Increase In Number Of Nodules Research Articles

The biochemical properties of Satureja species affected by micronutrients, genotype, and locations in drought stress conditions

Medicinal plants, as important sources of secondary metabolites, are used for treating different diseases. It is accordingly pertinent to find methods, which may improve their growth and quality in different conditions including variable stresses. It was hypothesized micronutrients use and suitable genotypes may improve Satureja growth and quality in drought stress conditions. The objective of this study was to investigate the effects of drought stress (irrigating plants each 3 (A1), 6 (A2) and 9 days (A3)), micronutrients (Mn and Cu at 0 (M1), 20 (M2) and 40 mgL−1 (M3)), and field location (Isfahan (F1) and Golpayegan (cooler) (F2), Isfahan province, Iran) on the biochemical properties of different Satureja species including S. bakhtiarica, S. khuzestanica and S. mutica. The experimental treatments significantly affected the measured parameters including nodule number, essential oil, antioxidant activity, proline, Mn and Cu contents, and relative water content. Although Cu and Mn, enhanced plant biochemical properties, especially in M2, in some cases, the two micronutrients, unfavorably affected plant properties in M3. The responses of genotypes were different in the two research fields and S. bakhtiarica performed better in F2. The highest essential oil was resulted by A2. The two micronutrients improved plant responses in drought stress by increasing nodule number (148 %), and essential oil yield (143 %) and decreasing plant relative water content and conserving plant water. The use of Mn and Cu is recommendable for planting Satureja species in drought stress conditions, as the two nutrients may enhance plant tolerance by increasing proline production and antioxidant activities.

Assessing the Effectiveness of Neem oil and Microalgae in the Management of Cowpea (Vigna unguiculata L.) Leaf Spot Caused by Alternaria spp.

The current study aimed to assess the effectiveness of neem oil and microalgae in controlling leaf spot caused by Alternaria spp. in cowpea (Vigna unguiculataL.). The research was conducted during the Zaid season of 2022 at the Central Research Field of the Department of Plant Pathology, SHUATS, Prayagraj, Uttar Pradesh, using a Randomized Block Design with three replications and seven treatments. Analysis of variance (ANOVA) was utilized to draw conclusions from the data. Leaf spot disease caused by Alternaria spp poses a significant threat to cowpea crops, resulting in yield losses and decreased plant vigor. An in vivo study was carried out to evaluate the impact of different concentrations of microalgae combined with neem oil at 1% on plant growth parameters and Disease Intensity (%). The application of microalgae @540 grams in various splits and neem oil @1% was done. Among all the treatments, T4 (Microalgae 48gms @5 DAS 96gms@15,45 DAS + Neem oil @1% showed promising results. Notably, the T4 treatment significantly increased plant height (84.63 cm) and the number of branches(10.83) at60DAS. Moreover, an increased numberof nodules per plant (21.44) was observed at 75 DAS, indicating improved root health and nitrogen fixation. Additionally, the treatment led to longer pod length (34.44 cm) in three pickings, suggesting enhanced yield potential. Furthermore, the combined application of microalgae and neem oil resulted in a significant reduction in disease intensity, with a notable decrease of 24.47% compared to untreated plants and those treated with chemicals (Bavistin). This indicates that the use of microalgae and neem oil together effectively suppressed leaf spot disease caused by Alternaria spp. in cowpea, thereby improving plant health and productivity. In conclusion, these findings underscore the potential use of eco-friendly alternatives like microalgae and neem oil for managing leaf spot disease in cowpea cultivation. Further research in this area is recommended for sustainable agricultural practices.

Role of a LORELEI- like gene from Phaseolus vulgaris during a mutualistic interaction with Rhizobium tropici

