ARTICLES RIA / Vol. 41 N.º 1 Strategies to modulate 1-MCP effects in ‘Packham’s Triumph’ pears: simultaneous application with ethylene or CO2 and temperature treatments CALVO, G.1; CANDAN, A. P.1 ABSTRACT Two trials were conducted in order to evaluate the effectiveness of several approaches to restore ripening ability of ‘Packham’s Triumph’ pears treated with 1-methylcyclopropene (1-MCP). Results showed that a simultaneous application of 0.3 μL L-1 1-MCP with 0.15 or 0.3 μL L-1 ethylene or with 5% CO2 allowed the fruit to ripen after 160d of storage. Among these treatments, 0.3 μL L-1 1-MCP with 0.15 μL L-1 ethylene absolutely controlled superficial scald even after 210d of storage. When 0.6 μL L-1 1-MCP were applied, the simultaneous application with 0.6 μL L-1 ethylene or with 5% CO2 allowed the softening of the fruit only after 230d, and also maintaining a very low incidence of superficial scald. The efficacy of temperature treatments depended on the time that fruit were warmed. A warming of 2 or 3 weeks was needed to restore ripening in fruit treated with 0.6 μL L-1 1-MCP and stored for 230 or 160d, respectively and 2 weeks was also effective in fruits treated with LSD 1-MCP and stored for 210d. However, these temperature treatments developed the highest incidence of superficial scald. In conclusion, the competition for the binding sites by ethylene or CO2 are the most promissory strategies since they modulate 1-MCP effects maintaining low incidence of superficial scald in ‘Packhams Triumph’ pears. Keywords: cold storage – ripening - superficial scald. INTRODUCTION Some european pears (Pyrus communis) cultivars, such as ‘Packham’s Triumph’, are highly susceptible to superficial scald, and postharvest treatments with diphenylamine and ethoxyquin are commercially used to prevent this very important physiological storage disorder. However, many countries have banned the use of such antioxidants, which mandates development of alternative methods to control scald (Calvo and Kupferman, 2012). The application of 1-methylcyclopropene (1-MCP) immediately after harvest greatly reduces superficial scald development and its effectiveness was associated to the reduction of ethylene synthesis, α-farnesenes and conjugated trienols (Chen and Spotts, 2005). In pears, 1-MCP treatment also allows delaying softening and loss of green colour (Mitcham et al., 2001; Calvo, 2004; Ekman et al., 2004). Pears are extremely sensitive to 1-MCP exposure, compared to apples and the residual effects of the current commercial applicable dose (0.3 μL L-1) are not easily dissipated during a reasonable marketing period (Blankeship and Dole, 2003) and the concentration that provides an effective control of superficial scald can inhibit the normal fruit ripening during the marketing period (Chen and Spotts, 2005). Thus, it is still a challenge to reach a balance between storage benefits and eventual ripening of the fruit for marketing (Mitcham et al., 2001; Villalobos-Acuña et al., 2011). In pears, the recovery of ethylene sensitivity mainly depends Area Poscosecha, EEA Alto Valle, Instituto Nacional de Tecnología Agropecuaria (INTA). CC782, CP(8332), Gral. Roca, Río Negro, Argentina. E-mail: [email protected]; [email protected] 1 Received June 17th 2014 // Accepted March 6th 2015 // Published online April 29th 2015 Strategies to modulate 1-MCP effects in ‘Packham’s Triumph’ pears: simultaneous application with ethylene or CO2 (...) April 2015, Argentina on 1-MCP concentration applied, storage length and fruit ripening stage at the time of treatment (Calvo, 2004). In order to re-start the ripening process of 1-MCP treated pears, several strategies have been investigated. The application of exogenous ethylene after cold storage does not reverse inhibition caused by 1-MCP in pears (Mitcham et al., 2001; Calvo, 2004). However, the simultaneous application of 1-MCP with ethylene in ratios from 1:0.5 to 1:2 could facilitate subsequent restoration