Functional Characterization of Core and Unique Calcite-Dissolving Bacteria Communities from Peanut Fields

Calcium deficiency is a leading cause of reduced peanut (Arachis hypogaea) seed quality and has been linked to increased disease susceptibility, specifically to soilborne fungal pathogens. Sufficient calcium at flowering time is critical to ensure proper pod development. Calcite-dissolving bacteria (CDB) isolated from farming fields can dissolve calcite (CaCO3) on plates and increase soluble calcium levels in soil. However, the phylogenetic diversity and geographic distribution of CDB is unclear. Here, we surveyed soil samples from 15 peanut-producing fields in three regions in southern Georgia, representing distinct soil compositions. We isolated CDB through differentiating media and identified 52 CDB strains. CDB abundance was not associated with any of the soil characteristics we evaluated. Three core genera, represented by 43 strains, were found in all three regions. Paenibacillus was the most common CDB found in all regions, making up 30 of the 52 identified strains. Six genera, represented by eight strains, are unique to one region. Members of the core and unique communities showed comparable solubilization indexes on plates. We conclude that a diversified phylogenetic population of CDB is present in Georgia peanut fields. Despite the phylogenetic diversity, as a population, they exhibit comparable functions in solubilizing calcite on plates.

Meta-transcriptomic identification of groundnut RNA viruses in western Kenya and the novel detection of groundnut as a host for Cauliflower mosaic virus

BACKGROUND

Groundnut (Arachis hypogaea L.) is the 13th most important global crop grown throughout the tropical and subtropical regions of the world. One of the major constraints to groundnut production is viruses, which are also the most economically important and most abundant pathogens among cultivated legumes. Only a few studies have reported the characterization of RNA viruses in cultivated groundnuts in western Kenya, most of which deployed classical methods of detecting known viruses.

METHODS

We sampled twenty-one symptomatic and three asymptomatic groundnut leaf samples from farmers' fields in western Kenya. Total RNA was extracted from the samples followed by First-strand cDNA synthesis and sequencing on the Illumina HiSeq 2500 platform. After removing host and rRNA sequences, high-quality viral RNA sequences were de novo assembled and viral genomes annotated using the publicly available NCBI virus database. Multiple sequence alignment and phylogenetic analysis were done using MEGA X.

RESULTS

Bioinformatics analyses using as low as ∼3.5 million reads yielded complete and partial genomes for Cauliflower mosaic virus (CaMV), Cowpea polerovirus 2 (CPPV2), Groundnut rosette assistor virus (GRAV), Groundnut rosette virus (GRV), Groundnut rosette virus satellite RNA (satRNA) and Peanut mottle virus (PeMoV) falling within the species demarcation criteria. This is the first report of CaMV and the second report of CPPV2 on groundnut hosts in the world. Confirmation of the detected viruses was further verified through phylogenetic analyses alongside reported publicly available highly similar viruses. PeMoV was the only seed-borne virus reported.

CONCLUSION

Our findings demonstrate the power of Next Generation Sequencing in the discovery and identification of novel viruses in groundnuts. The detection of the new viruses indicates the complexity of virus diseases in groundnuts and would require more focus in future studies to establish the effect of the viruses as sole or mixed infections on the crop. The detection of PeMoV with potential origin from Malawi indicates the importance of seed certification and cross-boundary seed health testing.

Improving chilling tolerance of peanut seedlings by enhancing antioxidant-modulated ROS scavenging ability, alleviating photosynthetic inhibition, and mobilizing nutrient absorption

Peanut production is threatened by climate change. Damage to seedlings from low temperatures in early spring can limit yield. Plant adaptations to chilling stress remain unclear in peanut seedlings. It is essential to understand how peanut acquires chilling tolerance. We evaluated effects of chilling stress on growth and recovery of peanut seedlings. We compared and analysed biological characteristics, antioxidants, photosynthesis, biochemical and physiological responses, and nutrient absorption at varying levels of chilling. Compared with chilling-sensitive FH18, the reduced impact of chilling stress on chilling-tolerant NH5 was associated with reduced ROS accumulation, higher ascorbate peroxidase activity and soluble sugar content, lower soluble protein content, and smaller reductions in nutrient content during stress. After removal of chilling stress, FH18 had significant accumulation of O2 •- and H2O2, which decreased photosynthesis, nutrient absorption, and transport. ROS-scavenging reduced damage from chilling stress, allowed remobilization of nutrients, improved chilling tolerance, and restored plant functioning after chilling stress removal. These findings provide a reference for targeted research on peanut seedling tolerance to chilling and lay the foundation for bioinformatics-based research on peanut chilling tolerance mechanisms.

Draft genome sequence data of Nothopassalora personata, peanut foliar pathogen from Argentina

Late leaf spot (LLS) caused by the Ascomycete Nothopassalora personata (N.p.) (Syn. Cercosporidium personatum) is the main foliar disease of peanuts in Argentina and in peanut producing areas of the world, causing up to 70% yield losses. The extremely slow growth of this fungus in culture, that takes around one month to form a 1 cm colony (0.45 mm/day), and the lack of adequate young tissues from where to extract nucleic acids, have hindered genetic studies of this pathogen. Here, we report the first genome sequence of a N. personata isolate from South America, as well as genetic variants on its conserved genes, and the complete sequence of its mating-type locus MAT1-2 idiomorph. The N. personata isolate IPAVE 0302 was obtained from peanut leaves in Córdoba, Argentina. The whole genome sequencing of IPAVE 0302 was performed as paired end 150 bp NovaSeq 6000 and de novo assembled. Clean reads were mapped to the reference genome for this species NRRL 64463 and the genetic variants on highly conserved genes and throughout the genome were analyzed. Sequencing data were submitted to NCBI GenBank Bioproject PRJNA948451, accession number SRR23957761. Additional Fasta files are available from Harvard Dataverse (https://doi.org/10.7910/DVN/9AGPMG and https://doi.org/10.7910/DVN/YDO3V6). The data reported here will be the basis for the analysis of genetic diversity of the LLS pathogen of peanut in Argentina, information that is critical to make decisions on management strategies.

Measuring the Distance and Effects of Weather Conditions on the Dispersal of Nothopassalora personata

Nothopassalora personata is one of the most economically severe pathogens of peanut in the United States. The fungus primarily relies on wind and rain for dispersal, which has been documented up to 10 m from an inoculum source. Spore traps have been used in a wide variety of pathosystems to study epidemiology, document detection, develop alert systems, and guide management programs. The objective of this study was to use spore traps and N. personata-specific qPCR primers to quantitatively evaluate dispersal of N. personata conidia at distances up to 70 m from an infected peanut field and to examine relationships between quantities captured and weather variables. Impaction spore samplers were placed at 4, 10, 30, 50, and 70 m from peanut fields at the Edisto Research and Education Center (six fields) and commercial peanut fields in Barnwell and Bamberg counties (one field each) from 2020 to 2022. Following initial detection, samples were collected at a 48-, 48-, 72-h interval until harvest. N. personata conidia were detected at all locations and distances, documenting dispersal up to 70 m from an inoculum source. This result is a reminder that volunteer management is crucial when rotating peanut in nearby fields. A model for predicting log spore quantities was developed using temperature and humidity variables. Temperature variables associated with observed sampling periods had a negative correlation with N. personata quantities, whereas parameters of relative humidity and mean windspeed were positively correlated.

Genome-wide analysis of the peanut CaM/CML gene family reveals that the AhCML69 gene is associated with resistance to Ralstonia solanacearum

BACKGROUND

Calmodulins (CaMs)/CaM-like proteins (CMLs) are crucial Ca2+-binding sensors that can decode and transduce Ca2+ signals during plant development and in response to various stimuli. The CaM/CML gene family has been characterized in many plant species, but this family has not yet been characterized and analyzed in peanut, especially for its functions in response to Ralstonia solanacearum. In this study, we performed a genome-wide analysis to analyze the CaM/CML genes and their functions in resistance to R. solanacearum.

RESULTS

Here, 67, 72, and 214 CaM/CML genes were identified from Arachis duranensis, Arachis ipaensis, and Arachis hypogaea, respectively. The genes were divided into nine subgroups (Groups I-IX) with relatively conserved exon‒intron structures and motif compositions. Gene duplication, which included whole-genome duplication, tandem repeats, scattered repeats, and unconnected repeats, produced approximately 81 pairs of homologous genes in the AhCaM/CML gene family. Allopolyploidization was the main reason for the greater number of AhCaM/CML members. The nonsynonymous (Ka) versus synonymous (Ks) substitution rates (less than 1.0) suggested that all homologous pairs underwent intensive purifying selection pressure during evolution. AhCML69 was constitutively expressed in different tissues of peanut plants and was involved in the response to R. solanacearum infection. The AhCML69 protein was localized in the cytoplasm and nucleus. Transient overexpression of AhCML69 in tobacco leaves increased resistance to R. solanacearum infection and induced the expression of defense-related genes, suggesting that AhCML69 is a positive regulator of disease resistance.

CONCLUSIONS

This study provides the first comprehensive analysis of the AhCaM/CML gene family and potential genetic resources for the molecular design and breeding of peanut bacterial wilt resistance.

Molecular tagging of seed size using MITE markers in an induced large seed mutant with higher cotyledon cell size in groundnut

A large seed mutant, TG 89 having a 76.7% increment in hundred kernel weight in comparison to its parent TG 26, was isolated from an electron beam-induced mutagenized population. Studies based on environmental scanning electron microscopy of both parent and mutant revealed that the mutant seed cotyledon had significantly bigger cell size than parent. A mapping population with 122 F2 plants derived from the mutant and a distant normal seed genotype (ICGV 15007) was utilized to map the QTL associated with higher HKW. Bulk segregant analysis revealed putative association of three markers with this mutant large seed trait. Further, genotyping of F2 individuals with polymorphic markers detected 14 linkage groups with a map distance of 1053 cM. QTL analysis revealed a significant additive major QTL for the mutant large seed trait on linkage group A05 explaining 12.7% phenotypic variation for the seed size. This QTL was located between flanking markers AhTE333 and AhTE810 having a map interval of 4.7 cM which corresponds to 90.65 to 107.24 Mbp in A05 chromosome, respectively. Within this genomic fragment, an ortholog of the BIG SEEDS 1 gene was found at 102,476,137 bp. Real-time PCR revealed down-regulation of this BIG SEEDS 1 gene in the mutant indicating a loss of function mutation giving rise to a large seed phenotype. This QTL was validated in 11 advanced breeding lines having large seed size from this mutant but with varied genetic backgrounds. This validation showcased a highly promising selection accuracy of 90.9% for the marker-assisted selection.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03909-0.

