Potential use of rhizobial bacteria as promoters of plant growth for increased yield in landraces of African cereal crops

Rhizobia form root nodules that fix nitrogen (N2) in symbiotic legumes. Extending the ability of these bacteria to fix N2 in non-legumes such as cereals would be a useful technology for increased crop yields among resource-poor farmers. Although some inoculation attempts have resulted in nodule formation in cereal plants, there was no evidence of N2 fixation. However, because rhizobia naturally produce molecules (auxins, cytokinins, abscicic acids, lumichrome, rhiboflavin, lipo-chito-oligosaccharides and vitamins) that promote plant growth, their colonization and infection of cereal roots would be expected to increase plant development, and grain yield. We have used light, scanning, and transmission electron microscopy to show that roots of sorghum and millet landraces from Africa were easily infected by rhizobial isolates from five unrelated legume genera. With sorghum, in particular, plant growth and phosphorus (P) uptake were significantly increased by rhizobial inoculation, suggesting that field selection of suitable rhizobia/cereal combinations could increase yields and produce fodder for livestock production

Assessing the biological potential of N2-fixing Leguminosae in Botswana for increased crop yields and commercial exploitation

The Leguminosae are a major source of food, fodder, timber, phytochemicals, phytomedicine, nutriceuticals and N fertility in Botswana. Although the country is beset by drought as a result of low rainfall (150 – 650 mm per year) and high potential evapotranspiration, the Leguminosae appear adapted to this low-nutrient environment. Conducting field inoculation trials with infective rhizobia and selecting legume genotypes or host/strain combinations for increased plant growth would help identify superior symbiotic performers under the environmental stress conditions of Botswana. Thus, selecting high N2-fixing legume genotypes has the potential to overcome low soil fertility as a production constraint in Botswana, and increase fodder and grain production to support the growing local livestock and wildlife industries. Additionally, identifying native rhizobia in Botswana that alleviate water stress when in symbioses with legumes could be a first step to tapping the biological potential of the Leguminosae for increased yields in drier environments

Strategic Options for the Expansion of South African Retail Businesses within Africa: Consequences on Operational Management

The expansion of retail companies across national borders is a global phenomenon that is becoming a reality in Africa. This phenomenon is led largely by South African retailers as they seek new markets in Africa. The continent presents both market opportunities as well as challenges. Yet there has been limited academic research on the management of the complexities faced by these retail companies. This paper examines the strategic options available to senior retail management regarding entry mode choices and the possible factors that influence management decisions as they expand their business activities into Africa. The paper also attempts to echo the consequences of such strategic decisions on operational management when it comes to managing operations abroad. It does so by employing mixed method approaches which include analysis of in-depth interviews with senior managers of five major South African retailers, and results of an online survey of retail workers in Cape Town, using the Principal Component (factor) Analysis technique in SPSS. This resulted in six broad factors which appear to provide unique insight on issues that affect the entry mode choices of South African retailers seeking new markets in Africa. The paper concludes that retail managements making this move are often caught up between management self-confidence and their ability to manage risk

Assessing the suitability of antibiotic resistance markers and the indirect ELISA technique for studying the competitive ability of selected Cyclopia Vent. rhizobia under glasshouse and field conditions in South Africa

