Effect of Drying Methods on Peanut Quality during Storage.

Storage is an important step after peanut harvest and drying. Many factors could affect the peanut quality during storage. The quality change differences of peanut after being dried by solar radiation and at 35°C, 40°C, 45°C, 50°C during later storage were investigated, including moisture content (MC) and germination percentage (GP) of peanut kernels, acid value (AV), peroxide value (PV), iodine value (IV), vitamin E (VE) content and fatty acid composition (FAC) of extracted peanut oil. And the impact of four storage conditions, air-room temperature (A-RT), air-low temperature (A-LT), vacuum-room temperature (V-RT) and nitrogen-room temperature (N-RT) on peanut quality after 10 months' storage were also studied in this paper. The results revealed that drying conditions had only a little influence on peanut quality during later storage. Peanut dried by solar radiation was more easily oxidized than that dried under other drying conditions. The effects of storage time were much greater. The GP, AV, PV, VE content and FAC, showed significantly changes along with storage. GP and VE content decreased, AV and PV increased, and some linoleic acid was oxidized to oleic acid after 10 months' storage. In addition, A-LT exhibited best performance in keeping peanut quality than A-RT, V-RT and N-RT, which demonstrated that low temperature was more advantageous for peanut storage than controlled atmosphere. These results above would provide useful information and reference for the peanut storage to apply in food industry.

Changes in peanut canopy structure and photosynthetic characteristics induced by an arbuscular mycorrhizal fungus in a nutrient-poor environment.

A well-developed canopy structure can increase the biomass accumulation and yield of crops. Peanut seeds were sown in a soil inoculated with an arbuscular mycorrhizal fungus (AMF) and uninoculated controls were also sown. Canopy structure was monitored using a 3-D laser scanner and photosynthetic characteristics with an LI-6400 XT photosynthesis system after 30, 45 and 70 days of growth to explore the effects of the AMF on growth, canopy structure and photosynthetic characteristics and yield. The AMF colonized the roots and AMF inoculation significantly increased the height, canopy width and total leaf area of the host plants and improved canopy structure. AMF reduced the tiller angle of the upper and middle canopy layers, increased that of the lower layer, reduced the leaf inclination of the upper, middle and lower layers, and increased the average leaf area and leaf area index after 45 days of growth, producing a well-developed and hierarchical canopy. Moreover, AMF inoculation increased the net photosynthetic rate in the upper, middle and lower layers. Plant height, canopy width, and total leaf area were positively correlated with net photosynthetic rate, and the inclination angle and tiller angle of the upper leaves were negatively correlated with net photosynthetic rate. Overall, the results demonstrate the effects of AMF inoculation on plant canopy structure and net photosynthetic rate.

Integrated microRNA and transcriptome profiling reveals a miRNA-mediated regulatory network of embryo abortion under calcium deficiency in peanut (Arachis hypogaea L.).

BACKGROUND: Peanut embryo development is a complex process involving a series of gene regulatory pathways and is easily affected by various elements in the soil. Calcium deficiency in the soil induces early embryo abortion in peanut, which provides an opportunity to determine the mechanism underlying this important event. MicroRNA (miRNA)-guided target gene regulation is vital to a wide variety of biological processes. However, whether miRNAs participate in peanut embryo abortion under calcium deficiency has yet to be explored. RESULTS: In this study, with the assistance of a recently established platform for genome sequences of wild peanut species, we analyzed small RNAs (sRNAs) in early peanut embryos. A total of 29 known and 132 potential novel miRNAs were discovered in 12 peanut-specific miRNA families. Among the identified miRNAs, 87 were differentially expressed during early embryo development under calcium deficiency and sufficiency conditions, and 117 target genes of the differentially expressed miRNAs were identified. Integrated analysis of miRNAs and transcriptome expression revealed 52 differentially expressed target genes of 20 miRNAs. The expression profiles for some differentially expressed targets by gene chip analysis were consistent with the transcriptome sequencing results. Together, our results demonstrate that seed/embryo development-related genes such as TCP3, AP2, EMB2750, and GRFs; cell division and proliferation-related genes such as HsfB4 and DIVARICATA; plant hormone signaling pathway-related genes such as CYP707A1 and CYP707A3, with which abscisic acid (ABA) is involved; and BR1, with which brassinosteroids (BRs) are involved, were actively modulated by miRNAs during early embryo development. CONCLUSIONS: Both a number of miRNAs and corresponding target genes likely playing key roles in the regulation of peanut embryo abortion under calcium deficiency were identified. These findings provide for the first time new insights into miRNA-mediated regulatory pathways involved in peanut embryo abortion under calcium deficiency.

