Scientia Horticulturae

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1 Scientia Horticulturae 125 (2010) Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: Preharvest aminoethoxyvinylglycine treatments reduce internal browning and prolong the shelf-life of early ripening pears Salvatore D Aquino a,, Mario Schirra a, Maria Giovanna Molinu a, Marco Tedde b, Amedeo Palma a a Institute of Sciences of Food Production, National Research Council, Traversa La Crucca 3, Regione Baldinca, Li Punti, Sassari, Italy b Agris Sardegna, Dipartimento per la Ricerca nell Arboricoltura, Servizio Arboricoltura, Sassari, Italy article info abstract Article history: Received 3 February 2010 Accepted 12 April 2010 Keywords: Aminoethoxyvinylglycine (AVG) Internal browning Color Decay Early season pear Ethylene Respiration Ripening The effect of aminoethoxyvinylglycine (AVG) on internal browning (IB) and keeping quality of early maturing European pears cv and was examined over of storage at 18 C. AVG was applied at 125 or 250 mg/l 2 weeks before harvest. At harvest fruit treated with AVG was less ripe than control fruit, being significantly firmer and experiencing lower values of maturity stage (based on ground color), maturity index (calculated value) and IB, depending on the AVG dose and cultivar. During storage, there was no treatment-dependent difference in titratable acidity and total soluble solids of juice, while both treatments reduced ethylene and respiration rates, delayed the ripening process and lowered the incidence of IB and the loss of firmness, especially when applied at 250 mg/l. In addition, AVG treatment significantly reduced decay development in both cultivars, mainly when it was applied at 250 mg/l. This effect was related to the delay of ripen and to possible inhibition of ethylene production by the pathogens and/or infected tissues Elsevier B.V. All rights reserved. 1. Introduction Most European pears (Pyrus communis L.), unlike other climacteric fruit, normally do not ripe on the tree and require a period of low temperature conditioning at 1 C and/or exposure to ethylene to acquire the typical quality traits of ripen fruit (Villalobos-Acuña and Mitcham, 2008). However, European pears also include a large number of early maturing cultivars which normally ripen on the tree in the summer season (between the end of May and July in Mediterranean Countries) (Mulas et al., 1990; Agabbio et al., 2000; D Aquino et al., 2000). Although early ripening pear cultivars differ in morphological, chemical, gustatory and agronomic characteristics, all of them have some important features in common. Those are: (a) the ripening process occurs in few days and frequently an overlapping of the final phase of cells enlargement and ripening can occur; (b) the metabolic activity is very high compared to late season ripening cultivars; (c) in contrast to winter pears, which are edible after the climacteric phase, early ripening pears can be eaten before ripening, when they usually have an acceptable sugar level and are still hard; (d) postharvest life is very short, varying from 2 to at 20 C, depending on the cultivar; (e) most of them are susceptible to ammezzimento (internal breakdown) (Bellini et Corresponding author. Tel.: ; fax: address: salvatore.daquino@ispa.cnr.it (S. D Aquino). al., 1986; Bell et al., 1996) which can precede, coincide or follow ripening. Internal breakdown (IB) is a physiological disorder typically found in early season pears. The susceptibility of early season pears varies with cultivar, growing area, season to season, environmental and horticultural practise. It appears as a brownish discoloration of the flesh generally starting from the core tissue between the seed cavities and moving outwards until the whole flesh will turn brown. The initial phase of the disorder, with firm and moist tissues, resembles the browning disorder of cold stored late season pears, but as the disorder progresses the flesh becomes watery. Although the tissues maintain their structure, taste and aroma are strongly altered. In severe cases, the brownish discoloration of the flesh in entire fruit can be seen from the outside (Fig. 1). Early ripening pears are in high demand by consumers because of their good taste and juicy flesh. However, due to the short postharvest life and high susceptibility to IB, they are generally cultivated for local markets. Thus any treatment that can reduce the metabolic activity, delay the ripening process and the occurrence of IB might improve marketability and profitability. In recent years, aminoethoxyvinylglycine (AVG), an ethylene biosynthesis inhibitor that suppresses ethylene production in climacteric fruit, has been approved by the U.S. Environmental Protection Agency (2001) as a preharvest plant growth regulator for apple, stone fruit and other horticultural crops. AVG applied before the climacteric rise reduced ethylene and carbon dioxide production rates, delayed the onset of the climacteric, prolonged /$ see front matter 2010 Elsevier B.V. All rights reserved. doi: /j.scienta

