1-Methylcyclopropene and extreme ULO inhibit superficial scald in a different way highlighting the physiological basis of this disorder in pear

Despite years of research on the biochemical basis of superficial scald in apples, relatively little is known about the specific regulatory processes involved in pears. To gain further knowledge on these processes, different storage scenarios, controlled atmosphere (CA), 1-methylcyclopropene treatment (1-MCP) and storage under very low O2 concentration (xULO) were used in the scald susceptible ‘Blanquilla’ pears. Ethylene production, α-farnesene (AF), conjugated trienols (CTols) content and changes in ethanol levels were evaluated during storage and further related to superficial scald development and changes in fruit quality upon removal. While 1-MCP completely inhibited ethylene production and fruit softening, only a partial and transient inhibition of these parameters was found for xULO-treated fruit. Both 1-MCP and xULO treatments completely controlled scald disorder, yet in different ways. The reduction in disorder incidence in 1-MCP treated fruit was the result of ethylene inhibition and reduced levels of α-farnesene and CTols. In contrast, xULO treatment only partially inhibited ethylene production and the levels of α-farnesene metabolites but led to increased ethanol levels that were directly related to the scald incidence inhibition. Collectively, these results highlight that superficial scald in pear is not strictly related to ethylene and α-farnesene metabolism and that other compounds, such as the weak antioxidant ethanol, play a determining role in ‘Blanquilla’ pear.info:eu-repo/semantics/acceptedVersio

A comprehensive study on the main physiological and biochemical changes occurring during growth and on-tree ripening of two apple varieties with different postharvest behaviour

Apple quality and the storage potential likely depend on a range of physiological and biochemical events occurring throughout fruit development and ripening. In this study, we investigated the major physiological (ethylene production and respiration) and biochemical changes (related to sugar and malic acid content as well as antioxidant metabolism) occurring during growth and on-tree ripening of two apple varieties (‘Granny Smith’ (GS) and ‘Early Red One’ (ERO)) with known differences in their postharvest behaviour, mainly firmness loss and susceptibility to superficial scald. Our results demonstrate that the higher storability and the limited loss of firmness of ‘GS’ fruit was associated to a higher acid content, mainly malic acid, that seemed to be regulated already at fruit set (20 DAFB). The reduced loss of firmness during storage in ‘GS’ was also associated to the fruit inability to produce ethylene upon harvest resulting from very low 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) activity. Sugar accumulation, on the other hand, was similar among both varieties as was also observed for the rate of fruit growth or the fruit respiration pattern. In addition, the higher susceptibility of ‘GS’ if compared to ‘ERO’ to superficial scald was not associated to peroxidative damage (malondialdehyde accumulation) nor to higher levels of the sesquiterpene α-farnesene but rather mediated by a fruit antioxidant imbalance resulting from higher H2O2 levels and lower antioxidant (peroxidase) enzymatic capacity. The interplay between ethylene, respiration and antioxidants or sugars and organic acids during apple growth and development is further discussed.info:eu-repo/semantics/acceptedVersio

Interplay between hormones and assimilates during pear development and ripening and its relationship with the fruit postharvest behaviour

The ability of European pears (Pyrus communis L.) to ripen immediately after harvest is cultivar-dependent and relies on a range of physiological and biochemical events occurring during fruit growth and development that remain largely unknown. To gain further knowledge on these events, changes in the content of sugars, acids, major hormones and ethylene precursors or related enzymes were studied in two pear varieties (‘Blanquilla’ and ‘Conference’) with known differences in their postharvest ripening behaviour. In both cultivars, low contents of abscisic acid (ABA) seemed to be a prerequisite to initiate on-tree fruit ripening including sugar accumulation and softening. In ‘Blanquilla’ pears, the enhanced potential to produce ethylene and thereby to ripen upon harvest was associated to a late increase in ABA content paralleled by an accumulation of indole 3-acetic acid (IAA). In turn, the inability of ‘Conference’ fruit to produce ethylene upon harvest appeared to be related to a coordinated action of gibberellins (more specifically GA1), salicylic acid (SA) and jasmonic acid (JA), which remained at high concentrations during the latest phases of fruit growth. Collectively, our results highlight that a complex hormonal cross-talk during the development and on-tree ripening of pear fruit may finally determine the ability of the fruit to ripen upon harvest.info:eu-repo/semantics/acceptedVersio