Enhancement of fermentative H2 production with peanut shell as supplementary substrate: Effects of acidification and buffer effect.

For bio-H2 fermentation, the progress and H2 yield were significantly affected by culture pH. Our previous research found peanut shell powder (PSP, as supplementary substrate) having a buffer effect on the fermentative time prolongation and H2 yield enhancement. The acid buffer action (ABA), cation exchange capacity (CEC), scanning electron microscope (SEM) and X-ray powder diffraction (XRD) were employed to explore the mechanism and structure changes of PSP. The superior ABA (57.44 ±â€¯0.65 mmol/pH-kg) and CEC (112 ±â€¯2.0 cmol/kg) of PSP, which provided high specific surface area and amorphous content, prolonged the fermentative time. The acidification of volatile fatty acids on PSP was effective to release reducing sugar and enhance hydrogen yield through breaking hemicellulose and amorphous components of cellulose, and enlarging specific surface area. The results indicated that buffer effect and acidification on PSP made positive effects on prolonging fermentation time and enhancing hydrogen yield.

Genotyping-by-sequencing based genetic mapping reveals large number of epistatic interactions for stem rot resistance in groundnut.

KEY MESSAGE: Genetic mapping identified large number of epistatic interactions indicating the complex genetic architecture for stem rot disease resistance. Groundnut (Arachis hypogaea) is an important global crop commodity and serves as a major source of cooking oil, diverse confectionery preparations and livestock feed. Stem rot disease caused by Sclerotium rolfsii is the most devastating disease of groundnut and can cause up to 100% yield loss. Genomic-assisted breeding (GAB) has potential for accelerated development of stem rot resistance varieties in short period with more precision. In this context, linkage analysis and quantitative trait locus (QTL) mapping for resistance to stem rot disease was performed in a bi-parental recombinant inbred line population developed from TG37A (susceptible) × NRCG-CS85 (resistant) comprising of 270 individuals. Genotyping-by-sequencing approach was deployed to generate single nucleotide polymorphism (SNP) genotyping data leading to development of a genetic map with 585 SNP loci spanning map distance of 2430 cM. QTL analysis using multi-season phenotyping and genotyping data could not detect any major main-effect QTL but identified 44 major epistatic QTLs with phenotypic variation explained ranging from 14.32 to 67.95%. Large number interactions indicate the complexity of genetic architecture of resistance to stem rot disease. A QTL of physical map length 5.2 Mb identified on B04 comprising 170 different genes especially leucine reach repeats, zinc finger motifs and ethyleneresponsive factors, etc., was identified. The identified genomic regions and candidate genes will further validate and facilitate marker development to deploy GAB for developing stem rot disease resistance groundnut varieties.

SNP genotyping reveals major QTLs for plant architectural traits between A-genome peanut wild species.