2 354 S. D Aquino et al. / Scientia Horticulturae 125 (2010) Fig. 1. Internal browning (IB) in pears. (A) Fruit showing different intensity of IB. (B) Severe IB visible from external side of the peel in entire fruit. postharvest life, minimised preharvest drop and decreased the loss of firmness in different commodities, including apples, pears and stone fruit (Romani et al., 1983; Jobling et al., 2003; Schupp and Greene, 2004; Torrigiani et al., 2004). In this study we determined the delaying and/or reducing effect of AVG on IB of early maturing pears cv and particularly susceptible to this physiological disorder. The impact of AVG on various physiological and quality characteristics was also evaluated over at 18 C. 2. Materials and methods AVG was applied in a mixture containing a commercial formulation of AVG (ReTain, Valent BioScience, IL, USA) containing 15% active ingredient (a.i.) and 0.05% of a non-ionic surfactant (ABG- 7044, Valent BioSciences, IL, USA). The experiment was carried out on early ripening summer pear (P. communis L.) and during two consecutive years in a randomized block design with six plants per treatment, similar in size, vigor and fruit-load uniformity, grafted on Provence Quince BA29 rootstock and trained to palmette. In the first year fruits were sprayed with AVG at 125 mg/l (AVG- 125), while the second year fruits were sprayed with AVG at either 125 or 250 mg/l (AVG-250). Control fruits were sprayed with a solution containing only the surfactant. AVG solutions were applied with a knapsack sprayer to run-off. Due to the short period between full bloom and maturity, plants were treated only once days before harvest. The whole yield was harvested the third week of June () or the first week of July (Camusina di Bonarcado), when the background color of most control fruit was between green and green-yellow, according to the local grower s custom Analyses and assessments at harvest Harvest maturity was subjectively scored, on the base of ground color, according to a 5-point scale, where 1 = fruit still completely green; 2 = light green; 3 = green-yellow; 4 = greenish yellow; 5 = yellow. To obtain a weighed average for the maturity index (MI) of a batch of fruit, the number of fruit in each maturity rating was

3 S. D Aquino et al. / Scientia Horticulturae 125 (2010) multiplied by the designated number and an average was calculated. IB was determined after cutting transversally at the equatorial region, according to a subjective 5-point scale, where 1 = no browning; 2 = browning in 2% of the section; 3 = browning in 3 10% of the section; 4 = browning in 11 20% of the section; 5 = browning in more than 25% of the section. All fruits picked from each cultivar and treatment (6583 ± 1393 fruits) were used for MI. For each cultivar and treatment IB was determined on a sample of 800 fruits. Fruit flesh firmness was measured with an Effegì penetrometer with an 8-mm-diameter plunger. Measurements were done at two opposite sides of the equatorial region. The fruit flesh firmness was read in kg. Chemical analyses were carried out on the combined juice of samples of 30 fruits per replicate. For each treatment and cultivar 5 replicates were used. Total soluble solids (TSS) were determined by means of a digital refractometer and expressed as %. The ph was measured by dipping the ph-meter probe into the juice. Titratable acidity, as g/l of malic acid, was determined by diluting 10 ml juice with 90 ml distilled water and titrating with 0.1 N NaOH until ph 8.2. Organoleptic analysis was carried out by a 5-member panel, who evaluated fruit showing no signs of IB, for sweetness, acidity, off-flavour, texture and overall preference on a 1 9 hedonic scale, according to the intensity of the attributes Analyses and assessments on stored fruit From each cultivar and treatment 750 fruits at harvest maturity 1 or 2 and free from visual defects were selected for postharvest studies, were divided into three lots of 250 fruits each and stored at 18 C and 60 65% relative humidity (RH) (simulated shelf-life conditions) for 3, 7 or, respectively. At each sampling date the fruits of each lot (5 replicates of 50 fruits each) were inspected for decay. All the sound fruits ( ) were first graded for maturity stage and then used for firmness