Spider plant (Cleome gynandra L.) contributes considerably to the nutrition and medicines of comm... more Spider plant (Cleome gynandra L.) contributes considerably to the nutrition and medicines of communities in southern Africa. However, its utilisation is limited by its bitterness caused by condensed tannins. Unfortunately, processing options that reduce the bitterness also remove nutritionally and medicinally useful compounds. The objective of this study was to assess the genetic variability of condensed tannins and their association with bitterness in C. gynandra so as to devise variety recommendations for either direct utilisation or for breeding programmes in Zimbabwe. Total phenolic compounds and condensed tannins were quantified in five genotypes. The amount of total phenolic compounds were not significant, but quite significant (P<0.001) for condensed tannins. Genotype CGSKGP had the highest (0.49 mg g-1) and twice as much condensed tannins as CGKEX and CGSKP. Bitterness was positively correlated with the concentrations of condensed tannins (r=0.94, P<0.05), but not with...
Soft rot of potatoes (Solanum tuberosum L.) caused by Pectobacterium and Dickeya subspecies leads... more Soft rot of potatoes (Solanum tuberosum L.) caused by Pectobacterium and Dickeya subspecies leads to economic losses in agriculture worldwide including Zimbabwe, where losses range from 20 – 60%. A laboratory experiment was carried out using the potato tuber maceration test to screen the effect of two botanicals extract, neem (Azadirachta indica A. Juss.) leaf and garlic (Allium sativum L.) cloves in controlling soft rot disease caused by bacterial pathogens, namely Pectobacterium carotovorum subspecies carotovorum (Pcc), Pectobacterium atrosepticum (Pa) and Dickeya dadantii (Dd). Preparations of two concentrations [(10 and 25% (w/v)] of the aqueous extracts of garlic and neem plants were used in dip and spray applications. Sterile distilled water was used as a negative control. Three tuber halves were used for each treatment. Five 10 mm filter paper discs (Whatman’s No. 1) pre-soaked in 1 x 106 cfu/mL bacterial cell suspensions of Pcc, Pa and Dd respectively were placed on each tub...
Effects of planting date (early: October-November, mid season: December, late: after first Januar... more Effects of planting date (early: October-November, mid season: December, late: after first January) and irrigation system (sprinkler, furrow) on seed quality (100 seed weight (g), percentage bad seed and seed germination) and health (percent infection by the seed borne pathogen Phaeoisariopsis griseola and subsequent angular leaf spot disease pressure in the crop were evaluated from data obtained in the field and laboratory from November 2002 to June 2005, in order to identify the best combinations of planting date and irrigation system able to improve seed characteristics. Planting date was significant (p<0.05) in all the parameters analysed and participated in different interactions with other factors studied. Compared to summer medium and late planting dates, summer early and winter crops were the best in improving seed quality and health in all the characteristics evaluated. Since sprinkler and furrow irrigation were equivalent in 71.9% of treatments comparing irrigation syst...
Late blight is caused by Phytopthora infestans (Mont.) de Bary which establishes quickly in Solan... more Late blight is caused by Phytopthora infestans (Mont.) de Bary which establishes quickly in Solanum esculentum L. (tomato); as a result, it makes the pathogen one of the most devastating plant diseases across the world. The control of late blight is difficult because P. infestans has advanced and complex enzymes and effecter molecules coded by avirulence genes. As such, a study was carried out at the University of Zimbabwe, Department of Plant Production Sciences and Technologies, between August 2018 and May 2019 to evaluate the efficacy of Moringa oleifera Lour. (moringa), Eucalyptus nigra R.T. Baker (gumtree), and Lantana camara L. (sensu lato) (lantana) extracts as biofungicides on late blight development on S. esculentum. The effect of acetone, ethyl acetate, and water extracts of M. oleifera, E. nigra, and L. camara on percent inhibition and radial growth were evaluated in the laboratory. In addition, the efficacy of different extract concentrations of M. oleifera, E. nigra, an...
