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N2 fixation in grain legumes: Its role in food and nutritional security in Africa
South African Journal of Botany 98 (2015) 167–216
Contents lists available at ScienceDirect
South African Journal of Botany j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / s a j b
Conference Abstracts
South African Association of Botanists (SAAB) - Annual meeting 2015 Abstracts of papers and posters presented at the 41st Annual Congress of the South African Association of Botanists held at the Tshipise Forever Resort, Venda, 11–15 January 2015 The presenter of multi-authored papers is underlined * Awards made to students.
Plenary lectures The late flowering of flammable ecosystems W. Bond SAEON, NRF, c/o Department of Biological Sciences, University of Cape Town, Private Bag, Rondebosch 7701, South Africa Over the last decade, fire has emerged as a global factor, second only to climate, in accounting for the major vegetation patterns of the world. Satellite imagery shows that about a third of the vegetated land surface burns every year. The mix of growth forms in flammable biomes generally diverges strongly from those selected by climate in the absence of fire. Yet, relative to the geological deep past, there is very little fossil evidence for high fire activity in the Cenozoic (last 65 million years), when modern biomes emerged. Here I review fossil and phylogenetic evidence for fire activity over this period. These reveal a surprising synchrony in the geographically widespread onset of high fire from about 7 million years ago. In Africa, this spike in fire was associated with the rapid spread of C4 grassy biomes, including South African savannas and highveld grasslands. Fynbos, the other major flammable biome in the country, has much older origins but there is growing phylogenetic evidence for a fire-driven expansion of fynbos also beginning ~7 Ma. Discussion on the causes of expansion of flammable biomes has generally had a regional focus though the phenomenon appears to be global. Ideas on the causes of the surge in fire from the Miocene are contentious and poorly explored. More certain is that human disruption of fire, at diverse scales, has had, and will continue to have, profound ecological effects on flammable ecosystems. doi:10.1016/j.sajb.2015.03.003
More than a music tree: 4400 years of Dalbergia melanoxylon trade in Africa A.B. Cunningham School of Plant Biology, University of Western Australia, Nedlands 6009, Australia 0254-6299/$ – see front matter.
Perhaps more than any other African tree species, the African blackwood (Dalbergia melanoxylon) symbolises the links between culture and nature. Widely used for its medicinal leaves, it is best known for its wood. Prized by Egyptian pharaohs, D. melanoxylon wood was traded from the Horn of Africa from 2400 BC. Although difficult to carve by hand, D. melanoxylon was traditionally used for sticks and was the wood of choice for Shona snuff containers. With the arrival of iron-smelting technology in southern and south-central Africa from about 1000 years ago, D. melanoxylon was in high demand as for smelting purposes, due to the high calorific value of the wood, which gets so hot that it is avoided as a firewood today, as it gets so hot that it melts pots. With its extremely dense, close-grained wood (1200 kg/m3), D. melanoxylon, this is the premier wood for oboes, clarinets and bag-pipe wood. D. melanoxylon has been traded to Europe for this purpose since the early 19th century, making it one of the world's most valuable timbers (US$14,000– 20,000 per m3). Today, D. melanoxylon stocks are dwindling due to four factors: (1) habitat loss due to agricultural expansion; (2) fire affecting recruitment from seed; (3) commercial trade to China for reproduction Ming and Ching dynasty furniture. This is driven by the depletion of Asian Dalbergia species traditionally used for Chinese Imperial style furniture, and their substitution with African