Genome-Wide Identification of the Ferric Chelate Reductase (FRO) Gene Family in Peanut and Its Diploid Progenitors: Structure, Evolution, and Expression Profiles

The ferric chelate reductase (FRO) family plays a vital role in metal ion homeostasis in a variety of locations in the plants. However, little is known about this family in peanut (Arachis hypogaea). This study aimed to identify FRO genes from the genomes of peanut and the two diploid progenitors (A. duranensis and A. ipaensis) and to analyze their gene/protein structures and evolution. In addition, transcriptional responses of AhFRO genes to Fe deficiency and/or Cu exposure were investigated in two peanut cultivars with different Fe deficiency tolerance (Silihong and Fenghua 1). A total of nine, four, and three FRO genes were identified in peanut, A. duranensis, and A. ipaensis, respectively, which were divided into three groups. Most AhFRO genes underwent WGD/segmental duplication, leading to the expansion of the AhFRO gene family. In general, clustered members share similar gene/protein structures. However, significant divergences occurred in AhFRO2 genes. Three out of five AhFRO2 genes were lowly expressed in all tissues under normal conditions, which may be beneficial for avoiding gene loss. Transcription analysis revealed that AhFRO2 and AhFRO7 genes might be involved in the reduction of Fe/Cu in plasma membranes and plastids, respectively. AhFRO8 genes appear to confer Fe reduction in the mitochondria. Moreover, Fe deficiency induced an increase of Cu accumulation in peanut plants in which AhFRO2.2/2.4/2.5 and FRO7.1/7.2 might be involved. Our findings provided new clues for further understanding the roles of AhFRO genes in the Fe/Cu interaction in peanut.

Genome-Wide Identification and Expression Profiling of Heavy Metal ATPase (HMA) Genes in Peanut: Potential Roles in Heavy Metal Transport

The heavy metal ATPase (HMA) family belongs to the P-type ATPase superfamily and plays an essential role in the regulation of metal homeostasis in plants. However, the gene family has not been fully investigated in peanut. Here, a genome-wide identification and bioinformatics analysis was performed on AhHMA genes in peanut, and the expression of 12 AhHMA genes in response to Cu, Zn, and Cd was evaluated in two peanut cultivars (Silihong and Fenghua 1) differing in Cd accumulation. A total of 21 AhHMA genes were identified in the peanut genome, including ten paralogous gene pairs derived from whole-genome duplication, and an additional gene resulting from tandem duplication. AhHMA proteins could be divided into six groups (I-VI), belonging to two clades (Zn/Co/Cd/Pb-ATPases and Cu/Ag-ATPases). Most AhHMA proteins within the same clade or group generally have a similar structure. However, significant divergence exists in the exon/intron organization even between duplicated gene pairs. RNA-seq data showed that most AhHMA genes are preferentially expressed in roots, shoots, and reproductive tissues. qRT-PCR results revealed that AhHMA1.1/1.2, AhHMA3.1/3.2, AhHMA7.1/7.4, and AhHMA8.1 might be involved in Zn transport in peanut plants, while AhHMA3.2 and AhHMA7.5 might be involved in Cd transport. Our findings provide clues to further characterize the functions of AhHMA genes in metal uptake and translocation in peanut plants.

Peanut (Arachis hypogaea L.) seeds and by-products in metabolic syndrome and cardiovascular disorders: A systematic review of clinical studies

BACKGROUND

Cardiovascular disease (CVDs) is the leading cause of death worldwide. The main risk factors are hypertension, diabetes, obesity, and increased serum lipids. The peanut (Arachis hypogaea L.), also known as the groundnut, goober, pindar, or monkey nut, belongs to the Fabaceae family and is the fourth most cultivated oilseed in the world. The seeds and skin of peanuts possess a rich phytochemical profile composed of antioxidants, such as phenolic acids, stilbenes, flavonoids, and phytosterols. Peanut consumption can provide numerous health benefits, such as anti-obesity, antidiabetic, antihypertensive, and hypolipidemic effects. Accordingly, peanuts have the potential to treat CVD and counteract its risk factors.

PURPOSE

This study aims to critically evaluate the effects of peanuts on metabolic syndrome (MetS) and CVD risk factors based on clinical studies.

METHOD

This review includes studies indexed in MEDLINE-PubMed, COCHRANE, and EMBASE, and the Preferred Reporting Items for a Systematic Review and Meta-Analysis guidelines were adhered to.

RESULTS

Nineteen studies were included and indicated that the consumption of raw peanuts or differing forms of processed foods containing peanut products and phytochemicals could improve metabolic parameters, such as glycemia, insulinemia, glycated hemoglobin, lipids, body mass index, waist circumference, atherogenic indices, and endothelial function.

CONCLUSION

We propose that this legume and its products be used as a sustainable and low-cost alternative for the prevention and treatment of MetS and CVD. However, further research with larger sample sizes, longer intervention durations, and more diverse populations is needed to understand the full benefit of peanut consumption in MetS and CVD.

Genome-Wide Identification of AhMDHs and Analysis of Gene Expression under Manganese Toxicity Stress in Arachis hypogaea

Malate dehydrogenase (MDH) is one kind of oxidation-reduction enzyme that catalyzes the reversible conversion of oxaloacetic acid to malic acid. It has vital functions in plant development, photosynthesis, abiotic stress responses, and so on. However, there are no reports on the genome-wide identification and gene expression of the MDH gene family in Arachis hypogaea. In this study, the MDH gene family of A. hypogaea was comprehensively analyzed for the first time, and 15 AhMDH sequences were identified. According to the phylogenetic tree analysis, AhMDHs are mainly separated into three subfamilies with similar gene structures. Based on previously reported transcriptome sequencing results, the AhMDH expression quantity of roots and leaves exposed to manganese (Mn) toxicity were explored in A. hypogaea. Results revealed that many AhMDHs were upregulated when exposed to Mn toxicity, suggesting that those AhMDHs might play an important regulatory role in A. hypogaea's response to Mn toxicity stress. This study lays foundations for the functional study of AhMDHs and further reveals the mechanism of the A. hypogaea signaling pathway responding to high Mn stress.

Diverse Bradyrhizobium spp. with Similar Symbiosis Genes Nodulate Peanut in Different Regions of China: Characterization of Symbiovar sv. Arachis

A total of 219 rhizobial strains isolated from peanut grown in soils from six peanut croplands in Zhengyang county, Henan Province, were typed by PCR-RFLP of IGS sequences. Their phylogenetic relationships were refined on representative strains using sequence analyses of 16S rRNA genes, housekeeping genes (atpD, recA, glnII) and symbiosis genes (nodA, nodC and nifH). The 219 rhizobial isolates were classified into 13 IGS types, and twenty representatives were defined within eight Bradyrhizobium genospecies: B. guangdongense covering 5 IGS types (75.2% of total isolates), B. guangzhouense (2 IGS types, 2.7% total isolates), B. zhengyangense (1 IGS type, 11.3% total isolates) and five novel genospecies (5 IGS types, 0.9 to 3.2% total isolates). All representative strains had identical nodA, nodC and nifH sequences except for one nifH sequence. With this one exception, these sequences were identical to those of the type strains of Bradyrhizobium species and several Bradyrhizobium genospecies isolated from peanut in different regions of China. The nodC sequences of all strains showed < 67% similarity to the closest strains on the Genbank database indicating that they are representative of a novel Bradyrhiobium symbiovar. This study has shown that (1) diverse Bradyrhizobium spp. with similar symbiosis genes nodulate peanut in different regions of China. (2) Horizontal transfer of genes involved in nodulating peanut is common between Bradyrhizobium species in soils used to grow the crop in China. (3) The strains studied here are representative of a novel Bradyrhizobium symbiovar that nodulates peanut in China. We propose the name sv. arachis for this novel symbiovar indicating that the strains were isolated from Arachis hypogaea. Results here have practical implications in relation to the selection of rhizobial inoculants for peanut in China.

Genome-wide identification and expression analysis of GA20ox and GA3ox genes during pod development in peanut

Background

Gibberellins (GAs) play important roles in regulating peanut growth and development. GA20ox and GA3ox are key enzymes involved in GA biosynthesis. These enzymes encoded by a multigene family belong to the 2OG-Fe (II) oxygenase superfamily. To date, no genome-wide comparative analysis of peanut AhGA20ox and AhGA3ox-encoding genes has been performed, and the roles of these genes in peanut pod development are not clear.

Methods

A whole-genome analysis of AhGA20ox and AhGA3ox gene families in peanut was carried out using bioinformatic tools. The expression of these genes at different stage of pod development was analyzed using qRT-PCR.

