Postharvest storability of ‘Isadora’ apples is unaffected by ethylene: Characterizing a new ethylene-insensitive cultivarAbstract:
The aim of this study was to evaluate the ethylene-sensitivity of ‘Isadora’ apples. Apples treated with 1-methylcyclopropene (1-MCP) and untreated were exposed to different concentrations of exogenous ethylene. The treatments tested were: 1) Ethylene at 0 (control), 1, 10, 100 µL L-1; 2) 0 µL L-1 ethylene + 1-MCP at 1µL L-1 applied every two days; and 3) 10 µL L-1 ethylene + 1-MCP at 1 µL L-1 at the beginning. Ethylene was applied daily, and the fruit were exposed for two hours over fifteen days. Exogenous application of ethylene and 1-MCP did not affect the ethylene production, skin background degreening, soluble solids content, titratable acidity, and flesh firmness in untreated apples. All treatments after fifteen days were compared with the values at harvest and even untreated fruit showed differences. Although the fruits were exposed to exogenous ethylene, no flesh firmness losses were observed. The impact of ethylene on the ripening of ‘Isadora’ apples was found to be insignificant. This suggests that thiscultivar tolerates high concentrations of ethylene, thereby maintaining its quality for a prolonged postharvest period and resulting in enhanced storability. It can be concluded that the ‘Isadora’ apples are either ethylene-insensitive ordisplays a low sensitivity.
Index terms
Malus domestica Borkh.; apple breeding; ripening; flesh firmness
Resumo:
O principal objetivo deste estudo foi avaliar a sensibilidade ao etileno das maçãs ‘Isadora’ e sua correlação com a capacidade de armazenamento póscolheita. As maçãs tratadas com 1-metilciclopropeno (1-MCP) e não tratadas foram expostas a diferentes concentrações de etileno exógeno. Os tratamentos testados foram: 1) Etileno a 0 (controle), 1, 10, 100 µL L-1; 2) 0 µL L-1 de etileno + 1-MCP a 1 µL L-1 aplicado a cada dois dias; e 3) 10 µL L-1 de etileno + 1-MCPa 1 µL L-1 no início. O etileno foi aplicado diariamente, e os frutos foram expostos durante duas horas ao longo de quinze dias. Os resultados mostraram que a aplicação exógena de etileno e 1-MCP não afetou a produção de etileno, a descoloração do fundo da casca, o teor de sólidos solúveis, a acidez titulável e a firmeza da polpa em maçãs não tratadas.Todos os tratamentos, após quinze dias, foram comparados com os valores aquando da colheita, e mesmo os frutos não tratados apresentaram diferenças. Apesar de os frutos terem sido expostos a etileno exógeno, não foram observadas perdas de firmezada polpa quando da colheita. O impacto do etileno no amadurecimento das maçãs ‘Isadora’foi considerado insignificante. Isto sugere que esta cultivar tolera concentraçõeselevadas de etileno, mantendo assim sua qualidade durante um período pós-colheita prolongado e resultando em melhor capacidade de armazenamento. Pode concluir-se que asmaçãs ‘Isadora’ não são sensíveis ao etileno ou apresentam uma sensibilidade reduzida.
Termos para indexação
Malus domestica Borkh.; melhoramento genético; amadurecimento; firmeza de polpa
Introducion
Significant physiological and biochemical changes occur during apple ripening. These changes result in a modification of the skin background degreening, the conversion of starch into soluble sugars content (SSC), a reduction in titratable acidity (TA) and flesh firmness, and the enhancement of volatile organic compounds content (JOHNSTON et al., 2009). In this sense, ethylene plays a key role on ripening changes (Wei et al., 2021), since the exposure of apples to exogenous ethylene triggers a rapid development of ripening with a climacteric peak in ethylene production and respiration rate (ZHENG et al., 2013; STORCH et al., 2015). Several technologies have an impact on the delay of fruit ripening and consequently on senescence during postharvest (HU et al., 2019).
