Elsevier

Scientia Horticulturae

Volume 244, 26 January 2019, Pages 134-140
Scientia Horticulturae

Preharvest aminoethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP) effects on ethylene and starch concentrations of ‘Empire’ and ‘McIntosh’ apples

https://doi.org/10.1016/j.scienta.2018.09.031Get rights and content

Highlights

  • Aminoethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP) are pre-harvest PGRs.

  • Effectiveness of PGRs is affected by cultivar and timing of application.

  • PGRs inconsistently lower IEC.

  • PGRs do not consistently affect the rate of fruit softening or starch hydrolysis.

Abstract

Aminoethoxyvinylglycine (AVG; ReTain®) and 1-methylcyclopropene (1-MCP; Harvista) are used to delay apple fruit maturation and ripening, and thereby reduce fruit drop and manage harvest logistics. In this study, ‘McIntosh’ and ‘Empire’ fruit were treated with AVG at four weeks or two weeks, or with 1-MCP one week, prior to the anticipated first harvest date, to assess effects of these chemicals on maturation and ripening in relation to starch degradation. In a second season, ‘Empire’ fruit were treated with either AVG or 1-MCP four weeks and one week prior to the anticipated first harvest. Fruit from this experiment were also harvested to investigate the effects of treatment on ripening in air storage. Cultivar and timing of application influenced the efficacy of both AVG and 1-MCP in delaying the increase of internal ethylene concentration (IEC) and the starch pattern index (SPI), and the decrease of starch concentration, in the fruit. Little effect of treatment was found for the high ethylene producing ‘McIntosh’, with only the SPI being affected on the date of first harvest. ‘Empire’ fruit from trees treated with 1-MCP or AVG had lower IEC and were greener (higher absorbance difference index (IAD) values), and had lower SPIs and higher starch concentrations, but the effects were inconsistent and limited to only some harvest dates. In storage, only 1-MCP applied 10 d before harvest markedly slowed the increase in IEC and the rate of softening. AVG treatment effects on IEC were intermediate, between the one week 1-MCP treatment and the untreated controls and 4 week 1-MCP treatment, while it did not affect softening. Treatments did not affect the rate of starch concentration loss during storage.

Introduction

Aminoethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP) inhibit ethylene production by inhibiting 1-aminocyclopropane-1-carboxylase (ACC) synthase activity (Adams and Yang, 1979; Boller et al., 1979) and ethylene perception by binding to ethylene receptors (Sisler and Blankenship, 1996; Sisler et al., 1996), respectively. These products are used extensively as plant growth regulators (PGRs) in North America and elsewhere under the commercial names of ReTain® and Harvista, respectively, to prevent premature fruit drop, delay harvest to better manage the harvest and allow the harvest of larger fruit, and to improve responses of fruit to postharvest 1-MCP (McArtney et al., 2008; DeEll and Ehsani-Moghaddam, 2010; Watkins et al., 2010; Doerflinger et al., 2015c; Scolaro et al., 2015; Watkins, 2016). In the U.S.A., it is now common to find blocks within orchards sprayed with either PGR.

Time of harvest is the most important factor determining fruit quality after storage. Prediction of the harvest window is very important, especially for long term storage. The starch pattern index (SPI) is commonly used for this purpose (Doerflinger et al., 2015a). Therefore, if the SPI is used to assess the effects of PGRs on fruit maturity and ripening, it is important to understand how changes in the production and perception of the ripening hormone ethylene influences starch hydrolysis. Whether PGR applications delay maturation overall or affect only some physiological changes is not fully understood. Differences in sensitivity and dependency of such factors to ethylene levels have been shown in fruit with antisense suppression of 1-amino-cycolopropane-carboxylase oxidase (MdACO1) (Johnston et al., 2009). Sensitivity to ethylene is negatively correlated to dependence on ethylene, therefore, the less sensitive a maturity aspect, the more dependent it is on ethylene (Johnston et al., 2009), e.g. low levels of ethylene (0.01 μL L−1) initiated the degradation of starch and increasing ethylene to 0.1 μL L−1 hastened starch degradation, but other factors, such as skin background color, were not affected by low levels of ethylene and only increased at climacteric ethylene levels (1 μL L−1).

