scholarly journals Report of Root Rot Caused by Pythium F-Group on Hydroponically Grown Celery in South Africa

Plant Disease ◽  
2002 ◽  
Vol 86 (4) ◽  
pp. 441-441
Author(s):  
N. Labuchagne ◽  
C. Gull ◽  
F. C. Wehner ◽  
W. J. Botha
Keyword(s):  
South Africa ◽  
Nutrient Solution ◽  
Root Rot ◽  
Apium Graveolens ◽  
Gauteng Province ◽  
Warm Summer ◽  
Hydroponic Systems ◽  
Hydroponically Grown ◽  
Zoospore Suspension ◽  
Group 1

Celery (Apium graveolens) is commonly grown in hydroponic systems in South Africa. During the warm summer months, plants often become stunted or die, with mortality as high as 70% in some systems. Affected plants show severe root rot and yellowing of the foliage. Root segments excised from symptomatic celery plants collected from various hydroponic systems in Gauteng Province, South Africa, were rinsed in sterile distilled water and plated on PARP medium (2). Pythium was isolated consistently from both rotted and symptomless roots. Isolates produced only noninflated filamentous sporangia and no oospores, conforming to the description of Pythium F-group (1). Koch's postulates were confirmed by inoculating 4-week-old celery seedlings cultivated in aerated nutrient solution in a hydroculture system in the greenhouse. A zoospore suspension (105 zoospores per ml) of Pythium F-group cultured on V8 juice agar was added to the nutrient solution at the rate of 3 ml/1iter. Control plants received no inoculum, and the experiment was repeated once. Plants were assessed after 4 weeks. All inoculated plants showed symptoms of root rot, stunting, and yellowing, whereas control plants remained healthy. Pythium F-group was recovered on PARP medium only from the roots of inoculated plants. Pythium F-group has been described as a pathogen of celery elsewhere, but to our knowledge, this is the first report of root rot caused by the fungus on celery in South Africa. References: (1) M. W. Dick. Keys to Pythium. University of Reading Press, Reading, UK, 1990. (2) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986.

scholarly journals Pythium spp. Infecting Hydroponically Grown Lettuce in South Africa

Plant Disease ◽  
2002 ◽  
Vol 86 (10) ◽  
pp. 1175-1175 ◽  
Author(s):  
N. Labuschagne ◽  
C. Gull ◽  
F. C. Wehner ◽  
W. J. Botha
Keyword(s):  
South Africa ◽  
Nutrient Solution ◽  
Root Rot ◽  
Species Group ◽  
Selective Medium ◽  
Plant Weight ◽  
Stunted Growth ◽  
Hydroponic Systems ◽  
Shoot Weight ◽  
Hydroponically Grown

Root rot and wilting of lettuce (Lactuca sativa L. var. capitata L.) commonly occur in hydroponic systems in South Africa. Plants showing stunted growth, wilt, and root rot were collected at two commercial hydroponic systems in Gauteng Province, and root segments were plated on a Pythium selective medium (1). P. irregulare and three species groups without oogonia (F, HS, and T) were identified (2). Pythium groups F, HS, and T, and P. irregulare were represented by 63, 6, 5, and 26% of the isolates, repectively. Koch's postulates were confirmed in two greenhouse experiments by inoculating 4-week-old lettuce cv. Lutetia seedlings grown in aerated nutrient solution at 21°C. Two V8 juice agar cultures of an isolate of each species or species group were blended in 500 ml of sterile water, and 166 ml of suspension was added to the nutrient solution in each of three 5-liter receptacles containing four lettuce seedlings. Control plants received sterile V8 juice agar suspension. After 4 weeks, all Pythium isolates caused root rot and reduced fresh plant weight significantly, although no wilting occurred. Symptoms were more severe with P. irregulare and Pythium group HS than with groups F and T. Compared to the control, P. irregulare reduced fresh root and shoot weight of plants by 51 and 38%, Pythium group HS by 41 and 33%, Pythium group T by 29 and 26%, and Pythium group F by 30 and 24%, respectively. References: (1) W. J. Botha and R. L. J. Coetzer. S. Afr. J. Bot. 62:196, 1996. (2) M. W. Dick. Keys to Pythium. University of Reading Press, Reading UK, 1990.

scholarly journals Root Rot and Stunting of Hydroponically Grown Endive, Fennel, and Sorrel Caused by Pythium F-group in South Africa

Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 875-875 ◽  
Author(s):  
N. Labuschagne ◽  
C. Gull ◽  
F. C. Wehner ◽  
W. J. Botha
Keyword(s):  
South Africa ◽  
Root Rot ◽  
Selective Medium ◽  
Vegetable Crops ◽  
Root Tips ◽  
Foeniculum Vulgare ◽  
Hydroponic System ◽  
Stunted Growth ◽  
Root Segments ◽  
Hydroponically Grown

Specialized vegetable crops such as endive (Cichorium endiva), fennel (Foeniculum vulgare), and sorrel (Rumex spp.) are being cultivated hydroponically in South Africa to be marketed as admixtures in salads. Stunted growth accompanied by browning and rotting of the root tips has been observed at a commercial recirculating gravel bed hydroponic system near Pretoria during the warm summer months. Root segments excised from symptomatic plants were rinsed in sterile water and plated on Pythium selective medium (1). Pythium F-group, characterized by the production of noninflated filamentous sporangia and no oospores (2), was isolated from 40% of endive, 60% of fennel, and 7% of sorrel root segments. Koch's postulates were confirmed by inoculating 4-week-old seedlings of each crop in the greenhouse with a Pythium F-group isolate from the particular crop. Inoculations were performed by adding 3 ml of suspension (105 zoospores per ml) to each liter of aerated nutrient solution. Control plants received no inoculum, and the experiment was repeated once. After 4 weeks, inoculated plants showed stunting of the foliage and slight to moderate root rot. Pythium F-group could readily be reisolated from roots of inoculated plants. To our knowledge, this is the first report of Pythium F-group on these crops in South Africa. References: (1) W. J. Botha and R. L. J. Coetzer. S. Afr. J. Bot. 62:196, 1996. (2) M. W. Dick. Keys to Pythium. University of Reading Press, Reading, UK, 1990.

scholarly journals Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives

2006 ◽  
Vol 32 (4) ◽  
pp. 307-321 ◽  
Author(s):  
John Clifford Sutton ◽  
Coralie Rachelle Sopher ◽  
Tony Nathaniel Owen-Going ◽  
Weizhong Liu ◽  
Bernard Grodzinski ◽  
...  
Keyword(s):  
Nutrient Solution ◽  
Root Rot ◽  
Root Zone ◽  
Pythium Ultimum ◽  
Stress Factors ◽  
Pythium Root Rot ◽  
Whole Plant ◽  
Phenolic Substances ◽  
Hydroponic Systems ◽  
The Impact

The etiology and epidemiology of Pythium root rot in hydroponically-grown crops are reviewed with emphasis on knowledge and concepts considered important for managing the disease in commercial greenhouses. Pythium root rot continually threatens the productivity of numerous kinds of crops in hydroponic systems around the world including cucumber, tomato, sweet pepper, spinach, lettuce, nasturtium, arugula, rose, and chrysanthemum. Principal causal agents include Pythium aphanidermatum, Pythium dissotocum, members of Pythium group F, and Pythium ultimum var. ultimum. Perspectives are given of sources of initial inoculum of Pythium spp. in hydroponic systems, of infection and colonization of roots by the pathogens, symptom development and inoculum production in host roots, and inoculum dispersal in nutrient solutions. Recent findings that a specific elicitor produced by P. aphanidermatum may trigger necrosis (browning) of the roots and the transition from biotrophic to necrotrophic infection are considered. Effects on root rot epidemics of host factors (disease susceptibility, phenological growth stage, root exudates and phenolic substances), the root environment (rooting media, concentrations of dissolved oxygen and phenolic substances in the nutrient solution, microbial communities and temperature) and human interferences (cropping practices and control measures) are reviewed. Recent findings on predisposition of roots to Pythium attack by environmental stress factors are highlighted. The commonly minor impact on epidemics of measures to disinfest nutrient solution as it recirculates outside the crop is contrasted with the impact of treatments that suppress Pythium in the roots and root zone of the crop. New discoveries that infection of roots by P. aphanidermatum markedly slows the increase in leaf area and whole-plant carbon gain without significant effect on the efficiency of photosynthesis per unit area of leaf are noted. The platform of knowledge and understanding of the etiology and epidemiology of root rot, and its effects on the physiology of the whole plant, are discussed in relation to new research directions and development of better practices to manage the disease in hydroponic crops. Focus is on methods and technologies for tracking Pythium and root rot, and on developing, integrating, and optimizing treatments to suppress the pathogen in the root zone and progress of root rot.