Nevertheless, genetic factors may influence the ripening and senescence, potentially resulting in either a slowing or fastening of these processes. Different plant species exhibit varying degrees of ethylene-sensitivity in relation to fruit ripening. However, apple cultivars are generally considered to be highly sensitive to ethylene action. This fact is related to that the effect of exogenous ethylene at low concentrations from 0.03 to 0.1 μL L-1 are effective in promoting the ripening process (HU et al., 2019). For instance, the ethylene exposure of ‘Gala’ apples at concentrations of ≥ 1 μL L-1 during controlled atmosphere (CA) storage resulted in a greater quality loss due to an increase in fruit ripening (BRACKMANN et al., 2001).
A new apple cultivar from Epagri, registered as ‘SCS443 Isadora’, has been highlighted for its storage potential, being the main characteristic its prolonged shelf life (KVITSCHAL et al., 2023; DENARDI et al., 2023). ‘Isadora’ apples are marketed in Europe with the Samboá® commercial name, although it has only recently been released as a new cultivar (SAMBOA, 2023).
Nevertheless, a significant knowledge gap remains regarding the storability of ‘Isadora’ apple. Our previous studies suggest that a low ethylene production of ‘Isadora’ apples could be an important factor that influence the storability compared to other apple cultivars.
Furthermore, is postulated that, in addition to low ethylene production, the slow ripening and extended shelf life tolerance of this cultivar could be associated with low sensitivity to ethylene. Therefore, the main aim of this study was to evaluate the effect of exogenous ethylene application on ripening changes of quality traits of ‘Isadora’ apples.
Apples were harvested from a commercial orchard located in Fraiburgo (State of Santa Catarina, Brazil) during the 2021-2022 season. The ripening stage of fifteen fruits per replicate (n = 4, 60 fruits per treatment in total) was analysed at harvest. During postharvest storage, a completely randomized design was followed with four replicates of fifteen apples for each treatment. The treatments tested were: 1) Ethylene at 0 (control), 1, 10, 100 μL L-1; 2) 0 μL L-1 ethylene + 1-MCP at 1 μL L-1 applied every two days; and 3) 10 μL L-1 ethylene + 1-MCP at 1 μL L-1 at the beginning. In control treatment, where the ethylene concentration was 0 μL L-1, Always Fresh® ethylene absorbers (Soloeste, Iomerê, Brazil) were used and placed with the fruit during the storage. The absorbers were maintained throughout the experiment to prevent the potential accumulation of ethylene around the stored fruit. In addition, 1-MCP was applied every two days in control treatment, effectively inhibiting the synthesis of new ethylene receptors by the fruit during storage. An initial application of 1-MCP at 1 μL L-1 and 10 μL L-1 ethylene was performed to inhibit the ethylene receptors and evaluate the synthesis of new ones. This evaluation will restore ethylene-sensitivity in the ‘Isadora’ apple. The fruit were placed in a six-litre airtight glass jar and exposed to the gas through the septum in the glass lid. Ethylene was applied by syringe for two hours daily for fifteen days at the different concentrations tested. After thirty minutes of ethylene application, the composition of the headspace in the jars was analysed to confirm that the desired concentration had been achieved. Then, the fruit was placed in eighty-litre plastic containers with airtight seals to apply 1-MCP (Smart Fresh®, Frankfurt, Germany). A dose of 1 μL L-1 was used and the fruit was treated for twelve hours. The treatments were carried out immediately after harvest and the fruit was stored at room temperature conditions (20 ± 3 °C and 60 ± 5% RH). Ethylene production was registered after 7, 10, 12 and 14 days of storage, while respiration rate, skin background degreening, flesh firmness, SSC and TA were analysed after fifteen days of storage.
Fifteen hours after the ethylene application, respiration rate and ethylene production, expressed as ηmol of CO2 kg-1 s-1 and ηmol of C2H4 kg-1 s-1, respectively, were analysed.
Fruits were placed in six-litre airtight glass jar, where the respiration rate and ethylene production were determined immediately after two hours by measuring the concentration of CO2 and C2H4 inside the jars.
Three samples of the headspace were taken using a 1 mL of plastic syringe to analyse the ethylene production. Then, syringes were injected into a gas chromatograph (PerkinElmer®, Clarus 580 model, Norwalk, United States of America) equipped with a 3-metre-long Porapak N® column (80-100 mesh) and flame ionisation detector. The temperatures of detector, column and injector were 250, 70 and 130 °C, respectively.
