Peanut Cultivars Research Articles

Genomic and Transcriptomic Analysis Identified Gene Clusters and Candidate Genes for Oil Content in Peanut (Arachis hypogaea L.)

Peanut (Arachis hypogaea), a major source of vegetable oil in many Asian countries, has become an integral part of human diet globally due to its high nutritional properties and option to consume in different forms. In order to meet the demand of vegetable oil, many peanut breeding programs of China have intensified their efforts in increasing oil content in newly bred varieties for reducing the import of edible oils in China. In this context, transcriptome sequencing data generated on 49 peanut cultivars were analyzed to identify candidate genes and develop molecular markers for seed oil content across multiple environments. Transcriptome analysis identified 5458 differentially expressed genes (DEGs) including 2243 positive DEGs and 3215 negative DEGs involved in oil synthesis process. Genome-wide association study identified 48 significant insertion/deletion (InDel) markers associated with seed oil content across five environments. A comparative genomics and transcriptomics analysis detected a total of 147 common gene clusters located in 17 chromosomes. Interestingly, an InDel cluster associated with seed oil content on A03 chromosome was detected in three different environments. Candidate genes identified on A03 form a haplotype, in which variable alleles were found to be different in oil content in an independent population. This locus is important for understanding the genetic control of peanut oil content and may be useful for marker-assisted selection in peanut breeding programs.

Evolution and characterisation of the AhRAF4 NB-ARC gene family induced by Aspergillus flavus inoculation and abiotic stresses in peanut.

Aflatoxin contamination in peanut is a serious food safety issue to human health around the world. Finding disease resistance genes is a key strategy for genetic improvement in breeding to deal with this issue. We identified an Aspergillus flavus-induced NBS-LRR gene, AhRAF4, using a microarray-based approach. By comparison of 23 sequences from three species using phytogenetics, protein secondary structure and three-dimensional structural analyses, AhRAF4 was revealed to be derived from Arachis duranensis by recombination, and has newly evolved into a family of several members, characterised by duplications and point mutations. However, the members of the family descended from A.ipaensis were lost following tetraploidisation. AhRAF4 was slightly up-regulated by low temperature, drought, salicylic acid and ethylene, but down-regulated by methyl jasmonate. The distinct responses upon As.flavus inoculation and the differential reactions between resistant and susceptible varieties indicate that AhRAF4 might play a role in defence responses. Temporal and spatial expression and the phenotype of transformed protoplasts suggest that AhRAF4 may also be associated with pericarp development. Because tetraploid cultivated peanuts are vulnerable to many pathogens, an exploration of R-genes may provide an effective method for genetic improvement of peanut cultivars.

Pod yield performance and stability of peanut genotypes under differing soil water and regional conditions

ABSTRACTGenetic gains of cultivated peanut (Arachis hypogaea L.) have increased harvest index and disease tolerance, resulting in improved yield potential and broad-range adaptability of peanut cultivars to United States (U.S.) peanut production regions. Although this strategy has been successful, future yield increases may require peanut cultivars specifically adapted to environmental and management systems of a particular production region. Irrigation is one major management factor that varies across U.S. production regions and influences yield stability. Therefore, peanut germplasm selection for developing specifically adapted cultivars depends on knowledge of genotypic (G) pod yield responses to irrigation (M) across contrasting environmental (E) conditions (G × E × M interaction). The objectives of this 2-year study were to characterize germplasm by: (i) examining genotypic pod yield response to irrigation at locations in Florida and Texas; and (ii) estimating the genotypic pod yield performance and stability using genotype plus genotype-by-environment interaction (GGE) biplots. At the Florida location, genotypes New Mexico Valencia C (NMVC), COC 041, and Chico responded positively to increasing water application, whereas FloRun™ ‘107ʹ, C76 16, and FlavorRunner 458 responded negatively. Genotypes C76 16, ICGS 76, Chico, and ICGV 86015 had pod yields greater than the population mean. The genotype ICGS 76 had both high pod yields and stability. Pod yields of Chico were greater at the southwest locations, whereas ICGV 86015 had greater pod yields at the southeast locations. These results demonstrate a range in adaptability of distinct peanut genotypes that can be used in breeding programs for developing improved cultivars.Abbreviations: G × E: genotype-by-environment interaction; G × E × M: genotype-by-environment-by-management interaction; G × M: genotype-by-management interaction; NMVC: New Mexico Valencia C; TWRPET: total water received as a percentage of ETo

Genotype-independent and enhanced in planta Agrobacterium tumefaciens-mediated genetic transformation of peanut [Arachis hypogaea (L.)