<p>Abstract</p> <p>Background</p> <p>Symbiotic N2 fixation in legumes is constrained by many factors, including the paucity of suitable soil rhizobia To maximise growth of legume species therefore often requires the application of effective rhizobia as inoculants. But where native strains out-compete introduced rhizobia for nodule formation, it is important that the competitiveness of selected strains is tested in the field and glasshouse prior to their recommendation as commercial inoculants. However the methodology for strain identification inside nodules has often proved difficult and thus limited this field of research. In this study, the suitability of the antibiotic resistance technique (both intrinsic low-resistance fingerprinting and high-resistance marking) and the serological indirect ELISA method were assessed for their ability to detect selected Cyclopia rhizobia under glasshouse and field conditions. The four rhizobial strains that were used, namely PPRICI3, UCT40a, UCT44b and UCT61a, were isolated from wild Cyclopia species growing in the Western Cape fynbos of South Africa.</p> <p>Results</p> <p>The test strains formed two distinct groups with regard to their intrinsic resistance to the antibiotics streptomycin sulphate and spectinomycin dihydrochloride pentahydrate, making it impossible to use intrinsic antibiotic resistance to distinguish strains from within the same intrinsic resistance group. The use of strains marked with double antibiotic resistance was also investigated. A number of these strains lost their antibiotic marker tags after one plant passage; and some also lost their competitive ability. The indirect ELISA technique provided a more satisfactory method of identifying selected Cyclopia strains under both field and glasshouse conditions. The primary antibodies raised against strains UCT40a, UCT61a and UCT44b gave absorbance readings that were unambiguously negative (0.30 OD405), while those of strain PPRICI3 were ambiguous (0.50 OD405) with many false positive readings (1.0 A405). The indirect ELISA method showed a high level of analytical sensitivity in glasshouse experiments and there were no cross-reactions between the four test strains. The method was also suitable for detecting three of the four test strains in competition studies under field conditions, and can also be used to identify some strains under field conditions.</p> <p>Conclusion</p> <p>The antibiotic marker method was found unsuitable for identifying Cyclopia rhizobia in competition experiments in both glasshouse and field conditions. However, the indirect ELISA technique was found suitable for identifying these strains in glasshouse studies. The method was also appropriate for identifying strains UCT40a, UCT44b and UCT61a, but not strain PPRICI3, in field competition studies.</p

Assessment of N2 fixation in 32 cowpea (Vigna unguiculata L. Walp) genotypes grown in the field at Taung in South Africa, using 15N natural abundance

The aim of this study was to evaluate plant growth, grain yield and symbiotic N contribution by 32 cowpea genotypes, at Taung in South Africa. The data from a 2-year field study conducted in 2005 and 2006 showed that genotypes Fahari, Pan 311 and Glenda exhibited the highest dry matter yield and N contribution as they produced 2.9-, 2.7- and 3.5-fold more dry matter than cv. ITH98-46 and yielded 2.7-, 2.2- and 3.2-fold more N than cultivar ITH98-46 from IITA. Except for Benpila, all the 32 cowpea genotypes derived between 52.0 and 80.9% of their N nutrition from symbiotic fixation in 2005, with IT82D-889, Botswana White, IT93K-2045-29 and Ngonji exhibiting the highest %Ndfa values. The genotype Fahari showed the highest amount N-fixed (182 kg N-fixed/ha), followed by Pan 311, Glenda, TVu11424 and Mamlaka which contributed 160, 146, 130 and 125 kg N/ha, respectively. Genotypes Pan 311, Fahari and Glenda were among those that produced highest grain yield in 2005 and except for CH14 and IT86S-2246 (which produced 131 kg N/ha each), Fahari, Glenda and Pan 311, were again the highest in symbiotic N contribution (112, 106 and 105 kg N/ha, respectively). Grain yield was similarly high in Glenda, Pan 311 and Fahari (3.3, 3.1 and 2.9 t/ha, respectively) in 2006. In general, these data show that genotypes that fixed more N also produced more biomass and grain yield and are therefore, the best candidates for inclusion in cropping systems as biofertilizers.Key words: Symbiotic performance, N nutrition, biomass, N-fixed, cowpea varieties

Potential use of rhizobial bacteria as promoters of plant growth for increased yield in landraces of African cereal crops