of ripening, probably by competition of both compounds for the ethylene binding sites (Manriquez and Defilippi, 2011; Cucci and Regiroli, 2011; Chiriboga et al., 2011). In this sense, a simultaneous application of 1-MCP and CO2 could also be effective, since CO2 can reduce the ethylene action due to a competition at the ethylene receptor site (Burg and Burg, 1967; Gorny and Kader, 1997) or to secondary effects such as pH changes (Sisler and Wood, 1988). However, this approach had not been analyzed until the present work. Finally, Bai et al. (2007) and Chiriboga et al. (2010) reported that warming the fruits at 10 to 20°C during or after the storage may restore the softening ability of several pear cultivars treated with 1-MCP, being the effect attributed to the stimulation of the synthesis of new receptors (Jiang et al., 1999). The current research was conducted to evaluate the efficacy of different strategies to modulate 1-MCP effects in ‘Packham’s Triumph’ in order to allow the ripening of the fruit and reducing the occurrence of superficial scald. 1-MCP treatments Fruit were treated with 0.3 or 0.6 µL L-1 1-MCP in a sealed chamber by adding warm water on SmartFreshTM powder. During treatment, fans inside the chambers ensured a fast and homogeneous gas distribution. Fruit were treated for 24 h during cooling and the chamber was then opened and thoroughly aerated. CH4 and CO2 treatments For simultaneous applications with ethylene, the volume of an enriched gaseous mixture (5% CH4 in air) needed to obtain 0.6, 0.3 and 0.15 μL L-1 ethylene in a sealed chamber was taken with a syringe and then injected immediately after beginning the release of 1-MCP treatment. To obtain 5% CO2 v/v in a sealed chamber, an enriched gaseous mixture (99% CO2 in air) was injected directly from a gas tube equipped with a flow-meter. Temperature treatments Post-storage temperature treatments were carried out prior each evaluation date, by warming the fruit in a 17 ºC room during 1, 2 or 3 weeks (according with each treatment) after which they were returned to cold storage for another 1 week. Analysis of ethylene production MATERIAL AND METHODS Plant material and treatments In a first trail ‘Packham’s Triumph’ pears from a commercial orchard were harvested at preclimacteric stage on February 10, 2009 (firmness: 64.1 N, soluble solids: 11.3%, titratable acidity: 2.68 g L-1, colour 117.3 hº, starch degradation: 45.0%). Fruits were treated with 0 μL L-1 (Control), LSD 1-MCP, 0.6 μL L-1 1-MCP. To modulate 1-MCP effects, the strategies evaluated were: simultaneous application of 0.3 μL L-1 1-MCP + 0.3 μL L-1 ethylene (0.3+0.3ET), LSD 1-MCP + 0.6 μL L-1 ethylene (0.6+0.6ET), 0.6 μL L-1 1-MCP + 5% v/v CO2 (0.6+CO2) and temperature treatments during 2 weeks for 0.3 μL L-1 1-MCP treated fruit (0.3+2W) or during 2 and 3 weeks for 0.6 μL L-1 1-MCP treated fruit (0.6+2W and 0.6+3W, respectively). Fruit were packaged in cardboard pear boxes with plastic liners (LDPE, 25 µm) and stored at -0.5 ºC for 160 and 230 days. In a second trial, ‘Packham’s Triumph’ from the same orchard were harvested at preclimacteric stage on February 23, 2010 (firmness: 60.8 N, soluble solids: 11.2%, titratable acidity: 2.28 g L-1, hº: 116.9, starch degradation: 39.7%). Fruit were treated with 0 μL L-1 (Control) or 0.3 μL L-1 1-MCP and the strategies assayed were: simultaneous application of 0.3 μL L-1 1-MCP + 0.15 μL L-1 ethylene (0.3+0.15ET), 0.3 μL L-1 1-MCP + 5% v/v CO2 (0.3+CO2) and temperature treatments during 1, 2 or 3 weeks (0.3+1W, 0.3+2W and 0.3+3W, respectively). Fruit were packaged in cardboard pear boxes with plastic liners (LDPE, 25 µm) and stored at -0.5 ºC for 150 and 210 days. The ethylene production (nl g-1 h-1) was measured on 3 replicates of 1 fruit each during the shelf life at 20 °C following each storage period. Fruit were placed into a 1.5 L sealed jar for 30 min. A sample of 1 mL from the headspace gas was evaluated by gas chromatography (GC-14A, Shimadzu, Japan) utilizing an alumina column and a FID detector. Maturity index assessment Maturity indexes were evaluated on 3 replicates of 20 fruit each, immediately after storage time and after 7 and 14 d of ripening at 20 °C. Firmness (N) was measured on two sides of each fruit using an electronic penetrometer (FTA14, Güss, South Africa) fitted with an 8 mm probe. Soluble solids (%) were measured with a digital refractometer (PAL1, Atago, Japan) on the juice from fruit of each replication. Titratable acidity (g L-1) was measured by titration of 10 ml of the juice with NaOH 0.1 N to pH 8.2 end point. Epidermis color was measured on two opposite sides of each fruit with a colorimeter (CR400, Minolta, Japan) and expressed as hue angle (hº), where: hº <102 indicated that fruit were essentially yellow (Ekman et al., 2004). Superficial scald assessment The percentage of fruit showing superficial scald was measured visually on 3 replicates of twenty fruit each one, immediately after each storage time and after 7 and 14 d of ripening at 20 °C. CALVO, GABRIELA1; CANDAN, ANA PAULA1 ARTICLES RIA / Vol. 41 N.º 1 Statistical analysis inhibited ethylene production until the end of the experimental period, and no differences were observed among concentrations (Figure 1 and 2). Data were analyzed by ANOVA and subjected to mean separation by DGC test (0.05) using the software INFOSTAT/ Professional Version 2006p.1. In ethylene production figures, LSD values according to Fisher test (0.05) are presented. RESULTS Ethylene production after storage Ethylene production (nl/g/h) 80 60 40 LSD=15,5 20 0 0 2 4 6 8 10 12 60 40 LSD=17,3 20 0 150 100 LSD=53,6 50 0 0 2 4 6 8 10 12 14 Time at 20ºC (days) 0.3 Control 0.6+0.6ET 0.6 0.6+CO2 0.6+2W 2 4 6 8 10 12 14 8 10 12 14 B 250 80 0 A 200 14 B 100 Ethylene production (nl/g/h) 250 A 100 Ethylene production (nl/g/h) Ethylene production (nl/g/h) In both trials, the ethylene production of control fruit was detected immediately after removal from cold storage and reached the climacteric peak after 5 days (160 and 150 d of storage) and after 2 days of shelf life at 20 ºC (230 and 210 d of storage). Treatments with 0.3 and 0.6 μL L-1 1-MCP Simultaneous pre-storage application of 1-MCP and ethylene allowed the ethylene production to resume during ripening, depending on the applied concentrations and the storage length. In trial 1, 0.3+0.3ET fruit exhibited similar behavior than controls after the two storage periods, showing that simultaneous application at this concentration completely restores the fruit ability of producing ethylene. In contrast, 0.6+0.6ET treatment produced a partial restoration (Figure 1). In trial 2, fruit treated with 0.3+0.15ET increased ethylene production in comparison with those treated with 0.3 μL L-1 1-MCP, but did not reach the climacteric peak (Figure 2). 200 LSD=36,1 150 100 50 0 0 2 4 6 Time at 20ºC (days) 0.3+0.3ET 0.3+2W 0.6+3W Figure 1. Ethylene production of during shelf life at 20 ºC after 160 (A) and 230 d (B) of storage ‘Packham’s Triumph’ pears in treated with different strategies to modulate 1-MCP (Trial 1). LSD according to Fisher test (0.05). Control 0.3+0.15ET 0.3 0.3+CO2 0.3+1W 0.3+3W 0.3+2W Figure 2. Ethylene production during shelf life at 20 ºC after 150 d (A) and 210 d (B) of storage of ‘Packham´s Triumph’ pears treated with different strategies to modulate 1-MCP (Trial 2). LSD according to Fisher test (0.05). Strategies to modulate 1-MCP effects in ‘Packham’s Triumph’ pears: simultaneous application with ethylene or CO2 (...) April 2015, Argentina The effectiveness of simultaneous application of 1-MCP and CO2 was dependent on the concentration of 1-MCP applied and the length of storage. In the first trial, 5% CO2 partially restored ethylene production of 0.6 μL L-1 1-MCP treated fruit only after 230 d of storage (Figure 1). However, in the second trial when 0.3 μL L-1 1-MCP was applied, the treatment with 5% CO2 allowed a