Results

In this study, a total of 15 AhGA20ox and five AhGA3ox genes were identified in peanut genome, which were distributed on 14 chromosomes. Phylogenetic analysis divided the GA20oxs and GA3oxs into three groups, but AhGA20oxs and AhGA3oxs in two groups. The conserved pattern of gene structure, cis-elements, and protein motifs further confirmed their evolutionary relationship in peanut. AhGA20ox and AhGA3ox genes were differential expressed at different stages of pod development. The strong expression of AhGA20ox1/AhGA20ox4, AhGA20ox12/AhGA20ox15, AhGA3ox1 and AhGA3ox4/AhGA3ox5 in S1-stage indicated that these genes could have a key role in controlling peg elongation. Furthermore, AhGA20ox and AhGA3ox also showed diverse expression patterns in different peanut tissues including leaves, main stems, flowers and inflorescences. Noticeably, AhGA20ox9/AhGA20ox11 and AhGA3o4/AhGA3ox5 were highly expressed in the main stem, whereas the AhGA3ox1 and AhGA20ox10 were strongly expressed in the inflorescence. The expression levels of AhGA20ox2/AhGA20ox3, AhGA20ox5/AhGA20ox6, AhGA20ox7/AhGA20ox8, AhGA20ox13/AhGA20ox14 and AhGA3ox2/AhGA3ox3 were high in the flowers, suggesting their involvement in flower development. These results provide a basis for deciphering the roles of AhGA20ox and AhGA3ox in peanut growth and development, especially in pod development.

Effect of Electron-Beam Irradiation on Functional Compounds and Biological Activities in Peanut Shells

Peanut shells, rich in antioxidants, remain underutilized due to limited research. The present study investigated the changes in the functional compound content and skin aging-related enzyme inhibitory activities of peanut shells by electron-beam treatment with different sample states and irradiation doses. In addition, phenolic compounds in the peanut shells were identified and quantified using ultra-performance liquid chromatography with ion mobility mass spectrometry-quadrupole time-of-flight and high-performance liquid chromatography with a photodiode array detector, respectively. Total phenolic compound content in solid treatment gradually increased from 110.31 to 189.03 mg gallic acid equivalent/g as the irradiation dose increased. Additionally, electron-beam irradiation significantly increased 5,7-dihydroxychrome, eriodictyol, and luteolin content in the solid treatment compared to the control. However, liquid treatment was less effective in terms of functional compound content compared to the solid treatment. The enhanced functional compound content in the solid treatment clearly augmented the antioxidant activity of the peanut shells irradiated with an electron-beam. Similarly, electron-beam irradiation substantially increased collagenase and elastase inhibitory activities in the solid treatment. Mutagenicity assay confirmed the stability of toxicity associated with the electron-beam irradiation. In conclusion, electron-beam-irradiated peanut shells could serve as an important by-product with potential applications in functional cosmetic materials.

Metabolic profiles of peanut (Arachis hypogaea L.) in response to Puccinia arachidis fungal infection

Background Puccinia arachidis fungus causes rust disease in the peanut plants (Arachis hypogaea L.), which leads to high yield loss. Metabolomic profiling of Arachis hypogaea was performed to identify the pathogen-induced production of metabolites involved in the defense mechanism of peanut plants. In this study, two peanut genotypes, one susceptible (JL-24) and one resistant (GPBD-4) were inoculated with Puccinia arachidis fungal pathogen. The metabolic response was assessed at the control stage (0 day without inoculation), 2 DAI (Day after inoculation), 4 DAI and 6 DAI by Gas Chromatography-Mass Spectrometry (GC-MS). Results About 61 metabolites were identified by NIST library, comprising sugars, phenols, fatty acids, carboxylic acids and sugar alcohols. Sugars and fatty acids were predominant in leaf extracts compared to other metabolites. Concentration of different metabolites such as salicylic acid, mannitol, flavonoid, 9,12-octadecadienoic acid, linolenic acid and glucopyranoside were higher in resistant genotype than in susceptible genotype during infection. Systemic acquired resistance (SAR) and hypersensitive reaction (HR) components such as oxalic acid was elevated in resistant genotype during pathogen infection. Partial least square-discriminant analysis (PLS-DA) was applied to GC-MS data for revealing metabolites profile between resistant and susceptible genotype during infection. Conclusion The phenol content and oxidative enzyme activity i.e. catalase, peroxidase and polyphenol oxidase were found to be very high at 4 DAI in resistant genotype (p-value < 0.01). This metabolic approach provides information about bioactive plant metabolites and their application in crop protection and marker-assisted plant breeding.

Overexpression of the First Peanut-Susceptible Gene, AhS5H1 or AhS5H2, Enhanced Susceptibility to Pst DC3000 in Arabidopsis

Salicylic acid (SA) serves as a pivotal plant hormone involved in regulating plant defense mechanisms against biotic stresses, but the extent of its biological significance in relation to peanut resistance is currently lacking. This study elucidated the involvement of salicylic acid (SA) in conferring broad-spectrum disease resistance in peanuts through the experimental approach of inoculating SA-treated leaves. In several other plants, the salicylate hydroxylase genes are the typical susceptible genes (S genes). Here, we characterized two SA hydroxylase genes (AhS5H1 and AhS5H2) as the first S genes in peanut. Recombinant AhS5H proteins catalyzed SA in vitro, and showed SA 5-ydroxylase (S5H) activity. Overexpression of AhS5H1 or AhS5H2 decreased SA content and increased 2,5-DHBA levels in Arabidopsis, suggesting that both enzymes had a similar role in planta. Moreover, overexpression of each AhS5H gene increased susceptibility to Pst DC3000. Analysis of the transcript levels of defense-related genes indicated that the expression of AhS5H genes, AhNPR1 and AhPR10 was simultaneously induced by chitin. Overexpression of each AhS5H in Arabidopsis abolished the induction of AtPR1 or AtPR2 upon chitin treatment. Eventually, AhS5H2 expression levels were highly correlated with SA content in different tissues of peanut. Hence, the expression of AhS5H1 and AhS5H2 was tissue-specific.

Genome-Wide Identification and Characterization of the Phytochrome Gene Family in Peanut

To investigate the potential role of phytochrome (PHY) in peanut growth and its response to environmental fluctuations, eight candidate AhPHY genes were identified via genome-wide analysis of cultivated peanut. These AhPHY polypeptides were determined to possess acidic and hydrophilic physiochemical properties and exhibit subcellular localization patterns consistent with residence in the nucleus and cytoplasm. Phylogenetic analysis revealed that the AhPHY gene family members were classified into three subgroups homologous to the PHYA/B/E progenitors of Arabidopsis. AhPHY genes within the same clade largely displayed analogous gene structure, conserved motifs, and phosphorylation sites. AhPHY exhibited symmetrical distribution across peanut chromosomes, with 7 intraspecific syntenic gene pairs in peanut, as well as 4 and 20 interspecific PHY syntenic gene pairs in Arabidopsis and soybean, respectively. A total of 42 cis-elements were predicted in AhPHY promoters, including elements implicated in phytohormone regulation, stress induction, physiology, and photoresponse, suggesting putative fundamental roles across diverse biological processes. Moreover, spatiotemporal transcript profiling of AhPHY genes in various peanut tissues revealed distinct expression patterns for each member, alluding to putative functional specialization. This study contributes novel insights into the classification, structure, molecular evolution, and expression profiles of the peanut phytochrome gene family, and also provides phototransduction gene resources for further mechanistic characterization.

A Comparison between High-Performance Countercurrent Chromatography and Fast-Centrifugal Partition Chromatography for a One-Step Isolation of Flavonoids from Peanut Hulls Supported by a Conductor like Screening Model for Real Solvents

Peanut hulls (Arachis hypogaea, Leguminosae), which are a side stream of global peanut processing, are rich in bioactive flavonoids such as luteolin, eriodictyol, and 5,7-dihydroxychromone. This study aimed to isolate these flavonoid derivatives by liquid-liquid chromatography with as few steps as possible. To this end, luteolin, eriodictyol and 5,7-dihydroxychromone were isolated from peanut hulls using two different techniques, high-performance countercurrent chromatography (HPCCC) and fast-centrifugal partition chromatography (FCPC). The suitability of the biphasic solvent system composed of n-hexane/ethyl acetate/methanol/water (1.0/1.0/1.0/1.5; v/v/v/v) was determined by the Conductor like Screening Model for Real Solvents (COSMO-RS), which allowed the partition ratio K_D-values of the three main flavonoids to be calculated. After a one-step HPCCC separation of ~1000 mg of an ethanolic peanut hull extract, 15 mg of luteolin and 8 mg of eriodictyol were isolated with purities over 96%. Furthermore, 3 mg of 5,7-dihydroxychromone could be isolated after purification by semi-preparative reversed-phase liquid chromatography (semi-prep. HPLC) in purity of over 99%. The compounds were identified by electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance spectroscopy (NMR).

In Vitro Digestion of Peanut Skin Releases Bioactive Compounds and Increases Cancer Cell Toxicity

Peanut skin is a rich source of bioactive compounds which may be able to reduce the risk factors associated with metabolic syndromes. This study aimed to characterize bio-compounds from peanut skin (Arachis hypogaea) and their bioactivity (antioxidant activity, inhibition of lipase, and carbohydrase enzymes) and to evaluate their anti-proliferative properties in colorectal cancer cells (HCT116) upon in vitro digestion. Peanut skin was digested in two sequential phases, and the final content, named phase-1 (P1) and phase-2 (P2) extracts, was evaluated. Several bioactive compounds were positively identified and quantified by liquid chromatography, including quinic acid, released especially after in vitro digestion. The total phenolic content and, regardless of the method, the antioxidant activity of P1 was higher than P2. P1 also showed a lower enzyme inhibitory concentration IC₅₀ than P2, lipase, and α-glucosidase. For cell viability in HCT116 cells, lower concentrations of P1 were found for IC₅₀ compared to P2. In conclusion, bioactive compounds were released mainly during the first phase of the in vitro digestion. The digested samples presented antioxidant activity, enzyme inhibitory activity, and cancer cell cytotoxicity, especially those from the P1 extract. The potential applications of such a by-product in human health are reported.

