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Wijnand J. Swart - One of the best experts on this subject based on the ideXlab platform.
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Soil amendments and watering influence the incidence of endophytic fungi in Amaranthus hybridus in South Africa
Applied Soil Ecology, 2007Co-Authors: J. T. Blodgett, Wijnand J. Swart, S. Vd M. Louw, W.j. WeeksAbstract:A study was conducted to determine the influence of soil amendments and irrigation on the incidence of endophytic fungi in Amaranthus hybridus. Five- and 6-month-old, asymptomatic tissues from A. hybridus were sampled from cultivated plots at Potchefstroom, South Africa in 1997 and 1998, respectively. Soil treatments consisted of the addition of commercial fertilizer or manure to irrigated soils, and wood ash to nonirrigated soils; control plots were neither amended nor irrigated. Ten leaves, 10 petioles, and 10 roots from each of five plants per soil treatment were surface disinfested and small sections from each were placed on corn-meal agar (8000 isolation attempts). After 5 days, the resulting fungal colonies were counted. Significant differences in recovery of fungi occurred among the soil treatments (P < 0.01) and among plant parts (P < 0.01). The highest recovery occurred from the commercial fertilizer and watered treatment (least stressed) for leaves and petioles in both years. Higher fungal recovery also occurred in the wettest year from leaves and petioles for all soil treatments. In contrast, roots yielded higher fungal recovery in the driest year for all soil treatments. These results show that soil attributes can influence frequency of endophytic fungi in both above- and below-ground tissues.
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Infection, Colonization, and Disease of Amaranthus hybridus Leaves by the Alternaria tenuissima Group
Plant disease, 2002Co-Authors: J. T. Blodgett, Wijnand J. SwartAbstract:Blodgett, J. T., and Swart, W. J. 2002. Infection, colonization, and disease of Amaranthus hybridus leaves by the Alternaria tenuissima group. Plant Dis. 86:1199-1205. With the increased use of Amaranthus hybridus as a leafy-vegetable crop in Africa and the recent identification of Alternaria leaf spot on this host in southern Africa, the role of this potentially damaging pathogen was investigated. The goals of this study were to test the pathogenicity of the Alternaria tenuissima group, determine how these fungi infect Amaranthus hybridus leaves, and examine the colonization pattern within host tissues. Asymptomatic leaves of Amaranthus hybridus were collected from two field sites in South Africa. Eight A. tenuissima group isolates collected from these leaves were used in inoculation experiments conducted in both greenhouse and growth chamber studies. Scanning electron microscopy revealed A. tenuissima– like conidia germinating on leaf surfaces and mycelia entering leaves only through stomata of both field-collected and artificially inoculated leaves. Unwounded, inoculated leaves had no symptoms, and light-microscopy observations of both asymptomatic field-collected and unwounded and inoculated leaves revealed hyphae in mesophyll tissue growing intercellularly with no host cell penetration or host-cell response. Seven of the eight isolates produced brown to black, circular to oval, necrotic lesions only at the wound site of injured and inoculated leaves. These results confirm that isolates of the A. tenuissima group can infect and colonize Amaranthus hybridus leaves in a manner consistent with other endophytic fungi, and suggest that these fungi can act as latent leaf pathogens when the host is altered by wounding.
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The in vitro phytotoxicity of culture filtrates of Fusarium oxysporum to five genotypes of Amaranthus hybridus
Euphytica, 2002Co-Authors: Weiqun Chen, Wijnand J. SwartAbstract:Stem decay and root rot of Amaranthus hybridus, caused by Fusarium oxysporum is a serious threat to the commercial production of this crop in South Africa. Five Amaranthus hybridus varieties were examined in vitro for sensitivity to a culture filtrate of Fusarium oxysporum. The phytotoxicity of the culture filtrate was assessed for its inhibitory effect on callus and seeding root growth, as well as on the viability of callus cells. The five varieties exhibited a significant amount of variation in response to the culture filtrate of the pathogen. Variety 17 was the most sensitive variety in each bioassay, whereas variety 20 displayed least sensitivity to the culture filtrate. Callus of variety 20 grew well in the presence of concentrations of culture filtrate that were toxic to another four varieties and the percentage mortality of callus cells after exposure to the filtrate was also the lowest of the five varieties. Root growth of variety 20 was also least affected by exposure to the culture filtrate for up to 6 days. To our knowledge, the presence of resistance in germplasm of A. hybridus to culture filtrates of F. oxysporum has not been demonstrated before. The present study is therefore of significant value to breeding programs aimed at speedily finding amaranth cultivars that are resistant to this important pathogen.
