Peanut Root Research Articles

Expressed sequence tags in cultivated peanut (Arachis hypogaea): discovery of genes in seed development and response to Ralstonia solanacearum challenge

Although an important oil crop, peanut has only 162,030 expressed sequence tags (ESTs) publicly available, 86,943 of which are from cultivated plants. More ESTs from cultivated peanuts are needed for isolation of stress-resistant, tissue-specific and developmentally important genes. Here, we generated 63,234 ESTs from our 5 constructed peanut cDNA libraries of Ralstonia solanacearum challenged roots, R. solanacearum challenged leaves, and unchallenged cultured peanut roots, leaves and developing seeds. Among these ESTs, there were 14,547 unique sequences with 7,961 tentative consensus sequences and 6,586 singletons. Putative functions for 47.8% of the sequences were identified, including transcription factors, tissue-specific genes, genes involved in fatty acid biosynthesis and oil formation regulation, and resistance gene analogue genes. Additionally, differentially expressed genes, including those involved in ethylene and jasmonic acid signal transduction pathways, from both peanut leaves and roots, were identified in R. solanacearum challenged samples. This large expression dataset from different peanut tissues will be a valuable source for marker development and gene expression analysis. It will also be helpful for finding candidate genes for fatty acid synthesis and oil formation regulation as well as for studying mechanisms of interactions between the peanut host and R. solanacearum pathogen.

Involvement of G1-to-S transition and AhAUX-dependent auxin transport in abscisic acid-induced inhibition of lateral root primodia initiation in Arachis hypogaea L

Previous study indicated that increasing endogenous abscisic acid (ABA) level could inhibit the lateral root (LR) formation of peanuts. In this study, we investigated the mechanisms by which ABA regulated lateral root primordia (LRP) initiation in peanuts (Arachis hypogaea L). Results suggested that ABA inhibited LRP initiation through blocking G1-to-S transition in seedlings and mature roots: e.g. 5.8% increase in the proportion of G1 phase and 18% decrease in the proportion of S phase after ABA treatment for 6 days. Further study of the expression of the cell cycle marker gene for G2-to-M transition in peanut roots suggested that AhCYCB1 expression was regulated by ABA. We also investigated the cooperative regulation of LRP initiation by ABA and indole-3-acetic acid (IAA). ABA treatment greatly reduced the effects of endogenous IAA on mature roots. The expression of the IAA polar transport gene AhAUX1 appeared to be regulated by ABA since ABA inhibited auxin-mediated LRP initiation by suppressing AhAUX-dependent auxin transport in peanut roots. We further examined the effect of ABA on the expression of DR5::GUS and AtAUX1 in the model plant Arabidopsis. The results of Arabidopsis were consistent with that of the peanut.

AhNRAMP1 iron transporter is involved in iron acquisition in peanut

Peanut/maize intercropping is a sustainable and effective agroecosystem to alleviate iron-deficiency chlorosis. Using suppression subtractive hybridization from the roots of intercropped and monocropped peanut which show different iron nutrition levels, a peanut gene, AhNRAMP1, which belongs to divalent metal transporters of the natural resistance-associated macrophage protein (NRAMP) gene family was isolated. Yeast complementation assays suggested that AhNRAMP1 encodes a functional iron transporter. Moreover, the mRNA level of AhNRAMP1 was obviously induced by iron deficiency in both roots and leaves. Transient expression, laser microdissection, and in situ hybridization analyses revealed that AhNRAMP1 was mainly localized on the plasma membrane of the epidermis of peanut roots. Induced expression of AhNRAMP1 in tobacco conferred enhanced tolerance to iron deprivation. These results suggest that the AhNRAMP1 is possibly involved in iron acquisition in peanut plants.

First Report of Cylindrocladium Black Rot of Peanut Caused by Cylindrocladium parasiticum (Teleomorph Calonectria ilicicola) in Jiangxi Province, China.