Agrobacterium infection and regeneration of the putatively transformed plant from the explant remains arduous for some crop species like peanut. Henceforth, a competent and reproducible in planta genetic transformation protocol is established for peanut cv. CO7 by standardizing various factors such as pre-culture duration, acetosyringone concentration, duration of co-cultivation, sonication and vacuum infiltration. In the present investigation, Agrobacterium tumefaciens strain EHA105 harboring the binary vector pCAMBIA1301-bar was used for transformation. The two-stage selection was carried out using 4 and 250mgl-1 BASTA® to completely eliminate the chimeric and non-transformed plants. The transgene integration into plant genome was evaluated by GUS histochemical assay, polymerase chain reaction (PCR), and Southern blot hybridization. Among the various combinations and concentrations analyzed, highest transformation efficiency was obtained when the 2-day pre-cultured explants were subjected to sonication for 6min and vacuum infiltrated for 3min in Agrobacterium suspension, and co-cultivated on MS medium supplemented with 150µM acetosyringone for 3days. The fidelity of the standardized in planta transformation method was assessed in five peanut cultivars and all the cultivars responded positively with a transformation efficiency ranging from minimum 31.3% (with cv. CO6) to maximum 38.6% (with cv. TMV7). The in planta transformation method optimized in this study could be beneficial to develop superior peanut cultivars with desirable genetic traits.

Drivers of Preference and Perception of Freshness in Roasted Peanuts (Arachis spp.) for European Consumers.

This study provides insight into which flavor, taste, and appearance attributes drive liking and disliking of roasted peanuts for European consumers. The drivers are linked back to analytical attributes that can be measured instrumentally, thereby reducing the reliance on costly sensory panels. Particular emphasis is placed on color as a predictor of preference, because of the low cost of the measuring equipment, it is available to even smaller producers. In addition to preference, the study also examines whether product attributes that drive perceived freshness exist. The results can be used to design products with high acceptability across several countries within Europe.

Photosynthetic efficiency among Indian peanut cultivars and influence of seasonal variation and zinc

Sixty high yielding Indian peanut cultivars were studied for net photosynthesis (PN), transpiration (E), stomatal conductance (gs), water use efficiency (WUE), radiation use efficiency (RUE), SPAD chlorophyll meter reading (SCMR) and chlorophyll fluorescence (Fv/Fm) at 70–75 days and pod and fodder yields at harvest in field during both the Kharif (Wet) and Rabi-summer (Dry) seasons to find out the efficient cultivars and seasons. The dry season crop showed higher values of these parameters except E and Fv/Fm than that of wet season crop and application of Zn increased all these but reduced gs and SCMR. On an average, the peanut cultivars showed 29.9 and 19.4 µmol (CO2) m2 s–1 PN, 0.57 and 0.26 m s−1 gs, 11.4 and 13.2 m mol m−2 s−1 E, 2.67 and 1.49 WUE, 0.018 and 0.012 RUE, 38.2 and 36.3 SCMR and 0.843 and 0.850 Fv/Fm during dry and wet seasons, respectively. The foliar application of zinc as 0.2% zinc-sulphate, during dry season, influenced all these parameters, with an average of 30.6 and 29.3 µmol (CO2) m−2 s−1 PN, 0.54 and 0.60 m s−1 gs, 11.7 and 11.2 m mol m−2 s−1 E, 2.69 and 2.65 WUE, 0.019 and 0.018 RUE, 37.8 and 38.7 SCMR and 0.844 and 0.842 Fv/Fm with and without Zn, respectively. The study identified several photosynthetically efficient cultivars. There were 18 cultivars with high PN and gs, 18 cultivars with high PN and E and 17 cultivars with high PN and pod yield. Based on the overall performance the peanut cultivars being recommended are Tirupati 3, TG 37A, CSMG 884, RS 1, S 230, LGN 2, TPG 41 and SG 99 for dry season and GG 20, Tirupati 4, M 197, ALR 2, JL 501 and RG 141 for wet season.

