Bonga Lewis Ngcobo

Berries are highly diverse, comprising a wide range of colors, including red, purple, and blue. Among berry fruits, strawberries, blueberries, cranberries, raspberries, and currants are the world’s most economically important temperate berries. The increasing popularity of these berries is linked to their attractive color, special taste, and nutritional and health benefits. In addition to color-imparting anthocyanins, berries can contain numerous other health-promoting metabolites, including vitamins C and E, ellagitannins, phenolics, sugars, and β‑carotene. All these compounds exhibit antioxidant properties, reducing the risk of chronic diseases. Berry quality, however, is influenced by preharvest factors, including those of genetic and environmental origins and cultural practices. The present analysis, therefore, aimed to comprehensively review the available literature on the influence of preharvest factors on the yield and the sensory, and nutritional attributes of temperate berries. Although individual preharvest factors influence berry quality, the genotype × environment × management (G × E × M) interaction remains the primary driver. The expression and activity of genes involved in key physiological processes, including carbohydrate partitioning, cell wall strengthening, color development, flavonoid biosynthesis (via MYB-bHLH-WD40 transcription complexes), and sugar metabolism, are modulated by prevailing environmental conditions and management practices. This review reveals that yield and sensory and nutritional quality parameters are influenced by the interaction effects of cultivar genotype, site-specific pedo-climatic conditions, and cultural practices. The selection of cultivars with superior genotypes and enhanced adaptation to site-specific environmental conditions, as well as the implementation of mechanism-based management strategies, is essential for achieving consistent, high-quality temperate berries.

Utilisation of biostimulants in agriculture has been prominent in recent years, as these compounds can be employed to counteract several challenges faced by horticultural crops. Biostimulants are convenient in a sense that to obtain optimal results they can be applied to both, crop’s phyllosphere and rhizosphere. They can improve yields, as well as tolerance of crops to abiotic stress. In economically important solanaceous crops (i.e., tomato, potato, eggplant, peppers and tobacco), biostimulants are used to enhance crop performance. Biostimulants are classified into several categories, including seaweed extracts (SWEs), humic substances, micro‐organisms, hydrolysed protein‐ and amino‐acid‐containing products. They are, therefore, not fertilisers per se, they are products that improve water and nutrient acquisition from the soil. Furthermore, biostimulants can be used in several forms, for example, as powders, pellets and liquid extracts. These substances can assist crops to cope and remain resilient even under abiotic stress, thereby improving crops yield and quality under adverse conditions. The latter includes cold, heat, nutrients deficiency, salinity and hail stress which are amongst prominent abiotic stresses in horticultural crops in South Africa. Biostimulants can be used to counteract negative effect caused by the aforementioned abiotic stresses under mild conditions by improving crop tolerance, from seed germination stage up to post‐harvest final product. In this review, the aforementioned abiotic stresses will be discussed in relation to the negative effects they cause on economic solanaceous crops, particularly potato and eggplant. Recommendations and suggestions will be made on how to mitigate these stresses using biostimulants to counteract losses.

Potato is an economically important non-grain, semi-perishable agricultural commodity. However, potato tubers become highly prone to moisture loss and quality deterioration after harvest, contributing to post-harvest losses. The present study, therefore, investigated the efficacy of various plant extracts on the retention of post-harvest quality of potato tubers. Freshly harvested ‘Sifra’ potato tubers were dipped into plant extracts (10 g/L level) and allowed to air-dry for 1 h on the benchtops before storage at ambient conditions (day: 22 ± 2 ℃ and 45 ± 5% RH). The treatments were as follows: Ascophyllum nodosum extract (ANE), aloe vera leaf extract (AVE), garlic bulb extract (GBE) and moringa leaf extract (MLE), as well as the control (water only). Plant extract applications, as post-harvest treatments, significantly ( p ≤ 0.05) influenced post-harvest quality of potato tubers. During storage, AVE application reduced physiological mass loss during storage by 60% compared with the control. Moreover, ANE and MLE treatment application considerably increased potato mineral concentrations and the presence of total soluble solids. These treatments also gave the most promising results as they showed the highest retention potential of tuber vitamin C, total carbohydrate, protein, phenolic and flavonoid concentrations, as well as antioxidant activity during storage. Based on these results, the use of natural plant extract, as an alternative to current chemical applications, is highly advisable and recommended to preserve post-harvest quality of potato tubers, without compromising consumers’ health.

The production of fruits and vegetables has increased globally due to the increasing demand by consumers. These commodities are rich in various phytochemical nutrients that can reduce disease occurrence and improve human health. However, a significant loss of fruits and vegetables occurs during the postharvest stage. In this sense, edible coatings application has been one of the reliable approaches to improving the quality and extending the shelf life of fresh fruits and vegetables. Researchers are continuously researching and introducing new novel concepts for possible modifications, resulting in the development of unique coating formulations. One of the approaches has been incorporating essential oils into edible coatings, and it is a successful method even though these oils are volatile compounds. Plant-based fixed oils also have similar benefits as essential oils, with the added advantage of being nonvolatile. This review establishes the potential contribution of fixed oils to the overall efficacy of edible coating formulations and highlights research opportunities for investigating the potential contribution of different plant-based fixed oils edible coating formulations in maintaining quality and prolonging the shelf life of fruits and vegetables.