AVG delayed some aspects of maturation in ‘Gala’ and ‘Fuji’ fruit (do Amarante et al., 2002; do Amarante and Steffens, 2009). Starch degradation was also delayed by AVG application in ‘McIntosh’ (Schupp and Greene, 2004). Stover et al. (2003) found that the effectiveness of AVG on internal quality parameters of ‘McIntosh’ was dependent on region; effects on starch hydrolysis were found for fruit grown in the Champlain region, but not for the Mid-Hudson growing region in New York. AVG delayed the onset of the ethylene climacteric (Schupp and Greene, 2004; Yuan and Carbaugh, 2007; Yuan and Li, 2008). Effectiveness of AVG on IEC was linearly correlated to the applied concentration (Schupp and Greene, 2004). Carry-over effects of AVG in reducing IECs after storage was dependent on cultivar (Elfving et al., 2007).

Neuwald et al. (2010) found little effect of preharvest 1-MCP on postharvest SPI changes in a comparison of on-tree maturation and postharvest ripening. Delayed starch degradation after treatment with preharvest 1-MCP was found in ‘Golden Delicious’ (McArtney et al., 2008) and ‘Bisbee Delicious’ (Yuan and Li, 2008) but to varying degrees. The effectiveness of slowing starch degradation was dependent on the concentration of preharvest 1-MCP in ‘Golden Delicious’, although no effect was detected for ‘Law Rome’ (McArtney et al., 2008). In a follow up trial (McArtney et al., 2009), preharvest 1-MCP effects on SPI or IEC of ‘Golden Delicious’ or ‘Law Rome’ were affected by application time and delays before harvest. Watkins et al. (2010) found a reduction of IEC by preharvest 1-MCP in both ‘McIntosh’ and ‘Delicious’, but effects on SPI in treated fruit of both cultivars were only found 14 d after the anticipated first harvest date. Treatment effects on IEC after storage were dependent on 1-MCP concentration and timing of application (Elfving et al., 2007; Watkins et al., 2010). Postharvest 1-MCP delayed the decrease of delta absorbance (IAD) values, an indicator of chlorophyll a concentration, in ‘Aurora Golden Gala’, ‘Empire’ and ‘Fuji’ fruit during ripening and storage (Toivonen and Hampson, 2014; Doerflinger et al., 2016). However, preharvest 1-MCP altered the relationships between IAD and harvest indices (Doerflinger et al., 2016).

The relationships between IECs and starch concentrations in relation to PGRs are still unclear. The objective of this study therefore was to investigate the effects of preharvest AVG and 1-MCP sprays, including application time, on maturity and starch concentration losses in fruit before harvest and during air storage.

Section snippets

Preharvest plant growth regulator applications

In 2012, trees of ‘McIntosh’ and ‘Empire’ cultivars in the Lansing Orchard in NY were sprayed with AVG (Valent BioSciences Corporation, Libertyville, IL) or 1-MCP (AfxRD038, AgroFresh Inc., Springhouse, PA). For ‘McIntosh’, AVG was applied on August 9 (4 w AVG) and 23 (2 w AVG), and 1-MCP on August 30 (1 w 1-MCP). For ‘Empire’, AVG was applied on August 21 (4 w AVG) and September 4 (2 w AVG), and 1-MCP on September 11 (1 w 1-MCP). AVG was applied at 823 g ha−1 and 1-MCP at a concentration of

‘McIntosh’

The anticipated first harvest date for ‘McIntosh’ fruit in this block was September 6, 2012. IECs were consistently preclimacteric (<1 μL L−1) on August 23 and then increased in fruit from all treatments at later dates (Table 1). There was variability in IEC in fruit from each treatment, e.g. ranging from 1 μL L−1 to over 880 μL L−1 in control fruit on August 30. Fruit with high IECs were found in all treatments, with 19, 17, 14, and 14% of fruit over 1 μL L-1 in control, 4 week AVG, 2 week AVG

Discussion

Manipulation of ethylene production does not affect all aspects of maturation equally. Some aspects are more affected by, or sensitive to, higher endogenous and exogenous ethylene concentrations than others (Johnston et al., 2009). The onset of the climacteric rise is typically delayed if fruit are treated with AVG and 1-MCP prior to harvest (do Amarante et al., 2002; Yuan and Carbaugh, 2007; McArtney et al., 2009; Watkins et al., 2010; Doerflinger et al., 2015c, 2016). IEC of ‘McIntosh’ was

Acknowledgements

F.C. Doerflinger was supported by a Horticulture Section Graduate Assistantship. We thank Rose Harmon for technical assistance. Funding for this research was provided by the NY Apple Research and Development Program and AgroFresh, and we thank Valent BioSciences for providing AVG. This work was also supported by the USDA National Institute of Food and Agriculture, Hatch project 2013-14-483, Improving Quality and Reducing Losses in Specialty Fruit Crops through Storage Technologies (NE-1336).

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    Current address: Plant & Food Research Australia, Hartley Grove, Waite Campus, Urrbrae, SA 5064 Australia.

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