Contribution of root uptake to cadmium accumulation in two peanut cultivars: evidence from a split-column soil experiment.

Cadmium (Cd) accumulation and internal Cd translocation in the peanut (Arachis hypogaea L.) are highly related to root uptake, which may largely depend on the cultivar variation and the depth of the Cd-contaminated soil. A split-column soil experiment was conducted using two common Chinese peanut cultivars (Huayu-20 and Huayu-23) known to relocate Cd to different tissues. The growth medium was separated into four layers and Cd solution was solely applied to one layer to determine the key depth affecting the Cd accumulation in a plant via root uptakes. The results showed that the biomass of Huayu-23 was significantly higher biomass (3.28-94.0%) than that of Huayu-20, especially in the aerial parts (stems and leaves) and kernels, implying the dilution of Cd. Following the addition of Cd to the soil, the Cd concentrations in peanut tissues increased on average by 28.9-172 and 28.3-111% in Huayu-20 and Huayu-23, respectively. The largest presence of Cd in a peanut plant was observed in the aerial parts, followed by the kernels. Huayu-20 accumulated more Cd in plant tissues than did Huayu-23 due to the former's high Cd translocation. These findings imply that peanut cultivars vary widely in biomass, Cd accumulation, and the percentage distribution of Cd among various plant tissues, especially kernels. Different Cd treatments in the full depth of the root zone induced significant alterations in Cd accumulation of peanut tissues, especially kernels, for both cultivars. The percentage distribution of Cd accumulation by kernels was significantly higher in the deeper layer than in the top layer of the root zone for both peanut cultivars. This study suggests that soil modifications performed during agronomic activities should take into account the full depth of root exploration as well as the peanut cultivars to manage plant Cd uptake.

Analysis of parental relationship of 106 peanut cultivars released in Henan Province

Analysis of parental relationship of 106 peanut cultivars released in Henan Province

Differential expression of leaf proteins in four cultivars of peanut (Arachis hypogaea L.) under water stress.

Drought is a major constraint to the productivity of many crops affecting various physiological and biochemical processes. Seventy percent of the peanuts are grown in semiarid tropics that are frequently prone to drought stress. So, we analyzed its effect in 4 cultivars of peanut, with different degrees of drought tolerance, under 10 and 20days of water stress using two-dimensional gel electrophoresis and mass spectrometry. A total of 189 differentially expressed protein spots were identified in the leaf proteome of all the 4 cultivars using PD Quest Basic software; 74 in ICGV 91114, 41 in ICGS 76, 44 in J 11 and 30 in JL 24. Of these, 30 protein spots were subjected to in-gel trypsin digestion followed by MALDI-TOF that are functionally categorized into 5 groups: molecular chaperones, signal transducers, photosynthetic proteins, defense proteins and detoxification proteins. Of these, 12 proteins were sequenced. Late embryogenesis abundant protein, calcium ion binding protein, sucrose synthase isoform-1, 17.3kDa heat shock protein and structural maintenance of chromosome proteins were overexpressed only in the 15 and 20days stressed plants of ICGV 91114 cultivar while cytosolic ascorbate peroxidase was expressed with varying levels in the 10 and 20days stressed plants of all the 4 cultivars. Signaling protein like 14-3-3 and defense proteins like alpha-methyl-mannoside-specific lectin and mannose/glucose-binding lectins were differentially expressed in the 4 cultivars. Photosynthetic protein like Rubisco was down-regulated in the stressed plants of all 4 cultivars while Photosystem-I reaction center subunit-II of chloroplast precursor protein was overexpressed in only 20days stressed plants of ICGV 91114, ICGS 76 and J11 cultivars. These differentially expressed proteins could potentially be used as protein markers for screening the peanut germplasm and further crop improvement.