Reactive oxygen species (ROS), produced by NADPH oxidases known as RBOHs in plants, play a key role in plant development, biotic and abiotic stress responses, hormone signaling, and reproduction. Among the subfamily of receptor-like kinases referred to as CrRLK, there is FERONIA (FER), a regulator of RBOHs, and FER requires a GPI-modified membrane protein produced by LORELEI (LRE) or LORELEI-like proteins (LLG) to reach the plasma membrane and generate ROS. In Arabidopsis, AtLLG1 is involved in interactions with microbes as AtLLG1 interacts with the flagellin receptor (FLS2) to trigger the innate immune response, but the role of LLGs in mutualistic interactions has not been examined. In this study, two Phaseolus vulgaris LLG genes were identified, PvLLG2 that was expressed in floral tissue and PvLLG1 that was expressed in vegetative tissue. Transcripts of PvLLG1 increased during rhizobial nodule formation peaking during the early period of well-developed nodules. Also, P. vulgaris roots expressing pPvLLG1:GFP-GUS showed that this promoter was highly active during rhizobium infections, and very similar to the subcellular localization using a construct pLLG1::PvLLG1-Neon. Compared to control plants, PvLLG1 silenced plants had less superoxide (O2-) at the root tip and elongation zone, spotty hydrogen peroxide (H2O2) in the elongation root zone, and significantly reduced root hair length, nodule number and nitrogen fixation. Unlike control plants, PvLLG1 overexpressing plants showed superoxide beyond the nodule meristem, and significantly increased nodule number and nodule diameter. PvLLG1 appears to play a key role during this mutualistic interaction, possibly due to the regulation of the production and distribution of ROS in roots.

The selenium-promoted daidzein production contributes to its induced nodulation in soybean plants

Selenium (Se) is an essential micronutrient to humans. Se biofortification in crops provides an effective means to enhance dietary Se intake. However, the effects of Se treatment on plant growth and development remain to be fully studied. In this study, we applied Se to soybean plants grown hydroponically and in soil. We observed that selenate treatment increased nodule number and fresh weight. Furthermore, Se supplementation increased isoflavone daidzein accumulation in roots and nodules. An exogenous supply of daidzein but not kaempferol was found to increase nodule number and fresh weight significantly, suggesting a role of daidzein in the Se-induced nodulation in soybean plants. In addition, the total sugar levels in nodules, roots, and leaves were significantly enhanced following selenate treatment. Subsequently, the N-compounds were greatly increased after Se treatment in all tissues examined. Transcriptome analysis revealed that Se treatment altered various metabolic and cellular processes to affect nodulation and nodule development. Se treatment upregulated GmNIN2b, an important nodule organogenesis gene, as well as genes associated with sugar metabolism and ureide transport. Our study provides insights underlying the Se-induced nodulation in soybean plants and further documents that Se biofortification in soybean can simultaneously improve not only the essential nutrient content but also nodulation for biological nitrogen fixation, a critically important agronomic trait in soybean plants.

Efficient dose of Bacillus subtilis UFMT-Pant001 as a plant growth promoter in soybean under greenhouse conditions

The potential for increasing soybean productivity and reducing diseases has become evident for Bacillus spp. The objective of this study was to evaluate the efficiency of B. subtilis strain UFMT-Pant001 as a plant growth promoter in soybean under greenhouse conditions. Four independent experiments were conducted in a greenhouse using a B. subtilis UFMT-Pant001 liquid inoculant at 1x109 CFU mL-1. The results showed significant increases in biomass, nodulation, nutrients in the shoot, number of internodes, and root length in soybean cultivars inoculated with B. subtilis UFMT-Pant001 in greenhouse experiments. Positive effects on soybean biomass and other evaluated characteristics were observed with different doses of B. subtilis UFMT-Pant001, with the best results observed when doses of 200 to 300 mL were used for 50 kg of seeds. The use of B. subtilis UFMT-Pant001 did not interfere with soybean nodulation and contributed to an increase in nodule number and weight.

GmNLP7a inhibits soybean nodulation by interacting with GmNIN1a

Nitrogen (N) is an essential macronutrient for plant growth and productivity. Leguminous plants establish symbiotic relationships with nitrogen-fixing rhizobial bacteria to use atmospheric dinitrogen gas to meet high N demand under low-N conditions. Nodule formation and N fixation are energy-consuming processes and are inhibited by nitrate present in the environment. Previous studies in model leguminous plants characterized NIN-LIKE PROTEIN (NLP) proteins that mediate nitrate control of root nodule symbiosis, but the mechanism by which nitrate regulates soybean root nodules via NLP remains unclear. In the soybean genome we found four homologs of AtNLP7, named GmNLP7a–GmNLP7d. We showed that the expression of GmNLP7s is responsive to nitrate but not to rhizobial infection and localized GmNLP7a to the nucleus. Downregulation of GmNLP7s increased nodule number, and overexpression of GmNLP7a (GmNLP7aOE) reduced nodule number regardless of nitrate availability, suggesting a negative role for GmNLP7s in nodulation. Nitrogenase activity in the GmNLP7aOE line was comparable to that of the wild type, indicating that GmNLP7a does not affect mature nodule activity. Overexpression of GmNLP7a downregulated the expression of GmNIN1a and GmENOD40-1. GmNLP7a interacted with GmNIN1a via the PB1 domain. Our results reveal a new regulator of GmNLP7 in nodulation and a molecular mechanism by which nitrate affects nodule number in soybean.