Overexpression of peanut (Arachis hypogaea L.) AhGRFi gene enhanced root growth inhibition under exogenous NAA treatment in Arabidopsis thaliana

The 14-3-3 protein is a kind of evolutionary ubiquitous protein family highly conserved in eukaryotes. Initially, 14-3-3 proteins were reported in mammalian nervous tissues, but in the last decade, their role in various metabolic pathways in plants established the importance of 14-3-3 proteins. In the present study, a total of 22 14-3-3 genes, also called general regulatory factors (GRF), were identified in the peanut (Arachis hypogaea) genome, out of which 12 belonged to the ε group, whereas 10 of them belonged to the non- ε-group. Tissue-specific expression of identified 14-3-3 genes were studied using transcriptome analysis. The peanut AhGRFi gene was cloned and transformed into Arabidopsis thaliana. The investigation of subcellular localization indicated that AhGRFi is localized in the cytoplasm. Overexpression of the AhGRFi gene in transgenic Arabidopsis showed that under exogenous 1-naphthaleneacetic acid (NAA) treatment, root growth inhibition in transgenic plants was enhanced. Further analysis indicated that the expression of auxin-responsive genes IAA3, IAA7, IAA17, and SAUR-AC1 was upregulated and GH3.2 and GH3.3 were downregulated in transgenic plants, but the expression of GH3.2, GH3.3, and SAUR-AC1 showed opposite trends of change under NAA treatment. These results suggest that AhGRFi may be involved in auxin signaling during seedling root development. An in-depth study of the molecular mechanism of this process remains to be further explored.

Purification and Identification of Novel Antioxidant Peptides from Hydrolysates of Peanuts (Arachis hypogaea) and Their Neuroprotective Activities

Peanut (Arachis hypogaea) peptides have various functional activities and a high utilization value. This study aims to isolate and characterize antioxidant peptides from peanut protein hydrolysates and further evaluate their neuroprotection against oxidative damage to PC12 cells induced by 6-hydroxydopamine (6-OHDA). After the peanut protein was hydrolyzed with pepsin and purified using ultrafiltration and gel chromatography, six peptides were identified and sequenced by high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Out of these six peptides, Pro-Gly-Cys-Pro-Ser-Thr (PGCPST) exhibited a desirable antioxidant capacity, as determined using the 1,1-diphenyl-2-picrylhydrazyl, 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, and hydroxyl radical scavenging assays. Moreover, our results indicated that the peptide PGCPST effectively increased the cell viability and reduced the cell apoptosis in 6-OHDA-induced PC12. RNA sequencing further showed that the neuroprotective effect of the peptide PGCPST was mediated via sphingolipid metabolism-related pathways. With further research efforts, the peptide PGCPST was expected to develop into a new neuroprotective agent.

The peanut root exudate increases the transport and metabolism of nutrients and enhances the plant growth-promoting effects of burkholderia pyrrocinia strain P10

BACKGROUND

Burkholderia pyrrocinia strain P10 is a plant growth-promoting rhizobacterium (PGPR) that can substantially increase peanut growth. However, the mechanisms and pathways involved in the interaction between B. pyrrocinia P10 and peanut remain unclear. To clarify complex plant-PGPR interactions and the growth-promoting effects of PGPR strains, the B. pyrrocinia P10 transcriptome changes in response to the peanut root exudate (RE) were elucidated and the effects of RE components on biofilm formation and indole-3-acetic acid (IAA) secretion were analyzed.

RESULTS

During the early interaction phase, the peanut RE enhanced the transport and metabolism of nutrients, including carbohydrates, amino acids, nitrogen, and sulfur. Although the expression of flagellar assembly-related genes was down-regulated, the expression levels of other genes involved in biofilm formation, quorum sensing, and Type II, III, and VI secretion systems were up-regulated, thereby enabling strain P10 to outcompete other microbes to colonize the peanut rhizosphere. The peanut RE also improved the plant growth-promoting effects of strain P10 by activating the expression of genes associated with siderophore biosynthesis, IAA production, and phosphorus solubilization. Additionally, organic acids and amino acids were identified as the dominant components in the peanut RE. Furthermore, strain P10 biofilm formation was induced by malic acid, oxalic acid, and citric acid, whereas IAA secretion was promoted by the alanine, glycine, and proline in the peanut RE.

CONCLUSION

The peanut RE positively affects B. pyrrocinia P10 growth, while also enhancing colonization and growth-promoting effects during the early interaction period. These findings may help to elucidate the mechanisms underlying complex plant-PGPR interactions, with potential implications for improving the applicability of PGPR strains.

Bacteroid Development, Transcriptome, and Symbiotic Nitrogen-Fixing Comparison of Bradyrhizobium arachidis in Nodules of Peanut (Arachis hypogaea) and Medicinal Legume Sophora flavescens

Bradyrhizobium arachidis strain CCBAU 051107 could differentiate into swollen and nonswollen bacteroids in determinate root nodules of peanut (Arachis hypogaea) and indeterminate nodules of Sophora flavescens, respectively, with different N2 fixation efficiencies. To reveal the mechanism of bacteroid differentiation and symbiosis efficiency in association with different hosts, morphologies, transcriptomes, and nitrogen fixation efficiencies of the root nodules induced by strain CCBAU 051107 on these two plants were compared. Our results indicated that the nitrogenase activity of peanut nodules was 3 times higher than that of S. flavescens nodules, demonstrating the effects of rhizobium-host interaction on symbiotic effectiveness. With transcriptome comparisons, genes involved in biological nitrogen fixation (BNF) and energy metabolism were upregulated, while those involved in DNA replication, bacterial chemotaxis, and flagellar assembly were significantly downregulated in both types of bacteroids compared with those in free-living cells. However, expression levels of genes involved in BNF, the tricarboxylic acid (TCA) cycle, the pentose phosphate pathway, hydrogenase synthesis, poly-β-hydroxybutyrate (PHB) degradation, and peptidoglycan biosynthesis were significantly greater in the swollen bacteroids of peanut than those in the nonswollen bacteroids of S. flavescens, while contrasting situations were found in expression of genes involved in urea degradation, PHB synthesis, and nitrogen assimilation. Especially higher expression of ureABEF and aspB genes in bacteroids of S. flavescens might imply that the BNF product and nitrogen transport pathway were different from those in peanut. Our study revealed the first differences in bacteroid differentiation and metabolism of these two hosts and will be helpful for us to explore higher-efficiency symbiosis between rhizobia and legumes. IMPORTANCE Rhizobial differentiation into bacteroids in leguminous nodules attracts scientists to investigate its different aspects. The development of bacteroids in the nodule of the important oil crop peanut was first investigated and compared to the status in the nodule of the extremely promiscuous medicinal legume Sophora flavescens by using just a single rhizobial strain of Bradyrhizobium arachidis, CCBAU 051107. This strain differentiates into swollen bacteroids in peanut nodules and nonswollen bacteroids in S. flavescens nodules. The N2-fixing efficiency of the peanut nodules is three times higher than that of S. flavescens. By comparing the transcriptomes of their bacteroids, we found that they have similar gene expression spectra, such as nitrogen fixation and motivity, but different spectra in terms of urease activity and peptidoglycan biosynthesis. Those altered levels of gene expression might be related to their functions and differentiation in respective nodules. Our studies provided novel insight into the rhizobial differentiation and metabolic alteration in different hosts.

Characterization and functional analysis of AhGPAT9 gene involved in lipid synthesis in peanut (Arachis hypogaea L.)

GPAT enzymes (glycerol-3-phosphate 1-O-acyltransferase, EC 2.3.1.15) catalyze the initial and rate-limiting step of plant glycerolipid biosynthesis for membrane homeostasis and lipid accumulation, yet little research has been done on peanuts. By reverse genetics and bioinformatics analyses, we have characterized an AhGPAT9 isozyme, of which the homologous product is isolated from cultivated peanut. QRT-PCR assay revealed a spatio-temporal expression pattern that the transcripts of AhGPAT9 accumulating in various peanut tissues are highly expressed during seed development, followed by leaves. Green fluorescent protein tagging of AhGPAT9 confirmed its subcellular accumulation in the endoplasmic reticulum. Compared with the wild type control, overexpressed AhGPAT9 delayed the bolting stage of transgenic Arabidopsis, reduced the number of siliques, and increased the seed weight as well as seed area, suggesting the possibility of participating in plant growth and development. Meanwhile, the mean seed oil content from five overexpression lines increased by about 18.73%. The two lines with the largest increases in seed oil content showed a decrease in palmitic acid (C16:0) and eicosenic acid (C20:1) by 17.35% and 8.33%, respectively, and an increase in linolenic acid (C18:3) and eicosatrienoic acid (C20:3) by 14.91% and 15.94%, respectively. In addition, overexpressed AhGPAT9 had no significant effect on leaf lipid content of transgenic plants. Taken together, these results suggest that AhGPAT9 is critical for the biosynthesis of storage lipids, which contributes to the goal of modifying peanut seeds for improved oil content and fatty acid composition.

Molecular cloning and functional characterization of the promoter of a novel Aspergillus flavus inducible gene (AhOMT1) from peanut

Peanut is an important oil and food legume crop grown in more than one hundred countries, but the yield and quality are often impaired by different pathogens and diseases, especially aflatoxins jeopardizing human health and causing global concerns. For better management of aflatoxin contamination, we report the cloning and characterization of a novel A. flavus inducible promoter of the O-methyltransferase gene (AhOMT1) from peanut. The AhOMT1 gene was identified as the highest inducible gene by A. flavus infection through genome-wide microarray analysis and verified by qRT-PCR analysis. AhOMT1 gene was studied in detail, and its promoter, fussed with the GUS gene, was introduced into Arabidopsis to generate homozygous transgenic lines. Expression of GUS gene was studied in transgenic plants under the infection of A. flavus. The analysis of AhOMT1 gene characterized by in silico assay, RNAseq, and qRT-PCR revealed minute expression in different organs and tissues with trace or no response to low temperature, drought, hormones, Ca2+, and bacterial stresses, but highly induced by A. flavus infection. It contains four exons encoding 297 aa predicted to transfer the methyl group of S-adenosyl-L-methionine (SAM). The promoter contains different cis-elements responsible for its expression characteristics. Functional characterization of AhOMT1P in transgenic Arabidopsis plants demonstrated highly inducible behavior only under A. flavus infection. The transgenic plants did not show GUS expression in any tissue(s) without inoculation of A. flavus spores. However, GUS activity increased significantly after inoculation of A. flavus and maintained a high level of expression after 48 hours of infection. These results provided a novel way for future management of peanut aflatoxins contamination through driving resistance genes in A. flavus inducible manner.