Effects of spraying paclobutrazol at different stages on physiological characteristics, yield and quality of peanut

To explore the optimum stage of spraying with paclobutrazol (PBZ) for different peanut cultivars under high yield condition, we investigated the effects of spraying PBZ at different stages on chlorophyll content, root activity, protective enzymes, nitrogen and carbon metabolism enzymes of leaves, pod yield and kernel quality of peanut, with Huayu 20 and Huayu 25 as materials. The results showed that spraying PBZ at different stages increased root activity, chlorophyll content, SOD, POD, CAT, SS, SPS, PEPC activities and decreased the MDA content, NR, GS, GDH and GOGAT activities for pod setting stage of two cultivars. These results suggested that the effects would be more obvious at earlier spray time. For HY25, the most significant effects of spraying PBZ on those parameters of pod filling stage could be obtained when the main stem height was 25 cm. For HY20, spraying PBZ when the main stem height was 25 cm decreased the activities of protective enzymes. Earlier spraying time to HY20 would lead to early senescence, lower chlorophyll content, root activity and carbon metabolism enzyme activity. For HY20, the most significant effects of spraying PBZ on those parameters of pod filling stage could be obtained when the main stem height was 30 cm. Our results indicated that PBZ treatments at the optimum stage could improve pod yield and economic coefficient of both cultivars and enhance the fat content and the relative content of oleic acid and the O/L. Under high yield condition, the optimum stage of spraying PBZ was 25 cm height of the main stem for HY25 and 30 cm for HY20.

DEVELOPMENT OF RAPD AND SSR MARKERS ASSOCIATED WITH OIL CONTENT IN FIVE PEANUT CULTIVARS

The peanut (Arachis hypogaea L.) is an important oilseed crop in tropical and subtropical regions of the world.Oil content has an important quality trait for peanut. However, the progress in genetic improvement of oil content is slow. Therefore, identification of molecular markers for oil content trait is a great impact in molecular breeding. Nineteen RAPD and ten SSR primers were used to detect markers related to oil content in peanut. The five peanut cultivars were grown for two seasons (2013, 2014) in El-Nubaria, Al-Beheira Governorate, and Egypt. The results showed that, Gregory cultivar recorded the highest value of oil content, while Giza5 cultivar exhibited the lowest value of oil content in both seasons. The results indicated the presence of five positive and nine negative RAPD markers and two positive and one negative SSR markers that could be considered as reliable markers for oil content in peanut.

Development of ic-Elisa for the screening of aflatoxin contamination in the peanut production chain

Abstract: The objective of this work was to standardize and validate an indirect competitive enzyme-linked immunosorbent assay (ic-Elisa), as a low-cost tool, to monitor the presence of aflatoxin in common and blanched peanuts (Arachis hypogaea) in the production chain. The presence of aflatoxin B1, moisture content, and water activity were analyzed in 60 samples of the peanut cultivar Runner IAC 886, from the 2014/2015 and 2015/2016 harvests of the region of Alta Paulista, in the state of São Paulo, Brazil. The validation showed an adequate linearity (R2 = 0.999), and limits of detection and quantification of 1.13 and 3.59 μg kg-1, respectively. Recovery rates of 104, 102, and 107% at the concentrations of 4, 10, and 20 μg kg-1 aflatoxin B1, respectively, were also recorded. The ic-Elisa showed a good reproducibility with a high-intraday precision, with 1.87% coefficient of variation (CV), and interday precision with 6.75% CV. The moisture content ranged from 4.0 to 7.2% (mean of 5.8%), and the water activity from 0.4848 to 0.6997 (mean of 0.5990) for the tested samples. Aflatoxin B1 was present in concentrations ranging from 1.13 to 29.2 μg kg-1, with only two samples (3.3%) exceeding the maximum allowed limit of 20 μg kg-1. The ic-ELISA developed here is an accessible tool for the rapid monitoring of aflatoxin contamination in the peanut production chain.