species such as Swartzia madagascariensis, Combretumimberbe, Millettia stuhlmannii and D. melanoxylon. (4) in Kenya, Tanzania and Malawi the commercial woodcarving trade. Despite the long history of trade in D. melanoxylon there are several unknowns that offer opportunities for research, ranging from studies of D. melanoxylon genetics across its range to archaeological studies in unrecorded iron smelting sites in northern Mozambique, where smelting continued until the early 1900's. What is also needed is a regional conservation strategy for both in situ and ex situ conservation. doi:10.1016/j.sajb.2015.03.004
N2 fixation in grain legumes: Its role in food and nutritional security in Africa F.D. Dakora Chemistry Department, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa Food grain legumes are important in meeting the food and nutritional security of about 1.1 billion people in Africa. They also
168
Abstracts
serve as biofertilizers in cropping systems. Studies of their grain yield and food quality are therefore crucial for human nutrition and health in Africa. The leaves and grain of cowpea, for example, are consumed in large quantities in Africa and elsewhere in the world. Protein levels in the edible leaves are high and range from 29 to 40%, while grain protein also ranges from 23 to 40% depending on the variety and its symbiotic functioning. In fact, the grain protein of farmerselected cowpea varieties such as Soronko and Bengpla can be as high as 40%, a level comparable to that of soybean. Both leaves and grain also contain very high concentrations/amounts of macronutrients and trace elements, the latter needed for overcoming micronutrient deficiency in rural Africa. Evidence from field and glasshouse studies has shown that, as with leaf and grain protein, the accumulation of mineral nutrients by cowpea is symbiosis-dependent. In the field, cowpea varieties with high N2-fixing ability accumulated more nutrient elements than low fixers, while in nodulation assays, rhizobia with high N2-fixing efficiency generally elicited greater mineral accumulation in cowpea shoots when compared to strains with low symbiotic efficacy. These findings on the symbiosis-induced mineral accumulation in cowpea offer an additional explanation for the benefits of legume/cereal rotations beyond the known N contribution by the legume and further validate cowpea as an important food legume for nutritional security in Africa. doi:10.1016/j.sajb.2015.03.005
The role of pollinators in the floral diversification and life history of Leucospermum (Proteaceae) C.M. Johnsona, T. Heb, B. Lamontb, A. Pauwa a Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa b Department of Environment and Agriculture, Curtin University, PO Box U1987, Perth WA 6845, Australia Leucospermum, commonly known as pincushions, are an endemic genus often associated with South Africa and, more specifically, the fynbos ecosystem and Cape Floral Kingdom. The staggering floral polymorphism within the genus suggests a wide variety of pollination modes. Despite this remarkable assortment of floral morphologies within Leucospermum only recently has any research been conducted to explain the role of pollinators in driving diversification. In this study we construct the first molecular phylogeny for the genus and, taking relatedness into account using a phylogenetic generalized least squares approach, determine how pollinators have driven floral divergence. Pollinators were assigned through direct observations and a suite of floral traits that are likely to reflect pollination mode were measured for each taxa. In addition, the ability to autonomously self-pollinate was determined for each taxon and used to test if autogamy is linked to specific classes of pollinators, specialized taxa or recently derived taxa. All fieldwork has been finalized and we are awaiting our phylogenetic analysis before any results can be determined.
Why has there been no success in finding new antibiotics from plants?
