The calcium nutrition of bambara groundnut (Vigna subterranea (L.) Verdc.)

Iron chlorosis induced by Fe-deficiency is a widespread nutritional disorder in many woody plants and in particular in grapevine. This phenomenon results from different environmental, nutritional and varietal factors. Strategy I plants respond to Fe-deficiency by inducing physiological and biochemical modifications in order to increase Fe uptake. Among these, acidification of the rhizosphere, membrane redox activities and synthesis of organic acids are greatly enhanced during Fe-deficiency. Grapevine is a strategy I plant but the knowledge on the physiological and biochemical responses to this iron stress deficiency in this plant is still very poor. In this work four different genotypes of grapevine were assayed for these parameters. It was found that there is a good correlation between genotypes which are known to be chlorosis-resistant and increase in both rhizosphere acidification and Fe^III reductase activity. In particular, when grown in the absence of iron, Vitis berlandieri and Vitis vinifera cv Cabernet sauvignon and cv Pinot blanc show a higher capacity to acidify the culture medium (pH was decreased by 2 units), a higher concentration of organic acids, a higher resting transmembrane electrical potential and a greater capacity to reduce Fe^III-chelates. On the contrary, Vitis riparia, well known for its susceptibility to iron chlorosis, fails to decrease the pH of the medium and shows a lower concentration in organic acids, lower capacity to reduce Fe^III and no difference in the resting transmembrane electrical potential. H Marschner Section editor     

The development and structure of root nodules on bambara groundnut [Voandzeia (Vigna)subterranea]

The infection of Vigna subterranea (formerly Voandzeia subterranea) by Bradyrhizobium strain MAO 113 (isolated from V. subterranea) was examined by light and transmission electron microscopy. Bacteria accumulated on the epidermis close to root hairs, and subsequently entered the latter via infection threads. Most of the steps involved in nodule formation were generally characteristic of determinate nodules, such as those which form on the closely related V. radiata. For example, nodule meristems were induced beneath the root epidermis adjacent to infected root hairs, but prior to infection of the meristem by rhizobia. Moreover, after the infection of some of the meristematic cells by the infection threads, and the release of the rhizobia into membrane-bound vesicles, the infection process ceased and dissemination of the rhizobia was by division of already-infected host cells. However, there were some aspects of this process in V. subterranea which have been more commonly described in indeterminate nodules. These include long infection threads entering a number of cells within the meristems simultaneously and a matrix within infection threads which was strongly labelled with immunogold monoclonal antibodies, MAC236 and MAC265, which recognize epitopes on an intercellular glycoprotein. The MAC236 and MAC265 antibodies also recognized material in the unwalled infection droplets surrounding bacteria which were newly-released from the infection threads. The amount of labelling shown was more characteristic of the long infection threads seen in indeterminate nodules such as pea (Pisum sativum) and Neptunia plena. The structure of mature V. subterranea nodules was similar to that described for other determinate nodules such as Glycine max, Vigna unguiculata and V.radiata, i.e. they were spherical and the infected zone consisted of both infected and uninfected cells. Surrounding the infected tissue was an inner cortex of uninfected cell layers containing the putative components of an oxygen diffusion barrier (including glycoprotein-occluded intercellular spaces), and an outer cortex with cells containing calcium oxalate crystals.     

The development and structure of root nodules on bambara groundnut [Voandzeia (Vigna)subterranea]

The infection of Vigna subterranea (formerly Voandzeia subterranea) by Bradyrhizobium strain MAO 113 (isolated from V. subterranea) was examined by light and transmission electron microscopy. Bacteria accumulated on the epidermis close to root hairs, and subsequently entered the latter via infection threads. Most of the steps involved in nodule formation were generally characteristic of determinate nodules, such as those which form on the closely related V. radiata. For example, nodule meristems were induced beneath the root epidermis adjacent to infected root hairs, but prior to infection of the meristem by rhizobia. Moreover, after the infection of some of the meristematic cells by the infection threads, and the release of the rhizobia into membrane-bound vesicles, the infection process ceased and dissemination of the rhizobia was by division of already-infected host cells. However, there were some aspects of this process in V. subterranea which have been more commonly described in indeterminate nodules. These include long infection threads entering a number of cells within the meristems simultaneously and a matrix within infection threads which was strongly labelled with immunogold monoclonal antibodies, MAC236 and MAC265, which recognize epitopes on an intercellular glycoprotein. The MAC236 and MAC265 antibodies also recognized material in the unwalled infection droplets surrounding bacteria which were newly-released from the infection threads. The amount of labelling shown was more characteristic of the long infection threads seen in indeterminate nodules such as pea (Pisum sativum) and Neptunia plena. The structure of mature V. subterranea nodules was similar to that described for other determinate nodules such as Glycine max, Vigna unguiculata and V.radiata, i.e. they were spherical and the infected zone consisted of both infected and uninfected cells. Surrounding the infected tissue was an inner cortex of uninfected cell layers containing the putative components of an oxygen diffusion barrier (including glycoprotein-occluded intercellular spaces), and an outer cortex with cells containing calcium oxalate crystals.     

