Groundnut Plants Research Articles

Distribution and abundance of white grubs (Coleoptera: Scarabaeidae) on groundnut in southern India

Scarab species associated with groundnuts were surveyed in Andhra Pradesh, Karnataka and Tamil Nadu, southern India, between 1995 and 2001. Scarab adults were collected from trees on which they were feeding and/or mating, and larvae (white grubs) from groundnut fields. Holotrichia species, especially H. reynaudi and H. serrata were the major species associated with groundnut. H. reynaudi predominated in the central Deccan area, while H. serrata was most abundant in the south and west. A new, undescribed, Holotrichia species near H. consanguinea was collected in south and southwest of Hyderabad in mixed populations with H. reynaudi. However, the full extent of this new species’ distribution remains uncertain. H. rufoflava was rarely associated with groundnut, but was common as an adult at some locations. Other genera encountered during surveys were Anomala, Adoretus, Schizonycha, and Autoserica. In survey data, densities of Holotrichia larvae and ‘all other white grubs’ were both very highly correlated with the percentage of damaged groundnut plants. These correlations in combination with concurrent observations of plant damage establish a causal link between white grubs and plant damage and death in southern Indian groundnut. Ranking of preferred host trees for adults were developed from field observations for four Holotrichia species and Schizonycha spp. and will assist grower-initiated surveys of pest occurrence. In combination with insecticide-efficacy data published elsewhere, the survey provides the basis for an environmentally friendly and economically viable pest-management system for white grubs on groundnut in southern India.

Effect of mulch on soil temperature, moisture, weed infestation and yield of groundnut in northern Vietnam

Groundnut ( Arachis hypogaea L.) is one of the chief foreign exchange earning crops for Vietnam. However, owing to lack of appropriate management practices, the production and the area under cultivation of groundnut have remained low. Mulches increase the soil temperature, retard the loss of soil moisture, and check the weed growth, which are the key factors contributing to the production of groundnut. On-farm trials were conducted in northern Vietnam to study the impact of mulch treatments and explore economically feasible and eco-friendly mulching options. The effect of three mulching materials (polythene, rice straw and chemical) on weed infestation, soil temperature, soil moisture and pod yield were studied. Polythene and straw mulch were effective in suppressing the weed infestation. Different mulching materials showed different effects on soil temperature. Polythene mulch increased the soil temperature by about 6 °C at 5 cm depth and by 4 °C at 10 cm depth. Mulches prevent soil water evaporation retaining soil moisture. Groundnut plants in polythene and straw mulched plots were generally tall, vigorous and reached early flowering. Use of straw as mulch provides an attractive and an environment friendly option in Vietnam, as it is one of the largest rice growing countries with the least use of rice straw. Besides, it recycles plant nutrients effectively.

STUDIES ON <i>Macrophomina phaseoli</i> (Maub.) ASHBY GROWTH AND SOME PHYSIOLOGICAL ASPECT OF GROUNDNUT (<i>Arachis hypogaea</i> L) PLANT INFECTED WITH THE FUNGUS

Some synthetic media used to investigate the best media to support growth of Macrophomina phaseoli. The fungus grew in both solid and liquid synthetic media, but best growth was recorded in peanut leaflet Oat meal (POMA) and potato dextrose agar (PDA). There was no absolute nutrient requirement for its growth. The best inoculation technique for disease symptom development was a juxtaposition of 48 - hour old mycelial mat on wounded roots of 10-day old groundnut plants. Infection of the groundnut plants increased with higher inoculum potential in the soil. Dry weight of diseased plants was drastically reduced as infection advanced, possibly due to decreased anabolic activities of the plants. In addition, the reduction in the leaf area equally led to reduction of photosynthesis. Transpiration in inoculated plants decreased and remained lower than that of the uninoculated plants. The disease may have caused plugging of the xylem vessels, hence reduction in the plants' water absorption capacity. KEY WORDS: Groundnut, Macrophomina phaseoli, physiology, juxtaposition, inoculum potential, dry weight, leaf area. Global Jnl Pure & Applied Sciences Vol.10(1) 2004: 23-29

Phytoalexins synthesis is enhanced in groundnut plants inoculated with Bradyrhizobium sp. ( Arachis)