Genome-Wide Identification and Expression Analysis Reveals Roles of the NRAMP Gene Family in Iron/Cadmium Interactions in Peanut

The natural resistance-associated macrophage protein (NRAMP) family plays crucial roles in metal uptake and transport in plants. However, little is known about their functions in peanut. To understand the roles of AhNRAMP genes in iron/cadmium interactions in peanut, genome-wide identification and bioinformatics analysis was performed. A total of 15 AhNRAMP genes were identified from the peanut genome, including seven gene pairs derived from whole-genome duplication and a segmental duplicated gene. AhNRAMP proteins were divided into two distinct subfamilies. Subfamily I contains eight acid proteins with a specific conserved motif 7, which were predicted to localize in the vacuole membrane, while subfamily II includes seven basic proteins sharing specific conserved motif 10, which were localized to the plasma membrane. Subfamily I genes contained four exons, while subfamily II had 13 exons. AhNRAMP proteins are perfectly modeled on the 5m94.1.A template, suggesting a role in metal transport. Most AhNRAMP genes are preferentially expressed in roots, stamens, or developing seeds. In roots, the expression of most AhNRAMPs is induced by iron deficiency and positively correlated with cadmium accumulation, indicating crucial roles in iron/cadmium interactions. The findings provide essential information to understand the functions of AhNRAMPs in the iron/cadmium interactions in peanuts.

Gene expression and DNA methylation altering lead to the high oil content in wild allotetraploid peanut (A. monticola)

INTRODUCTION

The wild allotetraploid peanut Arachis monticola contains a higher oil content than the cultivated allotetraploid Arachis hypogaea. Besides the fact that increasing oil content is the most important peanut breeding objective, a proper understanding of its molecular mechanism controlling oil accumulation is still lacking.

METHODS

We investigated this aspect by performing comparative transcriptomics from developing seeds between three wild and five cultivated peanut varieties.

RESULTS

The analyses not only showed species-specific grouping transcriptional profiles but also detected two gene clusters with divergent expression patterns between two species enriched in lipid metabolism. Further analysis revealed that expression alteration of lipid metabolic genes with co-expressed transcription factors in wild peanut led to enhanced activity of oil biogenesis and retarded the rate of lipid degradation. In addition, bisulfite sequencing was conducted to characterize the variation of DNA methylation between wild allotetraploid (245, WH 10025) and cultivated allotetraploid (Z16, Zhh 7720) genotypes. CG and CHG context methylation was found to antagonistically correlate with gene expression during seed development. Differentially methylated region analysis and transgenic assay further illustrated that variations of DNA methylation between wild and cultivated peanuts could affect the oil content via altering the expression of peroxisomal acyl transporter protein (Araip.H6S1B).

DISCUSSION

From the results, we deduced that DNA methylation may negatively regulate lipid metabolic genes and transcription factors to subtly affect oil accumulation divergence between wild and cultivated peanuts. Our work provided the first glimpse on the regulatory mechanism of gene expression altering for oil accumulation in wild peanut and gene resources for future breeding applications.

Integrated analyses reveal the response of peanut to phosphorus deficiency on phenotype, transcriptome and metabolome

BACKGROUND

Phosphorus (P) is one of the most essential macronutrients for crops. The growth and yield of peanut (Arachis hypogaea L.) are always limited by P deficiency. However, the transcriptional and metabolic regulatory mechanisms were less studied. In this study, valuable phenotype, transcriptome and metabolome data were analyzed to illustrate the regulatory mechanisms of peanut under P deficiency stress.

RESULT

In present study, two treatments of P level in deficiency with no P application (-P) and in sufficiency with 0.6 mM P application (+ P) were used to investigate the response of peanut on morphology, physiology, transcriptome, microRNAs (miRNAs), and metabolome characterizations. The growth and development of plants were significantly inhibited under -P treatment. A total of 6088 differentially expressed genes (DEGs) were identified including several transcription factor family genes, phosphate transporter genes, hormone metabolism related genes and antioxidant enzyme related genes that highly related to P deficiency stress. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that 117 genes were annotated in the phenylpropanoid biosynthesis pathway under P deficiency stress. A total of 6 miRNAs have been identified significantly differential expression between + P and -P group by high-throughput sequencing of miRNAs, including two up-regulated miRNAs (ahy-miR160-5p and ahy-miR3518) and four down-regulated miRNAs (ahy-miR408-5p, ahy-miR408-3p, ahy-miR398, and ahy-miR3515). Further, the predicted 22 target genes for 6 miRNAs and cis-elements in 2000 bp promoter region of miRNA genes were analyzed. A total of 439 differentially accumulated metabolites (DAMs) showed obviously differences in two experimental conditions.

CONCLUSIONS

According to the result of transcripome and metabolome analyses, we can draw a conclusion that by increasing the content of lignin, amino acids, and levan combining with decreasing the content of LPC, cell reduced permeability, maintained stability, raised the antioxidant capacity, and increased the P uptake in struggling for survival under P deficiency stress.

Nitrogen fertilizer amount has minimal effect on rhizosphere bacterial diversity during different growth stages of peanut

The impact of short-term nitrogen fertilizer input on the structure and diversity of peanut rhizosphere microbiota (RM) at different growth stages (GSs) was explored in the southern paddy soil planting environment. Three levels of nitrogen were applied in the field: control (LN, 0 kg/hm²), medium nitrogen (MN, 55.68 kg/hm²), and high nitrogen (HN, 111.36 kg/hm²). The rhizosphere soil was collected during four GSs for high-throughput sequencing and chemical properties analysis. The effect of nitrogen fertilizer application on peanut RM was minimal and was obvious only at the seedling stage. In the four peanut GSs, a significant increase in relative abundance was observed for only one operational taxonomic unit (OTU) of Nitrospira under HN conditions at the seedling stage and mature stage, while there was no consistent change in other OTUs. The difference in RM among different peanut GSs was greater than that caused by the amount of nitrogen fertilizer. This may be due to the substantial differences in soil chemical properties (especially alkali-hydrolyzable nitrogen, pH, and available potassium or total potassium) among peanut GSs, as these significantly affected the RM structure. These results are of great value to facilitate deeper understanding of the effect of nitrogen fertilizer on peanut RM structure.

Comparison of Current Peanut Fungicides Against Athelia rolfsii Through a Laboratory Bioassay of Detached Plant Tissues

Southern stem rot of peanut, caused by Athelia rolfsii, is an important fungal disease that impacts peanut production worldwide. Foliar-applied fungicides are used to manage the disease, and several fungicides have been recently registered for southern stem rot control in peanuts. This study compared fungicidal, residual, and potential systemic activity of current fungicides against A. rolfsii using a laboratory bioassay. Peanut plants grown in the field were treated with eight fungicides approximately 90 days after planting, and plants were collected for the laboratory bioassay weekly for 5 weeks following application. Peanut plants were separated into the newest fully mature leaf present at sample collection, the second newest fully mature leaf present at the time of fungicide application, the upper stem, and the crown tissues. Each plant tissue was inoculated with A. rolfsii then incubated at 30°C for 2 days. Lesion length was measured, and percent inhibition of fungal growth by each fungicide relative to the control was calculated. All fungicides provided the greatest inhibition of A. rolfsii on leaf tissues that were present at the time of fungicide application, followed by the newly grown leaf and upper stem. Little inhibition occurred on the crown. Fungal inhibition decreased at similar rates over time for all fungicides tested. Succinate dehydrogenase inhibitors provided less basipetal protection of upper stems than quinone outside inhibitor or demethylation inhibitor fungicides. Properties of the fungicides characterized in this study, including several newly registered products, are useful for developing fungicide application recommendations to maximize their efficacy in controlling both foliar and soilborne peanut diseases.

Does improved oleic acid content due to marker-assisted introgression of ahFAD2 mutant alleles in peanuts alter its mineral and vitamin composition?

Peanuts (Arachis hypogaea L.) with high oleic acid content have extended shelf life and several health benefits. Oleic, linoleic, and palmitic acid contents in peanuts are regulated by ahFAD2A and ahFAD2B mutant alleles. In the present study, ahFAD2A and ahFAD2B mutant alleles from SunOleic 95R were introgressed into two popular peanut cultivars, GG-7 and TKG19A, followed by markers-assisted selection (MAS) and backcrossing (MABC). A total of 22 MAS and three MABC derived lines were developed with increased oleic acid (78-80%) compared to those of GG 7 (40%) and TKG 19A (50%). Peanut kernel mineral and vitamin composition remained unchanged, while potassium content was altered in high oleic ingression lines. Two introgression lines, HOMS Nos. 37 and 113 had over 10% higher pooled pod yield than respective best check varieties. More than 70% recurrent parent genome recovery was observed in HOMS-37 and HOMS-113 through recombination breeding. However, the absence of recombination in the vicinity of the target locus resulted in its precise introgression along with ample background genome recovery. Selected introgression lines could be released for commercial cultivation based on potential pod yield and oleic acid content.

Engineered green nanoparticles interact with Nigrospora oryzae isolated from infected leaves of Arachis hypogaea

Oilseed crop diseases are a major concern around the world, particularly in India. The synthetic fungicides not only kill the pathogen, but they also harm the host plant and beneficial microbes and on continuous usage, they decrease the soil fertility. To overcome this problem, green nanotechnology has been a greater alternative with promising benefits. The green synthesized nanoparticles from the extract of various plant parts are an effective remedy for killing the pathogens without affecting the host plants and the environment. Hence, in our study silver nanoparticles were synthesized from Fennel seed (Foeniculum vulgare) extract. The synthesis of nanoparticles was confirmed using UV-vis, Fourier transform infrared, dynamic light scattering, zeta potential, and scanning electron microscopic analysis. The in vitro antifungal study was carried out and revealed that the nanoparticles had high efficacy against the isolated phytopathogen Nigrospora oryzae which causes tikka disease in Arachis hypogaea plants. Hence, F. vulgare seed nanoparticles can be used as an effective alternative to synthetic fungicides without causing any deleterious effect on soil microflora or the environment.

