Browsing by Author "Magwaza, Lembe Samukelo"
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Item Open Access Accelerating abscission of macadamia nuts using ethephon: are there implications for nut quality?(Taylor and Francis, 2024) Aruwajoye, Noluthando Noxolo; Olarewaju, Olaoluwa Omoniyi; Oluwalana-Sanusi, Abimbola E.; Mditshwa, Asanda; Magwaza, Lembe Samukelo; Tesfay, Samson ZerayMacadamia is a valuable nut due to its high content of healthy monounsaturated fats, dietary fibre, antioxidants, and essential minerals such as magnesium-B and potassium. One of the major issues affecting industries around the globe is the delayed nut abscission and a prolonged and expensive harvest. A delay in harvesting also reduces the quality of the kernel. To address this challenge, ethephon is used to accelerate abscission, helping to prevent delays in harvesting. Ethephon can cause up to a 15-fold increase in nut abscission within 4 weeks compared to untreated trees. We provide a brief overview of the use of ethephon and its effects on nut quality. The major side-effects of ethephon used to manage macadamia harvesting are associated with ethylene, which is released from ethephon during the acceleration of plant senescence. This process impacts nut quality and shelf life by modulating lipid composition and nut biochemistry. Additionally, ethephon influences the appearance of the nut and the expression and regulation of specific plant genes. This review bridges the information gap between the application of ethephon for harvesting and its effects on the nut quality.Item Open Access Advancing fruit preservation: ecofriendly treatments for controlling fruit softening(MDPI, 2024-08-26) Mthembu, Sisanda Sibusiso; Magwaza, Lembe Samukelo; Tesfay, Samson Zeray; Mditshwa, AsandaTextural softening is a major factor that limits the storage potential of fruit. Fresh produce markets incur severe financial losses due to excessive fruit softening. The application of preservation strategies aimed at mitigating fruit softening is crucial for optimising the marketability of fruit. Proposed preservation strategies include ecofriendly treatments, namely, hexanal, edible coatings, heat treatments, ozone and UV-C irradiation. These treatments optimise firmness retention by targeting the factors that affect fruit softening, such as ethylene, respiration rates, enzymes and pathogens. This review discusses the mechanisms by which ecofriendly treatments inhibit fruit softening, providing insights into their effect on ethylene biosynthesis, cell wall metabolism and disease resistance. Although ecofriendly treatments offer a promising and sustainable approach for delaying fruit softening, the optimisation of treatment application protocols is needed to improve their efficacy in retaining fruit firmness. Studies reporting on the molecular mechanisms by which ecofriendly treatments inhibit fruit softening are limited. Future studies should prioritise proteomic and transcriptome analyses to advance our understanding of the underlying molecular mechanisms by which ecofriendly treatments delay the fruit-softening process.Item Open Access Characterization of cannabis varieties and the intrinsic and extrinsic factors affecting cannabis germination and seedling establishment: a descriptive review(Elsevier, 2023-12-02) Langa, Sabeliwe; Magwaza, Lembe Samukelo; Mditshwa, Asanda; Tesfay, Samson ZerayCannabis sativa L. is the utmost consumed, grown, and produced illicit drug worldwide. The psychotropic activity of the component (-)-trans-∆9-tetrahydrocannabinol (∆9-THC), however, led to the banning of cannabis worldwide for many centuries. Besides being the most popular crop for recreational purposes, cannabis is grown globally as a multifunctional agricultural crop for its oily seeds and long, durable fibers. These properties have led to cannabis application in various industries, including agriculture, textile, bio-composite, papermaking, automotive, construction, and biofuel. Furthermore, medicinal cannabis constitutes of high concentration of cannabinoids, which have been discovered relevant in the pharmaceutical industry. As a result, various countries