Genetic diversity in bambara groundnut (Vigna subterranea (L.) Verdc) landraces revealed by AFLP markers.

Bambara groundnut (Vigna subterranea (L.) Verdc), an African indigenous legume, is popular in most parts of Africa. The present study was undertaken to establish genetic relationships among 16 cultivated bambara groundnut landraces using fluorescence-based amplified fragment length polymorphism (AFLP) markers. Seven selective primer combinations generated 504 amplification products, ranging from 50 to 400 bp. Several landrace-specific products were identified that could be effectively used to produce landrace-specific markers for identification purposes. On average, each primer combination generated 72 amplified products that were detectable by an ABI Prism 310 DNA sequencer. The polymorphisms obtained ranged from 68.0 to 98.0%, with an average of 84.0%. The primer pairs M-ACA + P-GCC and M-ACA + P-GGA produced more polymorphic fragments than any other primer pairs and were better at differentiating landraces. The dendrogram generated by the UPGMA (unweighted pair-group method with arithmetic averaging) grouped 16 landraces into 3 clusters, mainly according to their place of collection or geographic origin. DipC1995 and Malawi5 were the most genetically related landraces. AFLP analysis provided sufficient polymorphism to determine the amount of genetic diversity and to establish genetic relationships in bambara groundnut landraces. The results will help in the formulation of marker-assisted breeding in bambara groundnut.     

Effects of soil moisture deficits on the water relations of bambara groundnut (Vigna subterranea L. Verdc.)

The components of leaf water potential (_l) and relative watercontent (RWC) were measured for stands of bambara groundnut(Vigna subterranea) exposed to three soil moisture regimes incontrolled-environment glasshouses at the Tropical Crops ResearchUnit, Sutton Bonington Campus. Treatments ranged from fullyirrigated (wet) to no irrigation from 35 days after sowing (DAS)(dry). RWC values varied between 92–96% for the wet treatment,but declined from 93% to 83% in the dry treatment as the seasonprogressed. _l at midday decreased in both the wet and dry treatments,but the seasonal decline was more pronounced in the latter:seasonal minimum values were –1.19 and –2.08 MPa,respectively. Plants in the wet treatment maintained turgor(_p) at about 0.5 MPa throughout the season, whereas values inthe dry treatment approached zero towards the end of the season.There was a linear relationship between _p and _l9 with _p approachingzero at a _l of –2.0 MPa. Mean daily leaf conductance wasconsistently higher in the wet treatment (0.46–0.79 cm^-1)than in the intermediate and dry treatments (0.13–0.48cm s^-1 Conductances in the intermediate and dry treatments weresimilar, and the lower evapotranspirational water losses inthe latter were attributable to its consistently lower leafarea indices (L): L at final harvest was 3.3, 3.3 and 1.9 forthe wet, intermediate and dry treatments. Bambara groundnutwas apparently able to maintain turgor through a combinationof osmotic adjustment, reductions in leaf area index and effectivestomatal regulation of water loss. Key words: Vigna subterranea, water relations, soil moisture     

The effect of seed size on the development and yield ofVoandzeia subterranea (L.)Thouars. (Bambara groundnut)

Voandzeia subterranea (L.)Thouars (Bambara groundnut) is a drought and poor soil cultivated legume. The seeds vary both in colour and in size. The seed colour ranges from white, cream, ivory to dark brown red or black. The seed weight varies fromabout 0.15 g to 1.20 g. The effect of seed size on the development and yield of the cream coloured cultivar ofV. subterranea was investigated. The three size class of seeds used in the study are small (seeds weighing less than 0.40 g) medium (seeds weighing from 0.40–0.60g) and large (seeds weighing above 0.60g). The results of the investigation show that the number of leaves, pods and seeds, the leaf area, dry weight of plants and the seeds produced increased significantly with increase in the seed size.     

