Diallel analysis in groundnut (Arachis hypogaea L.)

Summary An 8 × 8 full diallel experiment based on 4 bunch plus 4 spreading types of groundnut (Arachis hypogaea L.) was conducted over three environments. For both number of pods and pod yield, additive, nonadditive and reciprocal cross effects were detected and these were also influenced by changes in environments. For number of pods additive genetic variance was predominant whereas it was approximately equal to non-additive genetic variance for pod yield. Graphical analysis revealed the presence of strong non-allelic interaction for number of pods whereas for pod yield absence of dominance and/or presence of non-allelic interaction was evident.Part of Ph.D. Thesis of the first author     

Endogenous Adenosine Modulation of 22Na Uptake by Rat Brain Synaptosomes

To evaluate if endogenous extracellular adenosine influences sodium channel activity in nerve terminals, we investigated how manipulations of extracellular adenosine levels influence ²²Na uptake by rat brain synaptosomes stimulated with veratridine (VT). To decrease extracellular adenosine levels, adenosine deaminase (ADA) that converts adenosine into an inactive metabolite was used. To increase extracellular adenosine levels, we used the adenosine deaminase inhibitor erythro-9(2-hydroxy-3-nonyl) adenine (EHNA), as well as the inhibitor of adenosine transport, nitrobenzylthioinosine (NBTI). ADA (0.1–5U/ml) caused an excitatory effect on ²²Na uptake stimulated by veratridine, which was abolished in the presence of the adenosine deaminase inhibitor erythro-9(2-hydroxy-3-nonyl) adenine (EHNA, 25M). Both the adenosine uptake inhibitor nitrobenzylthioinosine (NBTI, 1–10M) and the adenosine deaminase inhibitor EHNA (10–25M) inhibited ²²Na uptake by rat brain synaptosomes. It is suggested that adenosine is tonically inhibiting sodium uptake by rat brain synaptosomes.     

Transgenics in groundnut (Arachis hypogaea L.) expressing cry1AcF gene for resistance to Spodoptera litura (F.)

Large number of primary transgenic events were generated in groundnut by an Agrobacterium mediated, in planta transformation method to assess the efficacy of cry1AcF against the Spodoptera litura. The amplification of required size fragment of 750 bp with npt II primers and 901 bp with cry1AcF gene primers confirmed the integration of the gene. The expression of the cry gene was ascertained by ELISA in T₂ generation, and the maximum concentration of cry protein in transgenic plants reached approximately 0.82 μg/g FW. Further, Southern blot analysis of ten T₂ transgenic plants proved that transgene had been integrated in the genome of all the plants and Northern analysis of the same plants demonstrated the active expression of cry1AcF gene. The highest mean % larval mortalities 80.0 and 85.0 with an average mean % larval mortalities 16.25 (n = 369) and 26.0 (n = 80) were recorded in T₁ and T₂ generations, respectively. Segregation analysis of the selected lines in the T₃ generation demonstrated homozygous nature. This clearly proved that though there is considerable improvement in average mean % larval mortality in T₂ generation, the cry1AcF gene was effective against S. litura only to some extent.     

Effect of soil sodicity on the growth,yield and chemical composition of groundnut (Arachis hypogaea Linn.)

Summary A replicated field experiment was conducted to study the effect of exchangeable sodium percentage (ESP) on the yield, chemical composition, protein and oil content and uptake of nutrients by groundnut (Arachis hypogaea Linn.) variety M-13. ESP over 15 delayed germination and emergence of flowers. There was continuous decrease in dry matter yield at 30 and 60 days of growth, grain and straw yield after harvest and protein, oil and kernel percent with increase in soil ESP. A 50 per cent reduction in groundnut yield was observed at an ESP of 20. Increasing soil ESP, increased Na and decreased K, Ca and N contents, but had no effect on the Mg, P, S, Fe, Mn, Zn and Cu contents of the plant. Sodium content of the plant increased, while potassium and nitrogen decreased with age of the plant. The uptake of all the nutrients decreased with increase in soil ESP. The results showed that groundnut is a relatively sensitive crop to soil sodicity.     

