Apples are one of the most valuable fruits worldwide. ‘Honeycrisp’ is the top sales-producing cultivar in the US. Lack of red skin coloration and increased preharvest fruit drop significantly reduce ...the market value for cultivars such as ‘Honeycrisp’. The use of reflective groundcovers has been shown to enhance apple skin coloration. While the use of plant growth regulator AVG reduces fruit drop, it negatively affects skin coloration. Studies on the impacts of these practices in mid-Atlantic US-grown apples are limited. In this work, for two years, we compared differences in the light environment, fruit drop, internal ethylene concentration (IEC), physicochemical parameters, and skin coloration of ‘Honeycrisp’ apples in the lower third of the canopy. Apples were submitted to four treatment combinations of reflective groundcover (Extenday) and AVG (130 mg L−1). Assessments occurred throughout three ripening stages. Our results demonstrated that Extenday significantly promoted skin coloration (>75% blush) via the increased reflectance of photosynthetic photon flux density and UV radiation, and increased IEC, while also advancing fruit maturity, i.e., overripening. Conversely, AVG significantly minimized fruit drop and decreased EIC, delaying fruit maturity but drastically reducing red coloration (30–48% blush). The combined use of Extenday and AVG had a synergistic effect by decreasing fruit drop while enhancing fruit with >50% blush, without promoting overripening. Combining Extenday and AVG can boost the market value for ‘Honeycrisp’ apples in the mid-Atlantic US.
The decreased profitability of important apple cultivars, such as 'Honeycrisp', results from the poor red skin coloration and high fruit drop in the mid-Atlantic US. Apple red skin coloration is ...determined by the anthocyanin concentration. Reflective groundcovers promote red skin coloration, whereas aminoethoxyvinylglycine (AVG) decreases the ethylene production and fruit drop, thus reducing the coloration. Although our previous study showed that combinations of these practices impact the fruit quality and color, research is lacking regarding their effects at the gene and metabolite levels. In this work, for two years, we compared the differences in the internal ethylene concentration (IEC), red skin coloration, fruit drop, transcript accumulation of key ethylene and anthocyanin biosynthetic pathway-related genes, and total anthocyanin concentration of 'Honeycrisp' apples. The fruit was treated with combinations of reflective groundcover (Extenday) and AVG (130 mg L
) and was assessed throughout ripening. Extenday-only-treated fruit displayed the highest upregulation of ethylene and anthocyanin biosynthetic-related genes and of total anthocyanins, exceeding 50% blush, while boosting the IEC. In contrast, AVG significantly decreased the expression of key ethylene and anthocyanin biosynthetic-related genes and total anthocyanins, thus preventing apples from reaching 50% blush, while also decreasing the IEC and fruit drop. The combination of Extenday x AVG fine-tuned the transcript accumulation of ethylene and anthocyanin biosynthetic-related genes as well as the total anthocyanins, allowing the 'Honeycrisp' fruit to exceed 50% blush, while increasing the IEC moderately and reducing the fruit drop (as compared to Extenday-only and control), thus enhancing the fruit economic value.
We investigated sugar metabolism in leaves and fruits of two Japanese plum (Prunus salicina Lindl.) cultivars, the climacteric Santa Rosa and its bud sport mutant the non-climacteric Sweet Miriam, ...during development on the tree. We previously characterized differences between the two cultivars. Here, we identified key sugar metabolic pathways. Pearson coefficient correlations of metabolomics and transcriptomic data and weighted gene co-expression network analysis (WGCNA) of RNA sequencing (RNA-Seq) data allowed the identification of 11 key sugar metabolismassociated genes: sucrose synthase, sucrose phosphate synthase, cytosolic invertase, vacuolar invertase, invertase inhibitor, α-galactosidase, β-galactosidase, galactokinase, trehalase, galactinol synthase, and raffinose synthase. These pathways were further assessed and validated through the biochemical characterization of the gene products and with metabolite analysis. Our results demonstrated the reprogramming of sugar metabolism in both leaves and fruits in the non-climacteric plum, which displayed a shift towards increased sorbitol synthesis. Climacteric and nonclimacteric fruits showed differences in their UDP-galactose metabolism towards the production of galactose and raffinose, respectively. The higher content of galactinol, myo-inositol, raffinose, and trehalose in the non-climacteric fruits could improve the ability of the fruits to cope with the oxidative processes associated with fruit ripening. Overall, our results support a relationship between sugar metabolism, ethylene, and ripening behavior.