worldwide have relaxed regulations on cannabis. However, the cannabis products’ final use depends on the cultivar. Yet, the crop has hundreds of cultivars owing to constant breeding and human selection, which has altered the original plant with the spread of the crop worldwide. Generally, these cultivars possess chemical composition that varies genetically, and with the growing environmental conditions. Therefore, the current descriptive review of literature highlights the techniques available for classifying cannabis varieties, given the ongoing debate over classifying cultivars into distinct taxonomic groups. The effect of intrinsic and extrinsic factors on cannabis germination and seedling establishment are also highlighted.Item Open Access Effect of preharvest ethephon application on selected biochemical components and polyphenol oxidase activity in macadamia nuts(MDPI, 2023-10-04) Aruwajoye, Noluthando Noxolo; Mditshwa, Asanda; Magwaza, Lembe Samukelo; Ngidi, Mjabuliseni Simon C.; Tesfay, Samson ZerayEthephon is a plant growth regulator that triggers diverse responses in plants, such as fruit ripening, leaf senescence, hull senescence, stem elongation, and nut abscission. This study examined how the preharvest application of ethephon 480 SL® affects selected biochemical components and polyphenol oxidase (PPO) activity in two macadamia nut cultivars: ‘788’ and ‘Beaumont’. Ethephon was applied to the trees via a Cima mist blower at rates of 13.33 mL/L per hectare for the ‘788’ cultivar and 16.67 mL/L per hectare for the ‘Beaumont’. Following harvest, the nuts were stored at 25 °C for 72 days, and samples were taken at 18-day intervals. Standard procedures were used to assess the following: total phenolics, total flavonoids, 2,2,-diphenyl-1-picrylhydrazyl (DPPH) assay, Ferric reducing ability power (FRAP) assay, sucrose, total protein, and PPO activities. This evaluation was carried out across a total of four treatments: ethephon-treated nuts from the orchard floor (ED), ethephon-treated nuts from the tree (ET), untreated nuts from the orchard floor (CD), and untreated nuts from the tree (CT). The evaluation’s outcomes were analyzed using a principal component analysis (PCA), a correlation matrix heat map (CMHM), and a graphical assessment. The results unveiled significant correlations and associations among the assessed parameters. The correlation matrix heat map analysis highlighted a strong positive correlation (0.97) between the sucrose and the PPO activity in the ‘Beaumont’ cultivar, supported by the PCA analysis identifying the ED treatment as the most influential. At the storage period’s conclusion, the ED treatment had the highest sucrose content (18.63 mg/g) and polyphenol oxidase activity (1.06 U g−1). In the ‘788’ cultivar, a close relationship emerged between the phenolic content, the PPO activity, and the Ferric reducing antioxidant power (FRAP)’s antioxidant activity. Consistently, the CT treatment (untreated nuts) demonstrated positive correlations with several key parameters in both cultivars, displaying heightened phenolic content and antioxidant activities. Consequently, our findings indicate that the CT treatment, involving tree-harvested nuts without ethephon application, could be the preferred option for sustaining macadamia nuts’ quality and shelf life compared to other methods. Moreover, our study underscores the significance of proper storage conditions for maintaining the desired biochemical parameters of macadamia nuts. By comprehending the effects of distinct treatments and harvesting techniques, producers and processors can devise strategies to optimize storage conditions and uphold macadamia nut quality.Item Open Access Hexanal-containing dip treatment enhances kiwifruit resistance to Botrytis cinerea(Elsevier, 2025-01) Mthembu, Sisanda Sibusiso; Tesfay, Samson Zeray; Mditshwa, Asanda; Magwaza, Lembe SamukeloThis study evaluated the effectiveness of a hexanal-based enhanced freshness formulation (EFF), containing antioxidants such as geraniol, α-tocopherol and ascorbic acid, to inhibit the fungal decay caused by Botrytis cinerea in ‘Y368’ kiwifruit. In vitro and in vivo experiments using