Effects of Fogging System and Nitric Oxide on Growth and Yield of 'Naomi' Mango Trees Exposed to Frost Stress

In years with unfavorable weather, winter frost during the blossoming season can play a significant role in reducing fruit yield and impacting the profitability of cultivation. The mango Naomi cultivar Mangifera indica L. has a low canopy that is severely affected by the effects of frost stress. As a result of the canopy being exposed to physiological problems, vegetative development is significantly inhibited. The current investigation aimed to study the influence of spraying nitric oxide and fogging spray systems on Naomi mango trees grafted on 'Succary' rootstock under frost stress conditions. The treatments were as follows: nitric oxide (NO) 50 and 100 μM, fogging spray system, and control. In comparison to the control, the use of nitric oxide and a fogging system significantly improved the leaf area, photosynthesis pigments of the leaf, the membrane stability index, yield, and physical and chemical characteristics of the Naomi mango cultivar. For instance, the application of 50 μM NO, 100 μM NO, and the fogging spray system resulted in an increase in yield by 41.32, 106.12, and 121.43% during the 2020 season, and by 39.37, 101.30, and 124.68% during the 2021 season compared to the control, respectively. The fogging spray system and highest level of NO decreased electrolyte leakage, proline content, total phenolic content, catalase (CAT), peroxidases (POX), and polyphenol oxidase (PPO) enzyme activities in leaves. Furthermore, the number of damaged leaves per shoot was significantly reduced after the application of fogging spray systems and nitric oxide in comparison to the control. Regarding vegetative growth, our results indicated that the fogging spray system and spraying nitric oxide at 100 μM enhanced the leaf surface area compared to the control and other treatments. A similar trend was noticed regarding yield and fruit quality, whereas the best values were obtained when the fogging spray system using nitric oxide was sprayed at a concentration of 100 μM. The application of fogging spray systems and nitric oxide can improve the production and fruit quality of Naomi mango trees by reducing the effects of adverse frost stress conditions.

Detection of Chilling Injury in Pickling Cucumbers Using Dual-Band Chlorophyll Fluorescence Imaging

Pickling cucumbers are susceptible to chilling injury (CI) during postharvest refrigerated storage, which would result in quality degradation and economic loss. It is, thus, desirable to remove the defective fruit before they are marketed as fresh products or processed into pickled products. Chlorophyll fluorescence is sensitive to CI in green fruits, because exposure to chilling temperatures can induce detectable alterations in chlorophylls of tissues. This study evaluated the feasibility of using a dual-band chlorophyll fluorescence imaging (CFI) technique for detecting CI-affected pickling cucumbers. Chlorophyll fluorescence images at 675 nm and 750 nm were acquired from pickling cucumbers under the excitation of ultraviolet-blue light. The raw images were processed for vignetting corrections through bi-dimensional empirical mode decomposition and subsequent image reconstruction. The fluorescence images were effective for ascertaining CI-affected tissues, which appeared as dark areas in the images. Support vector machine models were developed for classifying pickling cucumbers into two or three classes using the features extracted from the fluorescence images. Fusing the features of fluorescence images at 675 nm and 750 nm resulted in overall accuracies of 96.9% and 91.2% for two-class (normal and injured) and three-class (normal, mildly and severely injured) classification, respectively, which are statistically significantly better than those obtained using the features at a single wavelength, especially for the three-class classification. Furthermore, a subset of features, selected based on the neighborhood component feature selection technique, achieved the highest accuracies of 97.4% and 91.3% for the two-class and three-class classification, respectively. This study demonstrated that dual-band CFI is an effective modality for CI detection in pickling cucumbers.

Regulation of Vitamin C Accumulation for Improved Tomato Fruit Quality and Alleviation of Abiotic Stress

Ascorbic acid (AsA) is an essential multifaceted phytonutrient for both the human diet and plant growth. Optimum levels of AsA accumulation combined with balanced redox homeostasis are required for normal plant development and defense response to adverse environmental stimuli. Notwithstanding its moderate AsA levels, tomatoes constitute a good source of vitamin C in the human diet. Therefore, the enhancement of AsA levels in tomato fruit attracts considerable attention, not only to improve its nutritional value but also to stimulate stress tolerance. Genetic regulation of AsA concentrations in plants can be achieved through the fine-tuning of biosynthetic, recycling, and transport mechanisms; it is also linked to changes in the whole fruit metabolism. Emerging evidence suggests that tomato synthesizes AsA mainly through the l-galactose pathway, but alternative pathways through d-galacturonate or myo-inositol, or seemingly unrelated transcription and regulatory factors, can be also relevant in certain developmental stages or in response to abiotic factors. Considering the recent advances in our understanding of AsA regulation in model and other non-model species, this review attempts to link the current consensus with novel technologies to provide a comprehensive strategy for AsA enhancement in tomatoes, without any detrimental effect on plant growth or fruit development.