doi:10.1016/j.sajb.2015.03.007
J.N. Eloff Phytomedicine Programme, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
Natural products for skin infections
There has been tens of thousands of publications on antimicrobial activity and plants in good journals and hundreds of thousands of publications on poor journals. The motivation is frequently that due to the increased resistance of microorganisms to current antibiotics there is an urgent need to find new antibiotics. With the multiplication of poor open access journals many publications in this area have hardly any value. In contrast to the use of plants for other indications where in the order of 25% of prescribed pharmaceuticals originated from plant leads and the majority of antibiotics originating from fungal leads there has been no commercial antibiotic developed from plants. Several actors may play a role including the methods used, the plants selected for investigation, low activity of isolated compounds in comparison to the activity of the crude extract and cellular toxicity of isolated compounds. Few compounds are ever tested on animals and factors such as a lack of bioavailability may also be involved. Because the same antimicrobial compounds are repeatedly isolated, it appears that plants use a limited number of compounds for protection against microorganisms, but enhances activity by synergism with other compounds present in extracts. There are two possible solutions to the problem. The first is to focus on developing herbal extracts with good activity. In the case of topical application safety may not be a major complication. Another alternative is to screen large number of plants using reproducible methods and then investigate species with high activity in depth. The phytomedicine has had success in this approach in isolating a novel compound with higher activity and better safety against Candida albicans than the commercially used fungicide amphotericin B. doi:10.1016/j.sajb.2015.03.006
S. Van Vuurena, H. De Wetb, A.M. Viljoenc, A.D. Van Eyka a University of the Witwatersrand, Johannesburg, South Africa b University of Zululand, KwaDlangezwa, South Africa c Tshwane University of Technology, Pretoria, South Africa Traditional medicine or natural products are often the first line in the therapeutic treatment for skin infections. This study explores some of the antimicrobial efficacies of natural products with special emphasis on their use to treat dermatological infections. Antimicrobial methods used include the minimum inhibitory concentration (MIC) assays and interaction studies where the calculation of fractional inhibitory concentrations ( FIC) and isobolograms are given. Studies on some of the most widely used essential oils for dermatological conditions demonstrated noteworthy antimicrobial activity, particularly against Propionibacterium acnes (ATCC 11827), having MIC values as low as 0.5 mg/ml against Cymbopogon citratus (lemon grass), Commiphora myrrha (myrrha), Pogostemonpatchouli (patchouli) and Andropogon zizanioides (vetiver). Of particular interest is the inhibitory effects (as low as 0.1 mg/ml) of commercial oils against Santalum album (sandalwood) and A. zizanioides against Brevibacterium spp., a group of bacteria responsible for foot odour. Synergistic interactions were noted between oils commonly used together. Naturally derived bee products (honey and propolis) are frequently used for wound healing and our studies show that some South African honey samples demonstrate activity (lowest activity 11% growth inhibition), equivalent to the gold standard Manuka honey, derived from Australia. South African propolis has shown excellent antimicrobial efficacy with activities of 6 μg/ml when tested against Staphylococcus aureus. This activity correlates with the high flavonoid content observed during chemical profiling studies. When examining the dermatological application of medicinal plants in the South African context, over 100 plant species were identified as being of importance. Some of these species will be highlighted where
Contents lists available at ScienceDirect
South African Journal of Botany j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / s a j b
Conference Abstracts
South African Association of Botanists (SAAB) - Annual meeting 2015 Abstracts of papers and posters presented at the 41st Annual Congress of the South African Association of Botanists held at the Tshipise Forever Resort, Venda, 11–15 January 2015 The presenter of multi-authored papers is underlined * Awards made to students.
Plenary lectures The late flowering of flammable ecosystems W. Bond SAEON, NRF, c/o Department of Biological Sciences, University of Cape Town, Private Bag, Rondebosch 7701, South Africa Over the last decade, fire has emerged as a global factor, second only to climate, in accounting for the major vegetation patterns of the world. Satellite imagery shows that about a third of the vegetated land surface burns every year. The mix of growth forms in flammable biomes generally diverges strongly from those selected by climate in the absence of fire. Yet, relative to the geological deep past, there is very little fossil evidence for high fire activity in the Cenozoic (last 65 million years), when modern biomes emerged. Here I review fossil and phylogenetic evidence for fire activity over this period. These reveal a surprising synchrony in the geographically widespread onset of high fire from about 7 million years ago. In Africa, this spike in fire was associated with the rapid spread of C4 grassy biomes, including South African savannas and highveld grasslands. Fynbos, the other major flammable biome in the country, has much older origins but there is growing phylogenetic evidence for a fire-driven expansion of fynbos also beginning ~7 Ma. Discussion on the causes of expansion of flammable biomes has generally had a regional focus though the phenomenon appears to be global. Ideas on the causes of the surge in fire from the Miocene are contentious and poorly explored. More certain is that human disruption of fire, at diverse scales, has had, and will continue to have, profound ecological effects on flammable ecosystems. doi:10.1016/j.sajb.2015.03.003
More than a music tree: 4400 years of Dalbergia melanoxylon trade in Africa A.B. Cunningham School of Plant Biology, University of Western Australia, Nedlands 6009, Australia 0254-6299/$ – see front matter.