Bradyrhizobium spp. colonize groundnut ( Arachis hypogaea) through cracks in roots and spreads intercellularly. Phytoalexin biosynthesis may be one mechanism by which groundnut plants respond to Bradyrhizobium inoculation; but this idea has not been sufficiently investigated to date. Therefore, phytoalexin production by roots and leaves of uninoculated and inoculated groundnut plants was studied by thin layer chromatography and standard bioassays using two fungal species: Aspergillus niger and Cladosporium cucumerinum. Phytoalexin production was significantly enhanced in leaf extracts of Bradyrhizobium-inoculated plants 50 days after planting. These phytoalexins were identified as medicarpin and formononetin. Formononetin was active only against Cladosporium cucumerinum and its concentration, estimated as total phenolic substances recovered from the inhibition halos obtained, was 1.5-fold increased in inoculated plants compared to the uninoculated controls. Medicarpin was active against both C. cucumerinum and A. niger. The extent of the inhibition zones detected for medicarpin in leaf extracts obtained from inoculated plants was twice that observed for uninoculated plants, corresponding to more than three-fold increase in concentration of medicarpin compared to formononetin. These results suggest that symbiotic interactions between Bradyrhizobium spp. ( Arachis) and its host trigger biochemical changes, which tend to reinforce natural groundnut defenses against pathogens.

PHOSPHORUS LEVELS IN SHOOTS OF BAMBARA GROUNDNUT IN BOTSWANA SOILS

ABSTRACT The critical phosphorus (P) concentration and range of bambara groundnut (Vigna subterranea) plants were determined from a sand culture experiment at Botswana College of Agriculture. Twelve P levels (0.207–159 mg P pot−1) were used for growing the plants for 78 days (early podding stage) and the shoot P concentrations determined. The critical P concentration was used for assessing the P nutritional status of bambara groundnut plants grown in farmers fields in Botswana. Plants from 10 farmers' fields were sampled at 78 days after sowing and analyzed for P. The critical shoot P concentration and range for bambara groundnut determined visually from graphs were 0.15% and 0.15–0.20%, respectively. In 80% of the farms, plants showed shoot P concentrations between 0.10% and 0.13% which correspond with moderate to severe P deficiency. Therefore, most of bambara groundnut farmers in Botswana grow the crop under limiting P conditions.

Synthesis and water absorbency of crosslinked superabsorbent polymers

AbstractA series of novel copolymer superabsorbents based on monomer acrylamide (AM), potassium methacrylate (KMA), and 2‐hydroxyethyl methacrylate (HEMA) were prepared by copolymerization using ammonium persulfate (APS) as an initiator and N,N‐methylenebisacrylamide (MBA) as a crosslinking agent. The synthetic variables (the monomer concentration, crosslinker concentration, and initiator concentration) were also studied. The experimental results of superabsorbent polymers (SAPs) show a better absorbency in both water and NaCl solutions. The copolymers were characterized by IR spectroscopy. The water retention in the soil was enhanced using the above superabsorbents. The use of SAPs for the growth of groundnut plants was also investigated. SAPs can be considered for water‐managing materials for agriculture and horticulture purposes in desert and drought‐prone areas. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1795–1801, 2002

Phenolic acid metabolism of groundnut (Arachis hypogaea L.) plants inoculated with VAM fungus and Rhizobium

Mycorrhizal and Rhizobiuminoculation resulted in a significant increase in the quantities of phenoliccompounds in roots and shoots of groundnut plants, as compared to uninoculatedplants. Production of some new compounds, and increase in the activity of theenzymes peroxidase and polyphenol oxidase, following inoculation was observed.Accumulation of phenolics and the activation of oxidative enzymes were morepronounced in the dual inoculated plants.

Translocation of <sup>14</sup>C-(Labelled) Photosynthates in Groundnut (Arachis Hypogaea L.) Infected with Macrophomina Phaseoli (Maub) Ashby

At various intervals after inoculation of the roots of groundnut plants with the fungus Macrophomina phaseoli, 14CO2 was administered to branch 2 (from the base) of the plants in the light. The effects of the disease on the translocation of 14C-photosynthates out of the source branch to the rest of the plant were studied 24 h after labelling. As the plant aged and the disease symptom development became more evident, an increasing percentage of the fixed 14C-photosynthates was exported from branch 2 of the inoculated plants (IP) compared to the non-inoculated plants (NIP). The apex, main stem, and branch 1 of NIP imported more of the total fixed 14C throughout the developmental stages of the plant except for day 10 after inoculation when branch 1 of IP imported almost 76 % of the total fixed 14C. The roots of IP were the major sink and imported higher percent of the total fixed 14C than the roots of NIP.