Impact of Processing Factors on Quality of Frozen Vegetables and Fruits

In this paper I review the production of frozen vegetables and fruits from a chain perspective. I argue that the final quality of the frozen product still can be improved via (a) optimization of the complete existing production chain towards quality, and/or (b) introduction of some promising novel processing technology. For this optimization, knowledge is required how all processing steps impact the final quality. Hence, first I review physicochemical and biochemical processes underlying the final quality, such as water holding capacity, ice crystal growth and mechanical damage. Subsequently, I review how each individual processing step impacts the final quality via these fundamental physicochemical and biochemical processes. In this review of processing steps, I also review the potential of novel processing technologies. The results of our literature review are summarized via a causal network, linking processing steps, fundamental physicochemical and biochemical processes, and their correlation with final product quality. I conclude that there is room for optimization of the current production chains via matching processing times with time scales of the fundamental physicochemical and biochemical processes. Regarding novel processing technology, it is concluded in general that they are difficult to implement in the context of existing production chains. I do see the potential for novel processing technology combined with process intensification, incorporating the blanching pretreatment—but which involves quite a change of the production chain.

Regulation of the Central Carbon Metabolism in Apple Fruit Exposed to Postharvest Low-Oxygen Stress

After harvest, fruit remain metabolically active and continue to ripen. The main goal of postharvest storage is to slow down the metabolic activity of the detached fruit. In many cases, this is accomplished by storing fruit at low temperature in combination with low oxygen (O2) and high carbon dioxide (CO2) partial pressures. However, altering the normal atmospheric conditions is not without any risk and can induce low-O2 stress. This review focuses on the central carbon metabolism of apple fruit during postharvest storage, both under normal O2 conditions and under low-O2 stress conditions. While the current review is focused on apple fruit, most research on the central carbon metabolism, low-O2 stress, and O2 sensing has been done on a range of different model plants (e.g., Arabidopsis, potato, rice, and maize) using various plant organs (e.g., seedlings, tubers, roots, and leaves). This review pulls together this information from the various sources into a coherent overview to facilitate the research on the central carbon metabolism in apple fruit exposed to postharvest low-O2 stress.

Integrative analysis of postharvest chilling injury in cherry tomato fruit reveals contrapuntal spatio-temporal responses to ripening and cold stress

Postharvest chilling injury (PCI) reduces fruit quality and shelf-life in tomato (Solanum lycopersicum L.). PCI has been traditionally studied in the pericarp, however its development is likely heterogeneous in different fruit tissues. To gain insight into PCI's spatio-temporal development, we used postharvest biomarkers e.g. respiration and ethylene rates, ion leakage etc., to confirm the occurrence of PCI, and compared these data with molecular (gene expression), biophysical (MRI data) and biochemical parameters (Malondialdehyde (MDA) and starch content) from the pericarp or columella. Tissues were stored at control (12.5 °C) or PCI-inducing temperatures (2.5 or 5 °C) followed by rewarming at 20 °C. MRI and ion leakage revealed that cold irreversibly impairs ripening-associated membrane liquefaction; MRI also showed that the internal and external fruit tissues responded differently to cold. MDA and especially starch contents, were affected by chilling in a tissue-specific manner. The expression of the six genes studied: ACO1 and ACS2 (ripening), CBF1 (cold response), DHN, AOX1a and LoxB (stress-related) showed non-overlapping temporal and spatially-specific responses. Overall, the data highlighted the interconnectedness of fruit cold response and ripening, and showed how cold stress reconfigures the latter. They further underscored that multidimensional spatial and temporal biological studies are needed to develop effective solutions to PCI.

Expression profile of transcripts encoding cell wall remodelling proteins in tomato fruit cv. Micro-Tom subjected to 15°C storage

To extend fruit market life, tomatoes are harvested before red ripe and kept at temperatures below optimum (20°C). In this work, Micro-Tom tomatoes stored at 20°C (normal ripening) were compared with those stored at 15°C or 4°C (chilling injury inducer) for 7 days. In contrast to 4°C, storage at 15°C delayed ripening with the benefit of not enhancing oxidative metabolism and of enabling ripening upon being transferred to 20°C. The transcriptional expression profile of enzymes related to cell wall metabolism was compared at the three temperatures. Although endo-β-1,4-glucanase (Cel1), which is associated with fruit decay, was largely increased after removal from 4°C storage, its expression was not modified in fruits stored at 15°C. Enhanced transcriptional expression of xyloglucan endotransgylcosylase/hydrolases (XTHs) XTH1, -2, -10 and -11, and of two β-xylosidases (Xyl1-2) was detected in fruits stored at 15°C with respect to those at 20°C. Following 2 days at 20°C, these transcripts remained higher in fruits stored at 15°C and XHT3 and -9 also increased. Ethylene evolution was similar in fruits kept at 15°C and 20°C; thus, the changes in the transcript profile and fruit properties between these treatments may be under the control of factors other than ethylene.