Germination and Food Reserves in Bambarra Groundnut Seeds (Voandzeia subterranea Thouars) after Different Periods of Storage

Studies were made on bambarranut seeds (Voandzeia subterraneaThouars) after 0, 6, 12, 18 and 24 months of storage in gunnybags under laboratory conditions (25–35 °C). Seeddeterioration during storage was indicated by delayed germination,reduced germinability, reduced growth of seedlings and increasednumber of stunted seedlings culminating in a total failure ofgermination after two years. Slight depletion of food reserves occurred during seed storage.The loss in fat was higher than starch or protein. Total solublesugars decreased while the content of total fatty acids andamino acids and soluble protein increased. Total nitrogen (N)remained unaffected while soluble-N and amino-N increased. Allthese components showed a rapid change (increase or decrease)from 12 months to 18 months of storage which was associatedwith commencement of rapid decline in germinability of the seedsand growth of the seedlings. Initial rapid imbibition of water was observed in viable aswell as non-viable seeds, though at a higher rate in the latterand followed by a lag period in both. At the end of 24 h ofimbibition, water content in non-viable seeds was less thanthat in viable ones. Key words: Voandzeia subterranea, Seed germination, Seed storage     

Auxins, Inhibitors and Phenolics in Bambarranut Seeds (Voandzeia subterranea Thouars) in Relation to Loss of Viability During Storage

Studies were made on seeds of bambarra groundnut (Voandzeiasubterranea Thouars) after 0, 6, 12, 18 and 24 months of storage. Germinability of the seeds was not adversely affected up to12 months of storage but it rapidly declined and after 24 monthsstorage no germination occurred. Growth of seedlings starteddecreasing in seeds stored for 12 months or more. Closely coincidingwith this, there was an increase in the contents of total phenoland inhibitory phenolic acids (p-hydroxybenzoic, p-coumaric,feruhc and vanillic acids) and a decrease in synergistic phenolicacids (chlorogenic, sinapic and protocatechuic acids). Auxincontent decreased in seeds stored for 18 months or more whilegrowth inhibitors appeared after 12 months of storage and increasedthereafter. Non-viable bambarranut seeds contained larger amounts of totalphenol, inhibitory phenolic acids and other growth inhibitorsand lower amounts of auxin and synergistic phenolic acids comparedwith the viable ones. Voandzeia subterranea Thouars, bambarranut, seed storage, germination, viability, auxins, inhibitors, phenol, phenolic acids     

Development of microsatellite markers for bambara groundnut (Vigna subterranea L. Verdc.) — an underutilized African legume crop species

Bambara groundnut is an indigenous African legume crop plant. It is largely grown by subsistence farmers, but can also be used as a cash crop to supplement family income. The fact that it is highly drought tolerant means that it has considerably potential to provide part of food security in regions of the world where water availability is a serious issue. As one part of the international effort to understand and improve this species, we report here the first 10 microsatellite markers derived from bambara groundnut.     

Genetic diversity in Bambara groundnut (Vigna subterranea L.) germplasm revealed by RAPD markers.

Random amplified polymorphic DNA (RAPD) markers were used to assess genetic diversity in Bambara groundnut (Vigna subterranea L.) germplasm using 25 African accessions from the collection in the International Institute for Tropical Agriculture, Ibadan, Nigeria. Fifty random decamer primers were screened to assess their ability to detect polymorphism in bambara; 17 of them were selected for this study. Considerable genetic diversity was found among the V. subterranea accessions studied. The relationships among the 25 accessions were studied by cluster analysis. The dendrograms showed two main groups of accessions mainly along the lines of their geographic origin. It is concluded that RAPD can be used for germplasm classification in bambara groundnut and hence for improving this crop.     

Fruit Development in Bambarra Groundnut (Voandzeia subterranea)

Flowers of Voandzeia subterranea are positively geotropic andthis helps their entry into the ground. The ovary develops onlywhen it is on the surface of, or inside, the soil. The transformationinto fruit occurs in two stages: (a) definite development of pod, followed by (b) development of seed. The first stage occurs during the first 30 days after fertilizationand the second stage lasts for about 10 days. Maturity is characterizedby dryness and browning of the interior of the shell and appearanceof brown patches on it. The part of the pod on which the pedicelsubsists is the upper part and the lower part is the portionwhere the style is attached.     