Impact of groundnut rosette disease on nutritive value and elemental composition of four varieties of peanut (Arachis hypogaea)

Proximate and elemental composition of four peanut genotypes infected with groundnut rosette disease (GRD) was examined. Moisture and ash content generally decreased while fat and energy content increased in seeds from diseased plants. Protein and carbohydrate varied between seeds of diseased and healthy plants of the different varieties with no consistent pattern. Instrumental neutron activation analysis of 10 elements within leaves, stems and seeds showed elevated levels of K, Al and Cl in leaves, stems and seeds in at least three of the four varieties infected with GRD while Na was decreased in stems but increased in seeds. While significant differences were found, Mg, Mn, Ca and Zn did not show any consistent change with respect to plant part or genotype, between diseased and healthy plants. V and Fe were found at low levels in leaves and stems and not detected in seeds. This represents the first report on the effect of GRD on the nutritive quality of peanuts.     

Variation and inheritance of the arachin polypeptides of groundnut (Arachis hypogaea L.)

Summary Variation in the arachin polypeptides of groundnut genotypes was observed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Three regions could be observed on the electropherogram. Region 1, corresponding to conarachin, did not show any variation; region 2, consisting of arachin acidic subunits, showed variation; region 3, containing the arachin basic subunits, did not show any variation. There are four varietal classes of arachin polypeptide patterns: class A comprised three acidic subunits of arachin of molecular weights 47.5, 45.1 and 42.6 kd and a basic subunit of 21.4 kd; class B, with three acidic subunits of molecular weights 47.5, 45.1 and 41.2 kd and a basic subunit of 21.4 kd; class C of an additive pattern of class A and class B; class D, of two acidic polypeptides of 47.5, 45.1 kd and the basic 21.4 kd subunit. Of the 90 genotypes studied, 73% belong to class A, 15% to class B and 6% each to class C and D. Analysis of F₂ seeds from a cross between class A and class B genotypes showed that the two polypeptides (42.6 kd and 41.2 kd) are coded by nonallelic genes and also revealed that class C and class D patterns arose as a result of hybridisation between class A and class B. A. monticola, the progenitor of A. hypogaea, showed a pattern similar to the additive pattern of class A and class B while some diploid Arachis species had the 41.2 kd polypeptide. Based on arachin polypeptide patterns the probable origin of A. hypogaea has been suggested.     

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.     

Potential for plant growth promotion in groundnut (Arachis hypogaea L.) cv. ALR-2 by co-inoculation of sulfur-oxidizing bacteria and Rhizobium

The use of Rhizobium inoculant for groundnut is a common practice in India. Also, co-inoculation of Rhizobium with other plant growth-promoting bacteria received considerable attention in legume growth promotion. Hence, in the present study we investigated effects of co-inoculating the sulfur (S)-oxidizing bacterial strains with Rhizobium, a strain that had no S-oxidizing potential in groundnut. Chemolithotrophic S-oxidizing bacterial isolates from different sources by enrichment isolation technique included three autotrophic (LCH, SWA5 and SWA4) and one heterotrophic (SGA6) strains. All the four isolates decreased the pH of the growth medium through oxidation of elemental S to sulfuric acid. Characterization revealed that these isolates tentatively placed into the genus Thiobacillus. Clay-based pellet formulation (2.5 x 10(7) cf ug(-1) pellet) of the Thiobacillus strains were developed and their efficiency to promote plant growth was tested in groundnut under pot culture and field conditions with S-deficit soil. Experiments in pot culture yielded promising results on groundnut increasing the plant biomass, nodule number and dry weight, and pod yield. Co-inoculation of Thiobacillus sp. strain LCH (applied at 60 kg ha(-1)) with Rhizobium under field condition recorded significantly higher nodule number, nodule dry weight and plant biomass 136.9 plant(-1), 740.0mg plant(-1) and 15.0 g plant(-1), respectively, on 80 days after sowing and enhanced the pod yield by 18%. Also inoculation of S-oxidizing bacteria increased the soil available S from 7.4 to 8.43 kg ha(-1). These results suggest that inoculation of S-oxidizing bacteria along with rhizobia results in synergistic interactions promoting the yield and oil content of groundnut, in S-deficit soils.     

