Yeasts form an important part of many ecosystems and significantly contribute to biodiversity. However, yeast biodiversity in the North West Province remains largely unexplored. The aim of this study was to determine the diversity and characteristics of yeasts from water sources in the North West Province, South Africa. Samples were collected over a two year period and included three rivers, a spruit and an inland lake. Temperature, pH, and electrical conductivity (EC) were measured on site using a multi-probe. Nitrate (NO3-N), nitrite (NO2-N) and phosphate (PO42-) levels were determined in the laboratory using Hatch kits and equipment. The pH ranged from 7.2 to 9.2. Elevated EC levels (36-70 mS) were detected especially at the Harts River and Barberspan (38-165 mS) sites. Physico-chemical parameter levels were higher during the cold dry sampling period compared to the warm rainy sampling period. Levels and diversity of yeasts were determined using the membrane filtration method. The highest level of yeasts was detected in the Mooi River and Schoonspruit during 2010 and 2011 sampling periods. Pigmented and non-pigmented yeasts were enumerated from all samples. Over the two year period the highest number of pigmented yeasts was detected in the Schoonspruit samples. In some cases there were significant (P<0.05) differences between pigmented and non-pigmented yeast levels among the sites. The diazonium blue B (DBB) test was carried out to distinguish between ascomycetous and basidiomycetous yeasts. These isolates were then identified using the API ID 32C system. Yeasts isolates were identified as belonging to the following genera: Candida, Cryptococcus, Pichia, Rhodotorula and Zygosaccharomyces. In addition using 26S rRNA gene sequencing Aureobasidium spp., Clavispora spp., Cystofilobasidium spp., Hanseniaspora spp., Meyerozyma spp., Sporidiobolus spp., and Wickerhamomyces spp.were also identified. The diversity and abundance of yeasts in the water sources demonstrated that opportunistic pathogens were present. This was supported by results that indicated some isolates could grow at 37°C and higher. In conclusion, our results provide preliminary information on the distribution and diversity of yeasts in water sources of the North West Province, South Africa. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013.

Yeasts form an important part of many ecosystems and significantly contribute to biodiversity. However, yeast biodiversity in the North West Province remains largely unexplored. The aim of this study was to determine the diversity and characteristics of yeasts from water sources in the North West Province, South Africa. Samples were collected over a two year period and included three rivers, a spruit and an inland lake. Temperature, pH, and electrical conductivity (EC) were measured on site using a multi-probe. Nitrate (NO3-N), nitrite (NO2-N) and phosphate (PO42-) levels were determined in the laboratory using Hatch kits and equipment. The pH ranged from 7.2 to 9.2. Elevated EC levels (36-70 mS) were detected especially at the Harts River and Barberspan (38-165 mS) sites. Physico-chemical parameter levels were higher during the cold dry sampling period compared to the warm rainy sampling period. Levels and diversity of yeasts were determined using the membrane filtration method. The highest level of yeasts was detected in the Mooi River and Schoonspruit during 2010 and 2011 sampling periods. Pigmented and non-pigmented yeasts were enumerated from all samples. Over the two year period the highest number of pigmented yeasts was detected in the Schoonspruit samples. In some cases there were significant (P<0.05) differences between pigmented and non-pigmented yeast levels among the sites. The diazonium blue B (DBB) test was carried out to distinguish between ascomycetous and basidiomycetous yeasts. These isolates were then identified using the API ID 32C system. Yeasts isolates were identified as belonging to the following genera: Candida, Cryptococcus, Pichia, Rhodotorula and Zygosaccharomyces. In addition using 26S rRNA gene sequencing Aureobasidium spp., Clavispora spp., Cystofilobasidium spp., Hanseniaspora spp., Meyerozyma spp., Sporidiobolus spp., and Wickerhamomyces spp.were also identified. The diversity and abundance of yeasts in the water sources demonstrated that opportunistic pathogens were present. This was supported by results that indicated some isolates could grow at 37°C and higher. In conclusion, our results provide preliminary information on the distribution and diversity of yeasts in water sources of the North West Province, South Africa. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013.