The gases used were nitrogen, as the carrier gas, hydrogen, and synthetic air, with flow rates of 70, 45 and 450 mL min-1, respectively.
The headspace flow was circulated in a closed system through a gas analyser (Schelle®, GA-S1 model, Überlingen, Germany) which registered both O2 and CO2 levels for respiration rate. The concentration of CO2, the area of ethylene, the fruit weight used for the analysis, the time, and the jar volume were the factors used to calculate the respiration rate and the ethylene production. The skin degreening was expressed as hue angle (h°) and performed in the red colourless fruit background by using a Konica Minolta® colorimeter (CR- 400 model, Tokyo, Japan). Flesh firmness (N) was measured in the two opposite backgrounds of the equatorial fruit diameter, where a thin layer of skin was previously removed, with an electronic penetrometer (Güss Manufacturing Ltd, Cape Town, South Africa) coupled with a 11-mm tip.
Apples from the same replicate were cut and two opposite slices per each fruit were used and mixed. Then, the juice was extracted and used to determine the levels of SSC (°Brix) and TA, expressed as the major organic acid (malic acid). The SSC was determined using a digital refractometer (Atago®, model PR201α, Tokyo, Japan), while TA was obtained by titrating NaOH at 0.1 N with an automatic titrator (SI Analytics®, model Titroline® 5000, Weilheim in Oberbayern, Germany) that had been homogenised in 45 mL of distilled water to pH 8.10. Data were subjected to an analysis of variance (ANOVA) and means comparison among treatments were performed when these differences were significant by using Tukey’s test (p < 0.05). Furthermore, the average of each treatment tested for flesh firmness, skin background degreening, SSC, and TA was compared with the average at harvest by using Dunnett’s test (p < 0.05) to evaluate the ripening changes in this cultivar.
The application of exogenous ethylene did not induce ethylene production at 7, 10, 12, and 14 days than control treatment.
Furthermore, the application of 1-MCP did not show a significant effect on the ethylene production, as it can be observed in Table 1. The results showed for the first time that ethylene treatment did not promote an autocatalytic biosynthesis in ‘Isadora’ apples and, consequently, 1-MCP did not interfere in this key ripening stage. Apples are classified as climacteric fruits and show a significant increase in respiration rate and ethylene production during ripening (YANG et al., 2013). Usually, exogenous application of ethylene accelerates apple ripening and induces climacteric changes. For instance, the peak of ethylene production and respiration rate in fruit exposed to ethylene has been observed to occur at an earlier stage than in fruit not exposed to phytohormones (ZHENG et al., 2013). The most apple cultivars characterized synthetise ethylene throughout two systems; The system 1 is responsible for ethylene production in fruit developmental stage, characterized for a low production rate and ethylene auto-inhibitory response. The system 2 modulates the ethylene production in ripening stage and is characterised by an autocatalytic biosynthesis (MCMURCHIE; MCGLASSON; EAKS, 1972). Both systems are regulated by the presence of the 1-aminocyclopropane- 1-carboxylate synthase (ACS) and oxidase (ACO) enzymes, which both are different modulated by the transcription of various genes (BARRY; LLOP-TOUS; GRIERSON, 2000; KUMAR; KHURANA; SHARMA, 2013).
The absence of autocatalytic ethylene-induction in ‘Isadora’ apples as well as the regulation of ethylene production systems by different genes suggest that this cultivar could have transcriptomic differences, specially related with the system 2.
Respiration rate did not show significant differences after the application of 100 μL L-1 ethylene compared with untreated fruit. Similarly, the 1-MCP treatments did not affect this physiological parameter significantly more than the control. However, the treatment resulted in a significant reduction of respiration rate compared to the exogenous application of ethylene when 1-MCP was applied every two days (Table 2). Previously, the application of ethylene in apples accelerated the fruit respiration rate, according to Yang et al. (2013). On the other hand, an application of 1-MCP delayed the onset of ripening and reduced intensity of fruit respiration peak (YANG et al., 2013; FERNANDES et al., 2021). Both effects of ethylene and 1-MCP treatments on respiration rate have been not observed in ‘Isadora’ apples. However, the differences observed among treatments with ethylene and 1-MCP may indicate a weak influence of ethylene on the respiration process of ‘Isadora’ apples.