In July 2010, a serious disease of peanut (Arachis hypogaea) resembling Cylindrocladium black rot (CBR) was found in Longnan County, Jiangxi Province, China. Symptoms included chlorotic, yellowish and blighted leaves, and wilting of the plants. Taproots and hypocotyls were blackened and rotted. Clusters of reddish orange spherical fruiting bodies appeared in the lesions present on basal stems, pegs, pods, and roots of peanut. Disease incidence reached as much as 50% in some patches of the field. Plants with symptoms were sampled from fields. Microscopic examination revealed that the reddish orange, spherical fruiting bodies were the perithecia and measured 461.6 (337.5 to 609.4) × 395.5 (309.4 to 496.9) μm. With gentle pressure, asci and ascospores were exuded from perithecia. The asci were hyaline, thin walled, and long stalked. Ascospores were hyaline, falcate with one septum, and measured 43.5 (27.3 to 54.5) × 5.6 (4.1 to 6.8) μm with a length/width (L/W) ratio of 7.8 ± 1.3. A fungus with white-to-pale buff border mycelia and yellowish brown pigment was consistently isolated from the edge of basal stem lesions on potato dextrose agar at 25°C. Mycelia grew at temperatures ranging from 8 to 32°C and the optimum was 25 to 26°C. To determine the species, single-conidial isolates of the fungus were cultured on carnation leaf agar for 7 days at 25°C and 12 h of light/dark conditions. Conidia were hyaline, cylindrical with one to three septa (mostly three septa), and measured 49.3 (27.3 to 70.9) × 5.9 (4.1 to 6.8) μm with L/W ratio of 8.4 ± 1.6. Vesicles were globose and measured 5.5 to 10.9 μm in diameter. The fungus was identified as Cylindrocladium parasiticum (teleomorph Calonectria ilicicola) (1,2). A PCR assay was conducted on one representative isolate (JXLN32) by analyzing multilocus sequences of the TUB2 (coding β-tubulin protein), ACT (coding actin), and CaM gene (coding calmodulin protein) and were amplified and sequenced using the primers reported by Crous et al. (3). Sequences of the studied DNA regions were submitted to GenBank (Accession Nos. TUB2: JF429649; ACT: JQ070809; and CaM: JQ070808). BLAST searches with the existing sequences in GenBank showed that there was 99 to 100% identity with the existing sequences of C. ilicicola (GenBank Accession Nos. TUB2: AY725643; ACT: GQ280446; and CaM: GQ267402). To complete Koch's postulates, inoculum was prepared by mixing the microsclerotia (MS) suspension of the isolate (JXLN32) with soil at a proportion of 10 MS per g of soil. Ten replicate plastic pots containing five peanut seeds (cv. Yueyou 7) each were planted and placed in a glasshouse at 25 ± 2°C. The same number of peanut seeds was used as an uninoculated control. Typical basal stem and roots rot symptoms of CBR were observed in 2 months and C. parasiticum was reisolated from these inoculated diseased plants. No symptoms were detected on the control plants. To our knowledge, this is the first finding of Cylindrocladium black rot in Jiangxi Province, which is the main peanut-producing area in China. The disease has been previously reported in Guangdong Province in southern China but is not known elsewhere (4). Because of its ability to spread through seed and soil and its destructive potential, this pathogen may pose a serious threat to peanut production in China.

Detection, Characterization, and Biological Effect of Quorum-Sensing Signaling Molecules in Peanut-Nodulating Bradyrhizobia

