Increased firmness and modified cell wall composition by ethylene were reversed by the ethylene inhibitor 1-methylcyclopropene (1-MCP) in the non-climacteric olives harvested at dark green stage - Possible implementation of ethylene for olive quality

Hormonal Content and Gene Expression during Olive Fruit Growth and Ripening

The cultivated olive (Olea europaea L. subsp. europaea var. europaea) is one of the most valuable fruit trees worldwide. However, the hormonal mechanisms underlying the fruit growth and ripening in olives remain largely uncharacterized. In this study, we investigated the physiological and hormonal changes, by ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS), as well as the expression patterns of hormone-related genes, using quantitative real-time PCR (qRT-PCR) analysis, during fruit growth and ripening in two olive cultivars, 'Arbequina' and 'Picual', with contrasting fruit size and shape as well as fruit ripening duration. Hormonal profiling revealed that olive fruit growth involves a lowering of auxin (IAA), cytokinin (CKs), and jasmonic acid (JA) levels as well as a rise in salicylic acid (SA) levels from the endocarp lignification to the onset of fruit ripening in both cultivars. During olive fruit ripening, both abscisic acid (ABA) and anthocyanin levels rose, while JA levels fell, and SA levels showed no significant changes in either cultivar. By contrast, differential accumulation patterns of gibberellins (GAs) were found between the two cultivars during olive fruit growth and ripening. GA1 was not detected at either stage of fruit development in 'Arbequina', revealing a specific association between the GA1 and 'Picual', the cultivar with large sized, elongated, and fast-ripening fruit. Moreover, ABA may play a central role in regulating olive fruit ripening through transcriptional regulation of key ABA metabolism genes, whereas the IAA, CK, and GA levels and/or responsiveness differ between olive cultivars during olive fruit ripening. Taken together, the results indicate that the relative absence or presence of endogenous GA1 is associated with differences in fruit morphology and size as well as in the ripening duration in olives. Such detailed knowledge may be of help to design new strategies for effective manipulation of olive fruit size as well as ripening duration.

Influence of 1-Methylcyclopropene (1-MCP) on the Processing and Microbial Communities of Spanish-Style and Directly Brined Green Table Olive Fermentations

This work evaluates the effect of 1-methylcyclopropene (1-MCP) on postharvest and fermentation of Manzanilla cultivar, processed as Spanish-style or directly brined table olives. During postharvest handling, 1-MCP (2.85 µL/L) reduced the number of colour-turning olives by 18.42% over the untreated fruits. In Spanish-style and directly brined fermentation, the 1-MCP treatment led to lower pH levels, higher titratable acidities, improved firmness and colour olives than untreated fruits. A panel of expert testers also gave higher scores, and overall acceptability to the 1-MCP treated fruits, especially in the case of Spanish-style fermented olives. Metagenomic analysis of olive biofilms at the end of the fermentation process (176 days) revealed that Lactiplantibacillus was the most abundant bacterial genus in both Spanish-style and directly brined olives (>72%). However, fungal biodiversity was higher than bacterial in all treatments. Saccharomyces was the predominant yeast genus associated with directly brined olives (>97%), whilst Wickerhamomyces (>37%) and Zygoascus (>18%) were with Spanish-style fermentations. The 1-MCP treatment doubled the presence of Wickerhamomyces in Spanish-style fruits (74%) whilst reducing the presence of Zygoascus and allowing the growth of Enterobacter (15%) in directly brined olives. Thus, the postharvesting treatment of table olives with 1-MCP could help reduce the maturation progress of olives and improve the organoleptic and quality characteristics of the products without affecting the microbiological evolution of the fermentations.