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Genetic Variation Among Fusarium oxysporum Isolates Associated with Root Rot of Amaranthus hybridus in South Africa.
Plant disease, 2001Co-Authors: Weiqun Chen, Wijnand J. SwartAbstract:ABSTRACT Thirty isolates of Fusarium oxysporum were recovered from six substrates: (i) tap roots of Amaranthus hybridus showing symptoms of root rot, (ii) side roots of A. hybridus showing symptoms of root rot, (iii) soil surrounding plants of A. hybridus, (iv) pigweed weevils (Hypolixus haerens) that feed on A. hybridus, (v) rhizosphere of maize plants growing adjacent to a field of amaranth, and (vi) rhizosphere of dry bean plants growing adjacent to a field of amaranth. The isolates were characterized by means of pathogenicity tests, isozyme analysis, and vegetative compatibility group (VCG) tests. In the pathogenicity tests, toothpick tips were infested with F. oxysporum and inserted into amaranth stems. All 30 isolates were pathogenic on A. hybridus, with significant differences in pathogenicity based on lesion length measured 4 weeks after inoculation. The isolates were grouped into nine VCGs by complementation tests using nitrate nonutilizing mutants. Self-incompatibility was not observed for any o...
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Species composition of endophytic fungi in Amaranthus hybridus leaves, petioles, stems, and roots
Mycologia, 2000Co-Authors: James T. Blodgett, Wijnand J. Swart, Schalk Vdm. Louw, William J. WeeksAbstract:The objectives of this study were to identify and quantify fungi in asymptomatic, 5-mo-old Amaranthus hybridus plants grown in cultivated plots and in a greenhouse, and determine the species compos...
E A Amankwah - One of the best experts on this subject based on the ideXlab platform.
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thin layer drying kinetics of solar dried Amaranthus hybridus and xanthosoma sagittifolium leaves
Journal of Food Processing and Technology, 2012Co-Authors: P T Akonor, E A AmankwahAbstract:The aim of the study was to model the solar drying characteristics of the leaves of Amaranthus hybridus and Xanthosoma sagittifolium dried in thin layers. Fresh leaves were obtained from Centre for Biodiversity Utilisation and Development (CBUD) farms, trimmed into strips of 0.3 cm x 3 cm and loaded into cabinet solar dryers up to a 5 mm layer. Drying was monitored and moisture loss was determined by loss in weight of samples at hourly interval. Drying data were fitted to five thin layer models, namely; Newton’s, Page’s, Modified Page, Handerson and Pabis and Logarithmic models by Non-linear Regression Analysis, the effective diffusivity was also determined for the two leafy vegetables. All five models showed a good fit between observed and predicted values, with Page’s model resulting in the highest r2 and lowest RMSE and X2 and hence the best model to describe the solar-drying characteristics of the two vegetables.
J. T. Blodgett - One of the best experts on this subject based on the ideXlab platform.
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Soil amendments and watering influence the incidence of endophytic fungi in Amaranthus hybridus in South Africa
Applied Soil Ecology, 2007Co-Authors: J. T. Blodgett, Wijnand J. Swart, S. Vd M. Louw, W.j. WeeksAbstract:A study was conducted to determine the influence of soil amendments and irrigation on the incidence of endophytic fungi in Amaranthus hybridus. Five- and 6-month-old, asymptomatic tissues from A. hybridus were sampled from cultivated plots at Potchefstroom, South Africa in 1997 and 1998, respectively. Soil treatments consisted of the addition of commercial fertilizer or manure to irrigated soils, and wood ash to nonirrigated soils; control plots were neither amended nor irrigated. Ten leaves, 10 petioles, and 10 roots from each of five plants per soil treatment were surface disinfested and small sections from each were placed on corn-meal agar (8000 isolation attempts). After 5 days, the resulting fungal colonies were counted. Significant differences in recovery of fungi occurred among the soil treatments (P < 0.01) and among plant parts (P < 0.01). The highest recovery occurred from the commercial fertilizer and watered treatment (least stressed) for leaves and petioles in both years. Higher fungal recovery also occurred in the wettest year from leaves and petioles for all soil treatments. In contrast, roots yielded higher fungal recovery in the driest year for all soil treatments. These results show that soil attributes can influence frequency of endophytic fungi in both above- and below-ground tissues.