higher recovery of ethylene production, mainly after 210 d of cold storage (Figure 2). The efficacy of temperature treatments depended on the time of exposure at 17 ºC and the storage length. In trial 1, the efficacy of a 3-week period (0.6+3W) to increase ethylene production was higher than a 2–week period (0.6+2W and 0.3+2W) (Figure 1). Similarly in trial 2, fruit stored for up 150 d required 3 weeks at 17 °C to recover the ability of produce ethylene, while only 1 or 2 weeks were enough when the fruit was stored longer (Figure 2). Fruit ripening after cold storage For pears, optimum fruit firmness to reach the desired texture and juiciness for consumption is 18-27 N (Bai et al., 2007; Kappel et al., 1995). According to results presented here, in both trials, control fruit softened beyond the recommended values for consumption after the 7 d at 20 ºC 160 day-storage Days at 20 ºC 0 7 Firmness Color Firmness Color (N) (hº) (N) (hº) Control 58.9 b 108.8 b 35.8 c 99.6 c 0.3 μL L-1 63.1 b 112.0 a 57.9 a 109.4 a 0.3+0.3ET 59.1 b 108.0 b 45.4 b 106.8 b 0.3+2W 64.7 a 109.9 b 59.6 a 101.9 c 0.6 μL L-1 62.2 b 113.1 a 49.3 b 110.3 a 0.6+0.6ET 58.7 b 110.8 b 63.0 a 109.3 a 0.6+CO2 61.2 b 109.6 b 60.7 a 110.5 a 0.6+2W 66.3 a 111.9 a 51.2 b 100.6 c 0.6+3W 58.8 b 106.4 c 45.0 b 95.5 d p Value 0.0144 0.0002 <0.0001 <0.0001 Control 10.8 e 106.7 c 17.7 c 92.5 c 0.3 μL L-1 60.9 a 113.0 a 56.6 a 109.8 a 0.3+0.3ET 12.2 e 103.1 d 20.5 c 100.7 b 0.3+2W 50.4 c 106.9 c 30.0 b 98.7 b 0.6 μL L-1 63.2 a 112.6 a 64.0 a 109.8 a 0.6+0.6ET 47.6 c 109.5 b 21.9 c 102.0 b 0.6+CO2 57.3 b 111.0 b 35.9 b 106.7 a 0.6+2W 52.6 c 107.2 c 26.1 b 98.6 b Treatment 0.6+3W 36.0 d 99.2 e 15.3 c P Value <0.0001 <0.0001 <0.0001 <0.0001 Control 7.3 d 95.4 d 15.2 b 86.7 c 63.7 a 109.3 a 58.4 a 102.8 a 5.0 d 94.4 d 15.6 b 95.4 b 0.3 μL L-1 0.3+0.3ET 14 230 day-storage 92.7 c 0.3+2W 32.4 c 97.4 c 16.5 b 91.6 c 0.6 μL L-1 71.6 a 110.8 a 57.8 a 102.5 a 0.6+0.6ET 27.1 c 99.9 c 9.6 b 96.2 b 0.6+CO2 46.1 b 104.9 b 12.6 b 94.3 b 0.6+2W 23.7 c 96.9 c 13.7 b 89.5 c 0.6+3W 13.1 d 93.1 d 8.3 b 85.4 d p Value <0.0001 <0.0001 <0.0001 <0.0001 Table 1. Firmness and epidermis colour of ‘Packham´s Triumph’ pears treated with different strategies to modulate 1-MCP effect (Trial 1). Evaluations were done after a 160 and 230 d of storage at -0.5 ºC and after 0, 7 and 14 d shelf life at 20 ºC. Mean separation DGC (0.05). CALVO, GABRIELA1; CANDAN, ANA PAULA1 ARTICLES RIA / Vol. 41 N.º 1 150 day-storage Days at 20 ºC 0 Firmness Color Firmness Color (N) (hº) (N) (hº) Control 47.6 b 110.3 b 45.5 b 108.1 c 0.3 μL L-1 54.4 a 115.6 a 51.7 a 113.9 a 0.3+0.15ET 50.9 b 115.0 a 50.7 a 113.9 a 108.2 c Treatment 0.3+CO2 51.4 b 112.0 b 46.7 b 0.3+1W 55.2 a 112.0 b 51.3 a 110.6 b 0.3+2W 58.0 a 111.1 b 44.4 b 102.4 d 0.3+3W 49.5 b 106.0 c 22.0 c 93.9 e p Value 0.0220 0.0001 <0.0001 <0.0001 Control 7 14 210 day-storage 8.0 d 102.9 b 7.6 c 102.5 b 0.3 μL L-1 58.8 a 114.6 a 50.6 a 112.7 a 0.3+0.15ET 42.5 b 112.8 a 37.0 b 110.5 a 105.6 b 8.3 c 104.0 b 0.3+CO2 13.3 d 0.3+1W 59.7 a 111.2 a 29.5 b 102.5 b 0.3+2W 54.3 a 107.5 b 11.0 c 97.2 c 0.3+3W 28.1 c 97.4 c 8.0 c 97.5 c p Value <0.0001 <0.0001 <0.0001 <0.0001 Control 3.3 c 94.8 b 0.3 μL L-1 51.5 a 107.9 a 0.3+0.15ET 15.8 c 99.1 b 5.5 c 93.5 b 0.3+1W 39.7 a 101.3 b 0.3+2W 23.6 b 96.5 b 0.3+CO2 0.3+3W 12.3 c 94.3 b p Value <0.0001 0.0002 Table 2. Firmness and epidermis colour of ‘Packham´s Triumph’ pears treated with different strategies to modulate 1-MCP effect (Trial 2). Evaluations were done after a 150 and 210 d of storage at -0.5 ºC and after 0, 7 and 14 d shelf life at 20 ºC. Mean separation DGC (0.05). subsequent to both storage periods. In contrast, fruit treated with 0.3 and 0.6 μL L-1 never reached eating quality, as they maintained firmness values over 50 N, even after 14 d of shelf life (Tables 1 and 2). All the strategies evaluated were effective to modulate, the effect of 1-MCP treatment on firmness, and the effect was greater as