Bacteria of the genus Bradyrhizobium are able to establish a symbiotic relationship with peanut (Arachis hypogaea) root cells and to fix atmospheric nitrogen by converting it to nitrogenous compounds. Quorum sensing (QS) is a cell-cell communication mechanism employed by a variety of bacterial species to coordinate behavior at a community level through regulation of gene expression. The QS process depends on bacterial production of various signaling molecules, among which the N-acylhomoserine lactones (AHLs) are most commonly used by Gram-negative bacteria. Some previous reports have shown the production of QS signaling molecules by various rhizobia, but little is known regarding mechanisms of communication among peanut-nodulating strains. The aims of this study were to identify and characterize QS signals produced by peanut-nodulating bradyrhizobial strains and to evaluate their effects on processes related to cell interaction. Detection of AHLs in 53 rhizobial strains was performed using the biosensor strains Agrobacterium tumefaciens NTL4 (pZLR4) and Chromobacterium violaceum CV026 for AHLs with long and short acyl chains, respectively. None of the strains screened were found to produce AHLs with short acyl chains, but 14 strains produced AHLs with long acyl chains. These 14 AHL-producing strains were further studied by quantification of β-galactosidase activity levels (AHL-like inducer activity) in NTL4 (pZLR4). Strains displaying moderate to high levels of AHL-like inducer activity were subjected to chemical identification of signaling molecules by high-performance liquid chromatography coupled to mass spectrometry (LC-MS/MS). For each AHL-producing strain, we found at least four different AHLs, corresponding to N-hexanoyl-dl-homoserine lactone (C6), N-(3-oxodecanoyl)-l-homoserine lactone (3OC10), N-(3-oxododecanoyl)-l-homoserine lactone (3OC12), and N-(3-oxotetradecanoyl)-l-homoserine lactone (3OC14). Biological roles of 3OC10, 3OC12, and 3OC14 AHLs were evaluated in both AHL-producing and -non-producing peanut-nodulating strains. Bacterial processes related to survival and nodulation, including motility, biofilm formation, and cell aggregation, were affected or modified by the exogenous addition of increasing concentrations of synthetic AHLs. Our results clearly demonstrate the existence of cell communication mechanisms among bradyrhizobial strains symbiotic of peanut. AHLs with long acyl chains appear to be signaling molecules regulating important QS physiological processes in these bacteria.

Efficient production of Agrobacterium rhizogenes-transformed roots and composite plants in peanut (Arachis hypogaea L.)

Recalcitrance of most large-seeded legumes, such as peanut, to regeneration and genetic transformation has hampered studies on gene function and efforts for genetic improvement. Agrobacterium rhizogenes-mediated transformation provides a system for rapid and efficient transformation of plant tissues. In this study, embryonic axes along with cotyledons of peanut were injected with a suspension culture of A. rhizogenes using microliter syringes. The influence of several factors such as plant genotype, A. rhizogenes culture stage, co-culture period of A. rhizogenes, and acetosyringone concentration in the co-cultivation medium have been evaluated. It is found that A. rhizogenes-mediated transformation of peanut is genotype-independent. Up to 61% transformation was recorded when embryonic axes were co-cultivated with 5 × 107 A. rhizogenes cells from logarithmic phase for 2 days on co-culture medium containing 50 μmol l−1 acetosyringone. Composite plants with transgenic roots were harvested after 45 days of treatment. Furthermore, this method was applied to assess the insecticidal activity of a synthetic cry8Ea1 gene against Holotrichia parallela in transgenic roots of peanut.

Contribution of phytochelatins to cadmium tolerance in peanut plants

Cadmium (Cd) is a well known heavy metal considered as one of the most toxic metals on Earth, affecting all viable cells that are exposed even at low concentration. It is introduced to agricultural soils mainly by phosphate fertilizers and causes many toxic symptoms in cells. Phytochelatins (PCs) are non-protein thiols which are involved in oxidative stress protection and are strongly induced by Cd. In this work, we analyzed metal toxicity as well as PCs implication on protection of peanut plants exposed to Cd. Results showed that Cd exposure induced a reduction of peanut growth and produced changes in the histological structure with a deposit of unknown material on the epidermal and endodermal cells. When plants were exposed to 10 μM Cd, no modification of chlorophyll, lipid peroxides, carbonyl groups, or hydrogen peroxide (H₂O₂) content was observed. At this concentration, peanut leaves and roots glutathione (GSH) content decreased. However, peanut roots were able to synthesize different types of PCs (PC2, PC3, PC4). In conclusion, PC synthesis could prevent metal disturbance on cellular redox balance, avoiding oxidative damage to macromolecules.