Spatiotemporal Separation of Groundnut Rosette Disease Agents

ABSTRACT Analysis by triple-antibody sandwich enzyme-linked immunosorbent assay of groundnut samples from fields in two seasons from different regions of Malawi showed the absence of groundnut rosette assistor virus (GRAV) from some plants showing groundnut rosette disease symptoms and the presence of GRAV in some symptomless plants. Viruliferous Aphis craccivora collected from fields transmitted either GRAV alone, groundnut rosette virus (GRV) with its satellite RNA (sat RNA), or all three agents together, in different proportions. More plants became infected with all three agents when increasing numbers of potentially viruliferous aphids were used per plant, suggesting a dosage response. Electrical pentration graph studies of aphid stylet activities indicated successful transmission of GRV and its sat RNA during both the "stylet pathway phase" and salivation into sieve elements, whereas GRAV was transmitted only during the latter phase. Aphids transmitted all three agents together only during the salivation phase. Reverse-transcriptase polymerase chain reaction testing of viruliferous aphids and of inoculated plants revealed no correlation between the presence of all three agents in prospective aphid vectors and their simultaneous transmission to groundnut plants. These results show that separation of the groundnut rosette disease agents occurs over time and space.

Autophosphorylation-dependent activation of a calcium-dependent protein kinase from groundnut

Ca2+-dependent protein kinases (CDPKs) containing a calmodulin-like domain integrated in their primary sequence are present primarily in plants. A member of this family was characterized from the groundnut (Arachis hypogea) plant and called GnCDPK (M. DasGupta [1994] Plant Physiol 104: 961-969). GnCDPK specifically uses the myosin light chain synthetic peptide (MLCpep), which is the phosphate-accepting domain of smooth muscle myosin light chains (KKRPQRATSNVFS), as an exogenous substrate under in vitro experimental conditions. In this report we show that GnCDPK undergoes intramolecular autophosphorylation. This self-phosphorylation occurs in threonine residues in a Ca2+-dependent (K0.5 = 0.5 &mgr;M) and calmodulin-independent manner. The kinase activity toward MLCpep and its sensitivity to Ca2+ were unaffected by prior autophosphorylation when measured under saturating ATP concentrations. The role of autophosphorylation in the exogenous substrate MLCpep phosphorylation reaction was reinvestigated at low ATP concentrations. A pronounced lag time of 1 to 2 min, followed by a linear increase of activity for 7.5 min, was seen in the initial rate of MLCpep phosphorylation under such suboptimal conditions. Prior autophosphorylation completely abolished this lag phase, and a sharp rise of exogenous substrate phosphorylation was seen from the 1st min. Our results suggest that autophosphorylation is a prerequisite for the activation of GnCDPK.

Root phenolic accumulation and loss of autoregulation of root nodule formation in Bambara groundnut (Vigna subterranea) following boron nutrition and cotyledon excision

Effects of boron nutrition and cotyledon removal on nodulation and N 2 fixation were investigated on Bambara groundnut (Vigna subterranea L. Verdc.) grown in the glasshouse. Nodule number was siginificantly lower in boron-deprived plants relative to those receiving 90 µM boron. As a result, the amount of N fixed was markedly reduced in the zero-boron control plants. Phenolic content, measured relative to the molar concentration of daidzein, an active phenolic nod gene inducer from this species, was significantly lower in roots of boron-deprived plants. However, with provision of 90 µM boron, plants significantly increased root accumulation of total phenolics by 37%. HPLC analysis of root extracts showed that the increase in phenolics was due to greater tissue accumulation of the nod-gene-inducing daidzein, following the supply of 90 µM boron. The correlation between nodulation performance and increase in tissue phenolics, especially daidzein, suggests that the increase in nodulation and N 2 fixation with boron supply (90 µM) to intact plants was triggered by the greater accumulation of the inducer molecule as a result of improved boron nutrition. However, removal of seedling cotyledons also affected the number of nodules formed per plant. Excision of cotyledons resulted in significantly reduced photosynthetic leaf area, followed by a marked increase in the number of nodules per plant due to loss of autoregulation of nodule formation. Boron supply and cotyledon removal both increased nodule formation in Bambara groundnut plants, but via different mechanisms.