KEY MESSAGE: QTL mapping of important architectural traits was successfully applied to an A-genome diploid population using gene-specific variations. Peanut wild species are an important source of resistance to biotic and possibly abiotic stress; because these species differ from the cultigen in many traits, we have undertaken to identify QTLs for several plant architecture-related traits. In this study, we took recently identified SNPs, converted them into markers, and identified QTLs for architectural traits. SNPs from RNASeq data distinguishing two parents, A. duranensis (KSSc38901) and A. cardenasii (GKP10017), of a mapping population were identified using three references-A. duranensis V14167 genome sequence, and transcriptome sequences of A. duranensis KSSc38901 and OLin. More than 49,000 SNPs differentiated the parents, and 87.9% of the 190 SNP calls tested were validated. SNPs were then genotyped on 91 F2 lines using KASP chemistry on a Roche LightCycler 480 and a Fluidigm Biomark HD, and using SNPType chemistry on the Fluidigm Biomark HD. A linkage map was constructed having ten linkage groups, with 144 loci spanning a total map distance of 1040 cM. Comparison of the A-genome map to the A. duranensis genome sequence revealed a high degree of synteny. QTL analysis was also performed on the mapping population for important architectural traits. Fifteen definitive and 16 putative QTLs for petiole length, leaflet length and width, leaflet area, leaflet length/width ratio, main stem height, presence of flowers on the main stem, and seed mass were identified. Results demonstrate that SNPs identified from transcriptome sequencing could be converted to KASP or SNPType markers with a high success rate, and used to identify alleles with significant phenotypic effects, These could serve as information useful for introgression of alleles into cultivated peanut from wild species and have the potential to allow breeders to more easily fix these alleles using a marker-assisted backcrossing approach.

Identification of the Candidate Proteins Related to Oleic Acid Accumulation during Peanut (Arachis hypogaea L.) Seed Development through Comparative Proteome Analysis.

Peanuts (Arachis hypogaea L.) are an important oilseed crop, containing high contents of protein and fatty acids (FA). The major components of FA found in peanut oil are unsaturated FAs, including oleic acid (OA, C18:1) and linoleic acid (LOA, C18:2). Moreover, the high content of OA in peanut oil is beneficial for human health and long-term storage due to its antioxidant activity. However, the dynamic changes in proteomics related to OA accumulation during seed development still remain largely unexplored. In the present study, a comparative proteome analysis based on iTRAQ (isobaric Tags for Relative and Absolute Quantification) was performed to identify the critical candidate factors involved in OA formation. A total of 389 differentially expressed proteins (DEPs) were identified between high-oleate cultivar Kainong176 and low-oleate cultivar Kainong70. Among these DEPs, 201 and 188 proteins were upregulated and downregulated, respectively. In addition, these DEPs were categorized into biosynthesis pathways of unsaturated FAs at the early stage during the high-oleic peanut seed development, and several DEPs involved in lipid oxidation pathway were found at the stage of seed maturation. Meanwhile, 28 DEPs were sporadically distributed in distinct stages of seed formation, and their molecular functions were directly correlated to FA biosynthesis and degradation. Fortunately, the expression of FAB2 (stearoyl-acyl carrier protein desaturase), the rate-limiting enzyme in the upstream biosynthesis process of OA, was significantly increased in the early stage and then decreased in the late stage of seed development in the high-oleate cultivar Kainong176. Furthermore, real-time PCR verified the expression pattern of FAB2 at the mRNA level, which was consistent with its protein abundance. However, opposite results were found for the low-oleate cultivar Kainong70. Overall, the comparative proteome analysis provided valuable insight into the molecular dynamics of OA accumulation during peanut seed development.

Improved laccase production by Funalia trogii in absorbent fermentation with nutrient carrier.

A novel strategy of enhancing laccase production by absorbent fermentation was investigated. Peanut shell was used as nutrient carrier for laccase production by Funalia trogii IFP0027 in the absorbent fermentation. The maximum laccase production was reached to 11,900 U/l, which was 4.97 times higher than that of the control group. The results indicated that carbohydrates and phenolic substances especially flavonoids contained in peanut shell stimulated laccase production by F. trogii. Meanwhile, the peanut shell nutrient carrier could not only alleviate the oxidative damage, owing to strong scavenging activity on hydroxyl, but also relieve the mechanical stresses to form small and regular microbial pellets. Therefore, the absorbent fermentation using peanut shell as nutrient carrier shows enormous potential in enhancing laccase production.

Phenotypic effects of allotetraploidization of wild Arachis and their implications for peanut domestication.