Transcriptomic analysis of cold response in tomato fruits identifies dehydrin as a marker of cold stress

Tomato is sensitive to cold during vegetative growth, fruit set, development, and ripening. We have characterized the effect of cold stress (6xC for up to 48 h) on the transcriptome of Micro-Tom tomato fruits during ripening by subtractive PCR. The cold stress caused modifications in gene expression of housekeeping genes. From a total of 38 genes up-regulated by cold, only one clone - a dehydrin homologue - was related to previously identified cold-stress genes. Phylogenetic analysis showed its clustering with other cold-induced dehydrins, and increased distances from dehydrins activated by abscisic acid. Quantitative expression analysis of tomato dehydrin showed it was activated by cold treatment in leaves and fruits. As dehydrin is a member of the Sl-CBF1 regulon from tomato, we analyzed the cold-responsive transcription factor Sl-CBF1 in mature leaves and ripening fruits stored at 6xC. Leaves of Micro-Tom showed high basal levels of the transcription factor Sl-CBF1, compared to fruits. Cold treatment caused increased levels of Sl-CBF1 expression in leaves but not in fruits of Micro-Tom and Demisem (a commercial cultivar). Tomato dehydrin can be used as a transcriptional marker of cold stress in leaves and ripening fruits. However, our results indicate that the cold response activation of dehydrin gene in tomato fruits is the consequence of an alternative pathway, different from the Sl-CBF1 regulon.

Methyl jasmonate reduces chilling injury and maintains postharvest quality of mango fruit

Exposure of mango (Mangifera indica cv. Tommy Atkins) fruit to methyl jasmonate (MJ) vapors (10(-)(4) M) for 24 h at 25 degrees C reduced chilling injury during subsequent storage for 21 days at 7 degrees C and after 5 days of shelf life at 20 degrees C. The chilling tolerance induced by MJ was positively correlated with the reduction in the percent ion leakage of mango tissue. The overall quality of MJ-treated fruit was also better than that of control fruit. MJ treatment increased the total soluble solids but did not affect titratable acidity or pH. MJ also did not change the normal climacteric rise in respiration, water loss, and softening rates. The efficacy of MJ to reduce chilling injury and decay of mango could be related to the tolerance induced at low temperature. It was concluded that MJ treatment may prevent chilling injury symptoms of mango without altering the ripening process.

Biological membrane deterioration and associated quality losses in food tissues

Biological membranes are rarely considered by food scientists when the deteriorative reactions that take place during the processing or storage of food tissues are studied. Yet, membranes and their deterioration play a major but underestimated role in food losses, and recent biochemical information indicates that at least some of these reactions can be controlled by procedures suited to food materials. Much of the present information available on membrane degradation in food systems is incomplete and speculative. It is known, however, that in order to accomplish their many indispensable functions in cells, membranes are constituted mainly of phospholipids, protein, and some carbohydrates arranged in thin, bimolecular sheet-like structures that serve to compartmentalize cells and their organelles. Membranes have embedded in their asymmetric surfaces complements of catalytic and cytoskeletal proteins that serve permeability and structural functions. Membrane surfaces exhibit fluidity, due partially to the continuous lateral diffusion of lipids and some proteins. Two important consequences of fluidity are the ability of membrane phospholipids to exist in different interconvertible conformational phase structures and the formation of heterogenous lipid domains on the membrane surface. Cellular death leads unavoidably to the initiation of membrane deterioration. While the time course of this series of reactions differs in animal and plant tissue, they are damaged by generally similar mechanisms. These include an initial peroxidative attack on polyunsaturated fatty acids, with the concomitant production of free radicals. Many biological agents can act as accelerating agents in these reactions, including transition metal ions, heme compounds, radiation, illuminated chlorophyll, calcium, and ethylene. Once formed, free radicals catalyze further reactions that can affect all aspects of membrane function and cellular metabolism, and lead ultimately to significant losses in food quality through defects such as chilling injury and cold shortening. These are aggravated by many food-processing steps, especially those that involve tissue disruption. Control of membrane breakdown by exogenous chemical intervention has been practiced, but, at best, this only slows the rate of these reactions. Newer approaches to this problem include dietary treatment of meat animals, modified storage and packaging conditions, and genetic interventions. This review advances the proposition that membrane deterioration can be considered a "universal mechanism" that leads to significant quality losses in food. Perhaps because the study of biological membranes and the biochemical and physiological properties has only begun recently, not much progress has been made in finding practical control mechanisms for these reactions in food systems.(ABSTRACT TRUNCATED AT 400 WORDS)