the length of cold storage increases (Tables 1 and 2). As observed for ethylene production, the efficacy of simultaneous application with ethylene depended on the concentration of 1-MCP used. In the first trial, 0.3+0.3ET treatment allowed a complete recovery after both storage periods, and the fruit reached similar firmness values as controls, but the fruit treated with the 0.6+0.6ET required 14 or 7 d to reach eating quality after 160 or 230 d of storage, respectively (Table 1). In the second trial, fruit from 0.3+0.15ET softened at a lower rate than controls and reached firmness lower than 18 N after 150 d of storage followed by 14 d of shelf life (Table 2). The recovery of fruit softening caused by CO2 was complete when it was simultaneously applied to fruit treated with 0.3 μL L-1 1-MCP (Table 2), but partial when the concentration was 0.6 μL L-1, requiring a longer storage period (230 d) to reach an appropriate firmness after 14 d of shelf life (Table 1). The effect of temperature treatments on restoring fruit ripening ability was greater when the period at 17 ºC and the cold storage time were longer. In the first trial we observed that 3 weeks at 17 ºC was effective to modulate 1-MCP effects after 160 d of storage while 2 weeks at 17 ºC were enough when storage extended up to 230 d irrespective of the applied dose (Table 1). In the second trial, 3 weeks at 17 ºC was the only effective temperature treatment allowing correct softening within 7 d of shelf life after 150 d storage, while 2 weeks at 17 ºC was enough after 210 d of storage (Table 2). Superficial scald In the first trail, superficial scald incidence in control fruit was 27% and 100%, after 160 and 230 d of storage + 7 d of shelf life respectively. In the second trial, control fruit Strategies to modulate 1-MCP effects in ‘Packham’s Triumph’ pears: simultaneous application with ethylene or CO2 (...) April 2015, Argentina showed 0% and 56% of affected fruit after 150 and 210 d of storage followed by 7 d of shelf life (Figure 3), denoting less susceptibility to scald in fruit of this season. Application of 0.3 μL L-1 and 0.6 μL L-1 1-MCP reduced the incidence of the disorder, with a maximum of 8% of affected fruit, after 230 d of storage + 7 d of shelf life in Trial 1 and a complete inhibition in Trail 2. The treatments applied to restore fruit ripening maintained a low incidence of scald (Figure 3) when the fruit were stored for up 150 or 160 d. When storage period was extended for up 230 or 210 d, scald incidence increased and some of the treatments that proved to be effective in modulating the effects of 1-MCP on firmness showed high incidence of scald. The simultaneous application with ethylene or CO2 reduced superficial scald respect to controls, with 0.6+0.6ET, 0.6+5%CO2 and 0.3+0.15ET the most effective Superficial Scald (%) 100 a A 80 b 60 40 c a 20 b b b b b b b b 0 Control 0.3 0.6+CO2 Superficial Scald (%) 100 d d d 160 + 7 d c c d 230 + 7 d 0.6 0.3+0.3ET 0.3+2W 0.6+2W 0.6+0.6ET 0.6+3W a a B 80 b 60 40 c 20 0 a b b b b b b d d 150 + 7 d Control d 210 + 7 d 0.3 0.3+1W 0.3+0.15ET 0.3+2W 0.3+CO2 0.3+3W Figure 3. Superficial scald incidence in ‘Packham´s Triumph’ pears treated with different strategies to modulate 1-MCP. Data correspond to the percentage of fruit from total population showing scald symptoms. Evaluations were done following 7 d of shelf life at 20 ºC, after 160 and 230 d of storage in Trial 1 (A) and after 150 and 210 d of storage in Trial 2 (B). Mean separation DGC (0.05). treatments in Trial 1 and Trial 2, respectively. In general, temperature treatments were less effective in controlling superficial scald and the percentage of affected fruit increased with the length of exposure at 17 ºC. Moreover, these treatments increased the incidence of this disorder compared to control fruit in 2010 (Figure 3). DISCUSSION Delaying pear ripening and senescence to extend fruit storage without the appearance of physiological disorders