No significant differences were observed among treatments in terms of skin background degreening, SSC, TA, and flesh firmness (Table 2). However, when values of each treatment after fifteen days of storage were compared with quality traits at harvest, results showed that ‘Isadora’ apples exposed to ethylene (1, 10, and 100 μL L-1) and those fruits with only one application of 1-MCP + ethylene (T6) exhibited a significantly reduction of 3.5 to 5.6 % on the hº value, which slightly changed the skin background degreening during the storage. On the other hand, the untreated fruits and those treated with ethylene at 1, 10, and 100 μL L-1 had a significantly 18.6 % lower and 9.1 % higher values of TA and SSC, respectively, after fifteen days than harvest.
However, those apples treated with 1-MCP (T5 and T6) did not exhibit significant differences on TA compared with values at harvest. The SSC did not show significant differences between harvest and the 1-MCP treatment applied at the beginning (T6).
Flesh firmness did not change in any of the treatments tested compared with the harvest values (Table 2). In this sense, the morphological changes that occur during apple ripening follow a sequence of overlapping events. These events begin with the conversion of starch into sugar and a reduction in acidity content, followed by degreening of the skin background and a reduction in flesh firmness and, finally, an increase in volatile organic compounds (JOHNSTON et al., 2009).
In the present study, the increase in SSC and the reduction in TA occurred at a similar intensity, irrespective of the dose of ethylene applied or the inhibition of its action.
However, the effects derived from the ethylene application were significant when values of quality traits were compared to harvest ones. A similar effect was also observed on the colour background degreening. The exposure to exogenous ethylene or its inhibition by the application of 1-MCP did not influence the flesh firmness of ‘Isadora’ apples.
However, significant ripening changes during the postharvest storage were more pronounced in other cultivars of apples. For instance, the flesh firmness of ‘Elstar’ and ‘Nicoter’ apples decreased by 28.6 and 16.2 %, respectively, when the fruit was stored at 20 ºC for 14 days (THEWES et al., 2021). On the other hand, Ahmad, Zaidi, and Arshad (2021) reported a 37.5 and 25 % reduction in TA and flesh firmness, respectively, after 15 days of storage in ‘Red Delicious’ cultivar.
Similarly, Johnston et al. (2009) observed a 12.9 % increase in SSC and a 23.1% decrease in TA in ‘Royal Gala’ apples.
The role of ethylene in fruit ripening involves a series of sequential events. Ethylene is detected by receptors, which transmit the signal through a cascade of factors to a transcriptional regulatory protein named ethylene response factors. These proteins bind to ethylene-responsive elements, which are the target genes that can be either expressed or suppressed, affecting the biochemical modifications of ripening (BAPAT et al., 2010). Several genes are involved in the ethylene biosynthesis, perception, and signalling, which can be differentially expressed in different cultivars (HARB et al., 2012). These aspects could explain the fact that the Isadora cultivar showed reduced or no ethylene-sensitivity, although targeted transcriptomic approaches in the Isadora cultivar are strongly recommended as future studies to fill this knowledge gap.
Contradictorily, 1-MCP binds to receptors, thereby preventing the binding of ethylene and the subsequent cascade of events associated with ripening. Nevertheless, the efficacy of 1-MCP can be negated by the formation of novel ethylene receptors, triggering ripening-related changes (DIAS et al., 2021). The present study did not reveal any general effects of 1-MCP in ‘Isadora’ apples. However, this outcome may be attributed to the relatively low ethylene production of the fruit of this new cultivar. It is not possible to state with certainty that no new ethylene receptors were formed during the study. Although this hypothesis remains plausible, particularly given the absence of discernible differences between the application of 1-MCP at the outset (T6) and its subsequent reapplication at twoday intervals (T5). In conclusion, ‘Isadora’ apples have a high storability as the main postharvest characteristic and could be correlated with its relative ethylene-insensitivity.