Rhizobia form root nodules that fix nitrogen (N2) in symbiotic legumes. Extending the ability of these bacteria to fix N2 in non-legumes such as cereals would be a useful technology for increased crop yields among resource-poor farmers. Although some inoculation attempts have resulted in nodule formation in cereal plants, there was no evidence of N2 fixation. However, because rhizobia naturally produce molecules (auxins, cytokinins, abscicic acids, lumichrome, rhiboflavin, lipo-chito-oligosaccharides and vitamins) that promote plant growth, their colonization and infection of cereal roots would be expected to increase plant development, and grain yield. We have used light, scanning, and transmission electron microscopy to show that roots of sorghum and millet landraces from Africa were easily infected by rhizobial isolates from five unrelated legume genera. With sorghum, in particular, plant growth and phosphorus (P) uptake were significantly increased by rhizobial inoculation, suggesting that field selection of suitable rhizobia/cereal combinations could increase yields and produce fodder for livestock production. Key Words: Rhizobia, N2 fixation, plant growth, sorghum, millet African Journal of Biotechnology Vol.3(1) 2004: 1-

Symbiotic functioning and bradyrhizobial biodiversity of cowpea (Vigna unguiculata L. Walp.) in Africa

<p>Abstract</p> <p>Background</p> <p>Cowpea is the most important food grain legume in Sub-Saharan Africa. However, no study has so far assessed rhizobial biodiversity and/or nodule functioning in relation to strain IGS types at the continent level. In this study, 9 cowpea genotypes were planted in field experiments in Botswana, South Africa and Ghana with the aim of i) trapping indigenous cowpea root-nodule bacteria (cowpea "rhizobia") in the 3 countries for isolation, molecular characterisation using PCR-RFLP analysis, and sequencing of the 16S - 23S rDNA IGS gene, ii) quantifying N-fixed in the cowpea genotypes using the ¹⁵N natural abundance technique, and iii) relating the levels of nodule functioning (i.e. N-fixed) to the IGS types found inside nodules.</p> <p>Results</p> <p>Field measurements of N₂fixation revealed significant differences in plant growth, δ¹⁵N values, %Ndfa and amounts of N-fixed between and among the 9 cowpea genotypes in Ghana and South Africa. Following DNA analysis of 270 nodules from the 9 genotypes, 18 strain IGS types were found. Relating nodule function to the 18 IGS types revealed significant differences in IGS type N₂-fixing efficiencies. Sequencing the 16S - 23S rDNA gene also revealed 4 clusters, with cluster 2 forming a distinct group that may be a new <it>Bradyrhizobium </it>species. Taken together, our data indicated greater biodiversity of cowpea bradyrhizobia in South Africa relative to Botswana and Ghana.</p> <p>Conclusions</p> <p>We have shown that cowpea is strongly dependant on N₂fixation for its N nutrition in both South Africa and Ghana. Strain IGS type symbiotic efficiency was assessed for the first time in this study, and a positive correlation was discernible where there was sole nodule occupancy. The differences in IGS type diversity and symbiotic efficiency probably accounts for the genotype × environment interaction that makes it difficult to select superior genotypes for use across Africa. The root-nodule bacteria nodulating cowpea in this study all belonged to the genus <it>Bradyrhizobium</it>. Some strains from Southern Africa were phylogenetically very distinct, suggesting a new <it>Bradyrhizobium </it>species.</p

Evaluating Retail Distribution Strategies During Covid-19 Pandemic in South Africa Using Best Worst Method Multicriteria Decision Technique

This paper evaluates the distribution strategies adopted by South African retailers during the Covid-19 pandemic and how such strategies have been adjusted for a more resilient post-Covid-19 world. Using the Best Worst method multicriteria decision technique and exploiting data collected from decision makers from the retail industry to rank the distribution strategies according to their level of importance, we show that omnichannel distribution strategy ranked highest, followed by direct shipment distribution capability in contributing to the success of retail distribution during the Covid-19 pandemic. On the other hand, inventory pooling, transhipment, centralised or decentralised strategy, and cross-docking ranked lower while retail distribution strategy was lowest ranked. Finally, particular emphasis must be placed on the critical factors identified in the evaluation in terms of their challenging dimension and impact as they pave way for a more capable retail resilience distribution capability