Characterization of Fruit Development, Antioxidant Capacity, and Potential Vasoprotective Action of Peumo (Cryptocarya alba), a Native Fruit of Chile

The peumo (Cryptocarya alba) is a native fruit from central Chile that belongs to the Lauraceae family. To characterize the development and the potential health benefits of this edible fruit, quality and physiological parameters, along with antioxidant capacity, were evaluated during three clearly defined developmental stages of the fruit in two seasons. The most distinguishable attributes of ripe fruit were the change in size and color. Low CO₂ production and no detectable ethylene levels suggested non-climacteric behavior of the peumo fruit. Peumo demonstrate a significant increase in their antioxidant capacity per 1 g of fresh weight (FW) of the sample, from small to ripe fruit. Higher values in ripe fruit (FRAP: 37.1–38.3 µmol FeSO4/gFW, TEAC: 7.9–8.1 mmol TE/gFW, DPPH: 8.4-8.7 IC₅₀ μg/mL, and ORAC: = 0.19–0.20 mmol TE/gFW) were observed than those in blueberry fruit (FRAP: 4.95 µmol FeSO4/gFW, TEAC: 1.25 mmol TE/gFW, DPPH: 11.3 IC₅₀ μg/mL, and ORAC: 0.032 mmol TE/ gFW). The methanol extracts of ripe fruit displayed the presence of polyphenol acids and quercetin, an ORAC value of 0.637 ± 0.061 mmol TE per g dried weight (DW), and a high cellular antioxidant and anti-inflammatory potential, the latter exceeding the effect of quercetin and indomethacin used as standard molecules. Also, the assay of isolated rat aorta with endothelium-dependent relaxation damage demonstrated that the peumo extract induced vascular protection, depending on its concentration under a high glucose condition. These results demonstrate that these endemic fruits have a good chance as ingredients or foods with functional properties.

Understanding In Vitro Tissue Culture-Induced Variation Phenomenon in Microspore System

In vitro tissue culture plant regeneration is a complicated process that requires stressful conditions affecting the cell functioning at multiple levels, including signaling pathways, transcriptome functioning, the interaction between cellular organelles (retro-, anterograde), compounds methylation, biochemical cycles, and DNA mutations. Unfortunately, the network linking all these aspects is not well understood, and the available knowledge is not systemized. Moreover, some aspects of the phenomenon are poorly studied. The present review attempts to present a broad range of aspects involved in the tissue culture-induced variation and hopefully would stimulate further investigations allowing a better understanding of the phenomenon and the cell functioning.

Primary Metabolism in Fresh Fruits During Storage

The extension of commercial life and the reduction of postharvest losses of perishable fruits is mainly based on storage at low temperatures alone or in combination with modified atmospheres (MAs) and controlled atmospheres (CAs), directed primarily at reducing their overall metabolism thus delaying ripening and senescence. Fruits react to postharvest conditions with desirable changes if appropriate protocols are applied, but otherwise can develop negative and unacceptable traits due to the onset of physiological disorders. Extended cold storage periods and/or inappropriate temperatures can result in development of chilling injuries (CIs). The etiology, incidence, and severity of such symptoms vary even within cultivars of the same species, indicating the genotype significance. Carbohydrates and amino acids have protective/regulating roles in CI development. MA/CA storage protocols involve storage under hypoxic conditions and high carbon dioxide concentrations that can maximize quality over extended storage periods but are also affected by the cultivar, exposure time, and storage temperatures. Pyruvate metabolism is highly reactive to changes in oxygen concentration and is greatly affected by the shift from aerobic to anaerobic metabolism. Ethylene-induced changes in fruits can also have deleterious effects under cold storage and MA/CA conditions, affecting susceptibility to chilling and carbon dioxide injuries. The availability of the inhibitor of ethylene perception 1-methylcyclopropene (1-MCP) has not only resulted in development of a new technology but has also been used to increase understanding of the role of ethylene in ripening of both non-climacteric and climacteric fruits. Temperature, MA/CA, and 1-MCP alter fruit physiology and biochemistry, resulting in compositional changes in carbon- and nitrogen-related metabolisms and compounds. Successful application of these storage technologies to fruits must consider their effects on the metabolism of carbohydrates, organic acids, amino acids and lipids.