Increasing socio-economic growth and development of South Africa’s freshwater systems require continuous augmentation of water sources to meet the growing water requirements of communities and industries. Anthropogenic disturbances have caused the water quality of many freshwater systems to drastically deteriorate due to constant disposal of domestic, industrial, and agricultural waste into surface waters. Government agencies make use of biomonitoring programmes to effectively manage the countries’ freshwater resources. These programmes use a variety of biological indicators (e.g., macroinvertebrates, fish, diatoms and algal species) and physico-chemical variables to determine the state of the environment. However, attempts to use microbial community structures as bioindicators of anthropogenic perturbations are greatly neglected. This study used molecular techniques (PCR-DGGE and 454-pyrosequencing) and multivariate analysis to develop a robust monitoring technique to determine the impacts of environmental disturbances on bacterial community compositions in river systems in the North West Province. Significant contributions made by this project included the establishment of a bacterial diversity framework for South African freshwater systems that are impacted by a variety of anthropogenic activities (e.g., urban and informal settlements, agriculture and mining). Furthermore, case studies demonstrated the prevalence of specific taxa at polluted sites, as well as positive and negative associations between taxa and environmental variables and pollutants. Finally, biogeochemical cycles could be partially matched to bacterial community structures in river systems. The first part of the project included a pilot study that investigated bacterial structures in a segment of the Vaal River in response to environmental parameters using molecular techniques and multivariate analysis. The most important observations made during this study included the generation of a larger bacterial diversity dataset by pyrosequencing compared to PCR-DGGE. In addition, metagenomic and multivariate analyses provided clues about potential biogeochemical roles of different taxa. The second and third part of the project included two case studies that investigated bacterial communities in the Mooi River and Wonderfonteinspruit in response to environmental activities. Both these systems are impacted by a variety of external sources such as urban and informal settlements, agriculture, and mining. The results demonstrated that perturbations nearby the Mooi River and Wonderfonteinspruit caused the overall water quality to deteriorate which in turn had a profound impact on bacterial community composition. Bacterial community structures at reference/control sites (Muiskraal and Turffontein dolomitic eye) had overall high species diversity (richness and evenness), whereas polluted sites showed lower species diversity and were dominated by the Beta- and Gammaproteobacteria, Bacteroidetes, and Verrucomicrobia. In addition, various potential pathogens (e.g. Eschirichia/Shigella, Legionella, Staphylococcus, Streptococcus etc.) were identified at impacted sites. Multivariate analysis suggested that bacterial communities and certain taxa (Malikia, Algoriphagus, Rhodobacter, Brevundimonas and Sphingopyxis) at polluted sites were mainly impacted by temperature, pH, nutrient levels, and heavy metals. Finally, the proportion of nitrogen and sulphur bacteria corresponded well with the nitrogen and sulphur levels measured in the Wonderfonteinspruit. Based on these results, it was concluded that bacterial community structures might provide a good indicator of anthropogenic disturbances in freshwater systems and may be incorporated into biomonitoring programs. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The main aim of the study was to analyse the impact of physico-chemical parameters on drinking water quality, biofilm formation and antibiotic resistant bacteria in the drinking water distribution system in Mafikeng, North West Province, South Africa. Another objective was to isolate and characterise Pseudomonas and Aeromonas species from drinking water distribution system and detect the virulence gene determinants in the isolates by PCR analysis. The physico-chemical data obtained were subjected to statistical analysis using Excel 2007 (Microsoft) and SPSS (version 14.0) programmes. Pearson’s correlation product of the moment was used to determine the correlation