Huertas M. Díaz-Mula

Maturity stage at harvest determines the fruit quality and antioxidant potential after storage of sweet cherry cultivars.

Eleven sweet cherry cultivars were harvested at three maturity stages (S1 to S3) based on skin color and stored at 2 degrees C for 16 days and a further period of 2 days at 20 degrees C (shelf life, SL) to analyze quality (color, total soluble solids, and total acidity) and bioactive compounds (total phenolics and anthocyanins) and their relationship to total antioxidant activity (TAA), determined in hydrophilic (H-TAA) or lipophilic (L-TAA) fraction. For all cultivars and maturity stages, the ripening process advanced during postharvest storage with increases in color intensity and decreases in acidity, as well as enhancements in phenolics, anthocyanins, and TAA in both H-TAA and L-TAA, although important differences existed among cultivars. The results showed that sweet cherry should be harvested at stage S3 (4 days later than the commercial harvest date) since after 16 days of cold storage + SL, the highest antioxidant capacity was achieved for both H-TAA and L-TAA.

Sensory, Nutritive and Functional Properties of Sweet Cherry as Affected by Cultivar and Ripening Stage

In this article 11 commercial sweet cherry cultivars were selected to evaluate sensory, nutritive and functional properties over the maturation process on tree. Fruit quality was significantly different among cultivars and maturity stages at harvest, with the highest quality scores being found in the harvest which was 4 days beyond current commercial harvest maturity for all the cultivars tested. Taking into account all of the measured parameters (weight, firmness, color, acidity and total soluble solids), ‘NY-6479’, ‘Prime Giant’ and ‘Sunburst’ could be classified as having the highest quality in terms of sensory attributes. However, ‘Cristalina’ and ‘Sonata’ had the highest functional quality, as determined by the measurement of bioactive compound content and antioxidant capacity. We conclude that a delay of a few days in harvesting of sweet cherries would lead to achieve maximal nutritional (highest sugar and organic acid contents), sensory (greatest firmness and color development) and functional (greatest phenolics content, anthocyanins and antioxidant capacity) quality to provide both eating enjoyment and health benefits to the consumer.

Metabolic engineering to simultaneously activate anthocyanin and proanthocyanidin biosynthetic pathways in Nicotiana spp.

Proanthocyanidins (PAs), or condensed tannins, are powerful antioxidants that remove harmful free oxygen radicals from cells. To engineer the anthocyanin and proanthocyanidin biosynthetic pathways to de novo produce PAs in two Nicotiana species, we incorporated four transgenes to the plant chassis. We opted to perform a simultaneous transformation of the genes linked in a multigenic construct rather than classical breeding or retransformation approaches. We generated a GoldenBraid 2.0 multigenic construct containing two Antirrhinum majus transcription factors (AmRosea1 and AmDelila) to upregulate the anthocyanin pathway in combination with two Medicago truncatula genes (MtLAR and MtANR) to produce the enzymes that will derivate the biosynthetic pathway to PAs production. Transient and stable transformation of Nicotiana benthamiana and Nicotiana tabacum with the multigenic construct were respectively performed. Transient expression experiments in N. benthamiana showed the activation of the anthocyanin pathway producing a purple color in the agroinfiltrated leaves and also the effective production of 208.5 nmol (-) catechin/g FW and 228.5 nmol (-) epicatechin/g FW measured by the p-dimethylaminocinnamaldehyde (DMACA) method. The integration capacity of the four transgenes, their respective expression levels and their heritability in the second generation were analyzed in stably transformed N. tabacum plants. DMACA and phoroglucinolysis/HPLC-MS analyses corroborated the activation of both pathways and the effective production of PAs in T0 and T1 transgenic tobacco plants up to a maximum of 3.48 mg/g DW. The possible biotechnological applications of the GB2.0 multigenic approach in forage legumes to produce “bloat-safe” plants and to improve the efficiency of conversion of plant protein into animal protein (ruminal protein bypass) are discussed.