This trait enables the apples to maintain their flesh firmness even after fifteen days at room temperature, despite exposure to exogenous ethylene. It is noteworthy that exposure to ethylene did not result in a further intensification of these changes, which serves to highlight the high storage potential of this new cultivar of apple.
Acknowledgements
Authors would like to express their gratitude to the retired EPAGRI researcher, Dr. Frederico Denardi.
References
-
AHMAD, F.; ZAIDI, S.; ARSHAD, M. Postharvest quality assessment of apple during storage at ambient temperature. Heliyon, London, v.7, p.e07714, 2021. https://doi.org/10.1016/j.heliyon.2021.e07714
» https://doi.org/10.1016/j.heliyon.2021.e07714 -
BAPAT, V.A.; TRIVEDI, P.K.; GHOSH, A.; SANE, V.A.; GANAPATHI, T.R.; NATH, P. Ripening of fleshy fruit: molecular insight and the role of ethylene. Biotechnology Advances, New York, v.28, p.94-107. https://doi.org/10.1016/j.biotechadv.2009.10.002, 2010
» https://doi.org/10.1016/j.biotechadv.2009.10.002 -
BARRY, C.S.; LLOP-TOUS, M.I.; GRIERSON, D. The regulation of 1-aminocyclopropane-1-carboxylic acid synthase gene expression during the transition from system-1 to system-2 ethylene synthesis in tomato. Plant Physiology, Washington, v.123, p.979-86, 2000. https://doi.org/10.1104/pp.123.3.979
» https://doi.org/10.1104/pp.123.3.979 -
BRACKMANN, A.; STEFFENS, C.A.; NEUWALD, D. A. MELLO, A. M. Storage of 'Royal Gala' apple under different temperatures and carbon dioxide and oxygen partial pressure. Revista Brasileira de Fruticultura, Jaboticabal, v.23, p.532-36, 2001. https://doi.org/10.1590/S0100-29452001000300016
» https://doi.org/10.1590/S0100-29452001000300016 -
DENARDI, F.; KVITSCHAL, M. V.; ARGENTA, L. C.; COUTO AND M.; ARAÚJO, L. SCS443 ISADORA: late ripening apple cultivar with very high fruit storage ability. Revista Brasileira de Fruticultura, Jaboticabal, v.45, p.e-161, 2023. https://doi.org/10.1590/0100-29452023161
» https://doi.org/10.1590/0100-29452023161 -
DIAS, C.; RIBEIRO, T.; RODRIGUES, A.C.; FERRANTE, A.; VASCONCELOS, M.W.; PINTADO, M. Improving the ripening process after 1-MCP application: Implications and strategies. Trends in Food Science and Technology, Oxford, v.113, p.382-96, 2021. https://doi.org/10.1016/j.tifs.2021.05.012
» https://doi.org/10.1016/j.tifs.2021.05.012 -
FERNANDES, R.C.; STEFFENS, C.A.; ANAMI, J.M.; MOSQUERA, D.J.C.; AMARANTE, C.V.T. de; BRACKMANN, A. Quality of ‘Cripps Pink’apples stored under controlled atmosphere with ultra-low and extremely low oxygen partial pressures or treated with 1-methylcyclopropene. Bragantia, Campinas, v.80, 2021. https://doi.org/10.1590/1678-4499.2021115
» https://doi.org/10.1590/1678-4499.2021115 -
HARB, J.; GAPPER, N. E.; GIOVANNONI, J. J.; WATKINS, C. B. Molecular analysis of softening and ethylene synthesis and signaling pathways in a non-softening apple cultivar ‘Honeycrisp’ and a rapidly softening cultivar ‘McIntosh’. Postharvest Biology and Technology, Amsterdam, v.64, p.94-103, 2012. https://doi.org/10.1016/j.postharvbio.2011.10.001
» https://doi.org/10.1016/j.postharvbio.2011.10.001 -
