Diana Marais - Academia.edu (original) (raw)
Thesis Chapters by Diana Marais
Various potential energy crops are being evaluated for biomass production to supplement non-renew... more Various potential energy crops are being evaluated for biomass production to supplement non-renewable fossil fuel-based energy. High biomass yielding grasses like Pennisetum spp. are good examples. A field study was conducted at the University of Pretoria Experimental Farm to evaluate the effects of nitrogen (N) levels on canopy development, biomass yield and quality of bana grass (Pennisetum spp.) grown as a biomass crop. Six nitrogen levels (0, 75, 150, 225, 300 and 375 kg N ha-1) were evaluated in a randomised complete block design (RCBD) experiment with three blocks. Nitrogen was split in two equal dressings, with one being applied in early growing season in November and the other at mid-growing season in February. Canopy height, leaf area index and light interception were measured bi-weekly starting from the beginning of the growing season in early December. Dry matter (DM) yield was estimated at the end of the growing season in April by harvesting herbage from four quadrats of 2m x 1m in each plot. A 500 g sub-sample of herbage was kept as composite for DM estimation, while ten representative tillers from each plot were hand-separated into stem and leaf components and oven-dried at 700 C to a constant weight and later analysed for neutral and acid detergent fibers (NDF and ADF), ash, N and gross energy (GE). There was a significant (p<0.0001) increase in canopy height, leaf area index (LAI), leaf area duration (LAD), PAR intercepted and DM yield in response to N level applied. Canopy height and LAI ranged from 20.00- 364.67 cm and 1.63-7.5, respectively. The respective values for LAD and PAR interception were 419.14 - 949.00 LAI. days and 0.26 - 0.95 %. The end of season DM yield ranged from 8.00-30.00 t DM ha-1. Nitrogen content for the composite, stem and leaf herbage increased significantly (p<0.0001) with N application and ranged from 3.50-9.30, 2.70-7.80 and 4.90-9.70 g kg-1 DM, respectively. Ash content increased significantly (p<0.0001) with N fertilization and ranged from 45.5-85.5, 42.5-76.5 and 33.5-80.5 g kg-1 DM for composite, stem and leaf samples, respectively. Average GE content increased (p<0.001) with N application and ranged from 16.26-16.34, 15.57-16.10 and 14.70-15.93 MJ kg-1 DM, for composite, stem and leaf, respectively. NUE decreased with increase in N levels applied and ranged from 59-26 kg DM kg-1 N. The results indicate potential of bana grass to produce high quality biomass that could be used for bioenergy and/or chemical production.
Key words: biomass, bioenergy, lignocellulosel, canopy height, nitrogen
Papers by Diana Marais
South African open field tomato production occurs primarily in the Limpopo province and contribut... more South African open field tomato production occurs primarily in the Limpopo province and contributes significantly to the socio-economic stability of thousands of employees, suppliers and their dependents. Since 2003, these South African tomato producers practiced intensive open field tomato production using a combination of synthetic and organic crop management technologies. The objective of this study was to analyse these production practices, and its effect on yield, in terms of the following: soil quality (texture and chemistry), synthetic fertilizer usage, synthetic and organic pest and disease control, ecological impact, soil conditioning via organic matter additions, microbial inoculants, and prevailing climate conditions. We studied these interactions for three different planting times within the year over an eight-year period by means of Classification and Regression Tree (CART) analysis. The results showed that complex interactions between biotic and abiotic variables influ...
