1,721,054 research outputs found
Characterization of XV7 and XV9 cDNA clones which confer osmotolerance to Eschericia coli
Full text linkThe sequence similarity between XV7 and the mammalian syntaxin-like protein kinase receptor shows that XV7 may function similar to that of animal protein kinases. The syntaxin-like protein kinase receptor was recently entered into the Genbank (Thoreau, unpublished), therefore not much is known about its characteristics. It does show similarity to a myotonin protein kinase, MtPK (Thoreau, unpublished). The plant receptor-like protein kinases (RLKs) are structurally related to the polypeptide growth factor receptors of animals (Walker, 1994). Although several ABA and stressresponsive gene have been characterised, their physiological role in the initial perception and transduction of stress signals is not well defined Recent reports suggest that characterising phosphorylation/ dephosphorylation responses and investigation of stress-responsive protein kinases may contribute towards identifying the pivotal regulatory steps in plant responses to environmental stress
Assessing the genetic diversity of 48 groundnut (Arachis hypogaea L.) genotypes in the Guinea savanna agro-ecology of Ghana, using microsatellite-based markers
No full textGroundnut (Arachis hypogaea L.) is the most important grain legume in Ghana. However, its production
is constrained by a myriad of biotic and abiotic stresses which necessitate the development and use of
superior varieties for increased yield. Germplasm characterisation both at the phenotypic and molecular
level is important in all plant breeding programs. The aim of this study was to characterise selected
advanced breeding groundnut lines with different phenotypic attributes at the molecular level using
simple sequence repeats (SSR) markers in Ghana. A total of 53 SSR markers were screened and 25 were
found to be polymorphic with an average polymorphic information content (PIC) value of 0.57. Of the 48
groundnut genotypes studied, 67% showed very close relationship (~100% similarity) with one or more
genotypes among themselves. In fact, there were 14 instances where two to three genotypes within the
same sub-cluster exhibited 100% similarity even though they displayed different phenotypic attributes.
The remaining 33% of the groundnut genotypes were distant from each other and could therefore serve
as effective parental material for future work. In this study, the SSR-based markers were found to be
quite discriminatory in discerning variations between and among groundnut lines even where the level
of variation was low. Microsatellite-based markers therefore represent a useful tool for dissecting
genetic variations in cultivated crops, especially groundnu
The symbiotic interaction of Bradyrhizobium japonicum with bambara groundnut and cowpea and the effects of NOD gene-inducers, daidzein and genistein
Full text linkThe aim of this project was to investigate whether nodulation, and nitrogen concentration of legumes can be increased by providing additional nod geneinducer compounds. Both daidzein and genistein are nod gene-inducers for rhizobia nodulating cowpea, bambara groundnut, soybean and the common bean
N2 fixation and rhizosphere ecology of aspalathus linearis subsp. linearis(rooibos tea)
No full textSummary in English.Bibliography: pages 117-138.Aspalathus linearis subsp. linearis grows in acid sands of the Cedarberg with pH ranging from 3.8-5.5. Under these conditions:, some essential nutrients are likely to be limiting. In this study, the response of Aspalathus linearis subsp. linearis to N, P, Ca and B was investigated I under field and glasshouse conditions to determine whether provision of supplemental mineral nutrients promotes growth and N2 fixation for increased tea production, and whether this legume from low nutrient environment responds to fertilization. Interestingly, provision of N and P stimulated plant growth and symbiotic performance under field and glasshouse conditions. However, like most legumes, there was sensitivity to high levels of N which resulted in a decline in nodulation and N2 fixation. Unlike P and N nutrition, Ca supply led to a significant decrease in symbiotic performance of the legume under both glasshouse and field conditions. The amounts of N fixed ranged from 50 to 225 mg N/plant under glasshouse conditions and 3.8 to 7.1 g N/plant in the field. When inoculated with soils collected from different areas outside the Cedarberg, Aspalathus linearis subsp. linearis failed to nodulate, suggesting the possible absence of specific bradyrhizobia which nodulate this legume