In Zimbabwe, the average sweet potato yield (6 t/ha) is relatively low when compared to Asian cou... more In Zimbabwe, the average sweet potato yield (6 t/ha) is relatively low when compared to Asian counterparts (17 t/ha). These low crop yields have been blamed on weevil infestations and viral infections which account for 60-90% of sweet potato yield losses in Africa. Meristem tip culture, a Centre for Potato Improvement (CIP) initiated tissue culture technique, has been widely used to eradicate viruses from clonally propagated crops and has been noted to be one of the instrumental techniques that helped China to increase sweet potato yields. In an effort to adopt the meristem tip culture technique for the production of virus-free planting material of a local sweet potato (cv Brondal), a study was conducted to evaluate the effect of Benzylamino purine (BAP), 1-Naphthaleneacetic acid (NAA) and Gibberellic acid (GA3) (either alone or in combination) on cultured Brondal meristems. The different hormonal treatments were assessed on the following parameters: plantlet regenerative capacity, ...
A research study was conducted to identify and characterise seed-borne fungal pathogens associate... more A research study was conducted to identify and characterise seed-borne fungal pathogens associated with maize (Zea mays L.) in storage. Seed-borne fungal pathogenic infections of maize were studied using seed samples collected from Gokwe South District in Zimbabwe. The agar plating method using PDA medium was used to detect fungal pathogens on the maize seeds. A total of 150 treatments were used for this experiment, which were replicated three times in a randomised complete block design (RCBD). Analysis of the grain showed the presence of Fusarium moniliforme, Rhizopus stolonifer, Penicillium citrinum, and mostly Aspergillus species, namely, Aspergillus flavus, Aspergillus parasiticus, Aspergillus niger, and Aspergillus tamarii. Significant differences ( p
Streptomyces species are aerobes and chemoorganotrophic bacteria. These microorganisms produce a ... more Streptomyces species are aerobes and chemoorganotrophic bacteria. These microorganisms produce a wide range of industrially significant compounds, specifically antibiotics and anti fungal substances. The objective of this study was to characterise soil-borne Streptomyces isolates using morphological and molecular traits in order to identify them to species level, and leverage from their potential to suppress the growth of Aspergillus flavus, Fusarium oxysporum and Penicillium italicum. Twenty-seven soil-borne putative Streptomyces, which elicited comprehensive antimicrobial activity against Aspergillus flavus, Fusarium oxysporum and Penicillium italicum, in a previous study, were evaluated. On the basis of morphology, the bacteria resembled the genus Streptomyces. Initially, colonies phenotypically appeared to have a relatively smooth surface but as growth progressed the bacteria developed a weft of aerial mycelium granular, powdery or velvety in appearance. Bacteria produced a wide...
The use of living organisms or natural enemies of pathogens to control their populations is calle... more The use of living organisms or natural enemies of pathogens to control their populations is called biological disease control. It involves harnessing and introduction of exotic species of microorganism in a natural form, with the intention of controlling pathogens that may exist naturally in the same ecosystem. Prospects for biological control of Aspergillus flavus, Fusarium oxysporum and Penicillium italicum were investigated using Streptomyces spp. isolated from Chinhoyi University of Technology Farm soils in Mashonaland West, Zimbabwe. Twenty seven Streptomyces spp were obtained from the soil, and screened for antimicrobial activity and antagonism in in vitro pathogen inhibition assays, replicated thrice. Although majority of the isolates tested elicited no effect on test pathogens, 22% of the Streptomyces isolates were able to effectively suppress A. flavus, F. oxysporum and P. italicum by at least 55%. There was a significant interaction between Streptomyces isolates and pathog...