G3: Genes|Genomes|Genetics, 2017
In the framework of a gene flow assessment, we investigated the natural hybridization rate betwee... more In the framework of a gene flow assessment, we investigated the natural hybridization rate between Gossypium hirsutum (AADD genome) and G. herbaceum (AA genome). The latter species, a diploid progenitor of G. hirsutum, is spontaneously present in South Africa. Reciprocal crosses were performed without emasculation between G. herbaceum and G. hirsutum. Neither examination of the morphological characteristics nor flow cytometry analysis of the 335 plants resulting from the G. hirsutum • G. herbaceum cross showed any hybrid features. Of the 148 plants produced from the G. herbaceum • G. hirsutum cross, three showed a hybrid phenotype, and their hybrid status was confirmed by SSR markers. Analysis of DNA content by flow cytometry and morphological traits clearly showed that two of these plants were triploid (AAD). The third plant had a flow cytometry DNA content slightly higher than G. hirsutum. In addition, its morphological characteristics (plant architecture, presence and size of petal spots, leaf shape) led us to conclude that this plant was AAAD thus resulting from fertilization with an unreduced AA gamete of the female G. herbaceum parent. Fluorescent In Situ Hybridization (FISH) and meiotic behavior confirmed this hypothesis. To the best of our knowledge, this is the first description of such gametes in G. herbaceum, and it opens new avenues in breeding programs. Furthermore, this plant material could provide a useful tool for studying the expression of genes duplicated in the A and D cotton genome. KEYWORDS Gene flow natural hybridization unreduced gamete Gossypium hirsutum Gossypium herbaceum Assessment of gene flow from a crop to a wild relative is particularly relevant in the case of allopolyploid species, which are formed by hybridization between related species, when one of its progenitors is present in cultivated areas. In certain geographical areas, this may be the case for the cultivated tetraploid cotton (Gossypium hirsutum, AADD, 2n = 4x = 52) and a wild diploid species (Gossypium herbaceum, AA, 2n = 2x = 26). Cultivated cotton, the most important source of natural fiber, has been the long-standing subject of a number of taxonomical studies (Watt 1907; Hutchinson et al. 1947; Saunders 1961; cited in Wendel et al. 2010; Fryxell 1979; Fryxell et al. 1992). The cotton genus (Gossypium L.) includes 50 diploid species (2n = 2x = 26) that can be differentiated cytogenetically into eight genome groups (A-G and K), and seven allotetraploid species (2n = 4x = 52) (
South African Journal of Plant and Soil, 2017
Alternaria solani is highly infective and can sporulate on tomato at 13.2 × 10 6 spores mL −1. Th... more Alternaria solani is highly infective and can sporulate on tomato at 13.2 × 10 6 spores mL −1. The fungicidal effect of Moringa oleifera leaf chloroform and aqueous extracts (MLCE and MLAE, respectively) was investigated in vitro to determine the inhibitory effect on germination of spores (conidia) of A. solani. Mixtures of spore suspension and MLCE, as well as MLAE (1:1), were prepared and dropped on slides by micropipette with 20 µL spore suspension of A. solani and 20 µL of MLCE and MLAE. The two treatments, MLCE and MLAE, were applied at four concentrations (62.5, 125, 250 and 500 mg mL −1) and compared with negative (distilled water; no extracts) and positive (diflucan, a commercial fungicide) controls with five replicates. The two extracts showed relatively high inhibitory effects on the germination of conidia from the lowest to the highest concentration. Germination of conidia decreased with increase in the concentrations of the extracts. The study showed that 250 mg mL −1 is the optimum concentration for both MLCE and MLAE. The highest concentration inhibited germination (0.0%) in both extracts. Based on the results from the present study, MLCE and MLAE are both effective in inhibiting germination of A. solani conidia.
Cotton (Gossypium hirsutum) was first introduced in the Cape, but the first successful plantings ... more Cotton (Gossypium hirsutum) was first introduced in the Cape, but the first successful plantings were reported to be in KwaZulu Natal in 1860 - 70. This, however, did not last long and after a 30 year period of virtually no cotton produced, the next successful plantings were reported to be in the old Transvaal. After ± 100 years, cotton is still being produced in the Limpopo, North West, Mpumalanga, KwaZulu Natal, Free State and Northern Cape provinces. In 1997, genetically modified cotton (Bt, RR and Bt+RR) has been introduced in South Africa. Cotton has close wild as well as cultivated relatives (G. barbadense, G. herbaceum, Hibiscus cannabinus, Abelmoschus esculentus etc.) in South Africa. Despite the presence of these relatives, Percival et al. (1999) concluded that the possibility of gene flow from Bt, RR and Bt+RR to the relatives is extremely unlikely, because: (i) wild cotton being diploid, is not likely to produce fertile offspring when crossed with the cultivated allotetra...
Frontiers in Plant Science
Common bean seeds are an excellent source of protein as well as of carbohydrates, minerals, vitam... more Common bean seeds are an excellent source of protein as well as of carbohydrates, minerals, vitamins, and bioactive compounds reducing, when in the diet, the risks of diseases. The presence of bioactive compounds with antinutritional properties (e.g., phytic acid, lectins, raffinosaccharides, protease inhibitors) limits, however, the bean’s nutritional value and its wider use in food preparations. In the last decades, concerted efforts have been, therefore, made to develop new common bean genotypes with reduced antinutritional compounds by exploiting the natural genetic variability of common bean and also applying induced mutagenesis. However, possible negative, or positive, pleiotropic effects due to these modifications, in terms of plant performance in response to stresses or in the resulting technological properties of the developed mutant genotypes, have yet not been thoroughly investigated. The purpose of the perspective paper is to first highlight the current advances, which h...