and IB. Chemical and taste analyses were done as described above, using 30 fruits per replicate. At harvest, 50 fruits were individually weighed; then, at the end of each storage period each fruit was reweighed and weight loss was determined as the percentage reduction of the initial weight. Before storage 60 fruits from each treatment were selected for color measurement, using a CR 300 Minolta portable colorimeter (Minolta Corp., Tokyo, Japan). The CIE L*, a* and b* values were recorded and the Chroma (color saturation, C =[a* 2 + b* 2 ] 1/2 ) and the hue angle (H = tan 1 [b*/a*]) were calculated (McGuire, 1992). Since the colored portion of the fruit was very variable from fruit to fruit and was not highly correlated with maturity stage, readings were only taken on the ground color portion of the skin. Measurements were done at harvest and after 4, 7 and of storage on the same fruit. In order to repeat measurements in the same points, at harvest the reading areas were marked by a circle. For respiration and ethylene production rate 15 fruits of each treatment, graded 2 as maturity stage were chosen. Measurements were taken on the same fruit daily for. Fruits were individually closed in 500 ml jars. After 2 h the headspace air was mixed with a 20 ml syringe and a 1-mL sample from each jar was withdrawn for ethylene analysis. Ethylene was determined by a 3300 Varian gas-chromatograph fitted up with a flame ionisation detector (FID) and a packed column (Unibeds, Alltech, Milan). Helium was used as carrier gas at a flow rate of 7 ml s 1. The temperatures of injector, oven and detector were 150 C, 60 C, and 200 C, respectively. For carbon dioxide determination, a combined CO 2 /O 2 analyser (Combi Check , PBI-Dansensor A/S, Table 1 Maturity index (MI) and stage of maturity at harvest in and pears subjected to preharvest treatments with aminoethoxyvinylglycine at 125 mg/l (AVG-125), at 250 mg/l (AVG-250) or not treated (Control). Treatments MI Stage of maturity a (% of fruit for each stage) Control a b 30.1 c 23.6 c 18.7 a 14.2 a 13.4 a AVG b 49.9 b 27.7 b 12.2 b 7.5 b 2.7 b AVG c 52.3 a 32.5 a 13.0 b 2.2 c 0 c Control a 0 c 48.1 a 37.8 b 10.5 a 3.6 a AVG b 24.9 b 21.9 c 42.0 a 8.8 ab 2.5 a AVG c 32.4 a 40.3 b 22.2 c 3.6 b 1.5 a a Maturity stage was subjectively estimated, on the base of ground color, rated according to a 1 5 stages scale, where 1 = fruit still completely green; 2 = light green; 3 = green-yellow; 4 = yellowish green; 5 = yellow. Multiplying the number of fruit of each stage by the number of the stages and then dividing for the total number of fruit a MI (maturity index) was calculated. b For each cultivar means in column followed by different letters are significantly different at P 0.05 according to the Fisher s test of the least significant difference. Denmarck) was used. Specifically, soon after sampling for ethylene, the analyser was connected with each jar by two tubes, each one ending with a needle inserted in one of the two septa, in order to form a close system. An incorporated-analyser-pump continually inspired headspace air through the inlet tube and reinjected after reading the same air into the jars through the outlet tube. The analysis lasted until the reading of CO 2 and O 2 was fairly constant, and this took about 90 s. Respiration activity was expressed as nmol CO 2 kg 1 s 1, while ethylene production rate as pmol C 2 H 4 kg 1 s 1. Data were subjected to a one-way analysis of variance (ANOVA) considering the experimental plan as a unifactorial complete randomized block design. Since results of the 2 years, with AVG at 125 mg/l AVG were similar, only data of the second year are presented. The work-package Statgraphics Centurion XV software (StatPoint Inc., Herdan, Virginia, USA, 2005) statistical program was used. The Fisher s test of the least significant mean was applied for mean separation at P Results 3.1. Analyses and assessments at harvest At harvest approximately 50% of untreated fruit was rated as 1 2 while the remaining as 3 5. Treatment with AVG at 125 mg/l and especially at 250 mg/l delayed the maturity stage with respect to control fruit, accounting for ca. 77% and 85% of fruit rated as 1 2, respectively (Table 1). As a result, MI of control fruit at harvest was lower or notably lower than that of fruit treated with AVG at 125 or 250 mg/l. A similar delaying effect of AVG treatments was observed in pears although their degree of maturity was higher than. The percentage of fruit affected by IB averaged 18% in Camusina di Genova and 25% in. AVG treatments effectively controlled the occurrence of IB at harvest in both cultivars especially when applied at 250 mg/l, resulting in 100% and 96% inhibition of IB development in and, respectively (Table 2). In addition, fruits of both cultivars treated with AVG were significantly firmer than control fruit (Table 3). Treatments with AVG did not affect ph and titratable acidity, whereas generally produced lower values of TSS (Table 3). No statistical difference was detected in taste