three treatments: control (untreated), 0.03 and 0.06 % (v/v) EFF were set up. In the in vitro experiment, mycelial growth and spore germination of Botrytis cinerea exposed to EFF were examined. In the in vivo experiment, disease incidence, lesion diameter, activity of defense-related enzymes (Phenylalanine Ammonia Lyase, Guaiacol Peroxidase, β-1,3-glucanase and Chitinase), total phenolics and flavonoids were evaluated. The results demonstrated that 0.03 and 0.06 % EFF treatments reduced mycelial growth of Botrytis cinerea by 41 and 89 %, respectively. The lesion diameter of the 0.03 and 0.06 % EFF-treated fruit was 28 and 76 % smaller than the control. Furthermore, EFF-treated fruit exhibited significantly higher activities of defense-related enzymes compared to the control, with total phenolic content increasing by 1.2 and 1.3-fold for the 0.03 and 0.06 % treatments, respectively. These findings provide compelling evidence regarding the efficacy of EFF in suppressing Botrytis cinerea and highlight the role of defense-related enzymes in enhancing the fruit's resistance to decay. Overall, the study underscores the potential of EFF as a valuable and practical method for controlling fungal decay in kiwifruit during postharvest storage.Item Open Access Investigating the influence of varying water regimes on the growth and development and nutritional water productivity of bush tea (Athrixia phylicoides DC.)(Wiley, 2024-07-29) Rumani, Muneiwa; Mabhaudhi, Tafadzwanashe; Mandizvo, Takudzwa; Ramabulana, Anza‐Tshilidzi; Madala, Ntakadzeni Edwin; Ramphinwa, Maanea Lonia; Magwaza, Lembe Samukelo; Mudau, Fhatuwani NixwellBush tea (Athrixia phylicoides DC.) is an indigenous shrub of South Africa known for its medicinal properties. However, due to a lack of comprehensive information to develop suitable irrigation management strategies, the cultivation of bush tea is currently limited to small‐scale operations. Considering this limitation, the current research investigated the effect of water regimes on the growth and development, yield, and nutrient content along with its nutritional water productivity (NWP) under field conditions. The treatment consisted of a crop water requirement (ETa) of 100%, 30%, and the control (stress) in a complete randomized block design (CRBD). Each treatment was replicated three times to ensure robustness and accuracy of the findings. Results demonstrated that the highest gravimetric moisture content readings were found in the control treatment and the lowest in the 100% treatment. Conversely, the 30% ETa treatment significantly (p < 0.05) impacted bush tea's growth, development, productivity, and NWP. However, it was observed that the 100% ETa treatment resulted in a higher biomass yield (259.1 kg/ha) compared to the 30% ETa treatment (171.2 kg/ha) and control (stress) (68.2 kg/ha). The water productivity exhibited notable differences across the varying water regimes. These findings contribute valuable insights for developing appropriate irrigation management strategies to overcome existing limitations in the scale of bush tea production. The research lays the groundwork for future studies and practical applications aimed to foster the sustainable cultivation of bush tea in South Africa.Item Open Access Investigating the involvement of ABA, ABA catabolites and cytokinins in the susceptibility of ‘Nules Clementine’ mandarin to rind breakdown disorder(Wiley, 2019-02-14) Magwaza, Lembe Samukelo; Alamar, M. Carmen; Tesfay, Samson Zeray; Mditshwa, Asandas; Opara, Umezuruike Linus; Terry, Leon A.Abstract BACKGROUND Nules Clementine’ mandarin was used to investigate the potential involvement of endogenous plant hormones in mediating the citrus fruit susceptibility to rind breakdown disorder (RBD). The effect of light exposure (viz. canopy position and bagging treatments) on the endogenous concentration of ABA, 7’hydroxy‐abscisic acid (7‐OH‐ABA), ABA‐glucose ester (ABA‐GE) and dihydrophaseic acid (DPA), and t‐zeatin was tested using four preharvest treatments: outside, outside bagged, inside and inside bagged. Phytohormones concentration was evaluated during 9 weeks of postharvest storage at 8 °C. RESULTS