between EC, TDS, pH and temperature. The two tailed test of significance (p<0.05) was used in order to determine the significance of the result. Antibiotic susceptibility tests were performed using Kirby-Bauer disk diffusion method. Cluster analysis based on the antibiotic inhibition zone diameter data of different organisms isolated from different sites was determined and was expressed as dendograms using Wards algorithm and Euclidean distance of Statistica version 7. Specific PCR was used to determine the identities of presumptive Pseudomonas and Aeromonas species through amplification of the gyrB, toxA and the ecfX gene fragments. Virulence gene determinants for the confirmed Pseudomonas and Aeromonas species were detected by amplifying the exoA, exoS and exoT genes and the aerA and hylH gene fragments, respectively. A Gene Genius Bio imaging system (Syngene, Synoptics; UK) was used to capture the image using GeneSnap (version 3.07.01) software (Syngene, Synoptics; UK) to determine the relative size of amplicons. Physico-chemical parameters were monitored from three drinking water sources three times a week and bacteriological quality was monitored weekly for four months from raw and treated drinking water. Water samples were analysed for pH, temperature, total dissolved solids (TDS) and electric conductivity (EC). Bacterial consortia from drinking water samples were isolated using selective media and enumerated. The results revealed a good chemical quality of water. However, the microbial quality of the water is not acceptable for human consumption due to the presence of Pseudomonas, Aeromonas, faecal coliforms (FC), total coliforms (TC) and Heterotrophic bacteria. The results showed that the drinking water is slightly alkaline with pH value ranging between7.7 to 8.32. What is of concern was the microbial quality of the water. Pseudomonas sp., faecal coliforms (FC), total coliforms (TC) and heterotrophic bacteria were present in some of the treated water samples. The most significant finding of this study is that all drinking water samples were positive for Pseudomonas sp.(>100/100ml), but also that when one considers the TDS it demonstrates that water from the Modimola Dam has an impact on the quality of the mixed water. The prevalence and antibiotic resistance profiles of planktonic and biofilm bacteria isolated from drinking water were determined. The susceptibility of these isolates was tested against 11 antibiotics of clinical interest and the multiple antibiotic resistance (MAR) patterns were compiled. The most prevalent antibiotic resistance phenotype observed was KF-AP-C-E-OT-K-TM-A. All isolates from all samples were susceptible to ciprofloxacin. However, all faecal coliforms and Pseudomonas spp. were susceptible to neomycin and streptomycin. On the contrary all organisms tested were resistant to erythromycin (100%) trimethoprim and amoxycillin. Cluster analysis based on inhibition zone diameter data could not differentiate the various isolated into sample types. The highest prevalence of antibiotic resistant isolates was observed in Modimola Dam and Molopo eye. Biofilms were investigated in both raw water and treated drinking water sources for the presence of faecal coliforms, total coliforms, Pseudomonas spp., Aeromonas spp. and heterotrophic bacteria based on conventional microbiology and molecular methods. Drinking water biofilms were grown twice and the biofilm developing device containing copper and galvanized steel coupons were utilized. The Mini Tap filter, a home water treatment device which can be used at a single faucet, under constant flow was used during the second collection of treated water samples from cold water taps. Scanning electron micrograph revealed the existence of biofilms in all the sites investigated and the highest density was obtained on galvanized steel coupons. Isolates were tested against the antibiotics ampicillin (10μg), cephalothin (5μg), streptomycin (10μg), erythromycin (15μg), chloramphenicol (30μg), neomycin (30 μg), amoxycillin (10 μg), ciprofloxacin (5 μg), trimethoprim (25μg), kanamycin (30μg), and oxytetracycline (30μg). The multiple antibiotic resistance profiles and the presence of virulence related genes were determined. Various types of drug resistance and presence of virulence genes were observed. The most prevalent resistance phenotype observed was KF-AP-C-E-OT-TM-A. In conclusion, the results indicated the occurrence of faecal indicator bacteria in the drinking water destined for human consumption. Faecal indicator bacteria are the major contributors of poor drinking water quality and may harbour opportunistic pathogens. This highlighted survival of organisms to treatment procedures and the possible regrowth as biofilms in plumbing materials. The detection of large proportion of MAR Aeromonas and Pseudomonas species which possessed virulent genes was a cause of concern as these could pose health risks to humans. The data obtained herein may be useful in assessing the health risks associated with the consumption of contaminated water. / PhD (Microbiology), North-West University, Potchefstroom Campus, 2014