Perhaps more than any other African tree species, the African blackwood (Dalbergia melanoxylon) symbolises the links between culture and nature. Widely used for its medicinal leaves, it is best known for its wood. Prized by Egyptian pharaohs, D. melanoxylon wood was traded from the Horn of Africa from 2400 BC. Although difficult to carve by hand, D. melanoxylon was traditionally used for sticks and was the wood of choice for Shona snuff containers. With the arrival of iron-smelting technology in southern and south-central Africa from about 1000 years ago, D. melanoxylon was in high demand as for smelting purposes, due to the high calorific value of the wood, which gets so hot that it is avoided as a firewood today, as it gets so hot that it melts pots. With its extremely dense, close-grained wood (1200 kg/m3), D. melanoxylon, this is the premier wood for oboes, clarinets and bag-pipe wood. D. melanoxylon has been traded to Europe for this purpose since the early 19th century, making it one of the world's most valuable timbers (US$14,000– 20,000 per m3). Today, D. melanoxylon stocks are dwindling due to four factors: (1) habitat loss due to agricultural expansion; (2) fire affecting recruitment from seed; (3) commercial trade to China for reproduction Ming and Ching dynasty furniture. This is driven by the depletion of Asian Dalbergia species traditionally used for Chinese Imperial style furniture, and their substitution with African species such as Swartzia madagascariensis, Combretumimberbe, Millettia stuhlmannii and D. melanoxylon. (4) in Kenya, Tanzania and Malawi the commercial woodcarving trade. Despite the long history of trade in D. melanoxylon there are several unknowns that offer opportunities for research, ranging from studies of D. melanoxylon genetics across its range to archaeological studies in unrecorded iron smelting sites in northern Mozambique, where smelting continued until the early 1900's. What is also needed is a regional conservation strategy for both in situ and ex situ conservation. doi:10.1016/j.sajb.2015.03.004
N2 fixation in grain legumes: Its role in food and nutritional security in Africa F.D. Dakora Chemistry Department, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa Food grain legumes are important in meeting the food and nutritional security of about 1.1 billion people in Africa. They also
168
Abstracts
serve as biofertilizers in cropping systems. Studies of their grain yield and food quality are therefore crucial for human nutrition and health in Africa. The leaves and grain of cowpea, for example, are consumed in large quantities in Africa and elsewhere in the world. Protein levels in the edible leaves are high and range from 29 to 40%, while grain protein also ranges from 23 to 40% depending on the variety and its symbiotic functioning. In fact, the grain protein of farmerselected cowpea varieties such as Soronko and Bengpla can be as high as 40%, a level comparable to that of soybean. Both leaves and grain also contain very high concentrations/amounts of macronutrients and trace elements, the latter needed for overcoming micronutrient deficiency in rural Africa. Evidence from field and glasshouse studies has shown that, as with leaf and grain protein, the accumulation of mineral nutrients by cowpea is symbiosis-dependent. In the field, cowpea varieties with high N2-fixing ability accumulated more nutrient elements than low fixers, while in nodulation assays, rhizobia with high N2-fixing efficiency generally elicited greater mineral accumulation in cowpea shoots when compared to strains with low symbiotic efficacy. These findings on the symbiosis-induced mineral accumulation in cowpea offer an additional explanation for the benefits of legume/cereal rotations beyond the known N contribution by the legume and further validate cowpea as an important food legume for nutritional security in Africa. doi:10.1016/j.sajb.2015.03.005
The role of pollinators in the floral diversification and life history of Leucospermum (Proteaceae) C.M. Johnsona, T. Heb, B. Lamontb, A. Pauwa a Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa b Department of Environment and Agriculture, Curtin University, PO Box U1987, Perth WA 6845, Australia Leucospermum, commonly known as pincushions, are an endemic genus often associated with South Africa and, more specifically, the fynbos ecosystem and Cape Floral Kingdom. The staggering floral polymorphism within the genus suggests a wide variety of pollination modes. Despite this remarkable assortment of floral morphologies within Leucospermum only recently has any research been conducted to explain the role of pollinators in driving diversification. In this study we construct the first molecular phylogeny for the genus and, taking relatedness into account using a phylogenetic generalized least squares approach, determine how pollinators have driven floral divergence. Pollinators were assigned through direct observations and a suite of floral traits that are likely to reflect pollination mode were measured for each taxa. In addition, the ability to autonomously self-pollinate was determined for each taxon and used to test if autogamy is linked to specific classes of pollinators, specialized taxa or recently derived taxa. All fieldwork has been finalized and we are awaiting our phylogenetic analysis before any results can be determined.