Metabolic and transcriptional elucidation of the carotenoid biosynthesis pathway in peel and flesh tissue of loquat fruit during on-tree development

BackgroundCarotenoids are the main colouring substances found in orange-fleshed loquat fruits. The aim of this study was to unravel the carotenoid biosynthetic pathway of loquat fruit (cv. ‘Obusa’) in peel and flesh tissue during distinct on-tree developmental stages through a targeted analytical and molecular approach.ResultsSubstantial changes regarding colour parameters, both between peel and flesh and among the different developmental stages, were monitored, concomitant with a significant increment in carotenoid content. Key genes and individual compounds that are implicated in the carotenoid biosynthetic pathway were further dissected with the employment of molecular (RT-qPCR) and advanced analytical techniques (LC-MS). Results revealed significant differences in carotenoid composition between peel and flesh. Thirty-two carotenoids were found in the peel, while only eighteen carotenoids were identified in the flesh. Trans-lutein and trans-β-carotene were the major carotenoids in the peel; the content of the former decreased with the progress of ripening, while the latter registered a 7.2-fold increase. However, carotenoid profiling of loquat flesh indicated trans-β-cryptoxanthin, followed by trans-β-carotene and 5,8-epoxy-β-carotene to be the most predominant carotenoids. High amounts of trans-β-carotene in both tissues were supported by significant induction in a chromoplast-specific lycopene β-cyclase (CYCB) transcript levels. PSY1, ZDS, CYCB and BCH were up-regulated and CRTISO, LCYE, ECH and VDE were down-regulated in most of the developmental stages compared with the immature stage in both peel and flesh tissue. Overall, differential regulation of expression levels with the progress of on-tree fruit development was more evident in the middle and downstream genes of carotenoid biosynthetic pathway.ConclusionsCarotenoid composition is greatly affected during on-tree loquat development with striking differences between peel and flesh tissue. A link between gene up- or down-regulation during the developmental stages of the loquat fruit, and how their expression affects carotenoid content per tissue (peel or flesh) was established.

Polyamines as an ecofriendly postharvest tool to maintain fruit quality

Polyamines (PAs) are natural compounds involved in a wide range of plant growth and developmental process, such as cell division, dormancy breaking, germination, development of flower buds, fruit set, growth and ripening, as well as in plant responses to environmental stresses including chilling injury. This chapter will focus on the role of PAs in fruit growth and ripening, with special emphasis on the effects of pre- and postharvest PA treatment on fruit quality attributes, bioactive constituents with antioxidant activity, and tolerance of fruit to chilling injury damage. The results of this chapter provide evidence for the numerous beneficial effects of the exogenous PA treatments, both at pre- and postharvest time in fruit quality attributes including their concentration in antioxidant compounds. Taking into account that PAs are naturally occurring molecules their application as pre- or postharvest treatment could be considered as an environmentally compatible tool as they can be metabolized by fruit cells. In addition, it should be pointed out that although exogenous application of PAs enhances their endogenous levels, the concentrations remain far lower than the toxic ones. Since modern agriculture is searching for effective biological molecules with well-known metabolic effects but without toxicological effects, a possible answer may be related to PA treatments.

Preharvest treatments with salicylates enhance nutrient and antioxidant compounds in plum at harvest and after storage

BACKGROUND Previous reports have addressed the effectiveness of salicylic acid (SA), acetylsalicylic acid (ASA) and methylsalicylate (MeSA) postharvest treatments on maintaining quality properties during storage in several commodities. However, there is no literature regarding the effect of preharvest treatments with salicylates on plum quality attributes (at harvest or after long-term cold storage), which was evaluated in this research. RESULTS At harvest, weight, firmness, individual organic acids, sugars, phenolics, anthocyanins and total carotenoids were found at higher levels in plums from SA-, ASA- and MeSA-treated trees than in those from controls. During storage, softening, colour changes and acidity losses were delayed in treated fruits as compared to controls. In addition, organic acids and antioxidant compounds were still found at higher levels in treated than in control plums after 40 days of storage. Results show a delay in the postharvest ripening process due to salicylate treatments, which could be attributed to their effect in delaying and decreasing ethylene production. CONCLUSION Preharvest treatment with salicylates could be a safety, eco-friendly and new tool to improve (at harvest) and maintain (during storage) plum quality and especially its content of bioactive compounds with antioxidant properties, increasing the health effects of plum consumption.