Increasing socio-economic growth and development of South Africa’s freshwater systems require continuous augmentation of water sources to meet the growing water requirements of communities and industries. Anthropogenic disturbances have caused the water quality of many freshwater systems to drastically deteriorate due to constant disposal of domestic, industrial, and agricultural waste into surface waters. Government agencies make use of biomonitoring programmes to effectively manage the countries’ freshwater resources. These programmes use a variety of biological indicators (e.g., macroinvertebrates, fish, diatoms and algal species) and physico-chemical variables to determine the state of the environment. However, attempts to use microbial community structures as bioindicators of anthropogenic perturbations are greatly neglected. This study used molecular techniques (PCR-DGGE and 454-pyrosequencing) and multivariate analysis to develop a robust monitoring technique to determine the impacts of environmental disturbances on bacterial community compositions in river systems in the North West Province. Significant contributions made by this project included the establishment of a bacterial diversity framework for South African freshwater systems that are impacted by a variety of anthropogenic activities (e.g., urban and informal settlements, agriculture and mining). Furthermore, case studies demonstrated the prevalence of specific taxa at polluted sites, as well as positive and negative associations between taxa and environmental variables and pollutants. Finally, biogeochemical cycles could be partially matched to bacterial community structures in river systems. The first part of the project included a pilot study that investigated bacterial structures in a segment of the Vaal River in response to environmental parameters using molecular techniques and multivariate analysis. The most important observations made during this study included the generation of a larger bacterial diversity dataset by pyrosequencing compared to PCR-DGGE. In addition, metagenomic and multivariate analyses provided clues about potential biogeochemical roles of different taxa. The second and third part of the project included two case studies that investigated bacterial communities in the Mooi River and Wonderfonteinspruit in response to environmental activities. Both these systems are impacted by a variety of external sources such as urban and informal settlements, agriculture, and mining. The results demonstrated that perturbations nearby the Mooi River and Wonderfonteinspruit caused the overall water quality to deteriorate which in turn had a profound impact on bacterial community composition. Bacterial community structures at reference/control sites (Muiskraal and Turffontein dolomitic eye) had overall high species diversity (richness and evenness), whereas polluted sites showed lower species diversity and were dominated by the Beta- and Gammaproteobacteria, Bacteroidetes, and Verrucomicrobia. In addition, various potential pathogens (e.g. Eschirichia/Shigella, Legionella, Staphylococcus, Streptococcus etc.) were identified at impacted sites. Multivariate analysis suggested that bacterial communities and certain taxa (Malikia, Algoriphagus, Rhodobacter, Brevundimonas and Sphingopyxis) at polluted sites were mainly impacted by temperature, pH, nutrient levels, and heavy metals. Finally, the proportion of nitrogen and sulphur bacteria corresponded well with the nitrogen and sulphur levels measured in the Wonderfonteinspruit. Based on these results, it was concluded that bacterial community structures might provide a good indicator of anthropogenic disturbances in freshwater systems and may be incorporated into biomonitoring programs. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The main aim of the study was to analyse the impact of physico-chemical parameters on drinking water quality, biofilm formation and antibiotic resistant bacteria in the drinking water distribution system in Mafikeng, North West Province, South Africa. Another objective was to isolate and characterise Pseudomonas and Aeromonas species from drinking water distribution system and detect the virulence gene determinants in the isolates by PCR analysis. The physico-chemical data obtained were subjected to statistical analysis using Excel 2007 (Microsoft) and SPSS (version 14.0) programmes. Pearson’s correlation product of the moment was used to determine the correlation between EC, TDS, pH and temperature. The two tailed test of significance (p<0.05) was used in order to determine the significance of the result. Antibiotic susceptibility tests were performed using Kirby-Bauer disk diffusion method. Cluster analysis based on the antibiotic inhibition zone diameter data of different organisms isolated from different sites was determined and was expressed as dendograms using Wards algorithm and Euclidean distance of Statistica version 7. Specific PCR was used to determine the identities of presumptive Pseudomonas and Aeromonas species through amplification of the gyrB, toxA and the ecfX gene fragments. Virulence gene determinants for the confirmed Pseudomonas and Aeromonas species were detected by amplifying the exoA, exoS and exoT genes and the aerA and hylH gene fragments, respectively. A Gene Genius Bio imaging system (Syngene, Synoptics; UK) was used to capture the image using GeneSnap (version 3.07.01) software (Syngene, Synoptics; UK) to determine the relative size of amplicons. Physico-chemical parameters were monitored from three drinking water sources three times a week and bacteriological quality was monitored weekly for four months from raw and treated drinking water. Water samples were analysed for pH, temperature, total dissolved solids (TDS) and electric conductivity (EC). Bacterial consortia from drinking water samples were isolated using selective media and enumerated. The results revealed a good chemical quality of water. However, the microbial quality of the water is not acceptable for human consumption due to the presence of Pseudomonas, Aeromonas, faecal coliforms (FC), total coliforms (TC) and Heterotrophic bacteria. The results showed that the drinking water is slightly alkaline with pH value ranging between7.7 to 8.32. What is of concern was the microbial quality of the water. Pseudomonas sp., faecal coliforms (FC), total coliforms (TC) and heterotrophic bacteria were present in some of the treated water samples. The most significant finding of this study is that all drinking water samples were positive for Pseudomonas sp.(>100/100ml), but also that when one considers the TDS it demonstrates that water from the Modimola Dam has an impact on the quality of the mixed water. The prevalence and antibiotic resistance profiles of planktonic and biofilm bacteria isolated from drinking water were determined. The susceptibility of these isolates was tested against 11 antibiotics of clinical interest and the multiple antibiotic resistance (MAR) patterns were compiled. The most prevalent antibiotic resistance phenotype observed was KF-AP-C-E-OT-K-TM-A. All isolates from all samples were susceptible to ciprofloxacin. However, all faecal coliforms and Pseudomonas spp. were susceptible to neomycin and streptomycin. On the contrary all organisms tested were resistant to erythromycin (100%) trimethoprim and amoxycillin. Cluster analysis based on inhibition zone diameter data could not differentiate the various isolated into sample types. The highest prevalence of antibiotic resistant isolates was observed in Modimola Dam and Molopo eye. Biofilms were investigated in both raw water and treated drinking water sources for the presence of faecal coliforms, total coliforms, Pseudomonas spp., Aeromonas spp. and heterotrophic bacteria based on conventional microbiology and molecular methods. Drinking water biofilms were grown twice and the biofilm developing device containing copper and galvanized steel coupons were utilized. The Mini Tap filter, a home water treatment device which can be used at a single faucet, under constant flow was used during the second collection of treated water samples from cold water taps. Scanning electron micrograph revealed the existence of biofilms in all the sites investigated and the