is the most important benefit of 1-MCP application (Villalobos-Acuña et al., 2011). However, the use of 1-MCP in European pears is potentially problematic because the residual effect is not easily dissipated during a reasonable marketing period following cold storage (Ekman et al., 2004; Chen and Spotts, 2005). The results of this study show that 1-MCP treatment is very effective in reducing ethylene production and in delaying ripening in ‘Packham´s Triumph’ pears, as already been reported in many pear cultivars (Calvo, 2004; Ekman et al., 2004; Calvo and Sozzi, 2004; Chen and Spotts, 2005). As was expected, 1-MCP treatment inhibited the normal ripening of the fruit maintaining firmness values above 50 N even after 14 d of shelf life. Since 1-MCP competes with ethylene for binding sites, its effectiveness depends on the applied concentration until receptor saturation (Ekman et al., 2004). However, no differences between 0.3 and 0.6 mL L-1 1-MCP were observed in this study, which suggests that 0.3 µL L-1 may be sufficient to block all the receptors and reduce ethylene production in ‘Packham´s Triumph’ pears. The development of superficial scald is the main limitation in ‘Packhams Triumph’ stored in regular air and the standard practice for scald control is a postharvest treatment with ethoxyquin or diphenylamine. However, regulations governing the use of chemicals to control diseases and disorders of apples and pears in storage are becoming increasingly stringent, especially in European Union (EU) countries, and it is essential to develop alternative methods to control this disorder (Calvo and Kupferman, 2012). Regarding the use of 1-MCP, it is a good alternative to current chemicals for control storage scald in apples. However it application to pears provides control of storage scald as well as the reduction in senescent scald, but ripening may be inhibited after storage (Calvo and Kupferman, 2012). Results presented here support that 1-MCP decreased the incidence of superficial scald but prevented the normal ripening of the fruits during the entire experimental period in both trials, which demonstrates the need to adapt this technology for commercial use. Competitive strategies of applying 1-MCP with ethylene showed to be effective to restore the ability of pear to ripen after long cold storage, though the treatment effectiveness depends strongly on the concentrations used. Ethylene application overcome the inhibitory effect of 0.3 mL L-1 of 1-MCP after 160d of storage and it was also effective to restore ripening in fruit treated with 0.6 mL L-1, after 230 d of storage. It suggests that a si- CALVO, GABRIELA1; CANDAN, ANA PAULA1 ARTICLES multaneous application of 1-MCP and ethylene (1:1 or 1:0.5 rate) will be effective according with the 1-MCP applied dose and the storage length. When 0.3 mL L-1 ethylene was applied to fruit treated with 0.3 mL L-1 1-MCP, ripening restoration was complete but when the concentration was 0.15 mL L-1 ethylene, the restoration was partial and fruit showed a ripening rate intermediate between control and 1-MCP treated fruit. Among these treatments, 0.6+0.6ET and 0.3+0.15 are the most interesting treatments, since 0.3+0.3ET showed higher incidence of superficial scald. The simultaneous application of 0.6 mL L-1 1-MCP and LSD ethylene (1:0.5 rates) was the most promising treatment in ‘Conference’ pears (Chiriboga et al., 2011). Additionally, 1-MCP treatment applied in combination with ethylene (1:1 rates) showed an effect in ripening of ‘Packham’s Triumph’ pears, being this response intermediate compared to 1-MCP applied immediately after harvest and the control fruit without treatment (Manriquez and Defilippi, 2011). The simultaneous application of 1-MCP with 5% CO2 was also effective to restart ripening. As was observed with ethylene application, the CO2 effect was dependent on the concentration of 1-MCP applied and restored ripening completely in 0.3 μL L-1 1-MCP