Symbiotic N² fixation in cyclopia vent. spp. (honeybush) : towards sustainable cultivation in the Western Cape of South Africa
No full textIncludes bibliographical references.An indigenous cash crop, called honeybush (Cyclopia spp., Fabaceae), has recently gained popularity in the Western Cape of South Africa and its potential for cultivation is being investigated. The crop is an N²-fixing legume and its yields would therefore be improved by enhancing its N²-fixing capacity. This would allow increased tea yields without the need for chemical fertilizers, promoting the crop's status as an organically farmed health product, limiting the environmental degradation associated with N fertilizer use and benefiting small-scale farmers in the region who cannot afford chemical fertilizers
Effects of seaweed concentrate (Kelpak) on nitrogen fixation of cowpea (Vigna ungulata L. Walp.) and soybean (Glycine max L. Merr.) and on the growth of their rhizobial symbionts (Bradyrhizobium strain CB756 and Bradyrhizobium japonicum strain CB1809)
Full text linkSeaweed extracts are known to have a stimulatory effect on the growth and development of plants. This study investigated the effect of applying a commercial seaweed concentrate (kelpak) on rhizobia growth (Bradyrhizobium strain CB756 and Bradyrhizobium japonicum strain CB 1809) and nitrogen fixation in cowpea ( Vigna ungulata L. Walp.) and soybean (Glycine ma.x L. Merr.) plants. Two concentrations of Kelpak (1:100 v/v and 1:500 v/v seaweed concentrate dilutions) were applied to pots with seeds or seedlings at sowing and after every 14 days (1:l00A; 1:500A), at sowing and after every 7 days (1:100B; 1:500B) or after germination and after every 14 days (1: l00C; 1:500C). From the first experiment, cowpea plants in the various treatments showed no change in shoot biomass. The root biomass was significantly inhibited in treatment 1:100B relative to the control. The nodule dry matter of cowpea was reduced in 1:100A, 1:100B and 1:100C Kelpak concentrations compared to control, with a significant increase only in 1:100B Kelpak concentration. As a result, cowpea plants showed the highest total biomass in 1:500B treatment. Although shoot N in cowpea plants remained unchanged under the various kelpak treatments, root N was significantly reduced. Soybean plants showed a significant decrease in shoot and root biomass compared to the control. Nodule dry matter was lowest for soybean plants in Kelpak treatments 1:500B, 1:100B and 1:100C. As a result, there was a decrease in soybean total growth in treatment 1:500B compared to the control. Total N in shoots and roots was highest in soybean plants growing in 1:500A relative to the control. Culturing cells of Bradyrhizobium strain CB756 with Kelpak showed a significant increase in growth at 1:100 and 1:500 dilutions compared to the control. However, over the 93 h period with sterile Kelpak culture there was an inhibition in growth of strain CB756 relative to the control. Beyond the 93 h there was a significant increase in growth of Bradyrhizobium japonicum strain CB 1809 in all Kelpak treatments. The 1:100 concentration showed the highest bacterial growth compared to the control and the other treatments. These data suggests the presence of an active molecule in Kelpak that stimulates rhizobial growth and its symbiotic interaction with legumes
Nutritional characterisation of the rhizosphere of symbiotic cowpea and maize plants in different cropping system
No full textThesis (DTech (Chemistry))--Cape Peninsula University of Technology, 2005A 2-factorial experiment, involving 3 levels of phosphorus (0, 40, and 80 kg P.ha-I ) as main treatment and 4 cropping systems (mono crop, maize/cowpea inter-row, maize/cowpea intra-row, and maize/cowpea intra-hole cropping) as sub-treatment was conducted in the field for 2 consecutive years in 2003 and 2004 to assess i) the effects of exogenous P supply and cropping system on the concentrations of plant-available nutrients in the rhizosphere of cowpea and maize; ii) the effect of exogenous P supply on tissue concentrations of minerals in nodulated cowpea and maize in mixed plant cultures iii) the effects of exogenous P supply and cropping system on plant growth and N2 fixation, and iv) the effects of exogenous P supply and cropping system on phosphatase activity and microbial biomass in the rhizosphere of cowpea and maize. At harvest, it was found that applying 40 or 80 kg P.ha-I significantly increased cowpea grain yields by 59-65% in 2003 and 44-55% in 2004. With maize, the increases in grain yield were 2037% in 2003 and 48-55% in 2004 relative to zero-P control. In both cropping seasons, the number of pod-bearing peduncles per plant, the number of pods per plant, the number of seeds per pod, and seed yield per cowpea plant were significantly increased with the application of exogenous P. In contrast, these parameters were all significantly depressed by mixed culture relative to mono crop cowpea. Intercropping maize with cowpea produced higher total yields per unit land area than the sole crop counterpart