highest density was obtained on galvanized steel coupons. Isolates were tested against the antibiotics ampicillin (10μg), cephalothin (5μg), streptomycin (10μg), erythromycin (15μg), chloramphenicol (30μg), neomycin (30 μg), amoxycillin (10 μg), ciprofloxacin (5 μg), trimethoprim (25μg), kanamycin (30μg), and oxytetracycline (30μg). The multiple antibiotic resistance profiles and the presence of virulence related genes were determined. Various types of drug resistance and presence of virulence genes were observed. The most prevalent resistance phenotype observed was KF-AP-C-E-OT-TM-A. In conclusion, the results indicated the occurrence of faecal indicator bacteria in the drinking water destined for human consumption. Faecal indicator bacteria are the major contributors of poor drinking water quality and may harbour opportunistic pathogens. This highlighted survival of organisms to treatment procedures and the possible regrowth as biofilms in plumbing materials. The detection of large proportion of MAR Aeromonas and Pseudomonas species which possessed virulent genes was a cause of concern as these could pose health risks to humans. The data obtained herein may be useful in assessing the health risks associated with the consumption of contaminated water. / PhD (Microbiology), North-West University, Potchefstroom Campus, 2014

Αντικείμενο της παρούσας διπλωματικής εργασίας είναι η μελέτη των περιβαλλοντικών παραμέτρων της λιμνοθάλασσας της Κλείσοβας, η οποία βρίσκεται στο ανατολικό άκρο του λιμνοθαλάσσιου συστήματος του Μεσολογγίου. Στο πρώτο στάδιο γίνεται επεξεργασία των περιβαλλοντικών δεδομένων με χρήση μεθόδων πολυδιάστατης στατιστικής ανάλυσης με σκοπό τον καθορισμό των κύριων διεργασιών που αναπτύσσονται στις υδάτινες μάζες της λιμνοθάλασσας με ιδιαίτερη έμφαση στον εντοπισμό διάφορων ρυπογόνων διεργασιών. Στο δεύτερο στάδιο γίνεται η επεξεργασία των περιβαλλοντικών δεδομένων με χρήση του αλγορίθμου CLEAN καιεφαρμόζεται πολυδιάστατη στατιστική ανάλυση στα επεξεργασμένα δεδομένα. / Subject of the current work is the study of the physico-chemical parameters of Kleisovas'lagoon which is located in SE part of Mesologgi lagoon complex. In the first part are defining the most important lagoon process with emphasis to pollution processes through the execution of multidimensional statistical methods. In the second part is implemented a spectrum analysis of the environmental data through the Clean algorithm. Through execution of multidimentional statistical methods of the cleaned data are defining, in correlation with the analysis of the raw data, the dominant lagoon processes which effect the water quality of the ecosystem.

Thesis (M. Sc. (Horticulture)) -- University of Limpopo, 2019 / The South African Avocado Industry is continuously expanding with ‘Hass’ cultivar occupying the largest land and therefore, the most exported cultivar. Expansion of the industry implies an increased demand for irrigation water. However, South Africa is a water scarce country characterised by low and erratic rainfall, where fruit production relies heavily on irrigation. The agricultural sector is under an obligation to reduce water use due to the increasing demand for water by other economic sectors. Therefore, it must find efficient water use techniques to save water and ensure water availability for other economic sectors. Partial root-zone drying (PRD) is an irrigation technique which may lead to 50% reduction in water use, half of the root system is kept wet while the other half is left dry to a predetermined level of soil water depletion, the dry and the moist sides are alternated at regular intervals. During storage and transportation of fresh produce, low temperature is a post-harvest tool used to maintain quality, especially when fruit are destined for long distant export markets. This study investigated the effect of PRD and low temperature storage on post-harvest quality parameters of ‘Hass’ avocado fruit. The experiment was laid as a factorial arranged in randomised complete block design (RCBD). The treatment factors for chilling injury, electrolyte leakage and vascular browning were 2 x irrigation regimes (Full Irrigation (FI) vs. PRD) and 2 x storage temperatures (2.0 and 5.5°C). However, treatment factors for fruit weight loss, respiration rate, fruit firmness, ripening percentage and fruit skin colour were 2 x irrigation regimes (Full Irrigation (FI) vs. PRD), 2 x storage temperatures (2.0 and 5.5°C) and 4 ripening days (0, 