Stem powder and its active carbon of Arachis hypogaea plant for lead (II) removal: application to treat battery-based industrial effluents

Stem powder and its active carbon of Arachis hypogaea plant are identified to have strong adsorptivity for lead ions. The bio-sorbents are characterized by conventional methods including XRD and FTIR analysis. These biomaterials are investigated for their maximum adsorption for lead ions by optimizing the extraction conditions. The maximum removal is observed in the pH range of 6-7 for both sorbents. With stem powders, the removal is 76.0% from a simulated lead solution of concentration: 20.0 mg/L with 1.5 g/L of the sorbent and at an equilibration time of 2.0 h. With the active carbon, the maximum extraction of: 86.0% is observed at pH: 6.5 with 1.0 g/L of the sorbent after an equilibration time of 1.5 h. The sorption capacities are 32.0 mg/g for stem powders, and 40.5 mg/g for active carbon. Many co-ions have marginal interference. Spent adsorbents can be recycled after regeneration. Thermodynamic investigations reveal the spontaneity and endothermic nature of adsorption. High ΔH values viz., 26.45 kJ/mole for AHSP and 46.40 kJ/mole for AHSAC, confirm the bonding of Pb²⁺ ions with the sorbents is either "ion-exchange" and/or a sort of "complex formation." The disorder at the solid and liquid boundary is indicated by high positive ΔS values and it is a favorable condition for good Pb²⁺ adsorption. On analysis of different kinetic and isotherm models, the sorption of Pb²⁺ ions follows Pseudo-2nd order and Langmuir models. This confirms the mono-layer adsorption of Pb²⁺ ions on the humongous surface of the sorbent. The adsorbents are successfully applied to treat industrial effluent samples.

Elite Bradyrhizobium strains boost biological nitrogen fixation and peanut yield in tropical drylands

Peanut (Arachis hypogaea L.) is an important crop for the family-based systems in the tropics, mainly in Brazil. In the Brazilian drylands, peanuts are cropped in low technological systems, and cheap and efficient technologies are needed to improve crop yield and sustainability. Despite this importance, few data are available on selecting efficient peanut rhizobia in experiments under different edaphoclimatic conditions. This work evaluated the agronomic efficiency and the biological nitrogen fixation (BNF) by two elite Bradyrhizobium strains under four different fields in the Brazilian semiarid region. We compared a new efficient strain Bradyrhizobium sp. ESA 123 with the reference strain B. elkanii SEMIA 6144, currently used in peanut rhizobial inoculants in Brazil. Besides the inoculated treatments, two uninoculated controls were assessed (with and without 80 kg ha^-1 of N-urea). The BNF was estimated by the δ¹⁵N approach in three out of four field assays. BNF contribution was improved by inoculation of both Bradyrhizobium strains, ranging from 42 to 51% in Petrolina and 43 to 60% in Nossa Senhora da Glória. Peanuts' yields benefited from the inoculation of both strains and N fertilization in all four assays. Nevertheless, the results showed the efficiency of both strains under different edaphoclimatic conditions, indicating the native strain ESA 123 as a potential bacterium for recommendation as inoculants for peanuts in Brazil, mainly in drylands.

Potassium deficiency stress tolerance in peanut (Arachis hypogaea) through ion homeostasis, activation of antioxidant defense, and metabolic dynamics: Alleviatory role of silicon supplementation

Potassium (K) scarcity of arable land is one of the important factors that hamper the growth of the plants and reduce yield worldwide. In the current study, we examine the physiological, biochemical, and metabolome response of Arachis hypogaea (GG7 genotype: fast-growing, tall, early maturing, and high yielding) under low K either solitary or in combination with Si to elucidate the ameliorative role of Si. The reduced fresh and dry biomass of peanut and photosynthetic pigments content was significantly alleviated by Si. Si application did not affect the leaf and stem K⁺, although it enhanced root K⁺ in K-limitation, which is probably due to up-regulated expression of genes responsible for K uptake. Si improves the potassium use efficiency in K-limitation as compared to control. K-deficiency increased MDA, O₂^•-, and H₂O₂ levels in leaf and root of peanut. Si improved/maintained the activity of antioxidative enzymes, which significantly lowered the ROS accumulation in K-limitation. The AsA/DHA and GSH/GSSG ratio was approximately unaffected in both leaf and root, suggesting the maintained cellular redox potential in K-starved peanut. Si promotes accumulation of sugars and sugar alcohols, phytohormones indicating their probable involvement in signal transduction, osmotic regulation, and improvement of stress tolerance. Down-regulation of aspartic acid and glutamic acid while up-regulation of lysine, histidine, and arginine could maintain charge balance in K-deprived peanut. The significant accumulation of polyphenols under K limitation supplemented with Si suggests the role of polyphenols for ROS scavenging. Our results demonstrated that Si as a beneficial element can mitigate K-nutrient toxicity and improve KUE of peanut under K-limitation conditions. Moreover, our results demonstrate that Si application can improve crop yield, quality, and nutrient use efficiency under nutrient limitation conditions.

The Mechanisms Underlying Salt Resistance Mediated by Exogenous Application of 24-Epibrassinolide in Peanut

Peanut is one of the most important oil crops in the world, the growth and productivity of which are severely affected by salt stress. 24-epibrassinolide (EBL) plays an important role in stress resistances. However, the roles of exogenous EBL on the salt tolerance of peanut remain unclear. In this study, peanut seedlings treated with 150 mM NaCl and with or without EBL spray were performed to investigate the roles of EBL on salt resistance. Under 150 mM NaCl conditions, foliar application of 0.1 µM EBL increased the activity of catalase and thereby could eliminate reactive oxygen species (ROS). Similarly, EBL application promoted the accumulation of proline and soluble sugar, thus maintaining osmotic balance. Furthermore, foliar EBL spray enhanced the total chlorophyll content and high photosynthesis capacity. Transcriptome analysis showed that under NaCl stress, EBL treatment up-regulated expression levels of genes encoding peroxisomal nicotinamide adenine dinucleotide carrier (PMP34), probable sucrose-phosphate synthase 2 (SPS2) beta-fructofuranosidase (BFRUCT1) and Na⁺/H⁺ antiporters (NHX7 and NHX8), while down-regulated proline dehydrogenase 2 (PRODH). These findings provide valuable resources for salt resistance study in peanut and lay the foundation for using BR to enhance salt tolerance during peanut production.

New disease and first report of marasmioid fungus, Marasmius palmivorus (Sharples), causing white root rot in Arachis hypogaea L

Groundnut (Arachis hypogaea L.) plants showing distinct symptoms of necrosis of leaves and severe rotting of roots were observed in the agricultural field at Arakkonam, Tamil Nadu, India. The rhizomorphs of the phytopathogenic fungus were obtained from the rotted roots of the diseased plants, cultured in the laboratory and based on the morphological characteristics and nucleotide sequencing analysis of ITS and nLSU region, the phytopathogen was identified as Marasmius palmivorus. The isolated fungus produced distinct fruiting bodies (basidiocarps) when grown under the laboratory conditions. The fungus grew as cottony white colony on Potato Dextrose Agar (PDA) medium and found to contain septate and clamp connections when examined under light microscope. The pathogenicity of the isolated fungus was assessed by inoculating it on healthy groundnut plant under the glasshouse condition, which resulted in the establishment of typical disease symptom and the pathogenicity of the fungus was confirmed. The fungal pathogen re-isolated from the artificially inoculated plants was used for molecular characterization and confirmed that the organism is Marasmius palmivorus. To the best of our knowledge, this is the first report on the occurrence of Marasmius palmivorus, causing white root rot disease in Arachis hypogaea L.

Developmental Analysis of Compound Leaf Development in Arachis hypogaea

Leaves are the primary photosynthetic structures, while photosynthesis is the direct motivation of crop yield formation. As a legume plant, peanut (Arachis hypogaea) is one of the most economically essential crops as well as an important source of edible oil and protein. The leaves of A. hypogaea are in the tetrafoliate form, which is different from the trifoliate leaf pattern of Medicago truncatula, a model legume species. In A. hypogaea, an even-pinnate leaf with a pair of proximal and distal leaflets was developed; however, only a single terminal leaflet and a pair of lateral leaflets were formed in the odd-pinnate leaf in M. truncatula. In this study, the development of compound leaf in A. hypogaea was investigated. Transcriptomic profiles revealed that the common and unique differentially expressed genes were identified in a proximal leaflet and a distal leaflet, which provided a research route to understand the leaf development in A. hypogaea. Then, a naturally occurring mutant line with leaf developmental defects in A. hypogaea was obtained, which displayed a pentafoliate form with an extra terminal leaflet. The characterization of the mutant indicated that cytokinin and class I KNOTTED-LIKE HOMEOBOX were involved in the control of compound leaf pattern in A. hypogaea. These results expand our knowledge and provide insights into the molecular mechanism underlying the formation of different compound leaf patterns among species.