HU, B.; SUN, D.W.; PU, H.; WEI, Q. Recent advances in detecting and regulating ethylene concentrations for shelf-life extension and maturity control of fruit: A review. Trends in Food Science and Technology, Oxford, v.91, p.66-82, 2019. https://doi.org/10.1016/j.tifs.2019.06.010
» https://doi.org/10.1016/j.tifs.2019.06.010 -
JOHNSTON, J. W.; GUNASEELAN, K.; PIDAKALA, P.; WANG, M.; SCHAFFER, R. J. Co-ordination of early and late ripening events in apples is regulated through differential sensitivities to ethylene. Journal of Experimental Botany, Oxford, v.60, p.2689-99, 2009. https://doi.org/10.1093/jxb/erp122
» https://doi.org/10.1093/jxb/erp122 -
KUMAR, R.; KHURANA, A.; SHARMA, A.K. Role of plant hormones and their interplay in development and ripening of fleshy fruits. Journal of Experimental Botany, Oxford, v.65, p.4561-75, 2013. https://doi.org/10.1093/jxb/eru277
» https://doi.org/10.1093/jxb/eru277 - KVITSCHAL, M.V.; CHIESA, R.; ARGENTA, L.C.; DENARDI, F.; COUTO, M. Flesh pattern of apples ‘SCS443 ISADORA’ after long storage period in common cold atmosphere. Agropecuária Catarinense, Florianópolis, v.36, p.15-17, 2023.
-
MCMURCHIE, E.J.; MCGLASSON, W.B.; EAKS, I.L. Treatment of fruit with propylene gives information about the biogenesis of ethylene. Nature, London, v.237, p.235-6, 1972. https://doi.org/10.1038/237235a0
» https://doi.org/10.1038/237235a0 -
SAMBOA. Sambóa soo sweeeet. Disponível em: https://www.samboa.it/ Acesso em: 04 jan. 2023.
» https://www.samboa.it/ -
STORCH, T.T.; FINATTO, T.; PEGORARO, C.; DAL CERO, J.; LAURENS, F.; ROMBALDI, C.V.; GIRARDI, C.L. Ethylene-dependent regulation of an a-l-arabinofuranosidase is associated to firmness loss in ‘Gala’ apples under long term cold storage. Food Chemistry, London, v.182, p.111-9, 2015. https://doi.org/10.1016/j.foodchem.2015.02.123
» https://doi.org/10.1016/j.foodchem.2015.02.123 -
THEWES, F.R.; BALKEES, B.M.; BÜCHELE, F.; WÜNSCHE, J.N.; NEUWALD, D.A.; BRACKMANN, A. Ethanol vapor treatment inhibits apple ripening at room temperature even with the presence of ethylene. Postharvest Biology and Technology, Amsterdam, v.173, p.e-111415, 2021. https://doi.org/10.1016/j.postharvbio.2020.111415
» https://doi.org/10.1016/j.postharvbio.2020.111415 -
WEI, H.; SEIDI, F.; ZHANG, T.; JIN, Y. XIAO, H. Ethylene scavengers for the preservation of fruits and vegetables: a review. Food Chemistry, London, v.337, p.e-127750, 2021. https://doi.org/10.1016/j.foodchem.2020.127750
» https://doi.org/10.1016/j.foodchem.2020.127750 -
YANG, X.; SONG, J.; CAMPBELL-PALMER, L.; FILLMORE, S.; ZHANG, Z. Effect of ethylene and 1-MCP on expression of genes involved in ethylene biosynthesis and perception during ripening of apple fruit. Postharvest Biology and Technology, Amsterdam, v.78, p.55-66, 2013. https://doi.org/10.1016/j.postharvbio.2012.11.012
» https://doi.org/10.1016/j.postharvbio.2012.11.012 -
ZHENG, Q.; SONG, J.; CAMPBELL-PALMER, L.; THOMPSON, K.; LI, L.; WALKER, B.; LI, X. A proteomic investigation of apple fruit during ripening and in response to ethylene treatment. Journal of Proteomics, v.93, p.276-294, 2013. https://doi.org/10.1016/j.jprot.2013.02.006
» https://doi.org/10.1016/j.jprot.2013.02.006
Edited by
-
Scientific Editor
Alexandre pio Viana
-
Associate Editor
Ricardo Antonio Ayub