scholarly journals First Report of Stem and Root Rot of Tomato Caused by Phytophthora capsici in South Africa

Plant Disease ◽  
2003 ◽  
Vol 87 (12) ◽  
pp. 1540-1540 ◽  
Author(s):  
N. Labuschagne ◽  
A. H. Thompson ◽  
W. J. Botha
Keyword(s):  
South Africa ◽  
Root Rot ◽  
Phytophthora Capsici ◽  
Pythium Aphanidermatum ◽  
Pine Bark ◽  
Tomato Plants ◽  
First Report ◽  
Vascular Tissues ◽  
Tomato Seedlings ◽  
Hydroponic Systems

Tomato plants, grown in open hydroponic systems under shadecloth and plastic near Barberton and Pretoria in South Africa and Srelebi Phikwe in Botswana, developed symptoms of wilting with brown-to-black cankers on the lower stems, blackening of the vascular tissues, and root rot. Pathogens isolated from affected tissues were identified as Phytophthora capsici Leonian (1) and Pythium aphanidermatum (Edson) Fitzp. (2).They occurred separately or together. Pythium aphanidermatum has previously been recorded on tomato in South Africa. P. capsici isolates were papillate, caducous, grew at >36°C, had tapered sporangial bases, and a maximum sporangial length of >70 μm. Koch's postulates were confirmed by inoculating 4-week-old tomato seedlings (cv. Floradade) grown at 22 to 30°C in a steam-pasteurized mixture of sawdust compost, pine bark, and vermiculite (3:2:1). Plugs from V8 juice agar cultures of P. capsici were placed on wounds made on the stems of 10 seedlings. Ten wounded uninoculated plants served as controls. Water-soaked lesions were visible on the stems of all inoculated plants after 2 days. Control plants remained healthy. After 4 days, lesions turned dark brown with affected plants wilted or dead. Reisolation yielded P. capsici. The experiment was repeated with similar results. To our knowledge, this is the first report of P. capsici on tomatoes in South Africa. References: (1) A. H. Thompson et al. S. Afr. J. Bot. 60:257, 1994.(2) W. Dick. Keys to Pythium. University of Reading Press, Reading, U.K., 1990.

scholarly journals First Report of Root Rot of Hydroponically Grown Lettuce Caused by Pythium myriotylum in a Commercial Production Facility

Plant Disease ◽  
1998 ◽  
Vol 82 (7) ◽  
pp. 831-831 ◽  
Author(s):  
M. E. Stanghellini ◽  
D. H. Kim ◽  
J. Rakocy ◽  
K. Gloger ◽  
H. Klinton
Keyword(s):  
Nutrient Solution ◽  
Root Rot ◽  
Virgin Islands ◽  
Production Facility ◽  
Pythium Myriotylum ◽  
Susceptible Host ◽  
Experimental Systems ◽  
Commercial Cultivation ◽  
Pure Cultures ◽  
Hydroponically Grown

Commercial cultivation of lettuce (Lactuca sativa L.) under hydroponic conditions was initiated in August 1997 in the U.S. Virgin Islands. One week following transplant into an outdoor growout system, several plants wilted and died. Over the next 2 weeks, approximately 50% of the 30,000 plants died and the remaining plants were severely stunted. Temperature of the nutrient solution ranged from 28 to 30°C. Root specimens received for diagnosis consistently yielded pure cultures of Pythium myriotylum Drechsler. To confirm Koch's postulates, lettuce seedlings were reared hydroponically in a greenhouse. Temperature of the nutrient solution ranged from 27 to 29°C. After 14 days, one plant in each hydroponic chamber (which contained six lettuce plants) was removed and the root system of the plant was placed in a beaker containing approximately 1,000 zoospores of P. myriotylum. After a 30-min incubation period, the artificially inoculated plant was replanted in the hydroponic chamber. Within 5 to 7 days all plants were severely wilted and exhibited extensive root rot. P. myriotylum was consistently reisolated from symptomatic plants. No wilt occurred on respective noninoculated plants. The above study was conducted three times with similar results. Although P. myriotylum has previously been isolated from hydroponically grown lettuce in experimental systems (1), this report demonstrates the destructiveness of this zoosporic pathogen in a commercial hydroponic lettuce production facility. Factors that contributed to the epidemic were an abundance of a susceptible host, a temperature regime optimum for pathogen growth and reproduction, and a mechanism for the rapid dispersal of the pathogen via the recirculating nutrient solution. Although the source of pathogen introduction into the facility is not known, the hydroponic system was located in an open field. Thus, the pathogen could have been introduced aerially via wind-blown dust, rain, or insects. We do know, however, that the transplants were pathogen-free. Reference: (1) A. C. Schuerger and K. G. Pategas. Phytopathology 74:796, 1984.

