The aim of this study was to determine the effects of antioxidant treatments, plant growth regulators (PGRs) and explants wounding in tissue culture involving Strelitzia reginae on total phenol exudation. Results showed that various 1-naphthalene acetic acid (NAA) and 6-benzylaminopurine (BAP) concentrations significantly affected phenolic exudation. The media containing the highest plant growth regulators concentration (that is, 0.5 mg L⁻¹ NAA and 6 mg L⁻¹ BAP) resulted in the highest phenol content. Whereas, the control (the treatment free of plant growth regulators), contained the lowest phenol content. Activated charcoal (AC) was found to significantly reduce the total phenol content of media by 53%, compared with ascorbic acid (AA). Furthermore, the wounding of explants significantly increased phenolic exudation. Interactions between the higher 1-naphthalene acetic acid and 6-benzylaminopurine concentrations and ascorbic acid significantly increased the total phenol content of media. A similar result was achieved in interactions between higher plant growth regulators concentrations and the wounding of explants. Interactions between antioxidants, wounding treatments and plant growth regulators concentrations resulted in activated charcoal significantly reducing the total phenol content in all plant growth regulators concentrations in both wounded and unwounded explants.

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The external and internal quality of citrus fruit determines consumer acceptance, thereby driving the consumption and demand for fresh fruit. Emphasis is placed on producing a high volume of fruit of good quality, and it is known that light intensity is especially important in influencing sugar content, rind color, and blemish incidence. Extreme environmental conditions are challenging controllable factors. Therefore shade netting is used especially on fruit crops for protection against dramatic climatic events that affect the appearance of the fruit, i.e., excess sunlight, wind, and hail. The study was conducted on 'Nadorcott' mandarin trees planted in 2012 in a commercial orchard in Citrusdal, Western Cape province, South Africa. The aim of this study was to determine the influence of 20% white shade nets on the quality of 'Nadorcott' mandarin fruit. Monthly evaluation of fruit size, rind color, internal quality parameters (°Brix/citric acid ratio) and the incidence of sunburn was performed. The fruit diameter was not influenced by shade net in 2016; however, in 2017 a larger fruit diameter was measured for shade net fruit. Rind color development and internal quality were not influenced negatively by the treatment. Shade net was effective, reducing the incidence of sunburn significantly in both seasons, 2016 and 2017. Moreover, postharvest fruit quality was not negatively affected by the shade net treatments. In summary, our results indicate that shade-netting is a potential preventative technology ensuring unblemished and high quality in 'Nadorcott' mandarins, but further studies are required to evaluate the influence of tree age and microclimatic effect on fruit production and postharvest storage behavior in other citrus cultivars.

Currently, there are differences in the quality loss between individual fruit upon arrival at retail. These differences in fruit quality stem from pre-harvest biological variability between individual fruit at harvest and postharvest variations in hygrothermal conditions between refrigerated shipments. The impact of these pre-harvest biological and postharvest variability on the final quality of each fruit that reaches the consumers remains largely uncharted. In this study, we addressed this knowledge gap by developing physics-based digital twins of orange fruit to unveil how pre-harvest and postharvest variability affect the final fruit quality upon arrival at retail. Markov chain Monte Carlo method was used to generate a realistic 'virtual' population of 1000 individual orange fruits at harvest. Afterwards, the impact of pre-harvest biological variability and variations in hygrothermal conditions between shipments on several orange quality metrics, including mass loss, fruit quality index (FQI), remaining shelf life (RSL), chilling injury severity (CI), total soluble solids (TSS), color, and Mediterranean fruit fly (MFF) mortality was quantified. Results showed that pre-harvest biological variability causes variations in mass loss of oranges at retail by up to 1.2%, FQI by up to 5% and RSL by more than 2 days. The postharvest variability between shipments causes high variations in mass loss of oranges at retail by up to 4%, FQI by more than 20%, RSL up to 3 days, and CI up to 5%. The study also revealed that compared to pre-harvest biological variability, postharvest variability between shipments could increase the variations in RSL of oranges at retail by 75%, FQI by 50%, and mass loss by ~10%. This work helps improve our understanding of the variability in the end fruit quality upon arrival at retail.