treated fruit but only partially in 0.6 μL L-1 1-MCP treated fruit. According to our knowledge, this would be the first study that demonstrates the efficacy of simultaneous application of CO2 and 1-MCP to reverse 1-MCP ripening inhibition in pears after a sufficient length of storage. The mechanism by which CO2 counteracts the inhibitor effect of 1-MCP allowing further fruit ripening has to be elucidated. Burg and Burg (1967) and Gorny and Kader (1997) proposed that inhibition of ethylene biosynthesis by CO2 is mediated through the receptor site. Then, the effect of the simultaneous application could be explained through the competition between CO2 and 1-MCP for ethylene receptors. On the other hand, it was also demonstrated that the inhibition by CO2 could influence ethylene production rather than ethylene perception (De Wild et al., 1999) mainly through secondary effects such as pH changes (Sisler and Wood, 1988). It is also important to use an appropriate CO2 concentration, since Chavez-Franco and Kader (1993) reported that in pear, ethylene production was stimulated by 1% CO2 and inhibited by 5-20% CO2. Previous studies showed that inhibition of ethylene synthesis or action reduces α-farnasene production and consequently inhibits superficial scald (Chen and Spotts, 2005). In this study, treatments that proved to be more effective in restoring fruit ripening in fruit treated with 1-MCP were those with a higher incidence of scald, while those that allowed a partial restoration, such as 0.6+1-MCP+5%CO2 and 0.3+0.15ET, maintained a lower scald incidence. Another promising strategy to restore ripening in pears treated with 1-MCP is to expose the fruit to temperatures in the range of 15-20 ºC for variable durations. Temperature exposure could favor the release of 1-MCP from the receptors or the synthesis of new ethylene receptors, or an interaction of both factors (Villalobos-Acuña et al., 2011). Temperature treatments were effective in restoring ripening of 1-MCP treated ‘Blanquilla’ and ‘Bartlett’ pears, but not in Conference and Beurré D’Anjou cultivars (Bai et al., RIA / Vol. 41 N.º 1 2007; Chiriboga et al., 2010). Results obtained in this study indicate that this strategy is effective also in restoring the ripening ability of ‘Packham’s Triumph’ pears, being the 0.3+1W the most interesting treatment, allowing softening after 230 d plus shelf life and even controlling superficial scald. In contrast, fruit treated with 0.3+2W and 0.3+3W recovered the ability to ripen but developed more superficial scald than control fruit. In ‘Bartlett’ pears, the most suitable combinations to restore the fruit ripening capability in 0.3 μL L-1 1-MCP treated fruit were 10 d at 20 ºC or 20 d at 10 ºC after 2 months of storage, and 10 d at 15 ºC after 4 months of storage 17. Similarly, 5 to 15 d at 15 ºC was enough to recover fruit ripening ability in ‘Blanquilla’ pears after 4 months of cold storage (Chiriboga et al., 2007). Besides the duration of temperature exposure, the cultivar and storage length, the temperature treatments are atmosphere dependent, since the fruit stored in controlled atmosphere required a longer storage than in regular air to restart the ripening process (Bai et al., 2007). The main advantage of temperature treatments lies on that they can be performed according to marketing needs, and not prior to storage, as is the case of other strategies involving simultaneous applications. In contrast, temperature treatments imply logistical problems, particularly if fruit are already packaged in bags. In terms of logistic, the simultaneous application of ethylene or CO2 could be an easy method to modulate 1-MCP effects in pears. However, one of the main disadvantages of this strategy is that the simultaneous application should be decided before knowing how long the fruit will be stored. Collectively, these results show the importance of considering the 1-MCP applied dose and the length of storage to decide the