4 356 S. D Aquino et al. / Scientia Horticulturae 125 (2010) Table 2 Internal browning (IB) index and percentages of affected fruit according to the severity of IB at harvest in and pears subjected to preharvest treatments with aminoethoxyvinylglycine at 125 mg/l (AVG-125), at 250 mg/l (AVG-250) or not treated (Control). Treatments IB index IB a (% of affected fruit for each class of severity) None Trace Slight Moderate Severe Control a b 82.4c 6.8 a 3.3 a 4.3 a 3.2 a AVG b 93.4 b 6.3 a 0.3 b 0 b 0 b AVG c 100 a 0 b 0 b 0 b 0 b Control a 75 c 18.8 a 2 a 2.5 a 1.7 a AVG b 90 b 4.5 b 3.9 a 1.6 a 0 b AVG a 96.1 a 3.9 b 0 b 0 b 0 b a IB was subjectively evaluated according to a scale ranging from 1 to 5, where 1 = no browning; 2 = browning in 2% of the section; 3 = browning in 3 10% of the section; 4 = browning in 11 20% of the section; 5 = browning in more than 25% of the section. Multiplying the number of fruit of each stage by the number of the stages and then dividing for the total number of fruit an IB index was calculated. b For each cultivar means in column followed by different letters are significantly different at P 0.05 according to the Fisher s test of the least significant difference. analysis between control fruit and AVG fruit (data not shown) Postharvest assessment and analyses At harvest there was no treatment-dependent difference in respiration rate of fruit. Afterwards, control fruit steadily increased respiration rate and reached a climacteric peak at day 2, then, gradually decreased to reach constant levels. In fruit treated with AVG at 125 mg/l respiration decreased during the first day, started to increase the second day and reached the climacteric peak at day 4, whereas in fruit treated with AVG at 250 mg/l, respiration rate remained quite stable during the first day, increased until day 3, but never showed a clear climacteric peak. During the first days of storage control fruit exhibited the highest respiration activity, while the lowest activity was detected in fruit treated with AVG at 250 mg/l, however, after the climacteric peak, respiration decreased in control and in fruit treated with AVG at 250 mg/l, and from day 5 on, no significant difference could be detected amongst treatments (Fig. 2A). The climacteric pattern in was similar as in, with the difference that control fruit and AVG-125 fruit peaked both at day 3, after that respiration declined in both treatments. From day 6 no statistical difference could be detected between control fruit and AVG-125 fruit, while significantly lower values of respiration rate were measured in AVG-250 fruit (Fig. 2B). Initial production rates of ethylene in, fruits treated with AVG were very low (<40 pmol C 2 H 4 kg 1 s 1 ). In control fruit ethylene rates averaged 247 pmol C 2 H 4 kg 1 s 1, then increased dramatically and reached a climacteric peak of 601 pmol C 2 H 4 kg 1 s 1 by day 2. In fruit treated with AVG at 125 mg/l ethylene peaked 1 day later than in control fruit, but its intensity was ca. 33% lower. Thereafter in both treatments the rates progressively decreased with AVG-125 fruit showing values similar or slightly lower than control fruit. In AVG-250 fruit ethylene peaked at day 3, but with rates similar to those of control fruit detected at harvest, thereafter a slight but continuous decline followed (Fig. 3A). In contrast, in, at harvest differences amongst the treatments were negligible. However, ethylene production suddenly increased in control fruit and AVG-125 fruit and peaked at day 3; thereafter in both treatments a gradual decline occurred, but with AVG-125 fruit generally showing lower levels than control fruit. AVG-250 fruit exhibited a slow increase in ethylene until day 4, without showing a clear climacteric peak and with values always lower than the other treatments; then no significant changes occurred until the end of storage (Fig. 3B). Although at harvest only fruits with similar stage of maturity were chosen, during storage remarkable treatment-dependent differences took place. In both cultivars MI in control fruit changed faster than AVG fruit. After of storage, in differences in MI between control fruit and AVG-125 fruit were not significant while lower values were found in AVG-250 fruit (Table 4). After 3 and of storage 78% and 12% of untreated fruit was unaffected by IB while