Rooting patterns of four crop legumes in response to seed-placement depths in the dry season

On sandy paddy fields, key factors for successful crops in the dry season without irrigation are a shallow water table and practices such as deep seed-placement but only some legume species are adapted to such conditions. To understand the adaptation of legume species to deep seed-placement over shallow water tables, we studied their rooting patterns on two sandy soils. Cowpea (Vigna unguiculata), mungbean (Vigna radiata), peanut (Arachis hypogaea) and soybean (Glycine max) seeds were sown shallow (∼5 cm) or deep (∼15 cm) in deep sandy soils after harvesting rice in two shallow water table locations in north-east Thailand. The legumes depended mainly on capillary water rising from the water table and none experienced water deficit throughout the growing season. Generally, deeper seed-placement decreased overall root dry weight, but it increased the root surface area to weight ratio. Deep seed-placement promoted a greater fraction of root growth into the subsoil for cowpea (86–99% of total root length), mungbean (61–93% of total root length) and peanut (78–98% of total root length) where the soil contained more water throughout the growing season. Moreover, deep seed-placement at the site with the lower water table promoted deeper penetration of roots of cowpea (∼20 cm deeper), mungbean (∼20–40 cm deeper) and peanut (∼20–40 cm deeper) which improved water access, especially late during the growing season when topsoils dried to close to wilting point. Unlike other species, the soybean rooting pattern did not respond much to seed-placement depths, or soil moisture.

Classification of root distribution patterns and their contributions to yield in peanut genotypes under mid-season drought stress

Peanut root distribution patterns are not well understood and have not been studied extensively. There is a lack of information on the classification of root distribution patterns for many peanut genotypes and the relationship between rooting traits and yield under mid-season drought, which could be useful for breeding for drought tolerance. In this study the root distribution of 40 peanut genotypes with different drought tolerance levels and different sources of origin was evaluated during the dry seasons of 2007 and 2008 at Khon Kaen University, Thailand. A randomized complete block design with four replications was used in both years. All plots were well-irrigated except when water was withheld from 50 to 83 days after planting (DAP) during the first season and from 50 to 87 DAP during the second season to emulate a mid-season drought. Top dry weight was observed at the most water-stressed date and at harvest, while root data were measured at the most water-stressed date using the auger method. The soil was sampled to a depth of 90cm and was separated into the upper (0–30cm), middle (30–60cm) and deeper (60–90cm) soil layers. For each peanut genotype, the relative contribution to each layer was calculated and defined as root length density percentage (%RLD). Pod yield was observed at final harvest date and pod harvest index (PHI) was calculated as pod dry weight per unit of total biomass. The forty peanut genotypes were categorized as either high or low %RLD depending on the mean of %RLD in each layer for the three soil layers. These peanut genotypes were then categorized into six combinative groups, based on the high vs. low %RLD for each of the three layers. The relationship between %RLD in the lower soil layer and yield was significant and positive for both seasons, indicating that %RLD in the lower layer is an important trait that affects pod yield under mid-season drought conditions. There was a negative relationship to %RLD in the upper layer in one season and no relationship to %RLD in the middle soil layer for both seasons. The results from this study also indicated that PHI was an important trait that is associated with maintaining pod yield under mid-season drought.

Pengaruh Penambahan Pupuk Bintil Akar Kacang Tanah Sebagai Sumber Nitrogen Dan Fosfor Terhadap Populasi Chlorella sp. <br><i>[The Effect Of Addition Fertilizer Roots Nodule Peanut As A Source Of Nitrogen And Phosphorus To The Population Of Chlorella sp. ]<i>