New insights on the ripening pattern of ‘Blanquilla’ pears: A comparison between on- and off-tree ripened fruit

To better understand the key processes involved in the ripening of attached fruit, we have investigated physico-chemical and biochemical changes occurring in ‘Blanquilla’ pear during on-tree (attached fruit) and off-tree ripening (harvested fruit). Flesh firmness, sugars, acids and the volatile profiles as well as ethylene metabolism, PG and PME enzyme activities and oxidative damage were measured. Firmness loss in detached ‘Blanquilla’ pear (off-tree), was initially mediated by oxidative stress (higher accumulation of malondialdehyde) and then by ethylene in a process in which 1-aminocyclopropene 1-carboxylic acid (ACC) synthase was the limiting factor. In contrast the progressive but slower softening observed during on-tree fruit ripening was not associated to oxidative damage but rather to a delayed production of ethylene limited, in turn, by the activity of ACC oxidase. An interesting association was found between the initiation of the ethylene production and a concomitant increase of sucrose levels during on-tree ripening also accompanied by a decline in hexanal. The putative role of these compounds as a tree-associated factor modulating on-tree pear ripening is discussed.info:eu-repo/semantics/acceptedVersio

New insights on the ripening pattern of ‘Blanquilla’ pears: A comparison between on- and off-tree ripened fruit

To better understand the key processes involved in the ripening of attached fruit, we have investigated physico-chemical and biochemical changes occurring in ‘Blanquilla’ pear during on-tree (attached fruit) and off-tree ripening (harvested fruit). Flesh firmness, sugars, acids and the volatile profiles as well as ethylene metabolism, PG and PME enzyme activities and oxidative damage were measured. Firmness loss in detached ‘Blanquilla’ pear (off-tree), was initially mediated by oxidative stress (higher accumulation of malondialdehyde) and then by ethylene in a process in which 1-aminocyclopropene 1-carboxylic acid (ACC) synthase was the limiting factor. In contrast the progressive but slower softening observed during on-tree fruit ripening was not associated to oxidative damage but rather to a delayed production of ethylene limited, in turn, by the activity of ACC oxidase. An interesting association was found between the initiation of the ethylene production and a concomitant increase of sucrose levels during on-tree ripening also accompanied by a decline in hexanal. The putative role of these compounds as a tree-associated factor modulating on-tree pear ripening is discussed.This work was supported by the CERCA Programme/ Generalitat de Catalunya and by the Ministerio de Economía y Competitividad / MINECO (grant AGL2017-87923-R)

PbSRT1 and PbSRT2 regulate pear growth and ripening yet displaying a species-specific regulation in comparison to other Rosaceae spp.

Epigenetic regulation is crucial to ensure a coordinated control of the different events that occur during fruit development and ripening. Sirtuins are NAD+-dependent histone deacetylases involved in the regulation of gene expression of many biological processes. However, their implications in the Rosaceae family remains unexplored. Accordingly, in this work, we demonstrated the phylogenetic divergence of both sirtuins among Rosaceae species. We then characterized the expression pattern of both SRT1 and SRT2 in selected pome and stone fruit species. Both SRT1 and SRT2 significantly changed during the fruit development and ripening of apple, nectarine and pear fruit, displaying a different expression profile. Such differences could explain in part their different ripening behaviour. To further unravel the role of sirtuins on the fruit development and ripening processes, a deeper analysis was performed using pear as a fruit model. In pear, PbSRT1 gene expression levels were negatively correlated with specific hormones (i.e. abscisic acid, indole-3-acetic acid, gibberellin A1 and zeatin) during the first phases of fruit development. PbSRT2 seemed to directly mediate pear ripening in an ethylene-independent manner. This hypothesis was further reinforced by treating the fruit with the ethylene inhibitor 1-methylcyclopropene (1-MCP). Instead, enhanced PbSRT2 along pear growth/ripening positively correlated with the accumulation of major sugars (R2 > 0.94), reinforcing the idea that sugar metabolism may be a target of epigenetic modifications during fruit ripening. Overall, the results from this study point out, for the first time, the importance that sirtuins have in the regulation of fruit growth and ripening of pear fruit by likely regulating hormonal and sugar metabolism.info:eu-repo/semantics/acceptedVersio

Investigation of the transcriptomic and metabolic changes associated with superficial scald physiology impaired by lovastatin and 1-methylcyclopropene in pear fruit (cv. “Blanquilla”)