2, 4 and 6 days). Mature ‘Hass’ avocado fruit were harvested from PRD and fully irrigated trees and thereafter fruit of each treatment were stored at 2.0 and 5.5°C for 28 days. Each treatment consisted of 6 replicates, with an exception of electrolyte leakage, whereby the experiment was replicated 4 times. After 28 days’ storage at 2.0 and 5.5°C, fruit were ripened at 21°C. The effect of PRD and low temperature storage was determined by evaluating the following physico-chemical fruit parameters during ripening: external chilling injury, electrolyte leakage, fruit weight loss, respiration rate, firmness, fruit skin colour and vascular browning. During ripening, ‘Hass’ avocado fruit stored at 2.0°C showed significantly higher incidences of external chilling injury symptoms compared with xiii 5.5°C, irrespective of irrigation treatment. Furthermore, an interaction between irrigation treatment and low storage temperature had a significant (P<0.05) effect on cell membrane electrolyte leakage. All evaluated fruit showed similar weight loss, irrespective of irrigation and storage treatment. Irrigation, storage temperature and ripening days did not have effect on respiration during ripening. Fruit reached the respiratory climacteric peak on the same day (day 2). Furthermore, there was no significant interaction effect (P˃0.05) on fruit firmness. However, PRD treated fruit showed slightly low firmness when compared with control fruit. ‘Hass’ avocado fruit harvested from PRD and fully irrigated trees and stored at 5.5°C ripened quicker compared to fruit stored at 2.0°C. There was no significant interaction effect (P˃0.05) on fruit skin lightness (L), chroma (C), hue angle (h°) and fruit eye colour due to irrigation and cold storage treatment. In general, fruit showed skin colour change from emerald green to approximately 75% coloured. Furthermore, irrigation and storage temperature did not have effect on vascular browning, however, there incidence was high on fruit stored at 2.0°C when compared with 5.5°C. The results of this study indicated that ‘Hass’ avocado fruit stored at 2.0°C was negatively affected by low temperature storage and this cold storage temperature is not recommended. PRD reduced water use during irrigation, however, its effect on post-harvest quality of ‘Hass’ avocado fruit subjected to 5.5°C must be further investigated before recommended for export markets. / Agricultural Research Council-Tropical and Subtropical Crops (ARC-TSC) and Agricultural Sector Education Training Authority (AgriSeta)

Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2020 / The South African Agricultural Sector has a mandate to reduce water use so that water can be available for other economic sectors. Thus, various water saving techniques must be continuously investigated in agricultural production to find efficient water use technique that saves water without compromising fresh fruit quality. Therefore, combined effect of irrigation method, 1-methylcyclopropene (1-MCP) and cold storage temperature on postharvest quality of ‘Hass’ avocado fruit was evaluated. Postharvest attributes of fruit colour, flesh firmness, ripening percentage, respiration, weight loss, body rot, stem end-rot, vascular browning, chilling injury and electrolyte leakage were assessed for 2 x irrigation methods [Full irrigation (FI) and Partial root-zone drying (PRD)], 2 x 1-methylcyclopropene (300 ng/L 1-MCP and untreated) and 2 x storage temperature (2.0 and 5.5°C) treatments. An interaction between the three treatments did not significantly (P > 0.05) influence fruit colour, flesh firmness, ripening percentage, fruit weight loss, body rot, stem end-rot, vascular browning, chilling injury and electrolyte leakage. Their combined effect was only significant (P = 0.019) on ‘Hass’ fruit respiration rate. The combination of full and PRD irrigation, 1-MCP and low storage temperature (2.0°C) did not negatively affect fruit quality. However, fruit stored at 2.0°C without 1-MCP treatment were affected by chilling injury when compared with fruit stored at 5.5°C. In conclusion, due to the inconclusiveness of results obtained, further studies, on the effect of these treatments especially under 5.5°C storage temperature should be carried out prior recommending the combination treatment for export markets. / Agricultural Research Council-Tropical and Subtropical Crops (ARC-TSC) and Agricultural Sector Education Training Authority (AgriSeta)

No description available.