after all fruits showed visible symptoms of IB (Table 5). Similar changes in IB development were recorded in untreated fruit. Treatments with AVG significantly reduced the incidence and severity of fruit affected by IB, especially when applied at 250 mg/l. When applied at half dose the efficacy of AVG in reducing IB of Camusina di Bonarcado was dependent by storage duration. However, the effectiveness of AVG in reducing IB was more evident after of storage, when about 50% of AVG-125 fruit and more than 90% Table 3 Firmness and chemical parameters at harvest in pears and pears subjected to preharvest treatments with aminoethoxyvinylglycine at 125 mg/l (AVG-125), at 250 mg/l (AVG-250) or not treated (Control). Treatments Firmness (kg) ph Titratable acidity (g/l malic acid) Total soluble solids (%) Control 5.43 c a 4.12 a 0.83 a 14.8 a AVG b 4.18 a 0.80 a 14.5 b AVG a 4.16 a 0.81 a 14.4 b Control 3.4 b 3.74 b 0.66 a 14.9 a AVG b 3.88 a 0.65 a 13.9 b AVG a 3.71 b 0.68 a 14.1 b a For each cultivar means in column followed by different letters are significantly different at P 0.05 according to the Fisher s test of the least significant difference.

5 S. D Aquino et al. / Scientia Horticulturae 125 (2010) Fig. 2. Respiration rate in (A) and (B) pears treated with aminoethoxyvinylglycine (AVG) at 125 mg/l ( ), at 250 mg/l ( ) or not treated (Control) ( ) and stored at 18 C. For each storage time vertical bars represent the least significant difference at P 0.05; overlapping of the bars denotes no statistical significant difference. Fig. 3. Mean rates of ethylene production in (A) and (B) pears treated with aminoethoxyvinylglycine (AVG) at 125 mg/l ( ), at 250 mg/l ( ) or not treated (Control) ( ) and stored at 18 C. For each storage time vertical bars represent the least significant difference at P 0.05; overlapping of the bars denotes no statistical significant difference. of that treated with AVG at 250 mg/l was still sound, against 12.5% and 16.2% of control fruit, in and Camusina di Bonarcado, respectively. At the last sampling date the activity of AVG dramatically decreased, and although at 250 mg/l AVG IB index was about twofold lower than the other treatments, the percentage of sound fruit was only about 25%; in contrast at 125 mg/l no sound fruit could be detected in while only 4.1% of fruit of showed no symptoms of AM. Weight loss was generally higher in control fruit than in AVG fruit. Specifically, in differences were always significant, while in weight loss was significantly lower than control fruit after of storage only in fruit treated with 250 mg/l AVG (Table 6). Firmness decreased with storage in AVG fruit at a lower rate than control fruit, especially in treatments with 250 mg/l (Table 6). A slight general increase of ph was detected in both cultivars over storage, counteracted by a decrease in titratable acidity, while changes in TSS were inconsistent (Table 6). The ph in AVG-250 fruit was higher than AVG-125 fruit, which in turn was higher than control fruit; an opposite trend was observed for titratable acidity. However, differences were not always statistically significant. Similarly, panellists did not find significant differences between control fruit and AVG fruit, apart texture, which generally was scored higher in AVG fruit than control fruit, but with differences not always statistically different between 125 and 250 mg/l AVG (data not shown). In L* values, after a slight increase in control fruit and AVG-125 fruit or a little fluctuation in AVG-250 fruit after 3 or, respectively, decreased in all treatments, with the highest reduction detected in control fruit and the smallest one in AVG-250 fruit (Fig. 4A). In L* values at harvest were similar in all treatments and increased until day 7 of storage, thereafter were quite stable in fruit treated with AVG, while slightly declined in control fruit (Fig. 5A). In both cultivars Chroma values underwent little changes during the first of storage, followed by a general decline during the last. In most cases averages were either similar in all treatments or significantly higher in AVG fruit, especially at the higher dose (Figs. 4B and 5B). The H angle showed no difference at the beginning of storage amongst treatments, but decreased with storage in both cultivars, with the largest changes occurring in control fruit and the smallest ones in AVG-250 fruit (Figs. 4C and 5C). Decay was detected only from the second inspection date in both cultivars and was mainly due to mucor rot (Mucor pyriformis Fisher) and, to a less extent, grey mould (Botrytis cinerea Pers.) and blue mould (Penicillium expansum Link). AVG reduced decay, especially at 250 mg/l (Table 7).