RNA interference-mediated resistance to Tobacco streak virus in transgenic peanut

Peanut stem necrosis disease (PSND) caused by Tobacco streak virus (TSV) is one of the important diseases of peanut (Arachis hypogaea L.) worldwide. In this study, we investigated the possibility of developing PSND- resistant transgenic peanut plants using RNAi technique. Peanut cultivar TMV-7 was transformed with a hairpin RNA (hpRNA) vector, pART27-TSV-IR-CP, containing inverted repeats of TSV-coat protein (CP) gene sequence flanking a spacer sequence (Pdk Intron) under the control of the CaMV 35S promoter using Agrobacterium tumefaciens -mediated transformation method. The presence of the TSV CP gene sequence in T0, T1 and T2 transgenic plants was confirmed by PCR analysis using CP gene specific primers. Evaluation of the transgenic plants (T2 generation) for resistance to TSV by using sap inoculation method revealed that none of the inoculated transgenic plants showed symptoms of infection, whereas non-transgenic control plants showed necrosis of leaves 7–9 days after inoculation and stem necrosis 16–19 days after inoculation. This study suggests that resistance against TSV can be induced in peanut plants through genetic engineering by expressing dsRNA of coat protein gene of TSV as target for RNAi.

Morphological and Genetic Characterization of Non‐Nodulating Peanut Recombinant Inbred Lines

Peanut (Arachis hypogaea L.) nodulation is relatively diverged from other legumes. Further understanding of nodulation mechanisms would facilitate improvement of biological N fixation and yield in peanut. The objective of this study was to characterize the non‐nodulating (Nod−) peanut recombinant inbred lines (RILs) in comparison to their nodulating (Nod+) sister RILs morphologically and genetically. Two pairs of Nod− and Nod+ RILs were inoculated with rhizobia for morphological observation. Nodules and root hairs were absent in Nod− lines and present in Nod+ lines. The Nod− lines had a much smaller canopy with yellow leaves and fewer pods than Nod+ lines. Simple‐sequence repeat (SSR) marker genotyping of the two pairs of RILs and their parental lines revealed several chromosome regions differing between Nod− and Nod+ sister lines, which potentially harbor the genes controlling nodulation. Two F2 populations segregating for nodulation were constructed by crossing the two Nod− lines with their Nod+ sister lines. The segregation ratios of Nod−/Nod+ of the two populations followed 7:9 and 7:57, respectively, indicating that multiple genes were involved in controlling peanut nodulation. The results from this study provided important morphological and genetic information related to peanut nodulation, which paved the road for further mapping and cloning of peanut nodulation genes and for eventually developing peanut cultivars with improved N fixation efficiency.

Antioxidant activities, polyphenol, flavonoid, and amino acid contents in peanut shell

Abstract Peanut shell; a byproduct of an important leguminous crop, peanut; is a potential source of different functional compounds. Antioxidant activities, secondary metabolites and amino acid contents in peanut shells of six Korean cultivars were studied in the present study. Peanut shells showed remarkable antioxidant potentials with high amounts of total polyphenol (428.1–739.8 µg gallic acid equivalents/g), flavonoid (142.6–568.0 µg quercetin equivalents/g), and amino acid (5.76–34.56 mg/g) contents. 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), superoxide dismutase (SOD)-like activity, and reducing power potential of the peanut shells were considerable. The results suggest that the shells of Korean peanut cultivars could be a potential source of natural antioxidants and functional compounds for various industrial uses including cosmetics.

Transcriptomic analysis and discovery of genes in the response of Arachis hypogaea to drought stress.

The peanut (Arachis hypogaea) is an important crop species that is threatened by drought stress. The genome sequences of peanut, which was officially released in 2016, may help explain the molecular mechanisms that underlie drought tolerance in this species. We report here a gene expression profiling of A. hypogaea to gain a global view of its drought resistance. Using whole-transcriptome sequencing, we analysed differential gene expression in response to drought stress in the drought-resistant peanut cultivar J11. Pooled samples obtained at 6, 12, 18, 24, and 48h were compared with control samples at 0h. In total, 51,554 genes were found, including 49,289 known genes and 2265 unknown genes. We identified 224 differentially expressed transcription factors, 296,335 SNPs and 28,391 InDELs. In addition, we detected significant differences in the gene expression profiles of the treatment and control groups. After comparing the two groups, 4648 genes were identified. An in-depth analysis of the data revealed that a large number of genes were associated with drought stress, including transcription factors and genes involved in photosynthesis-antenna proteins, carbon metabolism and the citrate cycle. The results of this study provide insights into the diverse mechanisms that underlie the successful establishment of drought resistance in the peanut, thereby facilitating the identification of important genes in the peanut related to drought management. Transcriptome analysis based on RNA-Seq is a powerful approach for gene discovery and molecular marker development for this species.