PREMISE OF THE STUDY: Several species of Arachis have been cultivated for their edible seeds, historically and to the present day. The diploid species that have a history of cultivation show relatively small signatures of domestication. In contrast, the tetraploid species A. hypogaea evolved into highly domesticated forms and became a major world crop, the cultivated peanut. It seems likely that allotetraploidization (hybridity and/or tetraploidization) in some way enhanced attractiveness for cultivation. Here we investigate this using six different hybridization and tetraploidization events, from distinct Arachis diploid species, including one event derived from the same wild species that originated peanut. METHODS: Twenty-six anatomical, morphological, and physiological traits were examined in the induced allotetraploid plants and compared with their wild diploid parents. KEY RESULTS: Nineteen traits were transgressive (showed strong response to hybridization and chromosome duplication): allotetraploids had larger leaves, stomata and epidermal cells than did their diploid parents. In addition, allotetraploids produced more photosynthetic pigments. These traits have the same trend across the different hybrid combinations, suggesting that the changes are more likely due to ploidy rather than hybridity. In contrast, seed dimensions and seed mass did not significantly change in response to hybridization or tetraploidization. CONCLUSIONS: We suggest that the original allotetraploid that gave rise to cultivated peanut may have been attractive because of an increase in plant size, different transpiration characteristics, higher photosynthetic capacity, or other characteristics, but contrary to accepted knowledge, increased seed size was unlikely to have been important in the initial domestication.

Construction of chromosome segment substitution lines in peanut (Arachis hypogaea L.) using a wild synthetic and QTL mapping for plant morphology.

Chromosome segment substitution lines (CSSLs) are powerful QTL mapping populations that have been used to elucidate the molecular basis of interesting traits of wild species. Cultivated peanut is an allotetraploid with limited genetic diversity. Capturing the genetic diversity from peanut wild relatives is an important objective in many peanut breeding programs. In this study, we used a marker-assisted backcrossing strategy to produce a population of 122 CSSLs from the cross between the wild synthetic allotetraploid (A. ipaënsis×A. duranensis)(4x) and the cultivated Fleur11 variety. The 122 CSSLs offered a broad coverage of the peanut genome, with target wild chromosome segments averaging 39.2 cM in length. As a demonstration of the utility of these lines, four traits were evaluated in a subset of 80 CSSLs. A total of 28 lines showed significant differences from Fleur11. The line×trait significant associations were assigned to 42 QTLs: 14 for plant growth habit, 15 for height of the main stem, 12 for plant spread and one for flower color. Among the 42 QTLs, 37 were assigned to genomic regions and three QTL positions were considered putative. One important finding arising from this QTL analysis is that peanut growth habit is a complex trait that is governed by several QTLs with different effects. The CSSL population developed in this study has proved efficient for deciphering the molecular basis of trait variations and will be useful to the peanut scientific community for future QTL mapping studies.

The role of different inoculum levels of Meloidogyne javanica juveniles on nematode reproduction and host response of peanut plant.

A pot experiment was conducted to determine the influence of three of inoculum levels (1000, 2000 and 3000 J2 pot(-1)) of Meloidogyne javanica on nematode reproduction and host response of peanut plant cv. Giza 4 under greenhouse conditions at 30 +/- 5 degrees C. In general, nematode reproduction and host damage were both affected by the initial inoculum levels. The greater reduction percentage of plant fresh (57.7%), shoot dry (38.82) and pods weights (52.59%) and nodules numbers (73.33%) were recorded at inoculum level 2000 J2/peanut plant, when rate of nematode build-up reached the maximum value of 1.64. Regression analysis of Pi vs. rate of nematode build-up on peanut plants gave value of R2 amounted to 0.3193. On the other hand, when the initial inoculum level added increased up to 3000 J2/peanut plant, the percentage reduction of whole plant fresh weight (47.07%) and other growth parameters as well as nematode build-up (0.8) also obviously decreased.

Developmental changes in peanut root structure during root growth and root-structure modification by nodulation.