The shaded fruit inside the canopy had the highest RBD score (0.88) at the end of postharvest storage, while sun‐exposed fruit had the lowest score (0.12). Before storage, ABA concentration was lowest (462.8 μg kg‐1) for inside fruit, and highest in outside bagged fruit (680.5 μg kg‐1). Although ABA concentration suddenly increased from the third week, reaching a maximum concentration of 580 μg kg‐1 at week 6 in fruit from inside position, it generally reduced 1.6‐fold ranging from 240.52 to 480.65 μg kg‐1 throughout storage. The increase of 7‐OH‐ABA was more prominent in fruit from inside canopy. Overall, the concentration of ABA‐GE increased 3‐fold with storage time. DPA concentration of bagged fruit from inside canopy position was significantly higher compared to outside fruit. The lower ABA‐GE and higher DPA concentration in inside bagged fruit throughout storage also coincided with higher RBD. CONCLUSION The strong positive correlations between 7‐OH‐ABA, DPA and RBD incidence demonstrated that these ABA catabolites could be used as biomarkers for fruit susceptibility to the disorder.Item Open Access Mechanism of enhanced freshness formulation in optimizing antioxidant retention of gold kiwifruit (Actinidia chinensis) harvested at two maturity stages(Frontiers, 2023-12-21) Mthembu, Sisanda S. L.; Magwaza, Lembe Samukelo; Tesfay, Samson Zeray; Mditshwa, AsandaKiwifruit exhibits a climacteric ripening pattern and has as an extremely perishable nature. Considering that high perishability leads to a loss in antioxidants and overall nutritional quality. This study aimed to examine the efficacy of enhanced freshness formulation (EFF), a hexanal-based formulation containing antioxidants such as geraniol, α-tocopherol and ascorbic acid, on maintaining the bioactive compounds of gold kiwifruit (cv. ‘Y368’) harvested at two maturity stages. Kiwifruits were treated with three treatments, namely, control (untreated fruit), 0.01 and 0.02% (v/v) EFF. Fruits were treated with 8 weeks of cold storage at 0°C and 90% relative humidity, then transferred to 20°C for 8 days. Three bioactive compounds (ascorbic acid, total phenolics and flavonoids), antioxidant capacities using DPPH and FRAP assays, polyphenol oxidase, ascorbate oxidase, phenylalanine and tyrosine ammonia lyase enzyme activities were evaluated. The results showed that EFF significantly (p < 0.05) influenced bioactive compounds, antioxidant capacities and the activity of enzymes involved in the synthesis and oxidation of bioactive compounds. The maturity stage significantly influenced the content of bioactive compounds. Later harvested kiwifruit had greater content of bioactive compounds, compared to earlier harvested kiwifruit. The total phenolic content was 0.77, 1.09 and 1.22 mg GAE g−1 FW for control, 0.01 and 0.02% EFF, respectively. The FRAP antioxidant concentration was 0.76, 0.91 and 0.96 μmol Fe (II) g−1 FW for control, 0.01 and 0.02% EFF. The findings illustrate the capacity of EFF to optimize bioactive compounds and storability of kiwifruit during postharvest storage.Item Open Access Prediction of ‘Nules Clementine’ mandarin susceptibility to rind breakdown disorder using Vis/NIR spectroscopy(Elsevier, 2012-07-15) Magwaza, Lembe Samukelo; Opara, Umezuruike Linus; Terry, Leon A.; Landahl, Sandra; Cronje, Paul J.; Nieuwoudt, Helene; Mouazen, Abdul Mounem; Saeys, Wouter; Nicolai, Bart M.The use of diffuse reflectance visible and near infrared (Vis/NIR) spectroscopy was explored as a non-destructive technique to predict ‘Nules Clementine’ mandarin fruit susceptibility to rind breakdown (RBD) disorder by detecting rind physico-chemical properties of 80 intact fruit harvested from different canopy positions. Vis/NIR spectra were obtained using a LabSpec® spectrophotometer. Reference physico-chemical data of the fruit were obtained after 8 weeks of storage at 8 °C using conventional methods and included RBD, hue angle, colour index, mass loss, rind dry matter, as well as carbohydrates (sucrose, glucose, fructose, total carbohydrates), and total phenolic acid concentrations. Principal component analysis (PCA) was applied to analyse spectral data to identify clusters