Early generation intermating for yield improvement in groundnut (Arachis hypogaea L.)

Summary Seeds of 4 crosses of groundnut (Arachis hypogaea L.), Robut 33-1 x Chico, Robut 33-1 x NC Ac 17090, Robut 33-1 x PI 298115 and MK 374 x GAUG 1, were irradiated with 30 kR. In the F₁, some branches of each plant were intermated with other plants at random and others selfed in each cross to produce S₂ and F₂ seeds. They were evaluated for pod yield, shelling percentage and 100-kernel weight. The frequency of plants superior to F[in1] was much higher in S₂ than in F₂, which was, in general, true for the values of yield and its components. The S₂ and F₂ were advanced to third generation by selfing. The families descending from S₂ showed clear superiority over those from F₂. The reason for such superiority was suggested to be the recombination of genes from the upper and lower ends of the genotypic distribution under intermating.     

Thidiazuron promotes high frequency regeneration of peanut (Arachis hypogaea) plants in vitro

Multiple shoots were induced on Valenciatype peanut (Arachis hypogaea L.) explants cultured in vitro on a nutrient medium supplemented with thidiazuron. Zygotic embryos excised from mature seeds were germinated on Murashige-Skoog nutrient medium, and the resulting plantlets (8 days-old) were used as a source of explants. When cultured on a nutrient medium with increasing levels of thidiazuron (0.5 to 30 mg/l), expiants from various parts of the peanut plant (except the root) produced multiple shoot primordia which subsequently developed into individual shoots. Hypocotyl and cotyledon explants produced shoots in higher numbers than other explants (20 shoots per hypocotyl explant at all thidiazuron concentrations and 15 shoots per cotyledon explant at 30 mg/l). Shoots rooted normally on a basal Murashige-Skoog medium containing charcoal and developed into healthy and fertile plants when planted in soil.Abbreviations TDZ thidiazuron - MSO Murashige and Skoog (1962) basal medium - BA 6-benzylaminopurine     

Genetic variation for VA mycorrhiza-dependent phosphate mobilisation in groundnut (Arachis hypogaea L.)

Nine cultivars of groundnut (Arachis hypogaea L.) were grown in a soil poor in available N or P. There was clearly genetic variation of characteristics indicative of VA mycorrhiza-dependent phosphate mobilisation, namely, VA mycorrhiza fungal spore count (SC), percentage of infection (IF) by VA mycorrhizal fungi (VAMF) and acid and alkaline phosphatase activities. Among the cultivars, one was non-nodulating with low values for all characteristics and in another experiment, this non-nodulating cultivar, one of its parents (PI 259747), a national check (Robut 33-1) and the highest yielding cultivar among the original nine (NFG 7), were grown and investigated for various P-mobilising properties and yield. The linear regression coefficient of pod yield on % VAMF infection was significant in both the experiments. Additionally, many of the correlation coefficients of pod yield and VAM dependent characteristics were positive and significant. From consideration of published evidence, it seems possible to breed for the desirable reinforcing effects of infestation, by VAMF and Rhizobium that can ultimately improve the productivity of groundnuts.     

Mechanistic distinction between activation and inhibition of (Na+K)-ATPase-mediated Ca influx in cardiomyocytes

(Na⁺+K⁺)-ATPase (NKA) mediates positive inotropy in the heart. Extensive studies have demonstrated that the reverse-mode Na⁺/Ca²⁺-exchanger (NCX) plays a critical role in increasing intracellular Ca²⁺ concentration through the inhibition of NKA-induced positive inotropy by cardiac glycosides. Little is known about the nature of the NCX functional mode in the activation of NKA-induced positive inotropy. Here, we examined the effect of an NKA activator SSA412 antibody on ⁴⁵Ca influx in isolated rat myocytes and found that KB-R7943, a NCX reverse-mode inhibitor, fails to inhibit the activation of NKA-induced ⁴⁵Ca influx, suggesting that the Ca²⁺ influx via the reverse-mode NCX does not mediate this process. Nifedipine, an L-type Ca²⁺ channel (LTCC) inhibitor, completely blocks the activation of NKA-induced ⁴⁵Ca influx, suggesting that the LTCC is responsible for the moderate increase in intracellular Ca²⁺. In contrast, the inhibition of NKA by ouabain induces 4.7-fold ⁴⁵Ca influx compared with the condition of activation of NKA. Moreover, approximately 70% of ouabain-induced ⁴⁵Ca influx was obstructed by KB-R7943 and only 30% was impeded by nifedipine, indicating that both the LTCC and the NCX contribute to the rise in intracellular Ca²⁺ and that the NCX reverse-mode is the major source for the ⁴⁵Ca influx induced by the inhibition of NKA. This study provides direct evidence to demonstrate that the activation of NKA-induced Ca²⁺ increase is independent of the reverse-mode NCX and pinpoints a mechanistic distinction between the activation and inhibition of the NKA-mediated Ca²⁺ influx path ways in cardiomyocytes.     