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identification of fungi and fungal pathogens associated with hypolixus haerens and decayed and cankered stems of Amaranthus hybridus
Plant Disease, 2004Co-Authors: J. T. Blodgett, W J Swart, Vdm S LouwAbstract:Blodgett, J. T., Swart, W. J., and Louw, S. vdM. 2004. Identification of fungi and fungal pathogens associated with Hypolixus haerens and decayed and cankered stems of Amaranthus hybridus. Plant Dis. 88:333-337. Discoloration, cankers, and decay in branches, stems, and root collars of Amaranthus hybridus were observed in Bloemfontein, South Africa. Examination of symptomatic stems revealed larval galleries of the pigweed weevil (Hypolixus haerens). The objectives of this study were to: identify the most common fungal species associated with this damage, determine if the adult pigweed weevil might be a vector for the fungi, and test if the associated fungi can cause the stem canker disease observed in the field. The most common fungal species isolated were Fusarium subglutinans from discolored tissues adjacent to insect galleries (42%), F. subglutinans from weevil larvae (29%), the Alternaria tenuissima group from adult weevils (31%), and the A. tenuissima group from cankered stems (40%). Three of the seven most common fungal species produced cankers following wounding and inoculation, with F. sambucinum and F. oxysporum being the most aggressive. Although fungal species compositions differed (P < 0.01) among the four tissue/insect stage combinations tested, all four had the same major fungal species, suggesting the pigweed weevil as a vector for the Fusarium pathogens. There is significant potential for yield loss affiliated with this insect–fungal association. The identification of this insect–fungal relationship and the pathogens involved in disease set the stage for further research on the etiology and disease management of this important insect–fungal relationship.
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Infection, Colonization, and Disease of Amaranthus hybridus Leaves by the Alternaria tenuissima Group
Plant disease, 2002Co-Authors: J. T. Blodgett, Wijnand J. SwartAbstract:Blodgett, J. T., and Swart, W. J. 2002. Infection, colonization, and disease of Amaranthus hybridus leaves by the Alternaria tenuissima group. Plant Dis. 86:1199-1205. With the increased use of Amaranthus hybridus as a leafy-vegetable crop in Africa and the recent identification of Alternaria leaf spot on this host in southern Africa, the role of this potentially damaging pathogen was investigated. The goals of this study were to test the pathogenicity of the Alternaria tenuissima group, determine how these fungi infect Amaranthus hybridus leaves, and examine the colonization pattern within host tissues. Asymptomatic leaves of Amaranthus hybridus were collected from two field sites in South Africa. Eight A. tenuissima group isolates collected from these leaves were used in inoculation experiments conducted in both greenhouse and growth chamber studies. Scanning electron microscopy revealed A. tenuissima– like conidia germinating on leaf surfaces and mycelia entering leaves only through stomata of both field-collected and artificially inoculated leaves. Unwounded, inoculated leaves had no symptoms, and light-microscopy observations of both asymptomatic field-collected and unwounded and inoculated leaves revealed hyphae in mesophyll tissue growing intercellularly with no host cell penetration or host-cell response. Seven of the eight isolates produced brown to black, circular to oval, necrotic lesions only at the wound site of injured and inoculated leaves. These results confirm that isolates of the A. tenuissima group can infect and colonize Amaranthus hybridus leaves in a manner consistent with other endophytic fungi, and suggest that these fungi can act as latent leaf pathogens when the host is altered by wounding.
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First Report of Alternaria tenuissima as a Leaf Pathogen of Amaranthus hybridus
Plant disease, 1999Co-Authors: J. T. Blodgett, Wijnand J. Swart, Weiqun ChenAbstract:Amaranthus hybridus is an important alternative leafy-vegetable crop with the potential for increased commercial production in southern Africa and other semi-arid regions of the world (2). In May 1998, extensive leaf spotting was observed on A. hybridus at Potchefstroom, South Africa. Many of the leaves had symptoms and most were severe. Symptoms were dark brown to black, circular to oval, necrotic lesions with a diameter ranging from
P T Akonor - One of the best experts on this subject based on the ideXlab platform.