Microscopic and Transcriptomic Analyses of Dalbergoid Legume Peanut Reveal a Divergent Evolution Leading to Nod-Factor-Dependent Epidermal Crack-Entry and Terminal Bacteroid Differentiation

Root nodule symbiosis (RNS) is the pillar behind sustainable agriculture and plays a pivotal role in the environmental nitrogen cycle. Most of the genetic, molecular, and cell-biological knowledge on RNS comes from model legumes that exhibit a root-hair mode of bacterial infection, in contrast to the Dalbergoid legumes exhibiting crack-entry of rhizobia. As a step toward understanding this important group of legumes, we have combined microscopic analysis and temporal transcriptome to obtain a dynamic view of plant gene expression during Arachis hypogaea (peanut) nodule development. We generated comprehensive transcriptome data by mapping the reads to A. hypogaea, and two diploid progenitor genomes. Additionally, we performed BLAST searches to identify nodule-induced yet-to-be annotated peanut genes. Comparison between peanut, Medicago truncatula, Lotus japonicus, and Glycine max showed upregulation of 61 peanut orthologs among 111 tested known RNS-related genes, indicating conservation in mechanisms of nodule development among members of the Papilionoid family. Unlike model legumes, recruitment of class 1 phytoglobin-derived symbiotic hemoglobin (SymH) in peanut indicates diversification of oxygen-scavenging mechanisms in the Papilionoid family. Finally, the absence of cysteine-rich motif-1-containing nodule-specific cysteine-rich peptide (NCR) genes but the recruitment of defensin-like NCRs suggest a diverse molecular mechanism of terminal bacteroid differentiation. In summary, our work describes genetic conservation and diversification in legume-rhizobia symbiosis in the Papilionoid family, as well as among members of the Dalbergoid legumes.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Effect of replacing soybean meal with peanut meal on milk production and fat composition in lactating dairy cows

The objective of this study was to evaluate the effects of replacing soybean meal with peanut meal on milk production, chemical and fatty acid composition, nutritional quality indicators of the lipid fraction, and the economic viability of the diets. Twelve crossbred cows in the initial lactation third, with a bodyweight of 545 ± 37 kg and average milk production of 28 kg/day of milk were distributed in a 4 × 4, triple Latin square design. The treatments consisted of diets with substitution levels of soybean meal for peanut meal (0; 330; 670; and 1000 g/kg in DM). The peanut meal inclusion to replace soybean meal in the diets provided a decreasing linear effect for the protein (P = 0.02) and casein (P = 0.01) concentration in milk. Milk production, total solids concentration, feed efficiency, fatty acid composition, and nutritional quality indicators of the milk lipid fraction were not influenced by the substitution levels. The diet cost per kg DM decreased due to the peanut meal inclusion as a protein source. The partial or total substitution of soybean meal for peanut meal in the feedlot cows diet reduces the cost of feed, without affecting milk production and total solids yield.

A protocol for the generation of Arachis hypogaea composite plants: A valuable tool for the functional study of mycorrhizal symbiosis

PREMISE

Agrobacterium rhizogenes-induced hairy root systems are one of the most preferred and versatile systems for the functional characterization of genes. The use of hairy root systems is a rapid and convenient alternative for studying root biology, biotic and abiotic stresses, and root symbiosis in in vitro recalcitrant legume species such as Arachis hypogaea.

METHODS AND RESULTS

We present a rapid, simplified method for the generation of composite A. hypogaea plants with transgenic hairy roots. We demonstrate a technique of hairy root induction mediated by A. rhizogenes from young A. hypogaea shoots. The efficacy of the system for producing transgenic roots is demonstrated using an enhanced green fluorescent protein (eGFP) expression vector. Furthermore, the application of the system for studying root branching is shown using the auxin-responsive marker DR5 promoter fused to β-glucuronidase (GUS). Finally, the success of the hairy root system for root symbiotic studies is illustrated by inoculating hairy roots with arbuscular mycorrhizal fungi.

CONCLUSIONS

In this study, we have developed a rapid, efficient, and cost-effective composite plant protocol for A. hypogaea that is particularly effective for root-related studies and for the validation of candidate genes in A. hypogaea during mycorrhizal symbiosis.

Silicon-induced mitigation of drought stress in peanut genotypes (Arachis hypogaea L.) through ion homeostasis, modulations of antioxidative defense system, and metabolic regulations

Drought stress considered as a major environmental constraint that frequently limits crop production globally. In the current investigation, drought stress-induced alterations in growth, ion homeostasis, photosynthetic pigments, organic osmolytes, reactive oxygen species (ROS) generation, antioxidative components, and metabolic profile were examined in order to assess the role of silicon (Si) in mitigation of drought effects and to understand the drought adaptive mechanism in two contrasting peanut genotypes (GG7: fast growing and tall, TG26: slow growing and semi-dwarf). Si application significantly improved the leaf chlorophyll content, relative water content % (RWC %), growth and biomass in GG7 compared with TG26 genotype under water stress. Si supplementation considerably promotes the uptake and transport of mineral nutrients under drought condition in both the genotypes, which eventually promote plant growth. Exogenous application of Si protects the photosynthetic pigments from oxidative damage by reducing membrane lipid peroxidation and either maintained or reduced H₂O₂ accumulation in both the genotypes. The activity of enzymatic antioxidants like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and glutathione reductase (GR) and non-enzymatic antioxidants like ascorbate (AsA) and glutathione (GSH) were either maintained or increased in both the genotypes in response to Si under drought as compared to those without Si. Silicon-induced higher accumulation of metabolites mainly sugars and sugar alcohols (talose, mannose, fructose, sucrose, cellobiose, trehalose, pinitol, and myo-inositol), amino acids (glutamic acid, serine, histidine, threonine, tyrosine, valine, isoleucine, and leucine) in GG7 genotype as compared to TG26, provides osmo-protection. Moreover, Si application increased phytohormones levels such as indole-3-acetic acid (IAA), gibberellic acid (GA₃), jasmonic acid (JA), and zeatin in GG7 genotype under drought stress compared to non-Si treated seedlings suggesting its involvement in signaling pathways for drought adaptation and tolerance. Noteworthy increment in polyphenols (chlorogenic acid, caffeic acid, ellagic acid, rosmarinic acid, quercetin, coumarin, naringenin, and kaempferol) in the Si treated seedlings of GG7 genotype as compared to TG26 under drought stress suggests an efficient mechanism of ROS sequestration in GG7 genotype. Our findings provide comprehensive information on physiological, biochemical, and metabolic dynamics associated with Si-mediated water stress tolerance in peanut. This study indicates that the drought tolerance efficacy of peanut genotypes can be improved by Si application.

Evaluation of phase transfer kinetics and thermodynamic equilibria of Reactive Orange 16 sorption onto chemically improved Arachis hypogaea pod powder

Biosorbent from pods of Arachis hypogaea (AhP) were inducted with sulphuric acid treatment and then the activated materials were employed to sequester a sulphonated textile dye; Reactive Orange 16 (RO16) from water system. The characteristic features of the surface functionalized AhP (Ct-AhP) were analysed using instrumentation techniques. The biosorption influencing variables like operating pH, agitating time, initial RO16 concentration and temperature effects were investigated. One-factor optimization revealed that 0.5 g Ct-AhP was sufficient to achieve maximum removal of RO16 (20-120 mg/L) within 180 min agitation at 150 rpm. The isotherm data were applied to non-linear isotherms viz., Freundlich, Langmuir and Temkin models as well as rate limiting steps were elucidated using kinetic models. Freundlich isotherm showed good fit and pseudo-second order kinetic data explained RO16 removal by Ct-AhP followed chemisorption. The outcome of thermodynamic parametric values infer that RO16 biosorption was spontaneous, feasible and involved exothermic type of heat. Elovich and intraparticle diffusion revealed the biosorption mechanisms. The maximum RO16 biosorption (56.48 mg/g) by 0.5 g Ct-AhP were witnessed in the system containing 120 mg/L RO16 agitated at 150 rpm operating at pH 7.0, 303 K for a span of 180 min. Thus, the Ct-AhP is considered to be a promising biosorbent which can be employed in treating the textile effluents.

Adsorption investigation of 2,4-D herbicide on acid-treated peanut (Arachis hypogaea) skins

In this work, peanut (Arachis hypogaea) skin, a by-product generated by the agricultural production of its seeds, was employed as a precursor in the preparation of an adsorbent for the 2,4-D removal in water. The skins were treated with sulfuric acid and characterized by different techniques. The adsorption was favored at acid pH = 2 with pH_pzc = 6. The dosage of 0.9 g L^-1 was considered ideal, obtaining satisfactory indications of removal and capacity. The kinetic curves were well represented by the general order model, with the equilibrium reached quickly in the first 30 min for all concentrations. Adsorption isotherm studies showed that the increase in temperature negatively affected the herbicide adsorption, obtaining a maximum capacity of 246.72 mg g^-1, by the Langmuir isotherm at 298 K. The remarkable adsorption efficiency presented by the adsorbent can be associated with the presence of new functional groups on the adsorbent surface generated after the acid treatment. Thermodynamic parameters confirmed the exothermic nature of the adsorptive system. In the treatment of synthetic wastewater consisting of a mixture of herbicides and salts, a high removal efficiency (72%) of herbicides was obtained. Therefore, the development of an adsorbent derived from peanut (Arachis hypogaea) skin treated with sulfuric acid is an excellent alternative, generating remarkable removal results towards 2,4-D herbicide.

Purification and Initial Characterization of Ara h 7, a Peanut Allergen from the 2S Albumin Protein Family

2S albumins are important peanut allergens. Within this protein family, Ara h 2 and Ara h 6 have been described in detail, but Ara h 7 has received little attention. We now describe the first purification of Ara h 7 and its characterization. Two Ara h 7 isoforms were purified from peanuts. Mass spectrometry revealed that both the isoforms have a post-translation cleavage, a hydroxyproline modification near the N-terminus, and four disulfide bonds. The secondary structure of both Ara h 7 isoforms is highly comparable to those of Ara h 2 and Ara h 6. Both Ara h 7 isoforms bind IgE, and Ara h 7 is capable of inhibiting the binding between Ara h 2 and IgE, suggesting at least partially cross-reactive IgE epitopes. Ara h 7 was found in all main market types of peanut, at comparable levels. This suggests that Ara h 7 is a relevant allergen from the peanut 2S albumin protein family.