Insecticidal potential of cashew (Anacardium occidentale L.) for control of the beetle,Callosobruchus subinnotatus (Pic.) (Bruchidae) on bambarra-groundnut (Voandzeia subterranea L.) Verde

Abstract

The nut and shell of cashew (Anacardium occidentale L.) were evaluated for insecticidal efficacy at concentrations of 2.5, 5.0 and 7.5% per 150 g bambarra groundnut (Voandzeia subterranea L.) Verde seeds against Callosobruchus subinnotatus (Pic.) (Bruchidae). Cashew nut shell was highly toxic to C. subinnotatus and achieved 100% insect mortality within 48 hours at 7.5% and 100% mortality within 72% hours at 2.5 and 5.0% concentrations. Oviposition and progeny development of the insect were severely suppressed while seeds were protected from damage by the bruchid. Seed germination was, however, impaired at all concentrations, suggesting that seed treated with cashew products may be suitable for consumption but not be suitable as planting stock.     

Genetic diversity of the Bambara groundnut (Vigna subterranea (L.) Verdc.) as assessed by SSR markers

Bambara groundnut ( Vigna subterranea (L.) Verdc.) is an important African legume crop. In this study, a collection consisting of 240 accessions was analyzed using 22 simple sequence repeat (SSR) markers. In total, 166 alleles were detected, with a mean of 7.59 alleles per locus. Allelic and gene diversities were higher in the west African and Cameroon/Nigeria regions with 6.68 and 6.18 alleles per locus, and 0.601 and 0.571, respectively. The genetic distance showed high similarity between west African and Cameroon/Nigeria accessions. Principal coordinate analyses and neighbor-joining analysis consistently revealed that the majority of west African accessions were grouped with Cameroon/Nigeria accessions, but they were differentiated from east African, central African, and southeast Asian accessions. Population structure analysis showed that two subpopulations existed, and most of the east African accessions were restricted to one subpopulation with some Cameroon/Nigeria accessions, whereas most of the west African accessions were associated with most of the Cameroon/Nigeria accessions in the other subpopulation. Comparison with SSR analysis of other Vigna cultigens, i.e., cultivated azuki bean ( Vigna angularis ) and mungbean ( Vigna radiata ), reveals that the mean gene diversity of Bambara groundnut was lower than azuki bean but higher than mungbean.     

Effect of NO3 on N2 fixation and nitrogenous solutes of xylem in two nodulated West African geocarpic legumes,Kersting's bean (Macrotyloma geocarpum L.) and Bambara groundnut (Vigna subterranea L.)

Nodulation, nitrogen (N₂) fixation and xylem sap composition were examined in sand cultured plants of Bambara groundnut (Vigna subterranea L.) and Kersting's bean (Macrotyloma geocarpum L.) inoculated with Bradyrhizobium strain CB756 and supplied via the roots for a 4 week period from the third week onwards with different levels of (¹⁵N)-nitrate (0–15 mM). The separate contributions of nitrate and N₂ to plant nitrogen were measured by isotope dilution. Increasing levels of nitrate inhibited nodule growth (measured as dry matter or nodule N) of both species parallel with decreased dependence on symbiotically-fixed N. Specific nodule activity (N₂ fixed g nodule dry⁻¹ d⁻¹ of nodules) was reduced progressively with time in V. subterranea at higher (5 or 15 mM) levels of NO₃, but this was not so for M. geocarpum. Root xylem bleeding sap of both species showed ureides (allantoin and allantoic acid) as predominant (>90%) solutes of nitrogen when plants were relying solely on atmospheric N. Levels of ureide and glutamine decreased and those of asparagine and nitrate in xylem increased with increasing level of applied nitrate. Relative levels of xylem ureide-N were positively correlated (R²=0.842 for M. geocarpum and 0.556 for V. subterranea), and the ratio of asparagine to glutamine in xylem exudate negatively correlated (R²=0.955 for M. geocarpum and 0.736 for V. subterranea) with plant reliance on nitrogen fixation. The data indicate that xylem sap analyses might be useful for indirect field assays of nitrogen fixation by the species and that Kersting's bean might offer some potential as a symbiosis in which N₂ fixation is relatively tolerant of soil N.     