Livingstone potato (Plectranthus esculentus N.E.Br) is an underutilised indigenous root vegetable... more Livingstone potato (Plectranthus esculentus N.E.Br) is an underutilised indigenous root vegetable grown by communal farmers in the eastern provinces of Zimbabwe. It is vegetatively propagated using unimproved retained tubers from the previous season. The risk of disease carryover is therefore high, leading to poor yields. The objective of the study was to exploit the tissue culture technique of micropropagation to produce a mass supply of healthy planting material for improved productivity. Two experiments were conducted: firstly, to determine the best explant type and secondly, to determine the best landrace and plant growth regulators for the growth of plantlets. The landraces, namely, Ndurwe, Musande, Chibanda, and Chizambezi, were sourced from communal farmers in the stated production areas. Naphthalene acetic acid (NAA) and benzyl amino purine (BAP) were the auxin and cytokinin used, respectively. The first experiment was laid out as a randomized complete block design (RCBD) wi...
Hyphaene petersiana is a naturally occurring palm tree in Zimbabwe. The tree provides an importan... more Hyphaene petersiana is a naturally occurring palm tree in Zimbabwe. The tree provides an important supplementary source of income to the communities where it is found, with a high demand for foliage for making baskets and sap for wine making. Propagation is both by vegetative and sexual methods, however, sexual propagation is constrained by the inherent dormancy of the seeds. Breaking seed dormancy is also the first step towards developing a conservation programme for the tree. The effect of water soaking (for 12, 24 and 48 hours), chemical scarification (sulphuric acid for 10 minutes), de-husking (tegument removal), sand papering as well as chemical treatment (thiourea and potassium nitrate) were compared with untreated seeds (control). No germination was observed for seeds treated with sulphuric acid. Water soaking for 12 hours gave the highest germination (71.7%) although not significantly different to other treatments.
A survey was carried out in the potato- (Solanum tuberosum L.) growing regions of Zimbabwe in Apr... more A survey was carried out in the potato- (Solanum tuberosum L.) growing regions of Zimbabwe in April 2009 to assess the prevalence of bacterial soft rot. A total of 125 tubers with soft rot symptoms were collected. The disease caused severe economic losses ranging from 20 to 60% on tubers in the field and in storage. Affected tubers had symptoms that ranged from light vascular discoloration to complete seed piece decay. Infected tuber tissue was often cream colored and soft to the touch. In the field, plants showed severe wilting, often accompanied by a slimy, brown necrosis of the lower stems. Seventy-five of 125 isolations from diseased tubers yielded pectolytic bacteria on crystal violet pectate (CVP) medium and colonies were characterized after purification on King's B medium. All 75 isolates were gram-negative rods, oxidase negative, facultatively anaerobic, able to degrade pectate, and rot potato slices. They grew at 37°C, were sensitive to erythromycin, positive for phosph...
Effects of planting date (early: October-November, mid season: December, late: after first Januar... more Effects of planting date (early: October-November, mid season: December, late: after first January) and irrigation system (sprinkler, furrow) on seed quality (100 seed weight (g), percentage bad seed and seed germination) and health (percent infection by the seed borne pathogen Phaeoisariopsis griseola and subsequent angular leaf spot disease pressure in the crop were evaluated from data obtained in the field and laboratory from November 2002 to June
2005, in order to identify the best combinations of planting date and irrigation system able to improve seed characteristics. Planting date was significant (p<0.05) in all the parameters analysed and participated in different interactions with other factors studied. Compared to summer medium and late planting dates, summer early and winter crops were the best in improving seed quality and health in all the characteristics evaluated. Since sprinkler and furrow irrigation were equivalent in 71.9% of treatments comparing irrigation systems, winter and early planting date can be associated with any of those two systems to produce good quality and healthy seed. Prevailing weather conditions in
summer early and winter crops, which were not conducive to disease pressure, supported the results obtained.
Spider plant (Cleome gynandra L.) contributes considerably to the nutrition and medicines of comm... more Spider plant (Cleome gynandra L.) contributes considerably to the nutrition and medicines of communities in southern Africa. However, its utilisation is limited by its bitterness caused by condensed tannins. Unfortunately, processing options that reduce the bitterness also remove nutritionally and medicinally useful compounds. The objective of this study was to assess the genetic variability of condensed tannins and their association with bitterness in C. gynandra so as to devise variety recommendations for either direct utilisation or for breeding programmes in Zimbabwe. Total phenolic compounds and condensed tannins were quantified in five genotypes. The amount of total phenolic compounds were not significant, but quite significant (P<0.001) for condensed tannins. Genotype CGSKGP had the highest (0.49 mg g-1) and twice as much condensed tannins as CGKEX and CGSKP. Bitterness was positively correlated with the concentrations of condensed tannins (r=0.94, P<0.05), but not with...