Agrobacterium-mediated genetic transformation of groundnut (arachis hypogaea L.): An assessment of factors affecting regeneration of transgenic plants

Transgenic groundnut (Arachis hypogaea L.) plants were produced efficiently by inoculating different explants withAgrobacterium tumefaciens strain LBA4404 harbouring a binary vector pBM21 containinguidA (GUS) andnptll (neomycin phosphotransferase) genes. Genetic transformation frequency was found to be high with cotyledonary node explants followed by 4 d cocultivation. This method required 3 days of precultivation period before cocultivation withAgrobacterium. A concentration of 75 mg/l kanamycin sulfate was added to regeneration medium in order to select transformed shoots. Shoot regeneration occurred within 4 weeks; excised shoots were rooted on MS medium containing 50 mg/I kanamycin sulfate before transferring to soil. The expression of GUS gene (uidA gene) in the regenerated plants was verified by histochemical and fluorimetric assays. The presence ofuidA andnptll genes in the putative transgenic lines was confirmed by PCR analysis. Insertion of thenptll gene in the nuclear genome of transgenic plants was verified by genomic Southern hybridization analysis. Factors affecting transformation efficiency are discussed.

Detection of each of the causal agents of groundnut rosette disease in plants and vector aphids by RT-PCR

Detection of the three agents of groundnut rosette disease (groundnut rosette assistor virus, groundnut rosette virus and its satellite RNA) in plants and vector aphids by reverse transcription-polymerase chain reaction (RT-PCR) is reported. Three procedures for extraction of total RNA from groundnut were tested, of which two were found to be useful in giving RNA of sufficient quality for RT-PCR. Of these two, the total RNA extraction kit supplied by Qiagen was found to be the most versatile for extraction of all three agents from individual vector aphids ( Aphis craccivora). Both groundnut rosette assistor virus and groundnut rosette virus could be detected from total RNA extracted from a single aphid that had been exposed to either green or chlorotic rosette-infected groundnut plants. They could be detected in aphids stored in 70% ethanol for up to 30 days at room temperature. However, satellite RNA could be amplified only when total RNA extracted from two or more aphids was used. Groundnut rosette assistor virus, groundnut rosette virus and its satellite RNA were detected by RT-PCR in aphids that had been exposed only to groundnut rosette diseased plants containing all three agents. The potential of RT-PCR in studying certain key issues of rosette disease epidemiology is discussed.

Dispersal of Passalora personata conidia from groundnut by wind and rain

In experiments where groundnut plants with sporulating late leaf spot lesions were exposed to increasing ‘gusty’ and ‘steady’ wind speeds, conidia were more effectively removed by gusty winds than by steady winds of the same mean wind speed. Rain drops dislodged conidia more efficiently than wint, with large drops dispersing conidia more effectively than small ones. No conidia were caught in still air. After most of the conidia had been removed by exposure to high wind speeds, rain was found to remove additional conidia. When plants were exposed to continuous wind or rain, most of the conidia were dispersed during the first few minutes, and the concentration of conidia then declined exponentially with time. From field observations on rain-free days, airborne concentrations of conidia tended to increase as the wind speed increased during the day and with a further increase in wind speed, concentrations decreased. On rainy days, the onset of the first shower coincided with a phenomenal increase in the airborne concentrations of conidia.

Flower production and growth in groundnut plants

Groundnut flowering was analyzed on plants whose growth was modified by changing planting density or by shading exposure during different periods of the growth cycle. Flowering was assessed at the level of the plant, branch, and inflorescence. The results showed that flowering progression along the branch reflected the flowering dynamics of the entire plant. The number of flowers produced was determined by the rate of progression of flowering along the branches and by the period from the beginning to the end of blooming. These features were closely dependent on plant growth conditions. Increasing the planting density slowed the flowering rate and shortened the blooming period. This allowed a better synchronization of pod maturity. Exposure to shade before flowering decreased the rate of production of flowers but prolonged its duration, whereas exposure at mid-flowering halted flower production. It is suggested that the different reproductive organs (flowers and pods) may compete for assimilates, thus explaining the various effects observed on daily flower production.

Selection and regeneration of groundnut plants resistant to the pathotoxic culture filtrate ofCercosporidium personation through tissue culture technology

Callus cultures were established from immature leaf expiants ofArachis hypogaea on MS medium supplemented with 2.0 mg/L of NAA and 0.5 mg/L of BAP of the susceptible cultivars namely VRI-2 and TMV-7. Three-week-old calli were subjected to mutagenic treatments (gamma rays: 50–250 Gy and EMS: 5–25 mM). Mutagen-treated calli were subcultured to fresh medium containing various concentrations (25–100% v/v) of pathotoxic culture filtrates. Calli were challenged in vitro with pathotoxic culture filtrate of the fungal pathogen and were assessed by visible growth ratings expressed as the percent response to the doses/concentrations of mutagen. Selected mutagen-treated calli showed resistance in vitro on media containingCercosporidium personatum pathotoxic culture filtrate. Resistance calli were then transferred to MS regeneration medium supplemented with BAP (2.0 mg/L) and NAA (0.5 mg/L) for shoot bud regeneration. The progeny of the plants produced 13 disease-resistant plants (R2) in both the cultivars. Among the eight R2 populations studied, 70.2–82.5% of the plants exhibited enhanced resistance. This study suggested that groundnut plants with resistance to C.personatum can be selected