Effect of different methods of inoculation and co-inoculation of Bradyrhizobium spp. and Azospirillum brasilense on soybean agronomic performance in fields with a history of inoculation

ABSTRACT The yield gain of soybean inoculated with Bradyrhizobium spp. or co-inoculated with Bradyrhizobium spp. and Azospirillum brasilense is variable. Inoculants can be applied in the sowing furrow or via seed treatment. There is a gap in our understanding of the efficacy of different inoculation methods. This study aimed to assess the agronomic efficiency of soybean inoculated and co-inoculated with Bradyrhizobium spp. and A. brasilense by different methods. The study was conducted in Paraná State, Brazil, in two seasons. Five treatments were tested: control; seed treatment with Bradyrhizobium spp. (SBr), seed treatment with Bradyrhizobium spp. + A. brasilense (SBr+Az), in-furrow treatment with Bradyrhizobium spp. (FBr), and in-furrow treatment with Bradyrhizobium spp. + A. brasilense (FBr+Az). Shoot dry weight, grain nitrogen content and grain yield were lower in 2018/19. In 2017/18, FBr+Az increased nodule number and dry weight compared with SBr. FBr+Az promoted a 47% increase in pods per plant compared with the control in both seasons. Regardless of season, grain nitrogen content was higher with FBr+Az (mean relative increase of 27%). FBr+Az was superior to SBr+Az in 2017/18, with a 12% increase in yield. Inoculation and co-inoculation improve morphological traits and soybean yield. In-furrow inoculation is more efficient than seed treatment.

Assessing Liquid Inoculant Formulation of Biofertilizer (Sinorhizobium meliloti) on Growth, Yield, and Nitrogen Uptake of Lucerne (Medicago sativa)

Lucerne is regarded as the best legume crop for forage to be cultivated in South Africa. It is commonly used to produce good quality hay. It also plays an important role in soil conservation, regeneration, and crop rotation systems as it supplies substantial amounts of nitrogen to succeeding crops through symbiotic N2 fixation, which makes it the preferable choice for intensive forage production systems. Fertilizer in liquid inoculant formulations has demonstrated to contribute growth and yield increase for leguminous crops. Therefore, the aim of this paper was to determine the effects of Sinorhizobium meliloti liquid formulation inoculation on the growth, yield, and nitrogen content in lucerne. The strain RF14 (Sinorhizobium meliloti) was collected from the Agricultural Research Council at Roodeplaat (Plant Health and Protection located (East), Pretoria (South Africa). The liquid inoculant contained 6.5 × 109 viable cells mL−1. According to the Kooen–Gieger climatic classification, the experiments were conducted on two different climatic zones. The first site was in Bronkhorspruit (Blesbokfontein farm) in the Gauteng province and the second was in Hartbeesfontein (Rietfontein Farm) in the Northwest province. The results showed that lucerne inoculation with liquid inoculant formulation of Sinorhizobium meliloti significantly increased nodule number, size, growth, and yield in both bioclimatic zones. The significantly increased were compared to the negative control. The Sinorhizobium meliloti inoculant increased nitrogen accumulation in all inoculated treatments compared to the control. The finding of this research provides important information on the impact of rhizobium microbial inoculant application in the improvement of soil fertility through nodule formation. In addition, seed vigor improvement was translated in overall growth and yield increase in lucerne plants.

Memory or acclimation of water stress in pea rely on root system's plasticity and plant's ionome modulation.

Peas, as legume crops, could play a major role in the future of food security in the context of worldwide human nutrient deficiencies coupled with the growing need to reduce consumption of animal products. However, pea yields, in terms of quantity and quality (i.e. grain content), are both susceptible to climate change, and more specifically to water deficits, which nowadays occur more frequently during crop growth cycles and tend to last longer. The impact of soil water stress on plant development and plant growth is complex, as its impact varies depending on soil water availability (through the modulation of elements available in the soil), and by the plant's ability to acclimate to continuous stress or to memorize previous stress events. To identify the strategies underlying these plant responses to water stress events, pea plants were grown in controlled conditions under optimal water treatment and different types of water stress; transient (during vegetative or reproductive periods), recurrent, and continuous (throughout the plant growth cycle). Traits related to water, carbon, and ionome uptake and uses were measured and allowed the identification typical plant strategies to cope with water stress. Our results highlighted (i) the common responses to the three types of water stress in shoots, involving manganese (Mn) in particular, (ii) the potential implications of boron (B) for root architecture modification under continuous stress, and (iii) the establishment of an "ecophysiological imprint" in the root system via an increase in nodule numbers during the recovery period.