African Journal of Microbiology Research, Feb 18, 2011
Recent trends in soil microbiology suggest that certain soil microbes have a positive effect on s... more Recent trends in soil microbiology suggest that certain soil microbes have a positive effect on seedling growth and development. A study was conducted to investigate the interactive effect of the plantgrowth promoting fungi Trichoderma harzianum and the arbuscular mycorrhizal fungi (AMF) in growth and development of tomato (Solanun lycopersicum) seedlings grown under greenhouse conditions. A 3 × 3 factorial experiment was laid out in a completely randomised design with six replications. At harvest (42 DAP), when compared with the control, T. harzianum and/or AMF treated plants improved shoot length, root length, dry shoot mass and dry root mass. Pre-inoculation with AMF increased shoot N, P and S content of tomato seedlings, whereas pre-sowing with T. harzianum alone increased the shoot N. Generally, shoot Zn and Mn content were affected by both fungi, with the best result observed when AMF was applied 2 weeks after T. harzianum. The percentage of roots colonised by AMF was less than 15% regardless of the time when T. harzianum was applied. However, the percentage of roots colonised by T. harzianum was greater than 90% at all times. In conclusion, this study suggested that T. harzianum and AMF have the potential to improve tomato seedling growth and development.
i UITTREKSEL iv ACKNOWLEDGEMENTS vii LIST OF TABLES viii LIST OF FIGURES x CHAPTER 1 GENERAL INTR... more i UITTREKSEL iv ACKNOWLEDGEMENTS vii LIST OF TABLES viii LIST OF FIGURES x CHAPTER 1 GENERAL INTRODUCTION 1 1.1 References 3 CHAPTER 2 WATER USE OF FIVE PERENNIAL SUB-TROPICAL GRASSES AT FOUR LEVELS OF WATER AVAILABILITY 6 Abstract 6 2.
Centre de Rennes-Le Rhe u Etude des flux de gènes entre le cotonnier cultivé et les espèces voisi... more Centre de Rennes-Le Rhe u Etude des flux de gènes entre le cotonnier cultivé et les espèces voisine s dans les agrosystèmes sud africains.
Cotton production in South Africa has been declining over the last 17 years from as high as 182 0... more Cotton production in South Africa has been declining over the last 17 years from as high as 182 000 ha in 1987/88 to as little as 32 000 ha in 2001/02. This has resulted in the import of thousands of cotton lint bales annually to supply the local demand. To rectify this situation, a strategic plan to improve local cotton production (from ± 130 000 to 370 000 bales by 2007) has been developed by Cotton SA. The only way that these aims can be met, is if farmers can be encouraged to farm with cotton in stead of other cash crops. In Cotton SA, A Journal to the Cotton Industry, a financial analysis was done in which the profit margins of white maize, sunflower and cotton were compared. Under the conditions set for the analysis, the profit margins were R1 602, R1 948 and R2 739 respectively for the three crops. It was then clear that cotton had the highest profit margin, so what is keeping the production back? It might be the high input costs and/or the way in which the pricing of cotton ...
The effect of four levels of water availability on the yield of five subtropical perennial grasse... more The effect of four levels of water availability on the yield of five subtropical perennial grasses (Cenchrus ciliaris, a Cynodon hybrid, Digitaria eriantha subsp. eriantha, Panicum maximum and Pennisetum clandestinum) was evaluated in a small plot trial under a rain shelter at the University of Pretoria. The four treatments were: soil profile brought to 25 (W1), 50 (W2), 75 (W3) and 100% (W4 - the control) of field capacity on a weekly basis. Under W4 (control) and W3 conditions, yields did not differ significantly (P$0.05). Where, however, less water was available (W2 and W1), yields were significantly (P #0.05) reduced in comparison with the control (W4). By bringing the soil profiles to field capacity at the beginning of the season, a water reservoir was established in the soil which buffered the effect of induced drought, leading to non-significant (P$0.05) differences in yield. The capacity of the reservoir, together with the factors affecting
Contrary to practices applied in food crops for which the use of fertilizer is quiet common in sm... more Contrary to practices applied in food crops for which the use of fertilizer is quiet common in small-scale farming, cotton farmers of the Makhathini Flats don't use any fertilizing program. The recent introduction of Bt cotton in this area is supposed to resolve a major yield-limiting factor. boll losses due to bollworms (mainly Helicoverpa armigera). Held surveys show that yields improved in a majority of cases but not enough to give comfortable incomes to emerging farmers. During the season 2003-2004, CIRAD (French Agricultural Research Centre for International Development) and the Department of Plant Production and Soil Science of the Faculty of Natural and Agricultural Sciences at the University of Pretoria conducted 20 on farm trials in the Maputaland (KwaZulu Natal), during the season 2003-2004, among small-scale farming communities relying on cotton cropping. Results show that with a minimum amount of fertilizer commonly found on the market, yields can increase by an aver...
Amidst conflicting narratives in development circles regarding the drive for nutrition-sensitive ... more Amidst conflicting narratives in development circles regarding the drive for nutrition-sensitive agriculture and the displacement of household production by supermarket penetration into deep rural areas, little is documented about the design of nutrition-sensitive agricultural programmes in the context of changing food systems. This is the first comparative assessment of the production and consumption patterns of South Africa’s poorest rural households. The study set out to identify programme elements necessary to improve nutrition outcomes. The poorest communities in four provinces were identified and surveyed using an extensive production and consumption survey. The survey was conducted in summer and winter for each community to capture seasonal differences. A total of 278 households were interviewed in summer and 280 in winter at the four sites. Even though most foods were purchased, crop production (beyond maize production) improved dietary diversity but selling produce and the ...
