AMF contribution to soybean seedling drought tolerance was more significant for the transgenic plants than for the wild plants under drought conditions. The current findings emphasize the possibility of growth and photosynthetic variation in the degree of AMF-associated drought resistance in soybean plants. Our findings suggest that future crop breeding challenges include developing cultivars for sustainable production and maximizing crop cultivar and fungal species (AMF) combinations in drought-stressed regions.

Characterization of fluorescence properties of wounds on soybean seedlings during healing process using excitation emission matrix and fluorescence imaging

To establish a simple and nondestructive method for measuring plant wound-healing ability, we characterized the fluorescence characteristics of wounds on hypocotyl of soybean seedlings during healing process. Wounds were manually created on the stem of soybean seedlings 7 days after sowing. The fluorescence time-series characteristics of the wounds were measured until 96 h after wounding using excitation emission matrix (EEM) and fluorescence images excited by wavelength of 365 nm. In the EEM of wounds, three main fluorescence peaks were observed, and the intensity decreased with time after wounding. The reddish color due to chlorophyll in fluorescence images also decreased with healing process. In addition, microscopic observation of the wounded tissue using a confocal laser microscope showed that the intensity of lignin or suberin like fluorescence increased with healing time, which might have blocked the excitation light. These results suggest that UV-excited fluorescence can be a new indicator of the healing ability of plant tissues.