Variations of peel essential oils during fruit ripening in four lemon (Citrus limon (L.) Burm. F.) cultivars.

BACKGROUND: Lemon processing procedures yield a significant amount of waste as peels, which are 57% of processed lemons and represent a possible source of bioactive compounds (essential oils, EOs). EOs were extracted from lemon fruits belonging to four cultivars harvested at four different sampling times (25 October, 23 November, 20 December, 1 February), characterized, and quantified through gas chromatography-mass spectrometry. RESULTS: The chemical composition of EOs highlighted that 26 compounds of the four lemon cultivars at the different ripening stages were clearly identified. The compounds analysed belonged to four chemical classes: monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpenes, and fatty alcohol esters. Among the monoterpene hydrocarbons, d-limonene, ß-pinene, and γ-terpinene were the most abundant; and among the oxygenated monoterpenes, α-terpineol, nerol, and geraniol were the most abundant. Quantitative gas chromatography-mass spectrometry analysis of the most abundant monoterpene hydrocarbons (α-pinene, ß-pinene, myrcene, d-limonene, and γ-terpinene) highlighted that the amount of EOs decreased during ripening stages. 'Ovale di Sorrento' and 'Sfusato Amalfitano' showed the highest level of EOs in December, whereas in 'Femminello Cerza' and 'Femminello Adamo' this occurred in November. EOs, as well as the phenolic compounds, were positively correlated with the antioxidant activity (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid). CONCLUSIONS: EOs reached the highest level in the four lemon cultivars at different ripening stages. Campanian cultivars ('Ovale di Sorrento' and 'Sfusato Amalfitano') showed the greatest EO content in November, whereas in Sicilian cultivars ('Femminello Cerza' and 'Femminello Adamo') this occurred in December. Besides phenolic compounds, measured in lemon peel extracts, EOs can contribute to antioxidant activity, as demonstrated by the positive correlation. © 2019 Society of Chemical Industry.

Characterization of autochthonous sweet cherry cultivars (Prunus avium L.) of southern Italy for fruit quality, bioactive compounds and antioxidant activity.

BACKGROUND: Characterizing germplasm collections of autochthonous cultivars for fruit quality traits could be a successful approach for selection, improvement of organoleptic quality and levels of antioxidants of crop produce, and development of new market opportunities and coherent strategies for conservation and valorization. The aim of the study was the evaluation of fruit physicochemical traits as well as the content of bioactive compounds and the antioxidant capacity in 25 sweet cherry autochthonous cultivars. RESULTS: Cultivars were a source of statistically significant variation for all evaluated traits. Notably, average fruit ascorbate levels ranged from 34.45 to 244.68 µg g-1 fresh weight (FW) , total flavonoids from 1396.40 to 4694.75 µg quercetin equiv. g-1 FW, monomeric anthocyanins from 4.80 to 360.90 µg g-1 FW, and total antioxidant capacity from 1.53 to 2.58 nmol Trolox equiv. mg-1 FW. Fruit profiling of eight cultivars by high-resolution mass spectrometry identified a total of eight different anthocyanins and twenty-five non-anthocyanin polyphenolic compounds - mostly coumaroylquinic acid and neochlorogenic acid. CONCLUSION: Among the better-performing cultivars for fruit quality traits, Mulegnana Nera and Pagliarella shared high fruit levels of phenolics, flavonoids and antioxidant capacity. This is a forerunner work on the characterization of genetic resources, which is critical to researchers and breeders for exploitation of the genetic potential of cultivars and for their conservation. © 2016 Society of Chemical Industry.

Transcriptome and metabolome of synthetic Solanum autotetraploids reveal key genomic stress events following polyploidization.

Polyploids are generally classified as autopolyploids, derived from a single species, and allopolyploids, arising from interspecific hybridization. The former represent ideal materials with which to study the consequences of genome doubling and ascertain whether there are molecular and functional rules operating following polyploidization events. To investigate whether the effects of autopolyploidization are common to different species, or if species-specific or stochastic events are prevalent, we performed a comprehensive transcriptomic and metabolomic characterization of diploids and autotetraploids of Solanum commersonii and Solanum bulbocastanum. Autopolyploidization remodelled the transcriptome and the metabolome of both species. In S. commersonii, differentially expressed genes (DEGs) were highly enriched in pericentromeric regions. Most changes were stochastic, suggesting a strong genotypic response. However, a set of robustly regulated transcripts and metabolites was also detected, including purine bases and nucleosides, which are likely to underlie a common response to polyploidization. We hypothesize that autopolyploidization results in nucleotide pool imbalance, which in turn triggers a genomic shock responsible for the stochastic events observed. The more extensive genomic stress and the higher number of stochastic events observed in S. commersonii with respect to S. bulbocastanum could be the result of the higher nucleoside depletion observed in this species.

Comparative transcriptomic profiling of two tomato lines with different ascorbate content in the fruit.

In recent years, interest in tomato breeding for enhanced antioxidant content has increased as medical research has pointed to human health benefits from antioxidant dietary intake. Ascorbate is one of the major antioxidants present in tomato, and little is known about mechanisms governing ascorbate pool size in this fruit. In order to provide further insights into genetic mechanisms controlling ascorbate biosynthesis and accumulation in tomato, we investigated the fruit transcriptome profile of the Solanum pennellii introgression line 10-1 that exhibits a lower fruit ascorbate level than its cultivated parental genotype. Our results showed that this reduced ascorbate level is associated with an increased antioxidant demand arising from an accelerated oxidative metabolism mainly involving mitochondria, peroxisomes, and cytoplasm. Candidate genes for controlling ascorbate level in tomato fruit were identified, highlighting the role of glycolysis, glyoxylate metabolism, and purine breakdown in modulating the ascorbate pool size.

The ascorbic acid content of tomato fruits is associated with the expression of genes involved in pectin degradation.

BACKGROUND: High levels of ascorbic acid (AsA) in tomato fruits provide health benefits for humans and also play an important role in several aspects of plant life. Although AsA metabolism has been characterized in detail, the genetic mechanisms controlling AsA accumulation in tomatoes are poorly understood. The transcriptional control of AsA levels in fruits can be investigated by combining the advanced genetic and genomic resources currently available for tomato. A comparative transcriptomic analysis of fruit tissues was carried out on an introgression line containing a QTL promoting AsA accumulation in the fruit, using a parental cultivar with lower AsA levels as a reference. RESULTS: Introgression line IL 12-4 (S. pennellii in a S. lycopersicum background) was selected for transcriptomic analysis because it maintained differences in AsA levels compared to the parental genotypes M82 and S. pennellii over three consecutive trials. Comparative microarray analysis of IL 12-4 and M82 fruits over a 2-year period allowed 253 differentially-expressed genes to be identified, suggesting that AsA accumulation in IL 12-4 may be caused by a combination of increased metabolic flux and reduced utilization of AsA. In particular, the upregulation of a pectinesterase and two polygalacturonases suggests that AsA accumulation in IL12-4 fruit is mainly achieved by increasing flux through the L-galactonic acid pathway, which is driven by pectin degradation and may be triggered by ethylene. CONCLUSIONS: Based on functional annotation, gene ontology classification and hierarchical clustering, a subset of the 253 differentially-expressed transcripts was used to develop a model to explain the higher AsA content in IL 12-4 fruits in terms of metabolic flux, precursor availability, demand for antioxidants, abundance of reactive oxygen species and ethylene signaling.