in the PCA score plots and outliers. Partial least squares (PLS) regression was applied to spectral data after PCA to develop prediction models for each quality attribute. The spectra were subjected to a test set validation by dividing the data into calibration (n = 48) and test validation (n = 32) sets. An extra set of 40 fruit harvested from a different part of the orchard was used for external validation. PLS-discriminant analysis (PLS-DA) models were developed to sort fruit based on canopy position and RBD susceptibility. Fruit position within the canopy had a significant influence on rind biochemical properties. Outside fruit had higher rind carbohydrates, phenolic acids and dry matter content and lower RBD index than inside fruit. The data distribution in the PCA and PLS-DA models displayed four clusters that could easily be identified. These clusters allowed distinction between fruit from different preharvest treatments. NIR calibration and validation results demonstrated that colour index, dry matter, total carbohydrates and mass loss were predicted with significant accuracy, with residual predictive deviation (RPD) for prediction of 3.83, 3.58, 3.15 and 2.61, respectively. The good correlation between spectral information and carbohydrate content demonstrated the potential of Vis/NIR as a non-destructive tool to predict fruit susceptibility to RBD.Item Open Access Response to various water regimes of the physiological aspects, nutritional water productivity, and phytochemical composition of bush tea (Athrixia phylicoides DC.) grown under a protected environment(MDPI, 2024-06-04) Rumani, Muneiwa; Mabhaudhi, Tafadzwanashe; Ramphinwa, Maanea Lonia; Ramabulana, Anza-Tshilidzi; Madala, Ntakadzeni Edwin; Magwaza, Lembe Samukelo; Mudau, Fhatuwani NixwellThe influence of water regimes on plants is crucial for integrating bush tea (Athrixia phylicoides DC.) into strategies in Sub-Saharan Africa to tackle food and nutritional insecurity by considering physiological aspects, nutritional yield, nutritional water productivity, and metabolite composition. The objective of the study was to determine the physiological aspects, including leaf gas exchange and chlorophyll fluorescence, nutritional yield, nutritional water productivity, and metabolite composition of bush tea under varying water regimes. The tunnel experiment was laid out in a randomized complete block design (RCBD) with treatments consisting of three water regimes: 100% of crop water requirement (ETa), 30% of ETa, and a control (no irrigation), all replicated three times. The morphological aspects were recorded on a weekly basis. However, yield, nutrient content, nutritional water productivity (NWP), and phytochemical composition were determined at harvest. The phytochemical analysis by liquid chromatography mass spectrometry (LC-MS), coupled with visualization of the detected chemical spaces through molecular networking, indicated Athrixia phylicoides DC. to be rich in various bioactive compound derivatives, including methyl chlorogenate, flavonoids, tartaric acid, caffeoylquinic acid, and glutinane. The results showed that 30% ETa enhanced plant growth, nutrient content, and nutritional water productivity compared to other water treatments. Nevertheless, 100% ETa yielded more (95.62 kg ha−1) than 30% ETa (60.61 kg ha−1) and control (12.12 kg ha−1). The accumulation of chlorogenic acids was higher under 30% ETa compared to 100% ETa and control. Therefore, this study is the first to determine the accumulation of various bioactive compounds in bush tea leaf extracts under varying water regimes. This confirms that in areas with low water availability, bush tea is well adapted for production without limiting nutrients.Item Open Access Seed dormancy and germination responses of cannabis landraces to various pre-treatments(Elsevier, 2023-12-22) Langa, Sabeliwe; Magwaza, Lembe Samukelo; Mditshwa, Asanda; Tesfay, Samson ZerayThe current study evaluated the effectiveness of different pre-treatments for dormancy breaking and seed germination of five cannabis landraces. These landraces were collected from local growers in three regions of KwaZulu-Natal Province in