Characterization of phosphate solubilizing Pseudomonas stutzeri for nodulation in chickpea

Phosphorus is a vital but least mobile element in plants and soil as compared to other macronutrients. Native phosphate solubilizing bacterial strains were isolated from the rhizosphere of chickpea. Based on in vitro study, the isolate showed lower pH, remarkable phosphate solubilizing index, and thermotolerant ability selected for further characterization. The 16 s rRNA sequencing confirmed that the isolate showed 99.23% similarity with Pseudomonas stutzeri CW202. Pot trial treatments include Rhizobium ciceri, Pseudomonas stutzeri, and fertilizer alone and in combination with inoculants and control. The results of co-inoculation with R. ciceri + P. stutzeri showed the highest germination rate, increase in nodule number, and fresh nodule weight. This treatment was at par in plant height, number of branches, shoot and root dry weight per plant, number of pods per plant, seeds per pod, 100 seed weight and phosphorus uptake in seed and straw over the best treatment R. ciceri + P. stutzeri + Fertilizer. Co-inoculation of R. ciceri + P. stutzeri shows not only significant enhancement in nodulation, nodule fresh weight but also yield attributes and phosphorous uptake as compared to R. ciceri alone, indicating its role in phosphorus nutrition in chickpea. The results infer that the native P. stutzeri could be considered as a proficient biofertilizer in the organic farming system.

Macrophage migration inhibitory factor MtMIF3 prevents the premature aging of Medicago truncatula nodules.

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in immune response in animals. However, the role of MIFs in plants such as Medicago truncatula, particularly in symbiotic nitrogen fixation, remains unclear. An investigation of M. truncatula-Sinorhizobium meliloti symbiosis revealed that MtMIF3 was mainly expressed in the nitrogen-fixing zone of the nodules. Silencing MtMIF3 using RNA interference (Ri) technology resulted in increased nodule numbers but higher levels of bacteroid degradation in the infected cells of the nitrogen-fixing zone, suggesting that premature aging was induced in MtMIF3-Ri nodules. In agreement with this conclusion, the activities of nitrogenase, superoxide dismutase and catalase were lower than those in controls, but cysteine proteinase activity was increased in nodulated roots at 28 days postinoculation. In contrast, the overexpression of MtMIF3 inhibited nodule senescence. MtMIF3 is localized in the plasma membrane, nucleus, and cytoplasm, where it interacts with methionine sulfoxide reductase B (MsrB), which is also localized in the chloroplasts of tobacco leaf cells. Taken together, these results suggest that MtMIF3 prevents premature nodule aging and protects against oxidation by interacting with MtMsrB.

A novel type of phytosulfokine, PSK-ε, positively regulates root elongation and formation of lateral roots and root nodules in Medicago truncatula

ABSTRACT Phytosulfokines (PSKs) are a class of tyrosine-sulfated pentapeptides. PSK-α, PSK-γ, and PSK-δ are three reported PSK members involved in regulating plant growth, development, and resistance to biotic and abiotic stresses. Here, we reported a novel type of PSK, PSK-ε with the sequence YSO3VYSO3TN, and its precursor proteins (MtPSKε, LjPSKε, and GmPSKε), specifically from legume species. PSK-ε peptide differs from PSK-δ by one amino acid and is close to PSK-δ in the phylogenetic relationship. Expression profile analysis showed that MtPSKε was highly expressed in Medicago truncatula roots, especially in root tips and emerged lateral roots. Application of the synthetic sulfated PSK-ε peptide and overexpression of MtPSKε significantly promoted M. truncatula root elongation and increased lateral root number, probably by inducing cell division and expansion in roots. Furthermore, MtPSKε expression was induced by rhizobia infection and was detected in root nodules including nodule primordia. Both PSK-ε peptide treatment and MtPSKε overexpression significantly increased nodule number in M. truncatula. Taken together, these results demonstrate that PSK-ε, a novel type of phytosulfokine, positively regulates root elongation and formation of lateral root and root nodule in M. truncatula.