Abstract Chlorella sp. is one natural food that widely used in hatchery fish, shrimp and oyster. The availability of natural food is a factor that has an important role in farming activities. Culture of Chlorella sp. generally use technical fertilizer (Walne) where nitrogen and phosporus in Walne beginning chemist fertilizer the price expensive. One source of nitrogen and phosphorus naturally obtained from the roots of peanuts. The root nodules contained peanut-containing nodule bacteria Rhizobium are able to bind nitrogen from the air element. By doing immersion can be obtained nutrients to the roots of peanuts are nitrogen and phosphorus that is soluble in water. So that the root nodules of peanuts can be used as a source of nitrogen and phosphorus to increase the population of Chlorella sp. The purpose of this study was to determine the effect of the addition of fertilizer and the concentration of peanut root nodules as a source of nitrogen and phosphorus to the population of Chlorella sp. The research was conducted in June until July in the Laboratory of Education Faculty of Fisheries and Marine Fisheries, Airlangga University, Surabaya. The study design used was Completely Randomized Design (CRD). Materials tested in this study was Chlorella sp. whereas fertilizer used is the root nodules of peanut fertilizer and manure Walne. The concentration of the addition of fertilizer peanut nodule is the treatment A (2.25 ppm), treatment B (4.5 ppm), treatment C (9 ppm) and treatment D (18 ppm). Control treatments using fertilizer Walne 0.5 ml/l (control 1) and 1 ml/l (control 2). The main parameter is observed population density, while supporters of the observed parameter is the measurement of temperature, pH and salinity. The results showed that the addition of fertilizer peanut nodule as a source nitrogen and phosporus influence population of Chlorella sp. The addition of fertilizer best peanut nodule is the treatment B of 1,43755x106 cells/ml on the third day. Water quality parameters during the study remained within the tolerance limit for the growth of Chlorella sp. is pH 7-8, room temperature 29-32 0C range, salinity range between 28-40 ppt and water temperature ranges between 28-30 0C.

Modified Fast Procedure for the Detection and Screening of Antiglycative Phytochemicals

In an attempt to elevate temperature to facilitate glycation, a nonenzymatic reaction by incubation of bovine serum albumin (BSA) and fructose at 50 °C for 24 h has been developed. As conducted and compared to a routine procedure by incubation of BSA and fructose at 37 °C for 168 h, the reactant fluorescence intensities and SDS-PAGE-detected glycated BSA quantities produced by both test temperatures increased with time of incubation. As the Amadori products and α-dicarbonyl compounds during incubation were quantified, both quantities produced at each temperature also increased with an increase of time of incubation, and their trends of changes at both temperatures were similar. In practical application for the detection and screening of the antiglycative phytochemicals, each of 20 peanut root extracts was introduced to a series of BSA-fructose solutions and incubated at 37 and 50 °C for 168 and 24 h, correspondingly. All extracts exhibited notable activities and varied depending on peanut origins. Pair comparison of the resultant antiglycative activities determined at 37 and 50 °C showed that both determined activities for each peanut root extract deviated limitedly. As further analyzed, SDS-PAGE-detected glycated BSA quantities formed at 50 °C were closely proportional to the antiglycative activities determined on the basis of their fluorescence intensities. It is of merit to demonstrate that fluorescence-based determination of BSA-fructose reactant after incubation at 50 °C for 24 h is practical and time-saving in the detection and screening of antiglycative phytochemicals.

Effect of continuous cropping on allelopathy of peanut root exudates

Root exudates of peanut at podding stage under 3 years and 5 years of continuous cropping,and rotation cropping were collected using the continuous collection method.Allelopathic effects of the collected root exudates on soil microbes,peanut seed germination,seedling growth and development and membrane peroxidation were analyzed.The effects of continuous cropping on allelopathic effectiveness of peanut root exudates were also investigated.Results showed that root exudates at peanut podding stage stimulated the growth of root rot fungi(Fusarium sp.) 36194 mycelium,and activities of superoxide dismutase(SOD),peroxidase(POD) and catalase(CAT) and the content of malondialdehyde(MDA) in peanut leaf.It,however,inhibited the growth of N-fixing bacteria(Bradyrhizobium vigna) 14046,the elongation of seedling radicle and height,the fresh weights of leaf and stem,and root,and leaf chlorophyll content.The stimulating and inhibitive effects of peanut root exudates increased with both the increasing concentration of exudates and the length of period of continuous cropping.Accumulation of allelopathic substances in root exudates at podding stage was a possible obstacle to continuous peanut cropping.