South African Journal of Plant and Soil, 2018
Tomato is often exposed to hormones and diseases, among other factors, to which responses in leaf... more Tomato is often exposed to hormones and diseases, among other factors, to which responses in leaf anatomy and yield are observed. This study evaluated responses in the leaf anatomy of Alternaria solani infected (IN) and non-infected (NIN) tomato (Solanum lycopersicum) to moringa leaf extract (MLE) application; the responses were then correlated with fruit yield. MLE concentrations of 0.5, 0.75 and 1.5 kg L −1 (w/v) were prepared. Controls were distilled water (negative) and 50 mg L −1 benzylanimopurine cytokinin (positive). Significant interactions were observed for stomatal density (p < 0.001). MLE increased lamina thickness, stomatal density, stomatal size and yield. There was a strong positive correlation between yield, stomatal density, stomatal size and lamina thickness. Stomatal density showed the strongest correlation (r = 0.7979) with fruit yield.
Plants, 2019
Several studies have demonstrated Si absorption in monocotyledon and dicotyledon species. Regardi... more Several studies have demonstrated Si absorption in monocotyledon and dicotyledon species. Regarding Si accumulation, studies in monocotyledons have identified Si deposition around the cell wall, cuticle layer bulliform cells, silica cells and endodermal cells. In previous studies with different citrus species there were evidence of Si accumulation, however no information on Si deposition can be found. Therefore, in this study, Si was applied (0 and 1000 mg L−1) to the roots of two citrus species, ‘Delta’ Valencia (Citrus sinensis) and ‘Nules’ Clementine (Citrus reticulata). Si accumulation were investigated in new, and old leaves and roots. Si deposition was investigated through scanning electron microscopy using energy dispersive analysis X-ray, environmental scanning electron microscopy and light microscopy. Si accumulation was significantly higher in Si treated leaves comparatively to the control in both young and mature leaves. Meanwhile, Si accumulation increased with leaf age....
South African Journal of Plant and Soil, 2019
Nitrogen (N) is a critical determinant of plant growth and productivity, but there is limited inf... more Nitrogen (N) is a critical determinant of plant growth and productivity, but there is limited information on the agronomic parameters of medicinal plants. Three levels of N fertiliser (0, 1.375 and 1.625 g plant −1) were used to investigate the effects of fertilisation on the growth and yield parameters of two ginger species (Siphonochilus aethiopicus and Zingiber officinale). The experiment was conducted in the glasshouse with six treatments (two ginger species and three levels of N fertiliser) arranged in a randomised complete block design and replicated four times. The results indicated that N application significantly affected plant height, leaf number, chlorophyll content and rhizome yield of the species for two cropping seasons. Scanning electron microscopy analyses of stomata opening revealed that a higher N level increased the number of open stomata in both ginger species. The results showed that with application of 1.625 g N plant −1 both ginger growth and yield were higher compared with the lowest N fertiliser application levels. However, the growth parameters of Z. officinale were variably greater than those of S. aethiopicus. Therefore, the present study demonstrates that application of 1.625 g N plant −1 to commercial ginger and African ginger can be used to improve growth and yield.
Water, 2019
Ginger species play an important economic role as medicinal plants, food flavourings, and dietary... more Ginger species play an important economic role as medicinal plants, food flavourings, and dietary supplements. Products from ginger, including oil and fresh and dried rhizomes can be used to treat malaria, asthma, headaches, and act as anti-inflammatory and anti-microbial agents. The cultivation of wild plant species can alleviate the pressure from harvesting from the wild. Under cultivation, the major constraints on crop yield and quality are water availability and plant nutrition. Therefore, the impact of water stress on commercial and African ginger was assessed in the rain shelter study. Irrigation treatments were based on the maximum allowable depletion (MAD) levels of plant available water in the root zone (T1: 20–25% MAD, the control; T2: 40–45% MAD; T3: 60–65% MAD; T4: 80–85% MAD). As water stress decreased, the plant height and number of stems per plant of both plant species were positively affected. The number of open stomata was higher for well-watered and less stressed t...
