Nitrogen Use Efficiency of Watermelon Grafted onto 10 Wild Watermelon Rootstocks under Low Nitrogen Conditions

Nitrogen availability is the key determinant of plant growth and development. The improvement of nitrogen use efficiency (NUE) in crops is an important consideration. In fruit and vegetables, such as watermelon, rootstocks are often utilized to control soil borne diseases and improve plant performance to a range of abiotic stresses. In this study, we evaluated the efficacy of 10 wild watermelon rootstocks (ZXG-516, ZXG-941, ZXG-945, ZXG-1250, ZXG-1251, ZXG-1558, ZXG-944, ZXG-1469, ZXG-1463, and ZXG-952) to improve the plant growth and nitrogen use efficiency (NUE) of the watermelon cultivar: Zaojia 8424. Nitrogen use efficiency (NUE) is a comprehensive parameter that represents the ability of a plant to absorb nitrogen (N) and convert the supplied resources to the dry biomass. Wild watermelon rootstocks substantially improved plant growth, rate of photosynthesis, stomatal conductivity, intercellular carbon dioxide concentration, rate of transpiration, nitrogen uptake efficiency, nitrogen use efficiency, and nitrogen utilization efficiency of watermelon. NUE of watermelon grafted onto ZXG-945, ZXG-1250, and ZXG-941 was improved by up to 67%, 77%, and 168%, respectively, at optimum N supply. Similarly, at low N supply (0.2 mM), NUE of watermelon grafted onto ZXG-1558 and ZXG-516 was improved by up to 104% and 175%, respectively. In conclusion, grafting onto some wild rootstocks can improve nitrogen use efficiency of watermelon, and this improved nitrogen use efficiency could be attributed to better N uptake efficiency of wild watermelon rootstocks

Genome-wide expression profiling of leaves and roots of watermelon in response to low nitrogen

Abstract Background Nitrogen (N) is a key macronutrient required for plant growth and development. In this study, watermelon plants were grown under hydroponic conditions at 0.2 mM N, 4.5 mM N, and 9 mM N for 14 days. Results Dry weight and photosynthetic assimilation at low N (0.2 mM) was reduced by 29 and 74% compared with high N (9 mM). The photochemical activity (Fv/Fm) was also reduced from 0.78 at high N to 0.71 at low N. The N concentration in the leaf, stem, and root of watermelon under low N conditions was reduced by 68, 104, and 108%, respectively compared with 9 mM N treatment after 14 days of N treatment. In the leaf tissues of watermelon grown under low N conditions, 9598 genes were differentially expressed, out of which 4533 genes (47.22%) were up-regulated whereas, 5065 genes (52.78%) were down-regulated compared with high N. Similarly in the root tissues, 3956 genes were differentially expressed, out of which 1605 genes were up-regulated (40.57%) and 2351 genes were down-regulated (59.43%), compared with high N. Our results suggest that leaf tissues are more sensitive to N deficiency compared with root tissues. The gene ontology (GO) analysis showed that the availability of N significantly affected 19 biological processes, 8 cell component metabolic pathways, and 3 molecular functions in the leaves; and 13 biological processes, 12 molecular functions, and 5 cell component metabolic pathways in the roots of watermelon. The low affinity nitrate transporters, high affinity nitrate transporters, ammonium transporters, genes related with nitrogen assimilation, and chlorophyll and photosynthesis were expressed differentially in response to low N. Three nitrate transporters (Cla010066, Cla009721, Cla012765) substantially responded to low nitrate supply in the root and leaf tissues. Additionally, a large number of transcription factors (1365) were involved in adaptation to low N availability. The major transcription factor families identified in this study includes MYB, AP2-EREBP, bHLH, C2H2 and NAC. Conclusion Candidate genes identified in this study for nitrate uptake and transport can be targeted and utilized for further studies in watermelon breeding and improvement programs to improve N uptake and utilization efficiency

Boron: Functions and Approaches to Enhance Its Availability in Plants for Sustainable Agriculture

Boron (B) is an essential trace element required for the physiological functioning of higher plants. B deficiency is considered as a nutritional disorder that adversely affects the metabolism and growth of plants. B is involved in the structural and functional integrity of the cell wall and membranes, ion fluxes (H+, K+, PO43−, Rb+, Ca2+) across the membranes, cell division and elongation, nitrogen and carbohydrate metabolism, sugar transport, cytoskeletal proteins, and plasmalemma-bound enzymes, nucleic acid, indoleacetic acid, polyamines, ascorbic acid, and phenol metabolism and transport. This review critically examines the functions of B in plants, deficiency symptoms, and the mechanism of B uptake and transport under limited B conditions. B deficiency can be mitigated by inorganic fertilizer supplementation, but the deleterious impact of frequent fertilizer application disrupts soil fertility and creates environmental pollution. Considering this, we have summarized the available information regarding alternative approaches, such as root structural modification, grafting, application of biostimulators (mycorrhizal fungi (MF) and rhizobacteria), and nanotechnology, that can be effectively utilized for B acquisition, leading to resource conservation. Additionally, we have discussed several new aspects, such as the combination of grafting or MF with nanotechnology, combined inoculation of arbuscular MF and rhizobacteria, melatonin application, and the use of natural and synthetic chelators, that possibly play a role in B uptake and translocation under B stress conditions

Optimizing efficacy of turnip growth through foliar application of glutamic acid under saline conditions