Apple (Malus domestica Borkh.) is usually produced in the form of a rootstock grafted scion. Rootstocks have important effects on several horticultural attributes. However, the results are not ...consistent regarding sites and scion–rootstock combinations. The aim of this research was to characterize the horticultural performance of ‘Buckeye Gala’ apple scion grafted onto ten rootstocks grown in Western Maryland during two harvest seasons. Our results demonstrated that, on average, tree size and yield in G.935, M.26 and G.969 rootstocks were 5–40% higher, but weight per fruit was 2–15% lower than in all other rootstocks. Fruit maturity was significantly delayed with increasingly vigorous rootstocks. There were no crop load differences. Overall, the assessed rootstocks were discriminated into seven significantly distinct clusters characterized by marked differences in vigor, yield, and fruit maturity. Moreover, significant correlations were obtained amongst all assessed variables. Rootstock impact must be considered when making management decisions in ‘Buckeye Gala’ fruit grown under Western Maryland conditions as they are critical in modulating fruit maturity and quality.
•Ethylene metabolism regulated flavonoid (and sugar) contents and composition.•Ethylene induced anthocyanin and reduced flavonol and flavan-3-ols in plum fruit.•Anthocyanins positively correlate with ...sucrose and galactose metabolic pathways.•Flavonol and flavan-3-ols associated with sorbitol, fructose, and glucose contents.
Plums are rich in flavonoids, key contributors to fruit coloration and putative health benefits. We studied the impact of changes in ethylene and sugars in flavonoid metabolism-related pathways of the climacteric Santa Rosa and its non-climacteric mutant Sweet Miriam, throughout the postharvest period. Fruits were harvested at optimal maturity, subjected to ethylene treatments, and evaluated during storage. We examined transcript profiles of structural and regulatory genes of flavonoid-related pathways and their associated metabolites in skin and flesh, integrated with multivariate analyses of ethylene and sugar metabolism. Ethylene treatments were positively correlated with anthocyanin and negatively correlated with flavonol and flavan-3-ol metabolism. Sucrose and galactose were positively associated with anthocyanin concentration, while sorbitol, fructose, glucose and minor sugars were correlated with flavonol and flavan-3-ol metabolism. Our results support the notion that ethylene is playing key roles in shifting plum fruit flavonoid profiles, which are also associated with changes in fruit sugars.
As peaches ripen and deteriorate quickly, cold storage is used to extend their marketability. However, peach cold storage is limited by the development of physiological disorders, such as chilling ...injury (CI), that express during subsequent shelf-life. The aim of this research was three-fold: first, to determine CI incidence in the melting flesh ‘Red Haven’ peach stored at different temperatures throughout postharvest; secondly, to characterize and compare differences among these fruit with regards to ethylene production rates, physicochemical properties, flesh texture, and aroma volatile profiles; and thirdly, to assess correlations among CI incidence and all the evaluated features, and identify potential key aroma volatile compounds that could predict early stage peach CI development during storage. Fruit were harvested at optimal maturity and stored at 0 °C, 5 °C, and 20 °C for up to 30 d. Evaluations were conducted at harvest (0) and after 1, 3, 5, 15, and 30 d of storage, with and without 3 d shelf-life period. Fruit stored at 5 °C were sensitive to CI displaying impaired capacity for ethylene production, and alterations in fruit textural properties, including reduced expressible juice contents and failure to soften. Chilling-injured fruit decreased accumulation of fruity note lactones, esters and terpenoids (i.e., linalool), and increased production of aldehydes and alcohols, as compared to sound fruit. Furthermore, multivariate regression identified thirteen potential key volatiles that could predict peach CI. These volatiles could be used as markers to discriminate chilling-injured from sound fruit at early stages of development of the disorder, optimizing cold storage and fruit handling practices, while decreasing loss and waste.
•Storage temperature and time impact development of chilling injury in peaches.•Chilling-injured fruit display an impaired capacity for ethylene production.•Decreased expressible juice and failure to soften associate with chilling injury.•Lactones, esters decreased but alcohols, aldehydes increased with chilling injury.•Volatiles may predict chilling injury thus could be used as markers for detection.