ORAChromatography and Total Phenolics Content of Peanut Root Extracts

A large number of compounds have been reported in peanut plants. Many of these compounds are phytoalexins, which are produced by plants experiencing environmental stress and often exhibit antioxidant activity. It is difficult to determine which of the many compounds has the greatest impact on total antioxidant capacity in a mixture. The objectives of this research were to examine the oxygen-radical absorbing capacity (ORAC) value and total phenolic contents of peanut root extracts and peanut root extract fractions collected via HPLC. Peanut roots were extracted from four different cultivars (Brantley, NC-12, Phillips, and Wilson) with 70% aqueous ethanol with ultrasonic assistance. Each cultivar was sampled in duplicate. The extracts were fractionated into 18 3-min fractions by HPLC using a C-18 column. Fractions and crude extracts were freeze dried. ORAC values and total phenolic content were then determined for all fractions and crude extracts. Fractions had a significant effect on the μM TE/mg gallic acid equivalents (GAE). ORAC values ranged from -46.89 μM TE to 185 μM TE in HPLC fractions. ORAChromatography can be used to focus on antioxidants in complex samples.

Rhizobial Nod factors are required for cortical cell division in the nodule morphogenetic programme of the Aeschynomeneae legume Arachis

Nod factors are among the best-studied molecules implicated in the signal exchange that leads to legume-rhizobia symbiosis. The role of these molecules in symbiosis development has been primarily studied in legumes invaded through infection threads. In these plants, Nod factors generate several responses required for nodulation, including the induction of cortical cell division to form the nodule primordium. Arachis hypogaea L. (peanut) exhibits a specific mode of rhizobial infection and nodule morphogenetic programme in which infection threads are never formed. The role of Nod factors in this particular mechanism is unknown. In this work, a peanut symbiont mutant strain unable to produce Nod factors was obtained and characterised. The strain Bradyrhizobium (Arachis) sp. SEMIA 6144 V2 is altered in the nodC gene, which encodes an N-acetylglucosaminyl transferase involved in the first step of the Nod factor biosynthetic pathway. Further research revealed that, although its ability to colonise peanut roots was unaffected, it is not capable of inducing the division of cortical cells. The results obtained indicate that rhizobial Nod factors are essential for the induction of cortical cell division that leads to nodule primordium formation.

First report ofNeocosmospora vasinfectaassociated with the root rot complex of peanuts in Vietnam

The occurrence of Neocosmospora vasinfecta is reported for the first time from Vietnam where it was found in association with peanut roots affected by root rot. It was isolated from diseased roots from peanut crops in Nghe An Province in March 2007 but perithecia were not observed on the diseased roots. However, characteristic perithecia were produced abundantly in pure cultures on potato dextrose agar and carnation leaf-piece agar. Subsequently, perithecia were observed on diseased peanut roots in Thua Thien Hue Province. Representative cultures from Nghe An were confirmed as Neocosmospora vasinfecta by the Centraalbureau voor Schimmelcultures (CBS).

Carbon mineralization of tree leaf litter and crop residues from poplar-based agroforestry systems in Northeast China: A laboratory study

Tree leaf litter and crop residues (fine roots and straw) of the two main crops (maize and peanut) collected from temperate poplar-based agroforestry systems in Liaoning Province, China, were used in a laboratory decomposition experiment. The objectives were to assess the decomposition dynamics of individual plant residues of varying quality and to examine whether interactive effects between poplar litter and crop residues exist during decomposition. Rates of residue decomposition were measured as CO 2 production. Peanut roots decomposed faster than the other individual residues due to their high N and P concentrations and low C/N ratio. There were additive effects between poplar litter and crop residues during decomposition, even though significant differences existed in the initial nutrient concentrations of residues. Our results suggest that legume crops can produce high quality residues and thus have the potential to promote nutrient cycling. Therefore, legume crops have an advantage over other crops for intercropping in temperate agroforestry systems from the viewpoint of sustaining soil fertility.