The majority of losses in horticultural produce occur during postharvest storage, particularly due to poor handling. Most fruit, especially climacteric fruit, have a short postharvest life due to an increase in ethylene synthesis which signals ripening and, subsequently, senescence. Traditional practices for preserving the postharvest quality of horticultural crops are chemical-based, a practice which has lately received enormous criticism. Recently, the use of postharvest illumination with LEDs as a nonchemical and environmentally friendly technique to preserve fruit and vegetables has been reported by various authors. Unique properties of LEDs such as low radiant heat, monochromatic nature and low cost have made this lighting gain popularity in the food industry. This paper, therefore, reviews the recent development in the postharvest applications of LEDs in horticultural crops, while focusing particularly on physical characteristics, nutritional value, and overall quality alterations of fruit and vegetables. According to the recently published research, red and blue LED lights are most valuable in terms of usage, while other wavelengths such as purple and yellow are slowly gaining attention. Furthermore, LEDs have been shown to affect fruit ripening and senescence, enhance bioactive compounds and antioxidants in produce, and prevent disease occurrence; however, there are some limitations associated with the use of this novel technology.

The extensive use of synthetic chemical fertilizers is associated with environmental pollution and soil degradation. In addition, the high costs of these fertilizers necessitate the search for alternative, eco-friendly and safe natural sources of phytonutrients. The liquid extracted from moringa (Moringa oleifera Lam.) leaves has been used in agriculture to improve the growth and productivity of several crops. The efficacy of moringa leaf extract (MLE) is attributed to its high content of mineral nutrients, protein, vitamins, sugars, fiber, phenolics and free proline. In addition, MLE contains significant amounts of phytohormones, such as auxins, cytokinins and gibberellins. Furthermore, MLE is a valuable product promoting seed germination, plant growth and deeper root development, delaying fruit senescence and increasing the yield and quality of crops grown under normal or stressful conditions. Here, we review the research on MLE as a biostimulant to enhance crop growth and productivity. Moreover, we emphasize its possible introduction to smallholder farming systems to provide phytonutrients, and we further highlight research gaps in the existing knowledge regarding MLE application. Generally, MLE is an inexpensive, sustainable, eco-friendly and natural biostimulant that can be used to improve the growth and productivity attributes of various crops under non-stressful and stressful conditions.

Green-mature and turning cherry tomatoes (Solanum lycopersicum L.) of a red (‘Cherry Little Wonder’) and a yellow (‘Goldilocks’) cultivar (cv) were illuminated, post-harvest, with either red (118 µmol m^–2 s – ¹ at 638 nm) or blue LED light (118 µmol m^–2 s – ¹ at 454 nm) for 48 h and subsequently stored for up to 21 days at room temperature. The effects of the treatments on colour, firmness, sugars and carotenoids were evaluated throughout storage. The light treatments did not have any effect on firmness and mass; however, light exposure, particularly red light, enhanced the a* colour component of the red cv significantly; similarly, colour coordinate b* of the yellow cv, treated at both stages of development, was significantly enhanced by both light treatments, resulting in visually redder and yellower tomatoes, respectively. These effects were more so observed on green-mature than on turning fruit. In addition, the treatments significantly increased lycopene concentrations in the red cv at both ripening stages, and β-carotene concentrations in both, the yellow and red cv treated at the green-mature stage. Total soluble solids (%TSS) also increased significantly following treatment. Findings reported suggest that illuminating tomato fruit with LED lights at the green-mature stage enhances colour development and the concentration of sugars, pigments and other health-related compounds without significantly affecting fruit mass and firmness.

The prevention of certain chronic diseases has been related to tomato (Solanum lycopersicum L.) consumption. The demand for high-quality tomatoes has, therefore, increased rapidly. As a climacteric fruit, tomato will only ripen to full colour postharvest. Trusses of mature-green greenhouse tomatoes of a red (‘Cherry Little Wonder’) and a yellow cultivar (‘Goldilocks’) were illuminated, preharvest, with either red (RL) (peak at 634 nm, 120 ± 20 µmol m^–2 s^–1) or blue (BL) LED lights (peak at 450 nm, 120 ± 20 µmol m^–2 s^–1) for 8 h per day for seven consecutive days. These on-plant RL and BL treatments significantly affected fruit colour and pigment concentration. Both light treatments enhanced the accumulation of lycopene, thereby significantly enhancing the nutritive value of the fruit. Similarly to lycopene, the β-carotene concentrations also increased following RL and BL exposure, again more so in the red than the yellow cultivar. Both light treatments also enhanced the speed of colour change by 5 days for the red and by 10 days for the yellow cultivar, resulting in either the desired red or the yellow colour. Our findings could be employed to improve quality and shorten the ripening period of tomato, while mechanisms involved in the biosynthesis and accumulation of these carotenoids require further investigation.