To elucidate the physiology underlying the development of superficial scald in pears, susceptible “Blanquilla” fruit was treated with different compounds that either promoted (ethylene) or repressed (1-methylcyclopropene and lovastatin) the incidence of this disorder after 4 months of cold storage. Our data show that scald was negligible for the fruit treated with 1-methylcyclopropene or lovastatin, but highly manifested in untreated (78% incidence) or ethylene-treated fruit (97% incidence). The comparison between the fruit metabolomic profile and transcriptome evidenced a distinct reprogramming associated with each treatment. In all treated samples, cold storage led to an activation of a cold-acclimation-resistance mechanism, including the biosynthesis of very-long-chain fatty acids, which was especially evident in 1-methylcyclopropane-treated fruit. Among the treatments applied, only 1-methylcyclopropene inhibited ethylene production, hence supporting the involvement of this hormone in the development of scald. However, a common repression effect on the PPO gene combined with higher sorbitol content was found for both lovastatin and 1-methylcyclopropene-treated samples, suggesting also a non-ethylene-mediated process preventing the development of this disorder. The results presented in this work represent a step forward to better understand the physiological mechanisms governing the etiology of superficial scald in pears.info:eu-repo/semantics/publishedVersio

Genetic analysis of the slow melting flesh character in peach

The slow-melting flesh (SMF) trait in peach [Prunus persica (L.) Batsch] defines a slower process of postharvest fruit-softening than the prevalent melting flesh (MF) types. This gives a longer shelf life and a delayed harvest-time resulting in better fruit quality. Unlike other known fruit texture traits, SMF is difficult to measure and has a complex inheritance. We examined this character over 2 years in the offspring of two crosses, both with "Big Top," an SMF nectarine, as the female parent, and with a melting flesh (MF) nectarine as the male parent ("Armking" and "Nectaross"). Following harvest, a texturometer was used to provide a textural profile analysis, and fruit firmness evolution was measured with a penetrometer over a period of 5 days' storage at 20 °C. Linkage maps were constructed with a high-density SNP chip, and a phenotype-genotype analysis allowed the detection of three independent genomic regions where most QTLs (quantitative trait loci) were located. Two of these, on linkage groups 4 and 5, explained the variability for two characters-maturity date and firmness loss-that is, the QTL on linkage group 4 found in the MF parents and that on linkage group 5 in Big Top. A third region on linkage group 6, which identified a QTL for maturity date only in Armking, has no apparent association to the softening process. The relationship between maturity date and fruit-firmness loss and a hypothesis on the inheritance of the SMF character are discussed

Comparative transcriptional profiling analysis of developing melon (Cucumis melo L.) fruit from climacteric and non-climacteric varieties