Ascertaining the Role of Leadership on Employee Satisfaction in Market and Social Research Industries in Gauteng Province of South Africa Using Qualitative Research

2015 ◽  
Vol 3 (2) ◽  
Author(s):  
Kingstone Mutsonziwa ◽  
Philip Serumaga-Zake
Keyword(s):  
South Africa ◽  
Employee Satisfaction ◽  
Quantitative Research ◽  
Social Research ◽  
Labour Productivity ◽  
Working Environment ◽  
Gauteng Province ◽  
Career Growth ◽  
Quantitative Results ◽  
Mixed Approach

This paper is based on the study a Doctor of Business Leadership (DBL) thesis titled A Statistical Model for Employee Satisfaction in the Market and Social Research Industries in Gauteng Province. The purpose of this study was to identify the attributes that affect employee satisfaction in the Market and Social Research Industries in Gauteng Province, South Africa. In order to address the overall objective of this study, the researcher used a two-tiered (mixed) approach in which both qualitative and quantitative research methodologies were used to complement and enrich the results. This paper is only based on the qualitative component of the study on leadership aspects based on six leaders (two from Social research and four from Market research) that were interviewed. The leaders were selected based on their knowledge of the industry and the expertise they have. Participation in the survey was voluntary. This paper illustrates the power of the qualitative techniques to uncover or unmask the leadership aspects in the Market and Social Research Industries and also gives the human touch to the quantitative results. It was found that leadership and management within the Market and Social Research Industries in Gauteng Province must ensure that they are accommodative in terms of mentoring their subordinates. The industry is driven by quality driven processes and strong leadership. More importantly, issues of a good working environment, remuneration, career growth, and recognition must always be addressed in order to increase employee satisfaction, reduce staff turnover, and attempt to optimize labour productivity. The qualitative findings also help a deeper understanding of leadership within the industry.

scholarly journals Content of inorganic solutes in lettuce grown with brackish water in different hydroponic systems

2017 ◽  
Vol 21 (3) ◽  
pp. 150-155 ◽  
Author(s):  
Alide M. W. Cova ◽  
Fabio T. O. de Freitas ◽  
Paula C. Viana ◽  
Maria R. S. Rafael ◽  
André D. de Azevedo Neto ◽  
...  
Keyword(s):  
Fresh Water ◽  
Nutrient Solution ◽  
Brackish Water ◽  
Dry Matter ◽  
Dry Matter Production ◽  
Matter Production ◽  
Water Plant ◽  
Hydroponic Systems ◽  
Inorganic Solutes

ABSTRACT The objective of this study was to evaluate the growth and accumulation of ions in lettuce grown in different hydroponic systems and recirculation frequencies. The experimental design was randomized blocks with 8 treatments and 4 replicates. The evaluated hydroponic systems were Nutrient Flow Technique (NFT) and an adapted Deep Flow Technique (DFT), the latter with recirculation frequencies of 0.25, 2 and 4 h. Both systems used fresh water and brackish water. Plant growth, accumulation of inorganic solutes (Na+, K+, Cl- and NO3-) and the correlation between dry matter production and Na+/K+ and Cl-/NO3- were evaluated. The salinity of the water used to prepare the nutrient solution caused decrease in growth and K+ and NO3- levels, and increased contents of Na+ and Cl- in the plants. When using fresh water the highest dry matter production was obtained in the NFT system. In case of brackish water the adapted DFT system increased the production, in relation to NFT system (at same recirculation frequency: 0.25 h). It was found that the choice of the type of hydroponic system and recirculation interval for the cultivation of lettuce depends on the quality of the water used to prepare the nutrient solution.

The Vergenoeg: Gauteng Province, South Africa Fluorite Mine

2008 ◽  
Vol 83 (5) ◽  
pp. 410-421 ◽  
Author(s):  
Bruce Cairncross ◽  
Wolfgang Windisch ◽  
Henk Smit ◽  
Allan Fraser ◽  
Jens Gutzmer
Keyword(s):  
South Africa ◽  
Gauteng Province
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