BACKGROUND AND AIMS: Basic information about the root and root nodule structure of leguminous crop plants is incomplete, with many aspects remaining unresolved. Peanut (Arachis hypogaea) forms root nodules in a unique process. Structures of various peanut root types were studied with emphasis on insufficiently characterized lateral roots, changes in roots during their ontogenesis and root modification by nodule formation. METHODS: Peanut plants were grown in the field, in vermiculite or in filter paper. The taproot, first-order and second-order lateral roots and root nodules were analysed using bright-field and fluorescence microscopy with hand sections and resin sections. KEY RESULTS: Three root categories were recognized. The primary seminal root was thick, exhibiting early and intensive secondary thickening mainly on its base. It was tetrarch and contained broad pith. First-order lateral roots were long and thin, with limited secondary thickening; they contained no pith. Particularly different were second- and higher-order lateral roots, which were anatomically simple and thin, with little or no secondary growth. Unusual wall ingrowths were visible in the cells of the central part of the cortex in the first-order and second-order lateral roots. The nodule body was formed at the junction of the primary and lateral roots by the activity of proliferating cells derived originally from the pericycle. CONCLUSIONS: Two morphologically and anatomically distinct types of lateral roots were recognized: long, first-order lateral roots, forming the skeleton of the root system, and thin and short second- and higher-order lateral roots, with an incomplete second state of endodermal development, which might be classified as peanut 'feeder roots'. Formation of root nodules at the base of the lateral roots was the result of proliferating cell divisions derived originally from the pericycle.

Genetic transformation of peanut (Arachis hypogaea L.) using cotyledonary node as explant and a promoterless gus::nptII fusion gene based vector.

We have generated putative promoter tagged transgenic lines in Arachis hypogaea cv JL-24 using cotyledonary node (CN) as an explant and a promoterless gus::nptII bifunctional fusion gene mediated by Agrobacterium transformation. MS medium fortified with 6-benzylaminopurine (BAP) at 4mg/l in combination with 0.1 mg/l alpha -napthaleneacetic acid (NAA) was the most effective out of the various BAP and NAA combinations tested in multiple shoot bud formation. Parameters enhancing genetic transformation viz. seedling age, Agrobacterium genetic background and co-cultivation periods were studied by using the binary vector p35SGUSINT. Genetic transformation with CN explants from 6-day-old seedlings co-cultivated with Agrobacterium GV2260 strain for 3 days resulted in high kanamycin resistant shoot induction percentage (45%); approximately 31% transformation frequency was achieved with p35S GUSINT in beta-glucuronidase (GUS) assays. Among the in vivo GUS fusions studied with promoterless gus::nptII construct, GUS-positive sectors occupied 38% of the total transient GUS percentage. We have generated over 141 putative T 0 plants by using the promoterless construct and transferred them to the field. Among these, 82 plants survived well in the green house and 5 plants corresponding to 3.54% showed stable integration of the fusion gene as evidenced by GUS, polymerase chain reaction (PCR) and Southern blot analyses. Twenty-four plants were positive for GUS showing either tissue-specific expression or blue spots in at least one plant part. The progeny of 15 T 0 plants indicated Mendelian inheritance pattern of segregation for single-copy integration. The tissue-specific GUS expression patterns were more or less similar in both T 0 and corresponding T 1 progeny plants. We present the differential patterns of GUS expression identified in the putative promoter-tagged transgenic lines in the present communication.

An application of NMR microimaging to investigate nitrogen fixing root nodules.

Various techniques to obtain high-resolution NMR images (voxel size down to 39 x 39 x 250 microns) of nitrogen-fixing root nodules from soybean [Glycine max (Merr.)] and peanut (Arachis hypogaea L.) are compared. We describe the artefacts arising from changes in the magnetic susceptibility throughout the sample and how these can be minimised. A series of T1 (TR = 220 to 3020 ms) and T2 (TE = 9.3 to 33.6 ms) weighted images are presented. From these it has been possible to locate the oxygen diffusion barrier. A possible interpretation in terms of nodule biochemistry and physiology are given. The data and parameters presented are shown to serve as a basis for more extensive investigations of root nodules (e.g., the oxygen diffusion barrier or the mechanisms driving the regulation of the oxygen concentration in the infected zone by leghemoglobin) by NMR microimaging.