best strategy to modulate 1-MCP effect and allowed to conclude that the competitive inhibition of 1-MCP by ethylene or CO2 are the most promissory strategies since they modulate 1-MCP effects maintaining low incidence of superficial scald in ‘Packhams Triumph’ pears. ACKNOWLEDGEMENTS The authors would like to acknowledge financial support from INTA (PNFRU-53911) and AgroFresh®. REFERENCES BAI, J.; MATTHEIS, J.P.; REED, N. 2007. Re-initiating softening ability of 1-methylcyclopropene-treated ‘Bartlett’ and ‘d’Anjou’ pears after regular air or controlled atmosphere storage. Journal of Horticultural Science and Biotechnology 81:959-964. BLANKENSHIP, S.M.; DOLE, J.M. 2003. 1-Methylcyclopropene: a review. Postharvest Biology and Technology 28:1-25. BURG, S.P.; BURG, E.A. 1967. Molecular requirements for the biological activity of ethylene. Plant Physiology 42:144-152. Strategies to modulate 1-MCP effects in ‘Packham’s Triumph’ pears: simultaneous application with ethylene or CO2 (...) April 2015, Argentina CALVO, G.; KUPFERMAN, E. 2012. Current DPA and ethoxyquin situation and alternatives to superficial scald control in apples and pears. Acta Horticulturae 945:51-54. CALVO, G.; SOZZI, G.O. 2004. Improvement of postharvest storage quality of ‘Red Clapp´s’ pears by treatment with 1-methylcyclopropone at low temperature. Journal of Horticultural Science and Biotechnology 79:930-934 CALVO, G. 2004. Effect of 1-methylcyclopropene (1MCP) on pear maturity and quality. Acta Horticulturae 628:203-211. CHAVES-FRANCO, S.H.; KADER, A.A. 1993. Effects of CO2 on ethylene biosynthesis in ‘Bartlett’ pears. Postharvest Biology and Technology 3:183-190. CHEN, P.M.; SPOTTS, R.A. 2005. Changes in ripening behaviour of 1-MCP-treated ‘d’Anjou’ pears after storage. International Journal of Fruit Science 5:3-18 CHIRIBOGA, M.A.; SCHOTSMANS, W.; LARRIGAUDIÈRE, C. 2010. Comparative study of techniques to restore the ripening process in 1-MCP treated ‘Blanquilla’ and ‘Conference’ pears. Acta Horticulturae 858:149-154 CHIRIBOGA, M.A.; SCHOTSMANS, W.; LARRIGAUDIÈRE, C.; DUPILLE, E.; RECASENS, I. 2011. How to prevent ripening blockage in 1-MCP-treated ‘Conference’ pears. Journal of the Science of Food and Agriculture 91(10):1781-1788. CUCCI, A.; REGIROLI, G. 2011. Temperature and Ethylene: Two useful tools to be used in combination with SmartFresh for delivering optimal quality pears. Acta Horticulturae 909:679-686. DE WILD, H.P.J.; WOLTERING, E.J.; PEPPELENBOS, H.W. 1999. Carbon dioxide and 1-MCP inhibit ethylene production and respiration of pear fruit by different mechanisms. Journal of Experimental Botany 50:837-844. EKMAN, J.H.; CLAYTON, M.; BIASI, W.V.; MITCHAM, E.J. 2004. Interactions between 1-MCP concentration, treatment interval and storage time for ‘Bartlett’ pears. Postharvest Biology and Technology 31:127-136. GORNY, J.R.; KADER, A.A. 1997. Low O2 and elevated CO2 atmospheres inhibit ethylene biosynthesis in preclimacteric and climacteric apple fruit. Journal of the American Society of Horticultural Science 124:542-546 JIANG, Y.; JOYCE, D.C.; MACNISH, A.J. 1999. Responses of banana fruit to treatment with 1-methylciclopropene. Plant Growth Regulators 28:77-82 KAPPEL, F.; FISHERFLEMING, R.; HOGUE, E.J. 1995. Ideal pear sensory attributes and fruit characteristics, HortScience 30:988-993. MANRÍQUEZ, D.; DEFILIPPI, B.G. 2011. Strategies for applying 1-MCP in Packham’s Triumph pears. Acta Horticulturae 909:699-703. MITCHAM, E.J.; MATTHEIS, J.P.; BOWER, J.; BIASIL, B.; CLAYTON, M. 2001. Responses of european pears to 1-MCP. Perishables Handling 108:16-19. SISLER, E.C.; WOOD, C. 1988. Interaction of ethylene and CO2. Physiologia Plantarum 73(3):440-444. VILLALOBOS ACUÑA, M.G.; BIASIA, W.V.; MITCHAM, E.J.; HOLCROFT, D. 2011. Fruit temperature and ethylene modulate 1-MCP response in “Bartlett” pears. Postharvest Biology and Technology 60:17-23. CALVO, GABRIELA1; CANDAN, ANA PAULA1
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