Efficient selection intensity in early generation index selection in groundnut (Arachis hypogaea L.)

Summary The F₂ potential of single and three-way crosses was evaluated using a set of physiological and yield components. Results were based on an index of selection using (a) only yield components and (b) both physiological and yield components. The indices were constructed using the percentage improvement of F₂ over the better parent of the corresponding F₁ cross for every character. The performance of F₂ plants assessed by the expected value of the regression index was ranked in descending order to provide a ranked F₂ distribution (FRD). The FRD was divided into four equal parts, T₂₅ (top 25%), T₅₀ (26–50%), T₇₅ (51–75%) and T₁₀₀ (76–100%). F₃ families derived from F₂ plants in T₂₅ were found to provide a higher frequency of selections for pod number than T₅₀, T₇₅ and T₁₀₀. The frequency of selections was higher in three-way than single crosses. Selection index based on physiological and yield components was more efficient in trapping F₂ plants providing selections in F₃ than the index based on yield components only. The results brought out the importance of bunch x bunch crosses as a complement to the usually advocated bunch x runner ones.     

Pod development of groundnut (Arachis hypogaea L.) in solution culture

Normal pods (containing seed) of groundnut (Arachis hypogaea L.) (cv. TMV-2) were successfully raised in darkened, aerated, nutrient solution, but not in the light. The onset of podding was evident 7 to 8 d after gynophores were submerged in the darkened nutrient solution. An examination of pods and submerged portions of gynophore surfaces by scanning electron microscopy showed the presence of two distinctly different protuberances: unicellular root-hair-like structures that first developed from epidermal cells of the gynophores and developing pods; and branched septate hairs that developed later from cells below the epidermal layer. The septate hairs became visible only after the epidermal and associated unicellular structures had been shed by the expanding gynophore and pods. Omission of Mn and Mg from the podding environment increased pod and seed weight, whilst omission of Zn reduced pod and seed weight.     

Enhanced cross pollination to widen the scope of breeding in groundnut (Arachis hypogaea L.)

Summary Six groundnut genotypes belonging to the Virginia and Valencia sub-groups were irradiated with gamma rays at doses of 5, 10, 15 and 20 kR, much below LD₅₀, and grown surrounded by a pollen parent in a split-plot design. The succeeding two generations were checked for the occurrence of hybrids by examining the segregation for pod and seed characteristics and the two quantitative characters, pod and seed yield. Cross-pollination up to 20.8% was observed in M13, a Virginia cultivar. There was a genotype-dose interaction for the extent of cross-pollination. Cross-pollination was higher in Virginia than Valencia genotypes and more frequent under 15 and 20 kR than under other doses, in general. The observed substantial enhancement of cross-pollination encourages the use of seed irradiation at proper doses as a method for increasing recombination in plant breeding programmes.     