Various potential energy crops are being evaluated for biomass production to supplement non-renew... more Various potential energy crops are being evaluated for biomass production to supplement non-renewable fossil fuel-based energy. High biomass yielding grasses like Pennisetum spp. are good examples. A field study was conducted at the University of Pretoria Experimental Farm to evaluate the effects of nitrogen (N) levels on canopy development, biomass yield and quality of bana grass (Pennisetum spp.) grown as a biomass crop. Six nitrogen levels (0, 75, 150, 225, 300 and 375 kg N ha-1) were evaluated in a randomised complete block design (RCBD) experiment with three blocks. Nitrogen was split in two equal dressings, with one being applied in early growing season in November and the other at mid-growing season in February. Canopy height, leaf area index and light interception were measured bi-weekly starting from the beginning of the growing season in early December. Dry matter (DM) yield was estimated at the end of the growing season in April by harvesting herbage from four quadrats of 2m x 1m in each plot. A 500 g sub-sample of herbage was kept as composite for DM estimation, while ten representative tillers from each plot were hand-separated into stem and leaf components and oven-dried at 700 C to a constant weight and later analysed for neutral and acid detergent fibers (NDF and ADF), ash, N and gross energy (GE). There was a significant (p<0.0001) increase in canopy height, leaf area index (LAI), leaf area duration (LAD), PAR intercepted and DM yield in response to N level applied. Canopy height and LAI ranged from 20.00- 364.67 cm and 1.63-7.5, respectively. The respective values for LAD and PAR interception were 419.14 - 949.00 LAI. days and 0.26 - 0.95 %. The end of season DM yield ranged from 8.00-30.00 t DM ha-1. Nitrogen content for the composite, stem and leaf herbage increased significantly (p<0.0001) with N application and ranged from 3.50-9.30, 2.70-7.80 and 4.90-9.70 g kg-1 DM, respectively. Ash content increased significantly (p<0.0001) with N fertilization and ranged from 45.5-85.5, 42.5-76.5 and 33.5-80.5 g kg-1 DM for composite, stem and leaf samples, respectively. Average GE content increased (p<0.001) with N application and ranged from 16.26-16.34, 15.57-16.10 and 14.70-15.93 MJ kg-1 DM, for composite, stem and leaf, respectively. NUE decreased with increase in N levels applied and ranged from 59-26 kg DM kg-1 N. The results indicate potential of bana grass to produce high quality biomass that could be used for bioenergy and/or chemical production.
Key words: biomass, bioenergy, lignocellulosel, canopy height, nitrogen
South African open field tomato production occurs primarily in the Limpopo province and contribut... more South African open field tomato production occurs primarily in the Limpopo province and contributes significantly to the socio-economic stability of thousands of employees, suppliers and their dependents. Since 2003, these South African tomato producers practiced intensive open field tomato production using a combination of synthetic and organic crop management technologies. The objective of this study was to analyse these production practices, and its effect on yield, in terms of the following: soil quality (texture and chemistry), synthetic fertilizer usage, synthetic and organic pest and disease control, ecological impact, soil conditioning via organic matter additions, microbial inoculants, and prevailing climate conditions. We studied these interactions for three different planting times within the year over an eight-year period by means of Classification and Regression Tree (CART) analysis. The results showed that complex interactions between biotic and abiotic variables influ...
G3: Genes|Genomes|Genetics, 2017
In the framework of a gene flow assessment, we investigated the natural hybridization rate betwee... more In the framework of a gene flow assessment, we investigated the natural hybridization rate between Gossypium hirsutum (AADD genome) and G. herbaceum (AA genome). The latter species, a diploid progenitor of G. hirsutum, is spontaneously present in South Africa. Reciprocal crosses were performed without emasculation between G. herbaceum and G. hirsutum. Neither examination of the morphological characteristics nor flow cytometry analysis of the 335 plants resulting from the G. hirsutum • G. herbaceum cross showed any hybrid features. Of the 148 plants produced from the G. herbaceum • G. hirsutum cross, three showed a hybrid phenotype, and their hybrid status was confirmed by SSR markers. Analysis of DNA content by flow cytometry and morphological traits clearly showed that two of these plants were triploid (AAD). The third plant had a flow cytometry DNA content slightly higher than G. hirsutum. In addition, its morphological characteristics (plant architecture, presence and size of petal spots, leaf shape) led us to conclude that this plant was AAAD thus resulting from fertilization with an unreduced AA gamete of the female G. herbaceum parent. Fluorescent In Situ Hybridization (FISH) and meiotic behavior confirmed this hypothesis. To the best of our knowledge, this is the first description of such gametes in G. herbaceum, and it opens new avenues in breeding programs. Furthermore, this plant material could provide a useful tool for studying the expression of genes duplicated in the A and D cotton genome. KEYWORDS Gene flow natural hybridization unreduced gamete Gossypium hirsutum Gossypium herbaceum Assessment of gene flow from a crop to a wild relative is particularly relevant in the case of allopolyploid species, which are formed by hybridization between related species, when one of its progenitors is present in cultivated areas. In certain geographical areas, this may be the case for the cultivated tetraploid cotton (Gossypium hirsutum, AADD, 2n = 4x = 52) and a wild diploid species (Gossypium herbaceum, AA, 2n = 2x = 26). Cultivated cotton, the most important source of natural fiber, has been the long-standing subject of a number of taxonomical studies (Watt 1907; Hutchinson et al. 1947; Saunders 1961; cited in Wendel et al. 2010; Fryxell 1979; Fryxell et al. 1992). The cotton genus (Gossypium L.) includes 50 diploid species (2n = 2x = 26) that can be differentiated cytogenetically into eight genome groups (A-G and K), and seven allotetraploid species (2n = 4x = 52) (