Constitutive overexpression of GsIMaT2 gene from wild soybean enhances rhizobia interaction and increase nodulation in soybean (Glycine max)

BackgroundSince the root nodules formation is regulated by specific and complex interactions of legume and rhizobial genes, there are still too many questions to be answered about the role of the genes involved in the regulation of the nodulation signaling pathway.ResultsThe genetic and biological roles of the isoflavone-7-O-beta-glucoside 6″-O-malonyltransferase gene GsIMaT2 from wild soybean (Glycine soja) in the regulation of nodule and root growth in soybean (Glycine max) were examined in this work. The effect of overexpressing GsIMaT2 from G. soja on the soybean nodulation signaling system and strigolactone production was investigated. We discovered that the GsIMaT2 increased nodule numbers, fresh nodule weight, root weight, and root length by boosting strigolactone formation. Furthermore, we examined the isoflavone concentration of transgenic G. max hairy roots 10 and 20 days after rhizobial inoculation. Malonyldaidzin, malonylgenistin, daidzein, and glycitein levels were considerably higher in GsMaT2-OE hairy roots after 10- and 20-days of Bradyrhizobium japonicum infection compared to the control. These findings suggest that isoflavones and their biosynthetic genes play unique functions in the nodulation signaling system in G. max.ConclusionsFinally, our results indicate the potential effects of the GsIMaT2 gene on soybean root growth and nodulation. This study provides novel insights for understanding the epistatic relationship between isoflavones, root development, and nodulation in soybean.Highlights* Cloning and Characterization of 7-O-beta-glucoside 6″-O-malonyltransferase (GsIMaT2) gene from wild soybean (G. soja).* The role of GsIMaT2 gene in the regulation of root nodule development.*Overexpression of GsMaT2 gene increases the accumulation of isoflavonoid in transgenic soybean hairy roots.* This gene could be used for metabolic engineering of useful isoflavonoid production.

Jumlah Bintil Fase Vegetatif Penentu Mutu dan Hasil Kacang Hijau (Vigna radiata L.) di Lahan Sawah Bekas Padi

Mungbean is one of leguminosae, that has profitable prospect therefore it has been cultivated by Indonesian society. Mungbean showed early maturity, easy management during cultivation and can produce more biomass, about 11.00-12.00 t/ ha. Wwhen the crop residue is left in field, it benefits of increasing the nutrients and improving soil fertility. Such reason makes mungbean becomes more profitable than soybean and peanut. The mungbean genetic material is significant to develop superior mungbean and support sustainable agriculture. This research was conducted to study the presence of rhizobium after continues rice grwon fields, to determine the bean accession responsive to Rhizobium sp., and to determine the impact of Rhizobium sp. on the mungbean yields components. This research was conducted at Agrotechnology Innovation Centre of Universitas Gadjah Mada (PIAT UGM) Kalitirto, Berbah, Sleman, Yogyakarta in splitted completely randomized design (CRD) with two factors. The main factor is inoculation treatment and the sub-factor is 18 mung beans accessions. Observations included rhizobium infection, nodule components, fresh weight of plant, dry weight of plant and yield components. The data obtained was further analyzed using analysis variance of completely randomized design, a further test of Scott Knott, and correlation analysis. All accessions can be infected by rhizobium and there was an increase in number of nodules and the effective number of nodules in each observation time with the result that inoculation treatment was superior to the one without inoculation. Number of nodules at time of observations have positive corellation with yield component, increased number of nodules followed increased variable of yield component.

GmSPX8, a nodule-localized regulator confers nodule development and nitrogen fixation under phosphorus starvation in soybean