Why has there been no success in finding new antibiotics from plants?
doi:10.1016/j.sajb.2015.03.007
J.N. Eloff Phytomedicine Programme, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
Natural products for skin infections
There has been tens of thousands of publications on antimicrobial activity and plants in good journals and hundreds of thousands of publications on poor journals. The motivation is frequently that due to the increased resistance of microorganisms to current antibiotics there is an urgent need to find new antibiotics. With the multiplication of poor open access journals many publications in this area have hardly any value. In contrast to the use of plants for other indications where in the order of 25% of prescribed pharmaceuticals originated from plant leads and the majority of antibiotics originating from fungal leads there has been no commercial antibiotic developed from plants. Several actors may play a role including the methods used, the plants selected for investigation, low activity of isolated compounds in comparison to the activity of the crude extract and cellular toxicity of isolated compounds. Few compounds are ever tested on animals and factors such as a lack of bioavailability may also be involved. Because the same antimicrobial compounds are repeatedly isolated, it appears that plants use a limited number of compounds for protection against microorganisms, but enhances activity by synergism with other compounds present in extracts. There are two possible solutions to the problem. The first is to focus on developing herbal extracts with good activity. In the case of topical application safety may not be a major complication. Another alternative is to screen large number of plants using reproducible methods and then investigate species with high activity in depth. The phytomedicine has had success in this approach in isolating a novel compound with higher activity and better safety against Candida albicans than the commercially used fungicide amphotericin B. doi:10.1016/j.sajb.2015.03.006
S. Van Vuurena, H. De Wetb, A.M. Viljoenc, A.D. Van Eyka a University of the Witwatersrand, Johannesburg, South Africa b University of Zululand, KwaDlangezwa, South Africa c Tshwane University of Technology, Pretoria, South Africa Traditional medicine or natural products are often the first line in the therapeutic treatment for skin infections. This study explores some of the antimicrobial efficacies of natural products with special emphasis on their use to treat dermatological infections. Antimicrobial methods used include the minimum inhibitory concentration (MIC) assays and interaction studies where the calculation of fractional inhibitory concentrations ( FIC) and isobolograms are given. Studies on some of the most widely used essential oils for dermatological conditions demonstrated noteworthy antimicrobial activity, particularly against Propionibacterium acnes (ATCC 11827), having MIC values as low as 0.5 mg/ml against Cymbopogon citratus (lemon grass), Commiphora myrrha (myrrha), Pogostemonpatchouli (patchouli) and Andropogon zizanioides (vetiver). Of particular interest is the inhibitory effects (as low as 0.1 mg/ml) of commercial oils against Santalum album (sandalwood) and A. zizanioides against Brevibacterium spp., a group of bacteria responsible for foot odour. Synergistic interactions were noted between oils commonly used together. Naturally derived bee products (honey and propolis) are frequently used for wound healing and our studies show that some South African honey samples demonstrate activity (lowest activity 11% growth inhibition), equivalent to the gold standard Manuka honey, derived from Australia. South African propolis has shown excellent antimicrobial efficacy with activities of 6 μg/ml when tested against Staphylococcus aureus. This activity correlates with the high flavonoid content observed during chemical profiling studies. When examining the dermatological application of medicinal plants in the South African context, over 100 plant species were identified as being of importance. Some of these species will be highlighted where