6 358 S. D Aquino et al. / Scientia Horticulturae 125 (2010) Table 4 Changes in maturity index (MI) and stage of maturity in and pears subjected to preharvest treatments with aminoethoxyvinylglycine (AVG) at 125 mg/l (AVG-125), at 250 mg/l (AVG-250) or not treated (Control) and stored for at 18 C and 60 65% RH. Storage period Maturity index Stages of maturity (% of fruits for each stage) Control a a 22 b 25.6 b 15.2 a 16.8 a 20.4 a AVG b 36 a 26.0 b 16.4 a 15.6 a 6.0 b AVG c 39.2 a 42.4 a 7.2 b 11.6 a 0.0 c Control a 0 b 29.2 c 30.4 a 14.6 a 25.8 a AVG b 0 b 38.1 b 31.6 a 19.4 a 10.9 b AVG c 14.0 a 52.0 a 28.0 a 6.0 b 0.0 c Control a 0 a 0 c 24.3 b 21.6 c 54.1 a AVG b 0 a 16.5 b 10.7 c 24.3 b 48.6 a AVG c 0 a 28.7 a 32.8 a 33.2 a 5.3 b Control a 0 b 30.8 ab 16.4 a 20 b 32.8 a AVG b 0 b 39.2 a 20.4 a 28 a 12.4 b AVG c 44 a 34.0 b 22.0 a 0 c 0 c Control a 0 b 13.5 c 15.3 b 26.1 a 45.5 a AVG b 0 b 28.6 b 25.6 a 23.2 a 22.6 b AVG c 10 a 53.8 a 27.1 a 9.2 b 0 c Control a 0 a 0 c 8.9 c 32.2 a 58.9 a AVG b 0 a 16.1 b 17.9 b 35.0 a 30.9 b AVG c 0 a 36.7 a 35.5 a 21.2 b 6.9 c a For each storage period means in column followed by different letters are significantly different at P 0.05 according to the Fisher s test of the least significant difference. Table 5 Internal browning (IB) index and percentages of affected fruit according to the severity of IB in and pears subjected to preharvest treatments with aminoethoxyvinylglycine at 125 mg/l (AVG-125), at 250 mg/l (AVG-250) or not treated (Control) and stored for at 20 C and 90%. Storage period IB index IB (% of affected fruits for each class of severity) None Trace Slight Moderate Severe Control a a 72.8 a 10.0 a 10.0 a 0.0 b 7.2 a AVG b 87.5 b 9.6 a 0.0 b 2.0 a 0.8 a AVG c 96.8 a 3.2 b 0.0 b 0.0 b 0.0 a Control a 12.5 c 19.2 a 30.4 a 18.3 a 19.6 a AVG b 42.9 b 22.7 a 18.1 b 8.5 b 19.8 a AVG c 91.2 a 9.2 b 5.6 c 0.0 c 0.0 b Control a 0.0 b 2.7 b 5.0 b 6.8 b 85.6 a AVG a 4.1 b 2.1 b 3.7 b 7.8 b 82.3 a AVG b 25.9 a 28.7 a 32.4 a 13 a 0.0 b Control a 86.0 b 9.2 a 4.4 a 0.4 b 0.0 a AVG a 88.4 b 4.8 b 4.0 a 2.8 a 0.0 a AVG b 100 a 0.0 c 0.0 b 0.0 b 0.0 a Control a 16.2 c 12.2 a 39.2 a 24.8 a 7.7 b AVG b 58.5 b 12.8 a 4.7 b 5.5 b 18.4 a AVG c 95.8 a 3.8 b 0.0 b 0.0 c 0.0 c Control a 0.0 b 10.4 a 19.8 b 14.9 b 55.0 a AVG b 0.0 b 15.4 a 21.1 b 40.8 a 22.9 b AVG c 26.9 a 13.9 a 32.0 a 13.0 b 15.2 b a For each storage period means in column followed by different letters are significantly different at P 0.05 according to the Fisher s test of the least significant difference. 4. Discussion The high metabolic activity and susceptibility to IB and uneven stage of maturity at harvest are the main causes limiting marketability of early season pears. Appropriate postharvest handling and specific treatments such as hydrocooling, controlled atmosphere storage, may only in part reduce the rate of deterioration, especially in fruit which at harvest are in advanced stage of maturity. Therefore control measure applied before harvest could be more effective than postharvest treatments. In this study aminoethoxyvinylglycine was evaluated for its efficacy in lowering metabolic activity, reducing the severity/delaying the occurrence of IB and, in turn, prolong postharvest life on two early season pears. The main effects observed at harvest included a delay in maturity, based on subjective evaluation of ground color, a lower incidence of IB and a higher flesh firmness. These results confirm previous findings in pears and other crops (Bramlage et al., 1980; Romani et al., 1983; Andreotti et al., 