South African Journal of Plant and Soil, 2017
Alternaria solani is highly infective and can sporulate on tomato at 13.2 × 10 6 spores mL −1. Th... more Alternaria solani is highly infective and can sporulate on tomato at 13.2 × 10 6 spores mL −1. The fungicidal effect of Moringa oleifera leaf chloroform and aqueous extracts (MLCE and MLAE, respectively) was investigated in vitro to determine the inhibitory effect on germination of spores (conidia) of A. solani. Mixtures of spore suspension and MLCE, as well as MLAE (1:1), were prepared and dropped on slides by micropipette with 20 µL spore suspension of A. solani and 20 µL of MLCE and MLAE. The two treatments, MLCE and MLAE, were applied at four concentrations (62.5, 125, 250 and 500 mg mL −1) and compared with negative (distilled water; no extracts) and positive (diflucan, a commercial fungicide) controls with five replicates. The two extracts showed relatively high inhibitory effects on the germination of conidia from the lowest to the highest concentration. Germination of conidia decreased with increase in the concentrations of the extracts. The study showed that 250 mg mL −1 is the optimum concentration for both MLCE and MLAE. The highest concentration inhibited germination (0.0%) in both extracts. Based on the results from the present study, MLCE and MLAE are both effective in inhibiting germination of A. solani conidia.
Cotton (Gossypium hirsutum) was first introduced in the Cape, but the first successful plantings ... more Cotton (Gossypium hirsutum) was first introduced in the Cape, but the first successful plantings were reported to be in KwaZulu Natal in 1860 - 70. This, however, did not last long and after a 30 year period of virtually no cotton produced, the next successful plantings were reported to be in the old Transvaal. After ± 100 years, cotton is still being produced in the Limpopo, North West, Mpumalanga, KwaZulu Natal, Free State and Northern Cape provinces. In 1997, genetically modified cotton (Bt, RR and Bt+RR) has been introduced in South Africa. Cotton has close wild as well as cultivated relatives (G. barbadense, G. herbaceum, Hibiscus cannabinus, Abelmoschus esculentus etc.) in South Africa. Despite the presence of these relatives, Percival et al. (1999) concluded that the possibility of gene flow from Bt, RR and Bt+RR to the relatives is extremely unlikely, because: (i) wild cotton being diploid, is not likely to produce fertile offspring when crossed with the cultivated allotetra...
Frontiers in Plant Science
Common bean seeds are an excellent source of protein as well as of carbohydrates, minerals, vitam... more Common bean seeds are an excellent source of protein as well as of carbohydrates, minerals, vitamins, and bioactive compounds reducing, when in the diet, the risks of diseases. The presence of bioactive compounds with antinutritional properties (e.g., phytic acid, lectins, raffinosaccharides, protease inhibitors) limits, however, the bean’s nutritional value and its wider use in food preparations. In the last decades, concerted efforts have been, therefore, made to develop new common bean genotypes with reduced antinutritional compounds by exploiting the natural genetic variability of common bean and also applying induced mutagenesis. However, possible negative, or positive, pleiotropic effects due to these modifications, in terms of plant performance in response to stresses or in the resulting technological properties of the developed mutant genotypes, have yet not been thoroughly investigated. The purpose of the perspective paper is to first highlight the current advances, which h...
African Journal of Microbiology Research, Feb 18, 2011
Recent trends in soil microbiology suggest that certain soil microbes have a positive effect on s... more Recent trends in soil microbiology suggest that certain soil microbes have a positive effect on seedling growth and development. A study was conducted to investigate the interactive effect of the plantgrowth promoting fungi Trichoderma harzianum and the arbuscular mycorrhizal fungi (AMF) in growth and development of tomato (Solanun lycopersicum) seedlings grown under greenhouse conditions. A 3 × 3 factorial experiment was laid out in a completely randomised design with six replications. At harvest (42 DAP), when compared with the control, T. harzianum and/or AMF treated plants improved shoot length, root length, dry shoot mass and dry root mass. Pre-inoculation with AMF increased shoot N, P and S content of tomato seedlings, whereas pre-sowing with T. harzianum alone increased the shoot N. Generally, shoot Zn and Mn content were affected by both fungi, with the best result observed when AMF was applied 2 weeks after T. harzianum. The percentage of roots colonised by AMF was less than 15% regardless of the time when T. harzianum was applied. However, the percentage of roots colonised by T. harzianum was greater than 90% at all times. In conclusion, this study suggested that T. harzianum and AMF have the potential to improve tomato seedling growth and development.
i UITTREKSEL iv ACKNOWLEDGEMENTS vii LIST OF TABLES viii LIST OF FIGURES x CHAPTER 1 GENERAL INTR... more i UITTREKSEL iv ACKNOWLEDGEMENTS vii LIST OF TABLES viii LIST OF FIGURES x CHAPTER 1 GENERAL INTRODUCTION 1 1.1 References 3 CHAPTER 2 WATER USE OF FIVE PERENNIAL SUB-TROPICAL GRASSES AT FOUR LEVELS OF WATER AVAILABILITY 6 Abstract 6 2.