•Maturity at harvest and after storage plus genotype impact melon fruit flavor.•Volatiles increased in storage for all melon genotypes with esters being dominant.•Short shelf-life melons associated ...with esters, sulphur compounds and a terpenoid.•Long shelf-life melons related with green/grassy aroma/flavor, firmness, aldehydes.
Flavor is a key attribute defining melon fruit quality and driving consumer preferences. We characterized and compared fruit ripening patterns (ethylene, respiration), physicochemical properties (rind/flesh color, firmness, soluble solids, acidity), aroma volatiles, and flavor-related sensory attributes in seven melon genotypes differing in shelf life capacity. Fruits were evaluated at optimal maturity and after storage for six days at 5 °C plus one day at room temperature. Total volatile content increased after storage in all genotypes, with esters being dominant. Shorter shelf-life genotypes, displaying a sharper climacteric phase, correlated with fruity/floral/sweet flavor-related descriptors, and with esters, sulfur-containing compounds and a terpenoid. Longer shelf-life types were associated with firmness, green and grassy aroma/flavor and aldehydes. Multivariate regression identified key volatiles that predict flavor sensory perception, which could accelerate breeding of longer shelf-life melons with improved flavor characteristics.
The enzyme 1-amino-cyclopropane-1-carboxylic acid synthase (ACS) participates in the ethylene biosynthesis pathways and it is tightly regulated transcriptionally and post-translationally. ...Notwithstanding its major role in climacteric fruit ripening, the transcriptional regulation of ACS during ripening is not fully understood. We studied fruit ripening in two Japanese plum cultivars, the climacteric Santa Rosa (SR) and its non-climacteric bud sport mutant, Sweet Miriam (SM). As the two cultivars show considerable difference in
expression, they provide a good system for the study of the transcriptional regulation of the gene. To investigate the differential transcriptional regulation of
genes in the SR and SM, their promoter region, which showed only minor sequence differences, was isolated and used to identify the binding of transcription factors interacting with specific
cis-acting elements. Three transcription factors (TFs), abscisic acid-insensitive 5 (ABI5), GLABRA 2 (GL2), and TCP2, showed specific binding to the
promoter. Synthetic DNA fragments containing multiple cis-acting elements of these TFs fused to β-glucuronidase (GUS), showed the ABI5 binding site mediated ethylene and abscisic acid (ABA) responses of the promoter. While TCP2 and GL2 showed constant and similar expression levels in SM and SR fruit during ripening, ABI5 expression in SM fruits was lower than in SR fruits during advanced fruit ripening states. Overall, the work demonstrates the complex transcriptional regulation of
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•Ethylene affects sugar metabolism in climacteric and non-climacteric plums.•Ethylene induces and reduces sucrose and sorbitol biosynthesis, respectively.•Ethylene decreases and stimulates sucrose ...and sorbitol catabolism, respectively.•There is a positive interaction between ethylene and galactose metabolism.•Ethylene negatively affects galactinol, raffinose, inositol and trehalose contents.
We studied the effect of ethylene regulation on sugar metabolism in fruit of two Japanese plum (Prunus salicina Lindl.) cultivars, the climacteric Santa Rosa and its non-climacteric bud mutant Sweet Miriam, throughout ripening in postharvest storage. These cultivars share the same genetic background but due to bud mutations differ in their ripening behavior. We examined the responses to ethylene (propylene) and 1-methylcyclopropane (1-MCP) treatments on 11 key sugar metabolism-associated genes by integrating gene expression profiling and their associated sugar contents. Our results demonstrated that ethylene was a crucial factor affecting overall sugar metabolism in both ripening types. More specifically, ethylene reduced sucrose catabolism and induced sucrose biosynthesis but inversely, stimulated sorbitol breakdown and decrease sorbitol biosynthesis. Our analyses indicated that glucose and fructose contents result from sorbitol and sucrose breakdown in climacteric and non-climacteric fruit, respectively. In addition, a positive interaction was observed between ethylene and galactose metabolism; while a negative effect of ethylene was reported on galactinol, raffinose, myo-inositol and trehalose, which were higher in non-climacteric Sweet Miriam fruit and could contribute to increased fruit tolerance towards the stress imposed by the ripening process per se and to withstand postharvest storage.
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