2004; McGlasson et al., 2005). However, AVG had little influence in reducing heterogeneity of the maturity stage. A lack of uniformity of maturity at harvest after preharvest treatments with AVG, was reported in peach (Byers, 1997), Bartlett pears (Romani et al., 1982) and muskmelons (Shellie et al., 1999). Ethylene synthesis might not be the only events predisposing pear fruit to ripen, as suggested by Romani et al. (1982, 1983); thus the lack of uniformity at harvest could depend by other factors. AVG strongly affected both ethylene and respiration patterns and results were dose-dependent: at 125 mg/l AVG reduced the rate of ethylene production and delayed of 1 day the climacteric in both cultivars, while at 250 mg/l the rates were two- to six- fold lower at the climacteric peak and clear climacteric patterns could not be detected, especially in. Similarly, respiration activity was lower in fruit treated with AVG than in control fruit, but differences amongst treatments were less marked than for ethylene and generally statistical differences were detected only during and soon after the climacteric phase. These results are in agreement with those reported on pears (Romani et al., 1982, 1983), peaches (Bregoli et al., 2002; Byers, 1997), nectarines (Torrigiani et al., 2004; McGlasson et al., 2005) and apples (Autio and Bramlage, 1982). AVG showed a high residual effect during the of simulated marketing conditions, even if for postharvest studies fruits were chosen with the same degree of maturity. In treated fruit ground color and firmness changed at a slower rate than control fruit. The slower changes in color in AVG fruit could be detected both subjectively and objectively; treated fruit showed higher values of L*, Chroma and H than control fruit. A reduction in L and Chroma values in early ripening pears is generally associated with loss of brightness and darkening of the peel, and both are indexes of senescence, while higher values of H mean greener color. Coloration in peaches, nectarines and apples (Layne et al., 2002; Johnson and Colgan, 2003; McGlasson et al., 2005; Hayama et al., 2008) was delayed following treatments with AVG. IB index increased at a lower rate in AVG fruit than in control fruit, although the efficacy of AVG at 125 mg/l was drastically reduced after of storage with a percentage of altered fruit too high from the commercial point of view, while after differences between control fruit and AVG-125 fruit were very low. In contrast, at 250 mg/l AVG prevented the appearance of IB in

7 S. D Aquino et al. / Scientia Horticulturae 125 (2010) Table 6 Weight loss and changes in firmness and chemical parameters in Camusina di Genova and pears subjected to preharvest treatments with aminoethoxyvinylglycine at 125 mg/l (AVG-125), at 250 mg/l (AVG-250) or not treated (Control) and stored for at 18 C and 60 65%. Storage period Weight loss (g) Firmness (kg) ph Titratable acidity (g/l malic acid) Total soluble solids ( Brix) Control 4.38 a a 3.28 b 4.10 a 0.73 a 15.4 b AVG b 4.68 a 4.20 a 0.74 a 16.0 a AVG b 4.82 a 4.19 a 0.76 a 15.4 b Control 7.15 a 2.39 c 4.33 a 0.64 a 15.3 ab AVG b 3.41 b 4.28 a 0.62 a 15.7 a AVG b 4.16 a 4.22 a 0.68 a 15.1 b Control a 0.65 c 4.46 a 0.55 b 15.9 a AVG b 1.45 b 4.43 a 0.54 b 15.6 a AVG b 2.87 a 4.34 b 0.61 a 14.9 b Control 2.16 a 3.15 b 3.76 a 0.73 b 14.0 a AVG a 3.36 b 3.75 a 0.75 ab 13.7 a AVG a 4.22 a a 13.1 b Control 4.56 a 1.86 c 3.96 a 0.69 b 13.4 b AVG a 2.49 b 3.78 b 0.75 a 13.3 b AVG a 3.35 a 3.71 b 0.76 a 13.8 a Control 6.51 a 0.59 b 3.95 a 0.67 a 14.9 a AVG ab 0.75 b 3.98 a 0.66 a 13.9 b AVG b 2.84 a 3.82 a 0.70 a 13.2 c a For each storage period means in column followed by different letters are significantly different at P 0.05 according to the Fisher s test of the least significant difference. 