Effects of Aluminum on Physiological Characteristics of Mitochondrial Membrane in Peanut Root Tips

Mitochondria play a vital role in plant life. Peanut (Arachis hypogaea L.) culitivars LH11 (Al-resistant) and R1549 (Al-sensitive) were selected through root elongation experiment, hematoxylin dying and Al3+ concentration detection in root tips. The concentration of mitochondrial MDA in two cultivars root tips increased after Al3+ treatment, that of R1549 was higher than that of LH11. The difference between two cultivars in mitochondrial MDA concentration was very significant in 20 and 100 μmol L?1 Al3+ treatment, but not significant in 400 μmol L?1 treatment. With the increase of Al3+ concentration, mitochondrial Ca2+-ATPase activity and Ca2+ concentration in two cultivars root tips decreased, and Ca2+ concentration of R1549 decreased faster than that of LH11. Under Al3+ stress, mitochondrial optical density decreased continuously, (mitochondrial permeability transition pore MPTP) enlarged, mitochondria ΔΨ decreased significantly, mitochondrial Cyt c/a ratio reduced, which was more obvious in R1549 than in LH11 with Al3+ concentration increasing. To sum up, high Al3+ concentration treatment induced mito- chondrial permeability transition pore opening, increased mitochondrial membrane permeability, decreased mitochondrial mem- brane Ca2+ transit system activity so that cytoplasm Ca2+ concentration increased, cytochrome c released into the cytoplasm, which might induce PCD (programmed cell death) in root tip, and inhibit root growth. Compared with Al-sensitive cultivar, Al-resistant cultivar has less Al3+ absorption and membrane lipid peroxidation level, higher control ability of Ca2+-ATPase activity, MPTP opening and ΔΨm maintaining so that is not easy to produce PCD under low Al3+ concentration stress. It may be one of reasons for Al resistance mechanism in plant.

Comparison of ELISA and RT-PCR assays for the detection of Tomato spotted wilt virus in peanut

Abstract Diagnosis of Tomato spotted wilt virus (TSWV) in peanut can be accomplished by enzyme-linked immunosorbent assay (ELISA) or reverse transcription polymerase chain reaction (RT-PCR) but there has been no report of a direct comparison of the success of the two assays in evaluating infection rates of field-grown peanut. We collected peanut root samples from field-grown plants, 76 in 2006 and 48 in 2007, and tested these samples by both ELISA and RT-PCR assays for the presence of TSWV. Out of 124 samples, 50 (40.3%) and 57 (46.0%) were positive for TSWV by ELISA and RT-PCR respectively. In 13.7% of these samples, ELISA and RT-PCR differed in their results. However, Chi square analysis showed no significant difference between the results for these two assays. This result supports the conclusion that ELISA and RT-PCR are comparable for detecting TSWV infection rates in field-grown peanuts.

Relationship between total nodulation and nodulation at the root crown of peanut, soybean and common bean plants

The objective of this study was to simplify the procedure for evaluation of legume nodulation, by examining if there is a relationship between the nodulation of the whole root system and at the crown region. Roots of peanut, soybean and common bean plants growing in soils were split in two parts (crown and bottom) and assessed for nodulation (nodule number and dry weight). In general, most nodules were concentrated at the crown, and crown nodulation was generally positively correlated with total nodulation of all three legume crops. The results are highly applicable in studies such as strain selection for inoculants and assessment of inoculation technologies, among others, and is an important contribution to help reduce the time and labor required for the evaluation of nodulation parameters.

Cadmium tolerance and accumulation in eight potential energy crops

The production of energy crops that can be used for biodiesel production is a sustainable approach for the removal of metal pollutants by phytoremediation. This study investigated the cadmium (Cd) accumulation and tolerance of eight potential energy crops. After growth for 28 days in substrates containing 0, 50, 100 or 200 mg Cd·kg − 1 , seedlings were evaluated for growth parameters, chlorophyll content, chlorophyll fluorescence parameters and Cd accumulation. All eight crops were moderately tolerant to Cd toxicity, with four [i.e., hemp ( Cannabis sativa), flax ( Linum usitatissimum), castor ( Ricinus communis) and peanut ( Arachis hypogaea)] being more tolerant than the others. Three of these crops (hemp, flax and peanut) had higher Cd accumulation capacities. The roots of peanut and hemp had high bioconcentration factors (BCF > 1000), while flax shoots accumulated a higher concentration of Cd (> 100 mg/kg). These results demonstrate that it is possible to grow energy crops on Cd-contaminated soil. Hemp, flax and peanut are excellent candidates for phytoremediation.