Soft rot of potatoes (Solanum tuberosum L.) caused by Pectobacterium and Dickeya subspecies leads... more Soft rot of potatoes (Solanum tuberosum L.) caused by Pectobacterium and Dickeya subspecies leads to economic losses in agriculture worldwide including Zimbabwe, where losses range from 20 – 60%. A laboratory experiment was carried out using the potato tuber maceration test to screen the effect of two botanicals extract, neem (Azadirachta indica A. Juss.) leaf and garlic (Allium sativum L.) cloves in controlling soft rot disease caused by bacterial pathogens, namely Pectobacterium carotovorum subspecies carotovorum (Pcc), Pectobacterium atrosepticum (Pa) and Dickeya dadantii (Dd). Preparations of two concentrations [(10 and 25% (w/v)] of the aqueous extracts of garlic and neem plants were used in dip and spray applications. Sterile distilled water was used as a negative control. Three tuber halves were used for each treatment. Five 10 mm filter paper discs (Whatman’s No. 1) pre-soaked in 1 x 106 cfu/mL bacterial cell suspensions of Pcc, Pa and Dd respectively were placed on each tub...
Effects of planting date (early: October-November, mid season: December, late: after first Januar... more Effects of planting date (early: October-November, mid season: December, late: after first January) and irrigation system (sprinkler, furrow) on seed quality (100 seed weight (g), percentage bad seed and seed germination) and health (percent infection by the seed borne pathogen Phaeoisariopsis griseola and subsequent angular leaf spot disease pressure in the crop were evaluated from data obtained in the field and laboratory from November 2002 to June 2005, in order to identify the best combinations of planting date and irrigation system able to improve seed characteristics. Planting date was significant (p<0.05) in all the parameters analysed and participated in different interactions with other factors studied. Compared to summer medium and late planting dates, summer early and winter crops were the best in improving seed quality and health in all the characteristics evaluated. Since sprinkler and furrow irrigation were equivalent in 71.9% of treatments comparing irrigation syst...
Late blight is caused by Phytopthora infestans (Mont.) de Bary which establishes quickly in Solan... more Late blight is caused by Phytopthora infestans (Mont.) de Bary which establishes quickly in Solanum esculentum L. (tomato); as a result, it makes the pathogen one of the most devastating plant diseases across the world. The control of late blight is difficult because P. infestans has advanced and complex enzymes and effecter molecules coded by avirulence genes. As such, a study was carried out at the University of Zimbabwe, Department of Plant Production Sciences and Technologies, between August 2018 and May 2019 to evaluate the efficacy of Moringa oleifera Lour. (moringa), Eucalyptus nigra R.T. Baker (gumtree), and Lantana camara L. (sensu lato) (lantana) extracts as biofungicides on late blight development on S. esculentum. The effect of acetone, ethyl acetate, and water extracts of M. oleifera, E. nigra, and L. camara on percent inhibition and radial growth were evaluated in the laboratory. In addition, the efficacy of different extract concentrations of M. oleifera, E. nigra, an...
In Zimbabwe, the average sweet potato yield (6 t/ha) is relatively low when compared to Asian cou... more In Zimbabwe, the average sweet potato yield (6 t/ha) is relatively low when compared to Asian counterparts (17 t/ha). These low crop yields have been blamed on weevil infestations and viral infections which account for 60-90% of sweet potato yield losses in Africa. Meristem tip culture, a Centre for Potato Improvement (CIP) initiated tissue culture technique, has been widely used to eradicate viruses from clonally propagated crops and has been noted to be one of the instrumental techniques that helped China to increase sweet potato yields. In an effort to adopt the meristem tip culture technique for the production of virus-free planting material of a local sweet potato (cv Brondal), a study was conducted to evaluate the effect of Benzylamino purine (BAP), 1-Naphthaleneacetic acid (NAA) and Gibberellic acid (GA3) (either alone or in combination) on cultured Brondal meristems. The different hormonal treatments were assessed on the following parameters: plantlet regenerative capacity, ...