South Africa, namely, Bergville (B), Hammersdale (H), and Ladysmith (L). Each genotype was assigned an alphabet and number based on where the seed material was collected. The five landraces were as follows, ‘B1’, ‘K1’, ‘H1’, ‘L1’, and ‘L2’. The study was conducted using various pre-treatments, including potassium nitrate (KNO3), hydrochloric acid (HCL), hot water (HW) at 70 °C, nitric acid (HNO3), dry prechilling at 10 °C, gibberellic acid (GA3), sulfuric acid (H2SO4), and water, which served as the control. Before the germination test, the seed viability of cannabis landraces was assessed using the tetrazolium chloride (TCC) test. Afterward, the seeds were germinated in Petri dishes with cotton pads moistened with distilled water for five (5) days. The study was later validated under tunnel conditions. The parameters such as germination percentage, germination rate, seedling length, and seed vigour index of the germinated seeds were then measured. The landraces, dormancy breaking treatments, and their interactions showed significant differences (p < 0.001) in germination percentage, germination rate index, seedling length, and seed vigour index under both laboratory and tunnel conditions. In summary, GA3, KNO3 and prechilling were the most effective pre-treatments to improve the germination and seedling growth of cannabis genotypes and breaking seed dormancy. Therefore, it was concluded that cannabis genotypes had physiological dormancy.Item Open Access Temperature effects on seed germination and seedling biochemical profile of cannabis landraces(MDPI, 2024-12-01) Langa, Sabeliwe; Magwaza, Lembe Samukelo; Mditshwa, Asanda; Tesfay, Samson ZerayThis study investigated the effect of temperature on the germination and seedling biochemical profiles of eight cannabis landraces, namely Ladysmith Ugwayi wesiZulu (L1) and Iswazi (L2), Durban Poison (H1), Bergville Ugwayi wesiZulu (B1), Natal (B2), and Iswazi (B3), and Msinga Ugwayi wesiZulu (M1) and Iswazi (M2). Seed viability, germination rate, and germination percentage were evaluated along with seedling amino acids, carbohydrates, and fatty acids methyl esters (FAMEs) under day/night temperature regimes of 20/15 °C, 30/25 °C, and 40/35 °C. Results showed a significant effect (p < 0.001) of temperature on germination percentage, rate, and biochemical profiles of cannabis landraces. Landraces L1, B1, H1, B2, and M1 had higher germination at 20/15 °C, while B3, M2, and L2 performed better at 30/25 °C. Biochemical profiles varied with temperature and landraces. Amino acid content increased with temperature but did not correlate with germination indexes. Carbohydrates and FAMEs decreased with rising temperature, peaking at 30/25 °C. FAMEs strongly correlated with germination indexes, linking lipid composition to seed performance. Sorbitol positively correlated with germination, while glucose and fructose showed indirect correlations. This study underscores the impact of temperature on germination and the biochemical profiles of cannabis landraces, highlighting the importance of considering genotype-specific responses in varietal selection.Item Open Access Unveiling biomarkers for postharvest resilience: the role of canopy position on quality and abscisic acid dynamics of ‘Nadorcott’ clementine mandarins(Frontiers, 2024-03-13) Navarro-Calderon, Angela; Magwaza, Lembe Samukelo; Terry, Leon A.; Alamar, M. CarmenClementine mandarins are categorised as non-climacteric fruit because they do not exhibit an increase in respiration rate and ethylene production during ripening. Recent studies have suggested that abscisic acid (ABA), a distinct ripening hormone, plays a pivotal role in the postharvest behaviour of this fruit. The present study aimed to identify biomarkers for enhancing the postharvest durability and flavour retention of imported ‘Nadorcott’ clementines (Citrus reticulata Blanco). To achieve this goal, an experiment was designed to investigate pre- and post-harvest factors influencing quality of clementine fruit, encompassing both physiological and biochemical aspects. Furthermore, the study investigated the role of ABA and ABA catabolites in the fruit senescence process.