Light, dark and growth regulator involvement in groundnut (Arachis hypogaea L.) pod development

Gynophore elongation and pod formation were studied in peanut plants (Arachis hypogaea L.) under light and dark conditions in vivo. The gynophores elongated until pod formation was initiated. Pod (3–20 mm length) development could be totally controlled by alternating dark (switched on) and light (switched off) conditions, repeatedly. Gynophore elongation responded conversely to light/dark conditions, compared to pods. In this study we aimed to correlate the light/dark effects with endogenous growth substances. The levels of endogenous growth substances were determined in the different stags of pod development. Gynophores shortly after penetration into the soil, white gynophores, released twice the amount of ethylene as compared to the aerial green ones, or to gynophores bearing pods. Ethylene inhibitors had no effect on the percent of gynophores that developed pods, but affected pod size which were smaller compared to the control. A similar level of IAA was extracted from gynophore tips of green gynophores, white gynophores and pods. ABA levels differed between the three stages and were highest in the green gynophores and lowest in the pods.Abbreviations ABA abscisic acid - AOA aminooxyacetic acid - ELISA enzyme linked immunosorbent assay - Ethrel 2-chloroethanephosphonic acid - GC gas chromatography - HPLC High Performance Liquid Chromatography - IAA indole-3-acetic acid - NAA naphthalene acetic acid - RIA radioimmunoassay - STS silver thiosulfhate - TIBA 2,3,6-triiodobenzoic acid     

Overexpression of Sorghum plasma membrane-bound Na+/H+ antiporter-like protein (SbNHXLP) enhances salt tolerance in transgenic groundnut (Arachis hypogaea L.)

Plant Cell, Tissue and Organ Culture (PCTOC) - Soil salinity and water-deficit conditions often affect crop productivity in groundnut. Therefore, developing transgenic groundnut that can grow under...     

Evaluation of early generations for iron chlorosis in relation to productivity in groundnut (Arachis hypogaea L.)

Five popular but iron-inefficient cultivars were crossed with three efficient genotypes and both parents and F₁s were evaluated for iron-efficiency in potted calcareous and noncalcareous soil. The iron-efficient genotypes were dark green or green in both noncalcareous and calcareous soils whereas inefficient types were light green to yellow in calcareous soil. The chlorophyll and active iron (Fe²⁺) concentration of leaves was less in iron-efficient genotypes compared to efficient types in calcareous soil and reduction of both the parameters from noncalcareous to calcareous soil was considerably high in iron-inefficient lines. There was significant correlation between visual scores, chlorophyll and active iron content. There were no differences among F₁s for iron chlorosis and they were all iron-inefficient. The frequency of iron-inefficient plants was higher than the efficient plants in all F₂ populations. But most of the productive plants came from iron-efficient segregants indicating strong association between iron-efficiency and productivity. Based on the results selection for iron-efficiency in early generations and extensive evaluation for productivity in advanced generations is suggested for developing varieties for cultivation in calcareous soils.     

Importance for absorption of Na+ from freshwater of lysine, valine and serine substitutions in the alpha1a-isoform of Na,K-ATPase in the gills of rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar)

In the gills of rainbow trout and Atlantic salmon, the alpha1a- and alpha1b-isoforms of Na,K-ATPase are expressed reciprocally during salt acclimation. The alpha1a-isoform is important for Na(+) uptake in freshwater, but the molecular basis for the functional differences between the two isoforms is not known. Here, three amino acid substitutions are identified in transmembrane segment 5 (TM5), TM8 and TM9 of the alpha1a-isoform compared to the alpha1b-isoform, and the functional consequences are examined by mutagenesis and molecular modeling on the crystal structures of Ca-ATPase or porcine kidney Na,K-ATPase. In TM5 of the alpha1a-isoform, a lysine substitution, Asn783 --> Lys, inserts the epsilon-amino group in cation site 1 in the E(1) form to reduce the Na(+)/ATP ratio. In the E(2) form the epsilon-amino group approaches cation site 2 to force ejection of Na(+) to the blood phase and to interfere with binding of K(+). In TM8, a Asp933 --> Val substitution further reduces K(+) binding, while a Glu961 --> Ser substitution in TM9 can prevent interaction of FXYD peptides with TM9 and alter Na(+) or K(+) affinities. Together, the three substitutions in the alpha1a-isoform of Na,K-ATPase act to promote binding of Na(+) over K(+) from the cytoplasm, to reduce the Na(+)/ATP ratio and the work done in one Na,K pump cycle of active Na(+) transport against the steep gradient from freshwater (10-100 microM: Na(+)) to blood (160 mM: Na(+)) and to inhibit binding of K(+) to allow Na(+)/H(+) rather than Na(+)/K(+) exchange.