Centre de Rennes-Le Rhe u Etude des flux de gènes entre le cotonnier cultivé et les espèces voisi... more Centre de Rennes-Le Rhe u Etude des flux de gènes entre le cotonnier cultivé et les espèces voisine s dans les agrosystèmes sud africains.
Cotton production in South Africa has been declining over the last 17 years from as high as 182 0... more Cotton production in South Africa has been declining over the last 17 years from as high as 182 000 ha in 1987/88 to as little as 32 000 ha in 2001/02. This has resulted in the import of thousands of cotton lint bales annually to supply the local demand. To rectify this situation, a strategic plan to improve local cotton production (from ± 130 000 to 370 000 bales by 2007) has been developed by Cotton SA. The only way that these aims can be met, is if farmers can be encouraged to farm with cotton in stead of other cash crops. In Cotton SA, A Journal to the Cotton Industry, a financial analysis was done in which the profit margins of white maize, sunflower and cotton were compared. Under the conditions set for the analysis, the profit margins were R1 602, R1 948 and R2 739 respectively for the three crops. It was then clear that cotton had the highest profit margin, so what is keeping the production back? It might be the high input costs and/or the way in which the pricing of cotton ...
The effect of four levels of water availability on the yield of five subtropical perennial grasse... more The effect of four levels of water availability on the yield of five subtropical perennial grasses (Cenchrus ciliaris, a Cynodon hybrid, Digitaria eriantha subsp. eriantha, Panicum maximum and Pennisetum clandestinum) was evaluated in a small plot trial under a rain shelter at the University of Pretoria. The four treatments were: soil profile brought to 25 (W1), 50 (W2), 75 (W3) and 100% (W4 - the control) of field capacity on a weekly basis. Under W4 (control) and W3 conditions, yields did not differ significantly (P$0.05). Where, however, less water was available (W2 and W1), yields were significantly (P #0.05) reduced in comparison with the control (W4). By bringing the soil profiles to field capacity at the beginning of the season, a water reservoir was established in the soil which buffered the effect of induced drought, leading to non-significant (P$0.05) differences in yield. The capacity of the reservoir, together with the factors affecting
Contrary to practices applied in food crops for which the use of fertilizer is quiet common in sm... more Contrary to practices applied in food crops for which the use of fertilizer is quiet common in small-scale farming, cotton farmers of the Makhathini Flats don't use any fertilizing program. The recent introduction of Bt cotton in this area is supposed to resolve a major yield-limiting factor. boll losses due to bollworms (mainly Helicoverpa armigera). Held surveys show that yields improved in a majority of cases but not enough to give comfortable incomes to emerging farmers. During the season 2003-2004, CIRAD (French Agricultural Research Centre for International Development) and the Department of Plant Production and Soil Science of the Faculty of Natural and Agricultural Sciences at the University of Pretoria conducted 20 on farm trials in the Maputaland (KwaZulu Natal), during the season 2003-2004, among small-scale farming communities relying on cotton cropping. Results show that with a minimum amount of fertilizer commonly found on the market, yields can increase by an aver...
Amidst conflicting narratives in development circles regarding the drive for nutrition-sensitive ... more Amidst conflicting narratives in development circles regarding the drive for nutrition-sensitive agriculture and the displacement of household production by supermarket penetration into deep rural areas, little is documented about the design of nutrition-sensitive agricultural programmes in the context of changing food systems. This is the first comparative assessment of the production and consumption patterns of South Africa’s poorest rural households. The study set out to identify programme elements necessary to improve nutrition outcomes. The poorest communities in four provinces were identified and surveyed using an extensive production and consumption survey. The survey was conducted in summer and winter for each community to capture seasonal differences. A total of 278 households were interviewed in summer and 280 in winter at the four sites. Even though most foods were purchased, crop production (beyond maize production) improved dietary diversity but selling produce and the ...