91.2% and 95.8% of fruits, respectively, in and. Generally, browning disorders in pears are associated with high concentrations of CO 2 and insufficient levels of O 2 in the flesh, especially at the inner sites. These conditions may reduce the production of energy and the capacity of the cells to neutralise reactive oxygen species and lead to membrane disruption, enzymatic oxidation of phenolic compounds, senescence and browning (Saquet et al., 2000, 2003; Frank et al., 2007). The delay in the ripening process and the reduction of respiration activity, which is associated with lower levels of endogenous CO 2, can in part justify the beneficial effect of AVG on IB. Table 7 Incidence of decay in and pears subjected to preharvest treatments with aminoethoxyvinylglycine at 125 mg/l (AVG-125), at 250 mg/l (AVG-250) or not treated (Control) after 7 or of storage at 20 C and 90%. Treatments Decay (%) Control 10.8 a a 19.2 a AVG b 9.6 b AVG b 7.6 b Control 5.2 a 11.2 a AVG b 2.8 b AVG c 1.2 c a For treatments and cultivars, means in column followed by different letters are significantly different at P 0.05 according to the Fisher s test of the least significant difference. Fig. 4. Changes in L* (A), Chroma (B) and H (C) in pears treated with aminoethoxyvinylglycine (AVG) at 125 mg/l ( ), at 250 mg/l ( ) or not treated (Control) ( ) and stored at 18 C. For each storage time vertical bars represent the least significant difference at P 0.05; overlapping of the bars denotes no statistical significant difference. It has been shown that AVG reduced the in vitro growth of various fungal species and decreased disease severity in artificial inoculated bean, cucumber, chickpea, and tomatoes (Hardan et al., 2005; Al-Masri et al., 2006). Present results reveal that AVG treatment strongly affected decay development in both cultivars, especially when it was applied at 250 mg/l. This effect was ascribed in part to the delay of ripeness as disease resistance decreases as the ripening process advance (Prusky, 2003) and, in part to inhibition of ethylene production by the pathogens and/or infected tissues (Shellie, 1999; Robison et al., 2001; Al-Masri et al., 2006). In summary, AVG delayed the occurrence of IB, retarded changes in ground color, maintained fruit firmer and reduced decay incidence. These effects were observed both at harvest and over the 10-day storage time at 18 C, even if at the 250 mg/l AVG was more

8 360 S. D Aquino et al. / Scientia Horticulturae 125 (2010) Fig. 5. Changes in L* (A), Chroma (B) and H (C) in pears treated with aminoethoxyvinylglycine (AVG) at 125 mg/l ( ), at 250 mg/l ( ) or not treated (Control) ( ) and stored at 18 C. For each storage time vertical bars represent the least significant difference at P 0.05; overlapping of the bars denotes no statistical significant difference. effective than at 125 mg/l. Preharvest AVG application on summer pear might be a useful tool to improve postharvest handling of summer pear, however further researches are needed to improve its use and to evaluate possible side effects on trees physiology. Acknowledgements Research supported by CNR-MiUR, Sviluppo delle Esportazioni di Prodotti Agroalimentari del Mezzogiorno. The authors thank Mr Domenico Mura for technical assistance. 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