N₂ fixation, plant mineral nutrition and C metabolites in cowpea/maize cropping systems
No full textThe objective of this study was (1) quantify N₂ fixation in sole and mixed cropped cowpea, (2) To access nutrient assimilation by component species in the cropping system, and (3) to determine the effects of cropping system on C metabolites. At harvest the dry mass of both cowpea and maize were highest in sole crops. There was a significant difference in % nitrogen of maize and cowpea plants from the different cropping systems. Total nitrogen content was highest in sole cropped maize and cowpea plants with sole cowpea fixing the most N₂. δ¹⁵N values were lower for the shoots of symbiotic cowpea compared to the maize. Root δ¹⁵N values were also generally lower in cowpea than in maize. The %N derived from fixation (Ndfa) was similar for sole, intra and intercropped cowpea. However the amount of N fixed was significantly greater in sole cowpea compared to intra- and intercropped cowpea. When nutrient uptake and assimilation was assessed in the cropping system, it was found that mineral elements such as Ca, Mg, Cu, Zn and B occurred in significantly greater concentrations in the N₂-fixing legume compared to the cereal partner. However the concentration of soluble sugars and starch remained the same for both shoot and roots of cowpea and maize plants in the cropping system
Ecology of the (Brady)rhizobium symbiotic relationship with Fabaceae in the south-western Cape
No full textThe mediterranean ecosystems of the south-western Cape, South Africa occur mainly on nutrient-poor acid sands and less often on limestone and mixed limestone soil types which support a high species diversity of Fabaceae. This species richness and diversity is suggested to be a result of a high incidence of microsymbiont/host specificity among the fynbos Fabaceae (Cowling et al. 1990). This hypothesis by Cowling et al. (1990) has ignored other factors which may possibly play a major role in microsymbiont/host relationships in the Cape Floristic Region, such as soil conditions, and bacterial strain competition which may also influence patterns of nodulation in the region. Cowling et al.'s (1990) hypothesis was speculative and was without any experimental basis. In this thesis investigations were carried out to assess the applicability of this hypothesis to fynbos, while at the same time other factors that could affect the microsymbiont/host relationship in fynbos were investigated. In order to test Cowling et al.'s (1990) hypothesis, various complementary methods were used to assess the nodulation patterns of several indigenous fynbos species. Extracts from a range of soils differing in chemical and physical properties were used to inoculate test species, and their nodulation parameters observed. However, a second more specific approach was used to confirm the results of the previous study. This method involved cross-inoculation of indigenous test species used in the previous study with nodule homogenates prepared from other fynbos species originating from various sites within the Cape Floristic Region
Marama bean (Tylosema esculentum), a non-nodulating high protein legume indigenous to the Kalahari sands : studies of its N nutrition
No full textIncludes bibliographical references (leaves 90-102)Marama bean is a non-nodulating perennial legume native to the nutrient-poor soils of the Kalahari Sands. In Botswana and Namibia, it is the staple food of the Khoisan people. Marama bean, however, still have not been cultivated or established as an agricultural crop in these countries. This study investigated soil factors affecting the distribution and growth of marama bean in the field and how it would respond to additional N and P supply both under field and glasshouse conditions. The study then attempts to explore and understand the mechanisms employed by marama bean to acquire high nutrient concentration in its organs
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