South African Journal of Plant and Soil, 2018
Tomato is often exposed to hormones and diseases, among other factors, to which responses in leaf... more Tomato is often exposed to hormones and diseases, among other factors, to which responses in leaf anatomy and yield are observed. This study evaluated responses in the leaf anatomy of Alternaria solani infected (IN) and non-infected (NIN) tomato (Solanum lycopersicum) to moringa leaf extract (MLE) application; the responses were then correlated with fruit yield. MLE concentrations of 0.5, 0.75 and 1.5 kg L −1 (w/v) were prepared. Controls were distilled water (negative) and 50 mg L −1 benzylanimopurine cytokinin (positive). Significant interactions were observed for stomatal density (p < 0.001). MLE increased lamina thickness, stomatal density, stomatal size and yield. There was a strong positive correlation between yield, stomatal density, stomatal size and lamina thickness. Stomatal density showed the strongest correlation (r = 0.7979) with fruit yield.
Plants, 2019
Several studies have demonstrated Si absorption in monocotyledon and dicotyledon species. Regardi... more Several studies have demonstrated Si absorption in monocotyledon and dicotyledon species. Regarding Si accumulation, studies in monocotyledons have identified Si deposition around the cell wall, cuticle layer bulliform cells, silica cells and endodermal cells. In previous studies with different citrus species there were evidence of Si accumulation, however no information on Si deposition can be found. Therefore, in this study, Si was applied (0 and 1000 mg L−1) to the roots of two citrus species, ‘Delta’ Valencia (Citrus sinensis) and ‘Nules’ Clementine (Citrus reticulata). Si accumulation were investigated in new, and old leaves and roots. Si deposition was investigated through scanning electron microscopy using energy dispersive analysis X-ray, environmental scanning electron microscopy and light microscopy. Si accumulation was significantly higher in Si treated leaves comparatively to the control in both young and mature leaves. Meanwhile, Si accumulation increased with leaf age....
South African Journal of Plant and Soil, 2019
Nitrogen (N) is a critical determinant of plant growth and productivity, but there is limited inf... more Nitrogen (N) is a critical determinant of plant growth and productivity, but there is limited information on the agronomic parameters of medicinal plants. Three levels of N fertiliser (0, 1.375 and 1.625 g plant −1) were used to investigate the effects of fertilisation on the growth and yield parameters of two ginger species (Siphonochilus aethiopicus and Zingiber officinale). The experiment was conducted in the glasshouse with six treatments (two ginger species and three levels of N fertiliser) arranged in a randomised complete block design and replicated four times. The results indicated that N application significantly affected plant height, leaf number, chlorophyll content and rhizome yield of the species for two cropping seasons. Scanning electron microscopy analyses of stomata opening revealed that a higher N level increased the number of open stomata in both ginger species. The results showed that with application of 1.625 g N plant −1 both ginger growth and yield were higher compared with the lowest N fertiliser application levels. However, the growth parameters of Z. officinale were variably greater than those of S. aethiopicus. Therefore, the present study demonstrates that application of 1.625 g N plant −1 to commercial ginger and African ginger can be used to improve growth and yield.
Water, 2019
Ginger species play an important economic role as medicinal plants, food flavourings, and dietary... more Ginger species play an important economic role as medicinal plants, food flavourings, and dietary supplements. Products from ginger, including oil and fresh and dried rhizomes can be used to treat malaria, asthma, headaches, and act as anti-inflammatory and anti-microbial agents. The cultivation of wild plant species can alleviate the pressure from harvesting from the wild. Under cultivation, the major constraints on crop yield and quality are water availability and plant nutrition. Therefore, the impact of water stress on commercial and African ginger was assessed in the rain shelter study. Irrigation treatments were based on the maximum allowable depletion (MAD) levels of plant available water in the root zone (T1: 20–25% MAD, the control; T2: 40–45% MAD; T3: 60–65% MAD; T4: 80–85% MAD). As water stress decreased, the plant height and number of stems per plant of both plant species were positively affected. The number of open stomata was higher for well-watered and less stressed t...
Agricultural Water Management, 2018
The worldwide decrease in available irrigation water is driving the need for the development of m... more The worldwide decrease in available irrigation water is driving the need for the development of methods to minimize water losses in crop production. A field experiment was conducted at the Hatfield Experimental Farm of the University of Pretoria, Pretoria, South Africa (25°45′0′'S, 28°16′0′'E and altitude of 1327 m.a.s.l.) in 2013. The objectives of the study were to determine crop-specific model parameters for dry beans and to successfully calibrate and validate the Soil Water Balance (SWB) model for predicting dry bean yield and water use from historical weather data. Model simulations of leaf area index, total dry mass, harvestable dry mass, and soil water deficits agreed reasonably well with measured values and statistical parameters for most variables were within acceptable limits. The SWB model simulated leaf area index, total dry mass, harvestable dry mass, and soil water deficits for drought stress treatments reasonably well. The calibrated model was then used to predict dry bean grain yield for three localities in Limpopo Province over a period of nine years. The scenario modelling results indicated that the model can be used as an irrigation scheduling tool and also be successfully used to estimate yields of dry beans under various conditions and at other localities.