Browsing by Author "Mditshwa, Asanda"
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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 Influence of animal manure extracts on physico-chemical and nutritional quality of tomatoes grown in soilless cultivation(MDPI, 2024-12-01) Luthuli, Ayanda; Magwaza, Lembe; Tesfay, Samson; Magwaza, Shirly; Mditshwa, AsandaIn response to environmental challenges facing the agricultural sector, growers are moving toward innovative and sustainable cultivation methods such as the hydroponic production system. This study evaluated the effect of different sources of manure on the physico-chemical and nutritional qualities of tomatoes (cv. CLX 532) grown under a hydroponic system. The experiment was set up in a completely randomized design with four treatments, which included three types of animal manure-derived hydroponic nutrient extracts, namely, chicken (CHME), cow (CME) and goat (GME), and a commercial fertilizer as a control. Tomato fruit from each treatment were harvested and analysed for macro- and micronutrients, physicochemical attributes such as total soluble solids (TSS), titratable acidity (TA), total soluble solid to titratable acidity ratio (TSS/TA), BrimA, colour index and firmness. The total phenolics and ascorbic acid content were also assessed. The results showed significant differences in physico-chemical and nutritional quality among different treatments. TSS was higher in CHME (6.47 °Brix) compared to other treatments. The TA was higher in both commercial fertilizer and CHME (0.62% and 0.61%) than in GME and CME (0.44% and 0.39%). Both TSS/TA and BrimA were lower in commercial fertilizer and than in animal manure extracts (AME). CHME had a higher colour index (30.32) while GME had higher firmness (316.9 N) than other treatments. The phenolic content was notably higher in GME compared to the commercial fertilizer and AME. Fruit fertigated with commercial fertilizer had more macronutrient content while fruit fertigated with animal manure-based nutrient solutions had high micronutrients. Based on these findings, animal manure extracts, specifically CHME and GME, can be used as a nutrient source in the production of tomatoes as it produces good fruit quality which is comparable to commercial fertilizers.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 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.