BackgroundBiological nitrogen fixation (BNF) is an important nitrogen source for legume plants, and highly efficient nitrogen fixation requires sufficient phosphorus (P). However, the mechanism of maintaining nitrogen fixation of the legume nodules under low P concentration remains largely unknown.ResultsA nodule-localized SPX protein, GmSPX8, was discovered by transcriptome and functional analysis of its role in N2 fixation was characterized in soybean nodules. GmSPX8 was preferentially expressed in nodules and its expression was gradually increased during nodule development. And also the expression pattern was investigated using reporter gene β-glucuronidase (GUS) driven by the promoter of GmSPX8. GmSPX8 was greatly induced and the GUS activity was increased by 12.2% under P deficiency. Overexpression of GmSPX8 in transgenic plants resulted in increased nodule number, nodule fresh weight and nitrogenase activity by 15.0%, 16.0%, 42.5%, subsequently leading to increased N and P content by 17.0% and 19.0%, while suppression of GmSPX8 showed significantly impaired nodule development and nitrogen fixation efficiency under low P stress. These data indicated that GmSPX8 conferred nodule development and nitrogen fixation under low P condition. By yeast two-hybrid screening, GmPTF1 was identified as a potential interacting protein of GmSPX8, which was further confirmed by BiFC, Y2H and pull down assay. Transcript accumulation of GmPTF1 and its downstream genes such as GmEXLB1 and EXPB2 were increased in GmSPX8 overexpressed transgenic nodules, and in the presence of GmSPX8, the transcriptional activity of GmPTF1 in yeast cells and tobacco leaves was greatly enhanced.ConclusionsIn summary, these findings contribute novel insights towards the role of GmSPX8 in nodule development and nitrogen fixation partly through interacting with GmPTF1 in soybean under low P condition.

Benefits of silicon-enhanced root nodulation in a model legume are contingent upon rhizobial efficacy

AimsSilicon (Si) uptake and accumulation improves plant resilience to environmental stresses, but most studies examining this functional role of Si have focussed on grasses (Poaceae) and neglected other important plant groups, such as legumes (Fabaceae). Legumes have evolved a symbiotic relationship with nitrogen-fixing bacteria (rhizobia) housed in root nodules. Our study determined the impacts of silicon (Si) supplementation on Medicago truncatula inoculated with Ensifer meliloti rhizobial strains that differed in their capacity for nitrogen fixation: Sm1021 (‘low-efficiency’) or Sm1022 (‘high-efficiency’).MethodsWe examined how Si and rhizobial efficacy influence nodule and plant functional traits, including their chemical aspects. These combinations were supplied with or without Si in a glasshouse experiment, where we quantified nodule flavonoids and foliar chemistry (free amino acids, soluble protein, elemental C, N and Si).ResultsSi supply increased nodule number per plant, specific nodule flavonoid concentrations, contents of foliar nitrogenous compounds and foliar C, but not foliar Si. We also demonstrated that rhizobial efficacy altered the magnitude of Si effects on certain traits. For example, Si significantly promoted concentrations of foliar N and soluble protein in the plants associated with the ‘low-efficiency’ strain only, and this was not the case with the ‘high-efficiency’ one.ConclusionsCollectively, our study indicates that Si generates positive effects on M. truncatula, particularly when the association with rhizobia is relatively inefficient, and may play a more prominent role in rhizobial functionality than previously thought.

A legume-specific novel type of phytosulfokine, PSK-δ, promotes nodulation by enhancing nodule organogenesis.

Phytosulfokine-α (PSK-α), a tyrosine-sulfated pentapeptide with the sequence YSO3IYSO3TQ, is widely distributed across the plant kingdom and plays multiple roles in plant growth, development, and immune response. Here, we report a novel type of phytosulfokine, PSK-δ, and its precursor proteins (MtPSKδ, LjPSKδ, and GmPSKδ1), specifically from legume species. The sequence YSO3IYSO3TN of sulfated PSK-δ peptide is different from PSK-α at the last amino acid. Expression pattern analysis revealed PSK-δ-encoding precursor genes to be expressed primarily in legume root nodules. Specifically, in Medicago truncatula, MtPSKδ expression was detected in root cortical cells undergoing nodule organogenesis, in nodule primordia and young nodules, and in the apical region of mature nodules. Accumulation of sulfated PSK-δ peptide in M. truncatula nodules was detected by LC/MS. Application of synthetic PSK-δ peptide significantly increased nodule number in legumes. Similarly, overexpression of MtPSKδ in transgenic M. truncatula markedly promoted symbiotic nodulation. This increase in nodule number was attributed to enhanced nodule organogenesis induced by PSK-δ. Additional genetic evidence from the MtPSKδ mutant and RNA interference assays suggested that the PSK-δ and PSK-α peptides function redundantly in regulating nodule organogenesis. These results suggest that PSK-δ, a legume-specific novel type of phytosulfokine, promotes symbiotic nodulation by enhancing nodule organogenesis.

Interactive Effects of Biochar, Nitrogen, and Phosphorous on the Symbiotic Performance, Growth, and Nutrient Uptake of Soybean (Glycine max L.)