A research study was conducted to identify and characterise seed-borne fungal pathogens associate... more A research study was conducted to identify and characterise seed-borne fungal pathogens associated with maize (Zea mays L.) in storage. Seed-borne fungal pathogenic infections of maize were studied using seed samples collected from Gokwe South District in Zimbabwe. The agar plating method using PDA medium was used to detect fungal pathogens on the maize seeds. A total of 150 treatments were used for this experiment, which were replicated three times in a randomised complete block design (RCBD). Analysis of the grain showed the presence of Fusarium moniliforme, Rhizopus stolonifer, Penicillium citrinum, and mostly Aspergillus species, namely, Aspergillus flavus, Aspergillus parasiticus, Aspergillus niger, and Aspergillus tamarii. Significant differences ( p
Streptomyces species are aerobes and chemoorganotrophic bacteria. These microorganisms produce a ... more Streptomyces species are aerobes and chemoorganotrophic bacteria. These microorganisms produce a wide range of industrially significant compounds, specifically antibiotics and anti fungal substances. The objective of this study was to characterise soil-borne Streptomyces isolates using morphological and molecular traits in order to identify them to species level, and leverage from their potential to suppress the growth of Aspergillus flavus, Fusarium oxysporum and Penicillium italicum. Twenty-seven soil-borne putative Streptomyces, which elicited comprehensive antimicrobial activity against Aspergillus flavus, Fusarium oxysporum and Penicillium italicum, in a previous study, were evaluated. On the basis of morphology, the bacteria resembled the genus Streptomyces. Initially, colonies phenotypically appeared to have a relatively smooth surface but as growth progressed the bacteria developed a weft of aerial mycelium granular, powdery or velvety in appearance. Bacteria produced a wide...
The use of living organisms or natural enemies of pathogens to control their populations is calle... more The use of living organisms or natural enemies of pathogens to control their populations is called biological disease control. It involves harnessing and introduction of exotic species of microorganism in a natural form, with the intention of controlling pathogens that may exist naturally in the same ecosystem. Prospects for biological control of Aspergillus flavus, Fusarium oxysporum and Penicillium italicum were investigated using Streptomyces spp. isolated from Chinhoyi University of Technology Farm soils in Mashonaland West, Zimbabwe. Twenty seven Streptomyces spp were obtained from the soil, and screened for antimicrobial activity and antagonism in in vitro pathogen inhibition assays, replicated thrice. Although majority of the isolates tested elicited no effect on test pathogens, 22% of the Streptomyces isolates were able to effectively suppress A. flavus, F. oxysporum and P. italicum by at least 55%. There was a significant interaction between Streptomyces isolates and pathog...
Livingstone potato (Plectranthus esculentus N.E.Br) is an underutilised indigenous root vegetable... more Livingstone potato (Plectranthus esculentus N.E.Br) is an underutilised indigenous root vegetable grown by communal farmers in the eastern provinces of Zimbabwe. It is vegetatively propagated using unimproved retained tubers from the previous season. The risk of disease carryover is therefore high, leading to poor yields. The objective of the study was to exploit the tissue culture technique of micropropagation to produce a mass supply of healthy planting material for improved productivity. Two experiments were conducted: firstly, to determine the best explant type and secondly, to determine the best landrace and plant growth regulators for the growth of plantlets. The landraces, namely, Ndurwe, Musande, Chibanda, and Chizambezi, were sourced from communal farmers in the stated production areas. Naphthalene acetic acid (NAA) and benzyl amino purine (BAP) were the auxin and cytokinin used, respectively. The first experiment was laid out as a randomized complete block design (RCBD) wi...