Salinity is assumed to be a distressing abiotic factor that mainly disrupts crop quality and yield by impairing plant cell mechanisms. Due to ion accumulation, salinity stress results in lowering growth rate and water uptake. This issue is being solved by the use of several plant growth regulators. Plant growth regulators have been proven to increase plants' ability to withstand against stress. In this study, turnip (purple top cultivar) was subjected to four distinct levels of salt (0, 4, 8, and 12 dS/m), as well as one level of gibberellic acid, in order to assess the function of exogenously applied plant growth regulator glutamic acid (GA) (10 mM). Results revealed that salt stress slowed plant growth and decreased the amount of chlorophyll in turnip leaves. Application of salt alone resulted in a considerable decline in biochemical characteristics. However, in salt-stressed conditions, exogenous application of GA improved the antioxidant activity, chlorophyll contents and plant growth in the turnip leaves. Moreover, results depict that under salt stress vitamin C decreased; however, exogenous application of GA enhanced the Vit. C in turnip plants. Further, the uptake of salt content in turnip roots and leaves was significantly lowered by the application of GA. Additionally, under salt stress; GA dramatically controlled the quantity of phenolic compounds in turnip.Keywords: Brassica rapa, Salinity, Glutamic acid, Morphological and biochemical assay, Reducing and non-reducing suga

Optimizing efficacy of turnip growth through foliar application of glutamic acid under saline conditions

Salinity is assumed to be a distressing abiotic factor that mainly disrupts crop quality and yield by impairing plant cell mechanisms. Due to ion accumulation, salinity stress results in lowering growth rate and water uptake. This issue is being solved by the use of several plant growth regulators. Plant growth regulators have been proven to increase plants' ability to withstand against stress. In this study, turnip (purple top cultivar) was subjected to four distinct levels of salt (0, 4, 8, and 12 dS/m), as well as one level of gibberellic acid, in order to assess the function of exogenously applied plant growth regulator glutamic acid (GA) (10 mM). Results revealed that salt stress slowed plant growth and decreased the amount of chlorophyll in turnip leaves. Application of salt alone resulted in a considerable decline in biochemical characteristics. However, in salt-stressed conditions, exogenous application of GA improved the antioxidant activity, chlorophyll contents and plant growth in the turnip leaves. Moreover, results depict that under salt stress vitamin C decreased; however, exogenous application of GA enhanced the Vit. C in turnip plants. Further, the uptake of salt content in turnip roots and leaves was significantly lowered by the application of GA. Additionally, under salt stress; GA dramatically controlled the quantity of phenolic compounds in turnip.Keywords: Brassica rapa, Salinity, Glutamic acid, Morphological and biochemical assay, Reducing and non-reducing suga

Additional file 3: of Genome-wide expression profiling of leaves and roots of watermelon in response to low nitrogen

Transcription factors (TFs) found to be affected in the leaf and root tissues of watermelon exposed to different levels of nitrogen (0.2 mM, 9 mM) (XLSX 76 kb

Additional file 2: of Genome-wide expression profiling of leaves and roots of watermelon in response to low nitrogen

The expression of chlorophyll, cytochrome 450, photosystem I, II, and phytochrome-related genes in watermelon leaves exposed to different levels of nitrogen supply (0.2 mM, 9 mM) (XLSX 27 kb

Additional file 6: of Genome-wide expression profiling of leaves and roots of watermelon in response to low nitrogen

The summary of five major transcription factor families in leaf and root tissues of watermelon exposed to different levels of N (0.2 mM, 9 mM) (XLSX 38 kb

Additional file 1: of Genome-wide expression profiling of leaves and roots of watermelon in response to low nitrogen

Table S1. Summary of sequencing data quality of leaves and roots of watermelon grown under hydroponic conditions at low N (0.2 mM) and high N (9 mM); Table S2. Summary of total, multiple and uniquely mapped reads of leaves and roots of watermelon grown under hydroponic conditions at low N (0.2 mM) and high N (9 mM); Table S3. Transcript abundance of the genes that were only expressed under low N (LLN) in the leaves of watermelon seedlings grown under hydroponic conditions; Table S4. Transcript abundance of the genes that were only expressed under high N (LHN) in the leaves of watermelon seedlings grown under hydroponic conditions; Table S5. Transcript abundance of the genes that were expressed either under low N (RLN) or high N (RHN) in the roots of watermelon seedlings grown under hydroponic conditions; Table S6. The list of primer sequences used for qRT-PCR analysis; Table S7. Arabidopsis thaliana Ortholog genes to the selected candidate genes that substantially responded to low N (0.2 mM) compared with high N (9 mM) in the leaf and root of watermelon; Figure S1. Correlation between expression value of selected genes obtained by RNA-seq and qPCR in the leaf (a) and root (b) tissues of watermelon seedlings grown under hydroponic conditions exposed to different levels of N (0.2 mM and 9 mM) for 14 days. FC: fold change; r: correlation coefficient; Figure S2. Hierarchical cluster analysis map presenting differential gene expression in the leaf and root of watermelon grown under hydroponic conditions at 0.2 mM and 9 mM N. LHN: leaf high N (9 mM); LLN: leaf low N (0.2 mM); RHN: root high N (9 mM); RLN: roots low N (0.2 mM). Samples for transcriptome analysis were harvested after 14 days of N treatment; and Figure S3. The cytoscape presenting protein interaction network analysis of differentially expressed genes of leaf and root of watermelon grown under hydroponic conditions at 0.2 mM and 9 mM N. (DOCX 1230 kb

Additional file 4: of Genome-wide expression profiling of leaves and roots of watermelon in response to low nitrogen

The expression pattern of different genes in the leaf tissues of watermelon exposed to different levels of nitrogen (0.2 mM, 9 mM) (XLSX 1109 kb