Headspace Solid-Phase Microextraction Analysis of Volatile Components in Peanut Oil

Peanut oil is favored by consumers due to its rich nutritional value and unique flavor. This study used headspace solid-phase microextraction (HS-SPME) combined with gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS) to examine the differences in the peanut oil aroma on the basis of variety, roasting temperatures, and pressing components. The results revealed that the optimal conditions for extracting peanut oil were achieved through the use of 50/30 μm DVB/CAR/PDMS fibers at 60 °C for 50 min. The primary compounds present in peanut oil were pyrazines. When peanuts were roasted, the temperature raised from 120 °C to 140 °C and the content of aldehydes in peanut oil increased; however, the content of aldehydes in No. 9 oil at 160 °C decreased. The components of peanut shell oil varied depending on the peanut variety. The most marked difference was observed in terms of the main compound at the two roasting temperatures. This compound was a pyrazine, and the content increased with the roasting temperature in hekei oils. When the roasting temperature was lower, No. 9 oil contained more fatty acid oxidation products such as hexanal, heptanal, and nonanal. When the roasting temperature increased, No. 9 oil contained more furfural and 5-methylfurfural. Heren oil was easier to oxidize and produced nonanal that possessed a fatty aroma.

Intercropping of Peanut-Tea Enhances Soil Enzymatic Activity and Soil Nutrient Status at Different Soil Profiles in Subtropical Southern China

Intercropping is one of the most widely used agroforestry techniques, reducing the harmful impacts of external inputs such as fertilizers. It also controls soil erosion, increases soil nutrients availability, and reduces weed growth. In this study, the intercropping of peanut (Arachishypogaea L.) was done with tea plants (Camellia oleifera), and it was compared with the mono-cropping of tea and peanut. Soil health and fertility were examined by analyzing the variability in soil enzymatic activity and soil nutrients availability at different soil depths (0-10 cm, 10-20 cm, 20-30 cm, and 30-40 cm). Results showed that the peanut-tea intercropping considerably impacted the soil organic carbon (SOC), soil nutrient availability, and soil enzymatic responses at different soil depths. The activity of protease, sucrase, and acid phosphatase was higher in intercropping, while the activity of urease and catalase was higher in peanut monoculture. In intercropping, total phosphorus (TP) was 14.2%, 34.2%, 77.7%, 61.9%; total potassium (TK) was 13.4%, 20%, 27.4%, 20%; available phosphorus (AP) was 52.9%, 26.56%, 61.1%; 146.15% and available potassium (AK) was 11.1%, 43.06%, 46.79% higher than the mono-cropping of tea in respective soil layers. Additionally, available nitrogen (AN) was 51.78%, 5.92%, and 15.32% lower in the 10-20 cm, 20-30 cm, and 30-40 cm layers of the intercropping system than in the mono-cropping system of peanut. Moreover, the soil enzymatic activity was significantly correlated with SOC and total nitrogen (TN) content across all soil depths and cropping systems. The depth and path analysis effect revealed that SOC directly affected sucrase, protease, urease, and catalase enzymes in an intercropping system. It was concluded that an increase in the soil enzymatic activity in the intercropping pattern improved the reaction rate at which organic matter decomposed and released nutrients into the soil environment. Enzyme activity in the decomposition process plays a vital role in forest soil morphology and function. For efficient land use in the cropping system, it is necessary to develop coherent agroforestry practices. The results in this study revealed that intercropping certainly enhance soil nutrients status and positively impacts soil conservation.

Comparative Transcriptome Analysis Identified Candidate Genes for Late Leaf Spot Resistance and Cause of Defoliation in Groundnut

Late leaf spot (LLS) caused by fungus Nothopassalora personata in groundnut is responsible for up to 50% yield loss. To dissect the complex nature of LLS resistance, comparative transcriptome analysis was performed using resistant (GPBD 4), susceptible (TAG 24) and a resistant introgression line (ICGV 13208) and identified a total of 12,164 and 9954 DEGs (differentially expressed genes) respectively in A- and B-subgenomes of tetraploid groundnut. There were 135 and 136 unique pathways triggered in A- and B-subgenomes, respectively, upon N. personata infection. Highly upregulated putative disease resistance genes, an RPP-13 like (Aradu.P20JR) and a NBS-LRR (Aradu.Z87JB) were identified on chromosome A02 and A03, respectively, for LLS resistance. Mildew resistance Locus (MLOs)-like proteins, heavy metal transport proteins, and ubiquitin protein ligase showed trend of upregulation in susceptible genotypes, while tetratricopeptide repeats (TPR), pentatricopeptide repeat (PPR), chitinases, glutathione S-transferases, purple acid phosphatases showed upregulation in resistant genotypes. However, the highly expressed ethylene responsive factor (ERF) and ethylene responsive nuclear protein (ERF2), and early responsive dehydration gene (ERD) might be related to the possible causes of defoliation in susceptible genotypes. The identified disease resistance genes can be deployed in genomics-assisted breeding for development of LLS resistant cultivars to reduce the yield loss in groundnut.

Molecular characterization of Leucoanthocyanidin reductase and Flavonol synthase gene in Arachis hypogaea

Arachis hypogaea (peanut) is a potential source of bioactive compounds including flavonols and proanthocyanidins, which have gained particular interest of metabolic engineering owing to their significance in the growth, development and defense responses in plants. To gain insight of proanthocyanidins and flavonols production in A. hypogaea, Leucoanthocyanidin reductase (AhLAR) and Flavonol synthase (AhFLS) enzymes responsible for their production, have been structurally, transcriptionally and functionally characterized. Structural and functional analysis of putative protein sequence of AhFLS indicated two functional motifs 2OG-FeII_Oxy and DIOX_N, while six functional motifs belonging to the families of NAD-dependent dehydratase, 3, β hydroxysteroid dehydrogenase and NmrA-like family were observed in case of AhLAR. Promoter sequence analysis unraveled several promoter elements related to the development regulation, environmental stress responses and hormonal signaling. Furthermore, the expression analysis of AhFLS and AhLAR and accumulation pattern analysis of proanthocyanidins and flavonols in three selected cultivars of A. hypogaea under saline environment confirmed their role against salinity in genotype-dependent and stress level-dependent manner. Correlation studies revealed that AhFLS and AhLAR expression is not directly dependent on the antioxidant enzymes activity, biochemical and growth parameters but higher Pearson r value depicted some level of dependency. This detailed study of AhLAR and AhFLS can assist in the metabolic engineering of flavonoid biosynthetic pathway to produce stress tolerant varieties and production of proanthocyanidins and flavonols at an industrial scale.

First Report of Macrophomina phaseolina Causing Charcoal Rot of Peanut (Arachis hypogaea L.) in Mexico

Peanut (Arachis hypogaea L.) is the third most important oilseed crop in the world. The cultivated area in Mexico is currently 52,046 ha with a production of 91,109 ton in 2018 (FAO, 2020). Puebla state ranks third in the national production with 9,313 ton (SIAP, 2020). In September 2019, typical symptoms of charcoal rot (Macrophomina phaseolina (Tassi) Goid.) were observed in about 50% of cultivar Virginia Champs peanuts, and it affecting 1.5 ha located in Chietla (18° 27' 39" N; 98° 37' 11" W), Puebla, Mexico. Diseased plants showed brown discoloration in stem and root rot, with chlorotic foliage, dark microsclerotia were observed on the stem and premature dying. To isolate the causal agent of these symptoms, 20 infected plants were recovered and processed in the laboratory. Ten pieces of stem and root tissue were selected from each plant, cut into small pieces 5-mm in length, superficially disinfested with 1% sodium hypochlorite for 3 min, followed by three rinses with sterile distilled water. Later, dried on sterile paper and placed on Petri plates containing potato dextrose agar (PDA) medium, which were kept at 28°C for 7 days (12 h light and 12 h dark). Four colonies were purified via hyphal tip culture, fungus was consistently isolated from the analyzed tissues; additional microcultures were prepared to observe phenotypic characteristics. Colonies showed dense growth, with a gray initial mycelium, becoming black after 7 days. Microesclerotia with spherical to oblong in shape were observed after 5 days on PDA, with a black coloration, measuring an average of 74 µm width × 110 µm length (n=40). Phylogenetic analysis was conducted by amplification and sequencing of the internal transcribed spacer (ITS) region with the ITS5 and ITS4 primers (White et al. 1990). The obtained sequences were deposited in GenBank database under accession numbers: MW585378, MW585379, MW585380, and MW585381 containing approximately 601 bp of the ITS1-5.8S-ITS2 region (complete sequence); they were 99% identical with the reference sequence of Macrophomina phaseolina (GenBank accession KF951698) isolated in Phaseolus vulgaris from Mexico. Based on the symptoms in the field, colony morphology, color, and shape of the microsclerotia, and molecular identification, the fungus was identified as M. phaseolina (Tassi) Goid. The pathogenicity test was performed on peanut plants cultivar Virginia Champs grown on plastic pots with an autoclaved peat/soil mixture under greenhouse conditions (70% relative humidity and 28°C). Fifty two-month-old peanut plants were inoculated using the toothpick method. The toothpicks were previously sterilized and then placed in Petri plates with each of the four colonies of M. phaseolina until colonization. Small wounds were made with those toothpicks in the roots, and a sterile toothpick was used in the control plants, the assays were performed twice. After three weeks, the inoculated plants exhibited symptoms of wilting chlorosis on the leaves and brown to dark brown discoloration of the vascular ring, while control plants remained healthy. M. phaseolina was re-isolated from symptomatic root tissues and identified by phylogenetic approach, fulfilling Koch's postulates. To date, this fungus affects at least 372 hosts globally causing yield losses. Although in Mexico this fungus has been documented in Glycine max, Ipomoea batatas, Phaseolus vulgaris, Physalis ixocarpa, Saccharum officinarum, Sesamum indicum, Solanum melongena, S. tuberosum, and Sorghum bicolor (Farr and Rossman 2021). However, there are no reports of M. phaseolina as a potential pathogen on peanut; therefore, according to our knowledge, this is the first report of this fungus affecting A. hypogaea in Mexico.