Hyphaene petersiana is a naturally occurring palm tree in Zimbabwe. The tree provides an importan... more Hyphaene petersiana is a naturally occurring palm tree in Zimbabwe. The tree provides an important supplementary source of income to the communities where it is found, with a high demand for foliage for making baskets and sap for wine making. Propagation is both by vegetative and sexual methods, however, sexual propagation is constrained by the inherent dormancy of the seeds. Breaking seed dormancy is also the first step towards developing a conservation programme for the tree. The effect of water soaking (for 12, 24 and 48 hours), chemical scarification (sulphuric acid for 10 minutes), de-husking (tegument removal), sand papering as well as chemical treatment (thiourea and potassium nitrate) were compared with untreated seeds (control). No germination was observed for seeds treated with sulphuric acid. Water soaking for 12 hours gave the highest germination (71.7%) although not significantly different to other treatments.
A survey was carried out in the potato- (Solanum tuberosum L.) growing regions of Zimbabwe in Apr... more A survey was carried out in the potato- (Solanum tuberosum L.) growing regions of Zimbabwe in April 2009 to assess the prevalence of bacterial soft rot. A total of 125 tubers with soft rot symptoms were collected. The disease caused severe economic losses ranging from 20 to 60% on tubers in the field and in storage. Affected tubers had symptoms that ranged from light vascular discoloration to complete seed piece decay. Infected tuber tissue was often cream colored and soft to the touch. In the field, plants showed severe wilting, often accompanied by a slimy, brown necrosis of the lower stems. Seventy-five of 125 isolations from diseased tubers yielded pectolytic bacteria on crystal violet pectate (CVP) medium and colonies were characterized after purification on King's B medium. All 75 isolates were gram-negative rods, oxidase negative, facultatively anaerobic, able to degrade pectate, and rot potato slices. They grew at 37°C, were sensitive to erythromycin, positive for phosph...
Effects of planting date (early: October-November, mid season: December, late: after first Januar... more Effects of planting date (early: October-November, mid season: December, late: after first January) and irrigation system (sprinkler, furrow) on seed quality (100 seed weight (g), percentage bad seed and seed germination) and health (percent infection by the seed borne pathogen Phaeoisariopsis griseola and subsequent angular leaf spot disease pressure in the crop were evaluated from data obtained in the field and laboratory from November 2002 to June
2005, in order to identify the best combinations of planting date and irrigation system able to improve seed characteristics. Planting date was significant (p<0.05) in all the parameters analysed and participated in different interactions with other factors studied. Compared to summer medium and late planting dates, summer early and winter crops were the best in improving seed quality and health in all the characteristics evaluated. Since sprinkler and furrow irrigation were equivalent in 71.9% of treatments comparing irrigation systems, winter and early planting date can be associated with any of those two systems to produce good quality and healthy seed. Prevailing weather conditions in
summer early and winter crops, which were not conducive to disease pressure, supported the results obtained.
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2005, in order to identify the best combinations of planting date and irrigation system able to improve seed characteristics. Planting date was significant (p<0.05) in all the parameters analysed and participated in different interactions with other factors studied. Compared to summer medium and late planting dates, summer early and winter crops were the best in improving seed quality and health in all the characteristics evaluated. Since sprinkler and furrow irrigation were equivalent in 71.9% of treatments comparing irrigation systems, winter and early planting date can be associated with any of those two systems to produce good quality and healthy seed. Prevailing weather conditions in
summer early and winter crops, which were not conducive to disease pressure, supported the results obtained.
2005, in order to identify the best combinations of planting date and irrigation system able to improve seed characteristics. Planting date was significant (p<0.05) in all the parameters analysed and participated in different interactions with other factors studied. Compared to summer medium and late planting dates, summer early and winter crops were the best in improving seed quality and health in all the characteristics evaluated. Since sprinkler and furrow irrigation were equivalent in 71.9% of treatments comparing irrigation systems, winter and early planting date can be associated with any of those two systems to produce good quality and healthy seed. Prevailing weather conditions in
summer early and winter crops, which were not conducive to disease pressure, supported the results obtained.