Down-regulation of Groundnut Rosette Virus Replication by a Variant Satellite RNA

Symptom production in groundnut plants infected with groundnut rosette virus (GRV) depends on the presence of satellite RNA (sat-RNA) in the GRV culture, and sat-RNA variants that induce only mild symptoms are known. One such variant drastically diminished the replication of GRV genomic RNA in infectedNicotiana benthamianaplants. This down-regulating ability did not involve either of the two open reading frames in the sat-RNA but was controlled by a region near its 5′ end, which is required for sat-RNA replication. WhenN. benthamianaplants were inoculated with GRV and the mild satellite and challenged by inoculation with a GRV isolate (YB) containing a sat-RNA that induces yellow blotch symptoms, no symptoms appeared and little GRV genomic RNA or sat-RNA was detected in the plants, provided the two inoculations were no more than 2 days apart. A GRV isolate containing a sat-RNA that neither induces symptoms inN. benthamiananor affects genomic RNA accumulation also provided protection against yellow blotch symptom production if inoculated before or up to 2 days after isolate YB. However, in this case protection was incomplete and both GRV RNA and sat-RNA accumulated to normal levels. It is suggested that sequences from the mild sat-RNA may provide a novel source of resistance against rosette disease.

Characterization of Two Strains of Cowpea Mild Mottle Virus Naturally Infecting Groundnut (Arachis hypogaea L.) in India

AbstractTwo viruses were isolated from commercial groundnut plants showing mild mottle (MM) and severe mottle (SM) symptoms in the Rayalaseema area of Andhra Pradesh State, India. The host range of both the isolates was restricted to Fabaceae. The physical properties of both isolates were: DEP 10‐6 to 10‐7. TIP 70–85 C and LIV 5–8 days. Partially purified virus preparations contained slightly flexuous filamentous particles. In ELISA and gel diffusion tests both isolates reacted similarly with anusera to the carlaviruses cowpea mild mottle, cassia mild mosaic and potato M. Particle morphology. sedimentation coefficient, and estimated sizes of the coat proteins and RNAs gave additional evidence that the viruses were carlaviruses. Bemisia labaci transmitted only the MM isolate and the two isolates also differed in electrophoretic mobility of intact particles and amino acid composition of the coat proteins. The isolates are identified as distinct strains of cowpea mild mottle virus.

The induction of 1,3-β-glucanases and other enzymes in groundnut leaves infected with Cercospora arachidicola

Infection of groundnut leaves with the early leaf spot pathogen Cercospora arachidicola leads to a marked increase in extracellular 1,3-β-glucanase activity, limited to the infected tissue. Three isoforms of low molecular weight and extreme pI values, typical of pathogenesis-related proteins, were induced. These β-glucanases, when acting together, were capable of degrading the pathogen cell wall in vitro. Glucanases from homogenates of infected leaf tissue were partially purified by ion-exchange chromatography to give enzymes with molecular weights of 35, 32 and 20 kDa and pI values of 3·8, 3·6 and > 9, respectively. They were electrophoretically identical to the β-glucanases found in the intercellular washing fluid. Treatment of groundnut plants with 200 μM mercuric chloride induced the accumulation of identical extracellular β-glucanases. During the course of the infection an increase in peroxidase activity was also observed, but chitinase activity remained more or less constant.

The toxicity of phytotoxins from Cercospora arachidicola and cercosporin from Cercospora species to tobacco, Swiss chard and groundnut plants

Nine of the 12 species of Cercospora isolated from various plants produced cercosporin. Some Cercospora spp. also produced a yellow fraction and C. arachidicola produced orange and yellow-orange fractions but not cercosporin. Neither cercosporin nor the orange fraction were host specific and caused similar damage on Swiss chard, tobacco and groundnuts. The amount of damage and toxin concentration were positively correlated. The orange fraction caused considerably less damage in the dark than in the light and young leaves were more resistant to damage than older leaves. The yellow-orange fraction was only weakly phytotoxic.