Nitrogen fixation by soybeans (Glycine max L.) in Zambia

Soybeans (Glycine max L.) are being introduced as a cash crop to small scale farmers in Zambia for rotation in their farming systems. The objectives of this study were to compare and select the most approriate non-fixing reference crop for estimating N₂ fixation by soybeans and assess yields and N₂ fixation of soybeans in Zambia. Nitrogen isotope dilution techniques using¹⁵N-labelled organic or inorganic materials were utilized. Two nonnodulating soybean cultivars, Clark RJ1 and N77 or in their absence Pearl millet (Panicum glaucum L.) were judged to be appropriate reference crops. A local soybean fixing cultivar (Glycine max L. cv. Magoye) rated highest among three cultivars tested for its ability to support symbiotic N₂ fixation byB. japonicum under the experimental conditions. Values of percent N derived from atomosphere for this cultivar were in the order of 65 to 70%.deceased.Contribution no R531 of the Saskatchewan Institute of Pedology. Present address (REK): Esso Chemical Canada, P.O. Box 3010, Lethbridge, Alberta Canada T1J 4A9.     

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     

Inheritance of resistance to groundnut rosette virus in groundnut (Arachis hypogaea L.)

A method of field screening groundnut seedlings for resistance to groundnut rosette virus (GRV), by means of which over 97% incidence was induced in rows of susceptible test plants, was developed at Chitedze Research Station in Malawi. Two GRV-resistant Virginia cultivars (RG 1 and RMP 40) were crossed with three susceptible cultivars, one from each of the Spanish (JL 24), Valencia (ICGM 48) and Virginia (Mani Pintar) botanical groups. Twelve F₁ reciprocal crosses and their F₂ and backcross generations were produced and the material screened in nurseries in 1985/86 and 1986/87. Seedlings raised from plants which did not become infected in the field were inoculated in the glasshouse in order to eliminate susceptible escapees. The numbers of diseased and healthy individuals in each population were subjected to χ² tests. In the majority of the F₂ populations a good fit was obtained for a ratio of one resistant to 15 susceptible plants, a ratio to be expected if resistance to GRV were determined by a pair of independent complementary recessive genes. This was further supported by data from backcross generations.     

Efficient in vitro direct shoot organogenesis and regeneration of fertile plants from embryo explants of Bambara groundnut (Vigna subterranea L. Verdc.)

An efficient protocol has been developed for direct shoot organogenesis from embryo axes derived from mature seeds of two different landraces of Bambara groundnut. Multiple shoots were initiated on several media containing different concentrations and combinations of benzylaminopurine (BAP) or thidiazuron (TDZ). Efficient regeneration occurred when the embryo axes were first plated for 6 days on a medium containing high concentrations of BAP (1 mg/l) and alpha-naphthaleneacetic acid (NAA, 1 mg/l) and then cut transversely and transferred onto a medium containing 1.5 mg/l BAP. Shoot regeneration frequency was 100% and from five to eight shoots per explant were obtained. The importance of using embryo explants and cytokinins in the culture media, with respect to controlling the development of a highly organogenic system, was demonstrated. Histological studies revealed that proliferating buds originated directly from the superficial layers of the explants without an intermediate callus phase. The regenerated shoots were rooted on a medium containing 1 mg/l NAA and then transferred to the greenhouse. Flow cytometric analyses and chloroplast counts of guard cells suggested that the regenerants were diploid. All were morphologically normal and fertile. The short duration, high efficiency and low frequency of somaclonal variation of this system make it well suited for wider biotechnological applications of Bambara groundnut-a neglected and under-utilized crop.     

Root turnover of groundnut (Arachis hypogaea L.) in soil tubes

Five groundnut cultivars were grown in transparent tubes of pasteurized loam compost in growth-chamber conditions. Weekly tracings were made of all the roots visible through the walls of the tubes. White roots were assessed as living, and brown or decayed roots as dead; this correlated with microscopical assessments of root viability based on cytoplasmic staining with neutral red followed by plasmolysis.For all five cultivars, root laterals began to die 3–4 weeks after plants were sown. Death of root laterals progressed down the soil profile with time, while new roots were produced successively deeper from the extending taproot. The half-life of individual roots was calculated as 3.7–4.4 weeks for all cultivars, based on assessments of the roots that died up to plant maturity (14–20 weeks, depending on cultivar). At maturity, 73–83% of the cumulative length of root systems had died. The onset and rate of root death were not related to onset of flowering or pod-filling; instead, the peak times of root death at different distances down the root system were related to earlier (3–5 week) peak times of root production in those regions. The net result of root turnover was that, despite continued new root production, the maximum length of living (white) roots of each cultivar was recorded at 2–4 weeks after sowing. Death of the earliest formed root laterals was also observed in the first five weeks after sowing of groundnut in an experimental field plot in Malawi. Progressive root turnover is considered to be a normal feature of groundnut, perhaps representing an energy-economy strategy.     

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.