Numerous studies reported the positive effect of soil amendment with biochar on plant development. However, little is known about biochar and its interrelation with nitrogen (N) and phosphorous (P) additions and their impact on plant growth. We carried out greenhouse experiments to understand the interactive effects of nitrogen and phosphorus supply, as well as biochar amendment, on the symbiotic performance of soybean (Glycine max L.) with Bradyrhizobium japonicum, and plant growth and nutrient uptake. The biochar was produced from maize by heating at 600 °C for 30 min and used for pot experiments at an application rate of 2%. Plants were fertilized with two different concentrations of P (KH2PO4) and N (NH4NO3). Biochar application significantly increased the dry weight of soybean root and shoot biomass, by 34% and 42%, under low nitrogen and low phosphorus supply, respectively. Bradyrhizobium japonicum inoculation enhanced the dry weight of shoot biomass significantly, by 41% and 67%, in soil without biochar and with biochar addition, respectively. The nodule number was 19% higher in plants grown under low N combined with low or high P, than in high N combinations, while biochar application increased nodule number in roots. Moreover, biochar application increased N uptake of plants in all soil treatments with N or P supply, compared with B. japonicum-inoculated and uninoculated plants. A statistical difference in P uptake of plants between biochar and nutrient levels was observed with low N and high P supply in the soil. Our results show that the interactions between nitrogen, phosphorus, and biochar affect soybean growth by improving the symbiotic performance of B. japonicum and the growth and nutrition of soybean. We observed strong positive correlations between plant shoot biomass, root biomass, and N and P uptake. These data indicated that the combined use of biochar and low N, P application can be an effective approach in improving soybean growth with minimum nutrient input.

Overexpression of Terpenoid Biosynthesis Genes From Garden Sage (Salvia officinalis) Modulates Rhizobia Interaction and Nodulation in Soybean.

In legumes, many endogenous and environmental factors affect root nodule formation through several key genes, and the regulation details of the nodulation signaling pathway are yet to be fully understood. This study investigated the potential roles of terpenoids and terpene biosynthesis genes on root nodule formation in Glycine max. We characterized six terpenoid synthesis genes from Salvia officinalis by overexpressing SoTPS6, SoNEOD, SoLINS, SoSABS, SoGPS, and SoCINS in soybean hairy roots and evaluating root growth and nodulation, and the expression of strigolactone (SL) biosynthesis and early nodulation genes. Interestingly, overexpression of some of the terpenoid and terpene genes increased nodule numbers, nodule and root fresh weight, and root length, while others inhibited these phenotypes. These results suggest the potential effects of terpenoids and terpene synthesis genes on soybean root growth and nodulation. This study provides novel insights into epistatic interactions between terpenoids, root development, and nodulation in soybean root biology and open new avenues for soybean research.

Biochar Amendments Improve Licorice (Glycyrrhiza uralensis Fisch.) Growth and Nutrient Uptake under Salt Stress.

Licorice (Glycyrrhiza uralensis Fisch.) is a salt and drought tolerant legume suitable for rehabilitating abandoned saline lands, especially in dry arid regions. We hypothesized that soil amended with maize-derived biochar might alleviate salt stress in licorice by improving its growth, nutrient acquisition, and root system adaptation. Experiments were designed to determine the effect of different biochar concentrations on licorice growth parameters, acquisition of C (carbon), nitrogen (N), and phosphorus (P) and on soil enzyme activities under saline and non-saline soil conditions. Pyrolysis char from maize (600 °C) was used at concentrations of 2% (B2), 4% (B4), and 6% (B6) for pot experiments. After 40 days, biochar improved the shoot and root biomass of licorice by 80 and 41% under saline soil conditions. However, B4 and B6 did not have a significant effect on shoot growth. Furthermore, increased nodule numbers of licorice grown at B4 amendment were observed under both non-saline and saline conditions. The root architectural traits, such as root length, surface area, project area, root volume, and nodulation traits, also significantly increased by biochar application at both B2 and B4. The concentrations of N and K in plant tissue increased under B2 and B4 amendments compared to the plants grown without biochar application. Moreover, the soil under saline conditions amended with biochar showed a positive effect on the activities of soil fluorescein diacetate hydrolase, proteases, and acid phosphomonoesterases. Overall, this study demonstrated the beneficial effects of maize-derived biochar on growth and nutrient uptake of licorice under saline soil conditions by improving nodule formation and root architecture, as well as soil enzyme activity.