Differential expression analysis of genes associated with anthocyanin synthesis in peanut cultivars with different testa color

Differential expression analysis of genes associated with anthocyanin synthesis in peanut cultivars with different testa color

Consideration of peg strength and disease severity in the decision to harvest peanut in southeastern USA

ABSTRACTThe indeterminate nature and underground fruiting habit of peanut (Arachis hypogaea L.) makes it a challenge to determine the optimal harvest time. The objectives of this study were (1) to gain additional information about how maturity and canopy health influence peg strength, yield, and grade and (2) to address anecdotal claims of differences in peg strength and digging losses among cultivars. Field trials were established in Citra, FL, and Tifton, GA. Two peanut cultivars (“Georgia-06G” and “Tifguard”) were grown under two fungicide programs (full program: every 14-day spraying interval; and reduced program: every 28-day spraying interval), and harvested at three different maturity levels (early, optimum, and late based on an accumulated growing degree day method). The fungicide program had a significant impact on yield only in 2013 at Citra, likely because the canopy structure was decreased because of fungal disease known as leaf spots (causal agents: Cercospora arachidicola and Cercosporidium personatum). The timing of the harvest had a significant impact on yield, grade, peg strength, and digging loss. In addition, yield, grade, peg strength, and digging losses differed between the peanut cultivars. These results show that reduced fungicide program might affect the yield because of the disease severity and that the optimal harvest time should consider the level of the defoliation. Although there was no correlation between peg strength and digging loss, over-maturity can cause more digging losses compared to optimal harvest time. Tifguard had higher digging loss than Georiga-06G. This study provides additional useful information on cultivars to growers.

Transgressive Segregation and Long-Term Consistency for High TSWV Field Resistance in the ‘Georgia-06G’ Peanut Cultivar

Tomato spotted wilt disease caused by tomato spotted wilt virus (TSWV) is a major peanut (Arachis hypogaea L.) production problem in the United States. TSWV has become endemic since the mid-1980s in the southeastern U.S. peanut production area. ‘Georgia-06G’ is a large-seeded, TSWV-resistant, runner-type peanut cultivar, whereas ‘Georgia Greener’ is a sister line with a smaller seed size than Georgia-06G. Both Georgia-06G and Georgia Greener have greater TSWV general field resistance with higher yields, total sound mature kernels grade, and dollar values than the parents (‘Georgia Green’ and ‘C-99R’), which shows transgressive segregation for these desirable quantitative traits. Therefore, the objective of this 12-year study was to evaluate the higher TSWV host-plant resistance found in the Georgia-06G over time compared with many other runner- and virginia-type peanut cultivars and advanced breeding lines. Despite yearly variability in TSWV and total disease incidence, the data indicate that Georgia-06G exhibited long-term high TSWV and total disease field resistance at midseason and late season, respectively. Georgia-06G was also found to have among the highest pod yield and dollar value every year. The higher general TSWV field resistance of Georgia-06G appears to be consistent across many years and locations, similar to the moderate TSWV resistance in Georgia Green.

Development of a Ground-Based Peanut Canopy Phenotyping System

Phenotypic information of peanut canopy, including height, width, shape, and density are important in the selection of the best cultivars of peanuts. However, current methods to acquire these data are mainly by manual measurements or qualitative scorings. These methods are laborious, time-consuming, and subjective. In this study, a ground-based peanut canopy phenotypic system was developed to improve the efficiency and accuracy of the data collection on peanut canopy architecture. The system was on a ground-based, remote controlled cart with a sensor suite of two RGB cameras, a thermal camera, a laser scanner and an RTK GPS. Software programs was developed to control the system and collect, store, and analyze the data. This system was tested in the peanut growth season of 2017. The result showed that the system was able to complete the data collection at least four times faster than previous manual collection. The data collected were with a much higher resolution, thus could be used to acquire detailed features of peanut canopy.