[EN] Background: In climacteric fruit-bearing species, the onset of fruit ripening is marked by a transient rise in respiration rate and autocatalytic ethylene production, followed by rapid deterioration in fruit quality. In non-climacteric species, there is no increase in respiration or ethylene production at the beginning or during fruit ripening. Melon is unusual in having climacteric and non-climacteric varieties, providing an interesting model system to compare both ripening types. Transcriptomic analysis of developing melon fruits from Védrantais and Dulce (climacteric) and Piel de sapo and PI 161375 (non-climacteric) varieties was performed to understand the molecular mechanisms that differentiate the two fruit ripening types. Results: Fruits were harvested at 15, 25, 35 days after pollination and at fruit maturity. Transcript profiling was performed using an oligo-based microarray with 75 K probes. Genes linked to characteristic traits of fruit ripening were differentially expressed between climacteric and non-climacteric types, as well as several transcription factor genes and genes encoding enzymes involved in sucrose catabolism. The expression patterns of some genes in PI 161375 fruits were either intermediate between. Piel de sapo and the climacteric varieties, or more similar to the latter. PI 161375 fruits also accumulated some carotenoids, a characteristic trait of climacteric varieties. Conclusions: Simultaneous changes in transcript abundance indicate that there is coordinated reprogramming of gene expression during fruit development and at the onset of ripening in both climacteric and non-climacteric fruits. The expression patterns of genes related to ethylene metabolism, carotenoid accumulation, cell wall integrity and transcriptional regulation varied between genotypes and was consistent with the differences in their fruit ripening characteristics. There were differences between climacteric and non-climacteric varieties in the expression of genes related to sugar metabolism suggesting that they may be potential determinants of sucrose content and post-harvest stability of sucrose levels in fruit. Several transcription factor genes were also identified that were differentially expressed in both types, implicating them in regulation of ripening behaviour. The intermediate nature of PI 161375 suggested that classification of melon fruit ripening behaviour into just two distinct types is an over-simplification, and that in reality there is a continuous spectrum of fruit ripening behaviourWe wish to thank Marta Casado for assistance with qRT-PCR analysis, Anna Orozco and Rosa Rodriguez for help with carotenoid measurements, Kostas Alexiou for uploading the microarray data at GEO and Walter Sanseverino for obtaining the correspondence of the microarray contigs with the melon annotated genes. We thank Beatrice Encke and Nicole Krohn for technical help with the sugar analysis. We also thank Laura Pascual for a critical reading of the manuscript. MSa was supported by a JAE-Doc grant from the Spanish Ministry of Science. This work was supported by the Spanish Ministry of Science and Innovation (MICINN project GEN2006-27773-C2-1-E to JGM) and the German Federal Ministry of Education and Research (BMBF project 0313987 to MSt) within the framework of the EU Framework 6 ERA-NET Plant Genomics programme.Saladie, M.; Cañizares Sales, J.; Michael A. Phillips; Rodriguez Concepcion, M.; Larrigaudière, C.; Gibon, Y.; Stitt, M.... (2015). Comparative transcriptional profiling analysis of developing melon (Cucumis melo L.) fruit from climacteric and non-climacteric varieties. BMC Genomics. 16(440):1-20. https://doi.org/10.1186/s12864-015-1649-3S12016440McMurchie EJ, McGlasson WB, Eaks IL. Treatment of fruit with propylene gives information about the biogenesis of ethylene. 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Postharvest quality and chilling injury of plums: benefits of 1-methylcyclopropene

The aim of this work was to evaluate the effect of 1-methylcyclopropene (1-MCP) treatment on the development of chilling injury (CI) symptoms in four plum cultivars and to determine the relationship between the climacteric behavior of the cultivar and its sensitivity to this disorder. Significant differences in ripening pattern were found between the cultivars after long-term storage. Among the climacteric cultivars, �Royal Zee� plums showed a higher ethylene production rate than �Linda Rosa and �Friar� cultivars. On the other hand, the �Angeleno� cultivar behaved as a suppressed climacteric type. The development of translucency symptoms was higher in �Royal Zee� than in �Linda Rosa� and �Friar� plums, and was almost absent in the suppressed climacteric cultivar. 1-MCP treatment significantly reduced ethylene production and the percentage of fruit affected by translucency in all climacteric cultivars. This treatment also delayed the ripening of the fruit during shelf life. In contrast, 1-MCP treatment did not affect the quality of �Angeleno� plums. Collectively these results suggest that the development of chilling injury in plums is related to the climacteric behavior of the cultivar and demonstrated the beneficial effects of 1-MCP maintaining plum quality during storage.El objetivo de este trabajo fue evaluar el efecto del tratamiento con 1-metilciclopropeno (1-MCP) sobre el desarrollo de los síntomas de daños por frío (DF) en cuatro cultivares de ciruela y determinar la relación entre el patrón de maduración de los cultivares y su sensibilidad a este desorden. Se encontraron diferencias significativas en el patrón de maduración de los cultivares después de un almacenamiento a largo plazo. Entre los cultivares climatéricos, �Royal Zee� mostró una tasa de producción de etileno superior a la de los cultivares �Linda Rosa� y �Friar�. Por otra parte, el cultivar �Angeleno� presentó un comportamiento climatérico suprimido. El desarrollo de síntomas de transparencia fue mayor en �Royal Zee� que en �Linda Rosa� y �Friar�, y casi ausente en el cultivar climatérico suprimido. El tratamiento con 1-MCP redujo significativamente la producción de etileno y el porcentaje de frutos afectados por la transparencia en todos los cultivares climatéricos. Este tratamiento también retrasó la maduración de la fruta durante la vida en estante. En cambio, el tratamiento 1-MCP no afectó a la calidad de ciruelas �Angeleno�. En conjunto, estos resultados sugieren que el desarrollo de DF en ciruelas está relacionado con el comportamiento climatérico del cultivar y demuestran los efectos beneficiosos del tratamiento 1-MCP sobre la calidad de las ciruelas durante el almacenamiento