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thin layer drying kinetics of solar dried Amaranthus hybridus and xanthosoma sagittifolium leaves
Journal of Food Processing and Technology, 2012Co-Authors: P T Akonor, E A AmankwahAbstract:The aim of the study was to model the solar drying characteristics of the leaves of Amaranthus hybridus and Xanthosoma sagittifolium dried in thin layers. Fresh leaves were obtained from Centre for Biodiversity Utilisation and Development (CBUD) farms, trimmed into strips of 0.3 cm x 3 cm and loaded into cabinet solar dryers up to a 5 mm layer. Drying was monitored and moisture loss was determined by loss in weight of samples at hourly interval. Drying data were fitted to five thin layer models, namely; Newton’s, Page’s, Modified Page, Handerson and Pabis and Logarithmic models by Non-linear Regression Analysis, the effective diffusivity was also determined for the two leafy vegetables. All five models showed a good fit between observed and predicted values, with Page’s model resulting in the highest r2 and lowest RMSE and X2 and hence the best model to describe the solar-drying characteristics of the two vegetables.
Zhi Shan - One of the best experts on this subject based on the ideXlab platform.
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Purification, characterization and antioxidant activities in vitro of polysaccharides from Amaranthus hybridus L.
PeerJ, 2020Co-Authors: Zizhong Tang, Hui Chen, Caixia Zhou, Yi Cai, Yujia Tang, Wenjun Sun, Huipeng Yao, Tianrun Zheng, Yirong Xiao, Zhi ShanAbstract:Amaranthus hybridus L. is an annual, erect or less commonly ascending herb that is a member of the Amaranthaceae family. Polysaccharides extracted from traditional Chinese medicines may be effective substances with antioxidant activity. In this study, we isolated crude polysaccharides from A. hybridus (AHP-M) using microwave-assisted extraction. Then, the AHP-M was purified by chromatography with DEAE-32 cellulose, and two fractions, AHP-M-1 and AHP-M-2, were obtained. The structural characteristics of AHP-M-1 and AHP-M-2 were investigated, and their antioxidant activities were analyzed in vitro. We found that the monosaccharide composition of AHP-M-1 was different from that of AHP-M-2. The molecular weights of AHP-M-1 and AHP-M-2 were 77.625 kDa and 93.325 kDa, respectively. The results showed that the antioxidant activity of AHP-M-2 was better than that of AHP-M-1. For AHP-M-2, the DPPH radical scavenging rate at a concentration of 2 mg/mL was 78.87%, the hydroxyl radical scavenging rate was 39.34%, the superoxide anion radical scavenging rate was 80.2%, and the reduction ability of Fe3+ was approximately 0.90. The total antioxidant capacity per milligram of AHP-M-2 was 6.42, which was higher than that of Vitamin C (Vc). The in vitro test indicated that AHP-M-1 and AHP-M-2 have good antioxidant activity, demonstrating that A. hybridus L. polysaccharide has immense potential as a natural antioxidants. © 2020 Tang et al.
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purification characterization and antioxidant activities in vitro of polysaccharides from Amaranthus hybridus l
PeerJ, 2020Co-Authors: Zizhong Tang, Hui Chen, Caixia Zhou, Yi Cai, Yujia Tang, Wenjun Sun, Huipeng Yao, Tianrun Zheng, Yirong Xiao, Zhi ShanAbstract:Background Amaranthus hybridus L. is an annual, erect or less commonly ascending herb that is a member of the Amaranthaceae family. Polysaccharides extracted from traditional Chinese medicines may be effective substances with antioxidant activity. Methods In this study, we isolated crude polysaccharides from A. hybridus (AHP-M) using microwave-assisted extraction. Then, the AHP-M was purified by chromatography with DEAE-32 cellulose, and two fractions, AHP-M-1 and AHP-M-2, were obtained. The structural characteristics of AHP-M-1 and AHP-M-2 were investigated, and their antioxidant activities were analyzed in vitro. Results We found that the monosaccharide composition of AHP-M-1 was different from that of AHP-M-2. The molecular weights of AHP-M-1 and AHP-M-2 were 77.625 kDa and 93.325 kDa, respectively. The results showed that the antioxidant activity of AHP-M-2 was better than that of AHP-M-1. For AHP-M-2, the DPPH radical scavenging rate at a concentration of 2 mg/mL was 78.87%, the hydroxyl radical scavenging rate was 39.34%, the superoxide anion radical scavenging rate was 80.2%, and the reduction ability of Fe3+ was approximately 0.90. The total antioxidant capacity per milligram of AHP-M-2 was 6.42, which was higher than that of Vitamin C (Vc). Conclusion The in vitro test indicated that AHP-M-1 and AHP-M-2 have good antioxidant activity, demonstrating that A. hybridus L. polysaccharide has immense potential as a natural antioxidants.
