Postharvest Biology and Technology 36 (2005) 61–68 Aroma volatile biosynthesis in apples affected by 1-MCP and methyl jasmonate S. Kondo a, ∗, S. Setha a, D.R. Rudell b, D.A. Buchanan b, J.P. Mattheis b a Graduate School of Applied Biosciences, Hiroshima Prefectural University, Shobara, Hiroshima 727-0023, Japan b Tree Fruit Research Lab, United States Department of Agriculture—ARS, Wenatchee, WA 98801, USA Received 13 August 2004; received in revised form 8 November 2004; accepted 24 November 2004 Abstract Effects of 1-methylcyclopropene (1-MCP), 2-chloroethyl phosphonic acid (ethephon), and methyl jasmonate (MeJA) on production of aroma volatile compounds and ethylene by ‘Delicious’ and ‘Golden Delicious’ apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] during ripening were investigated. Forty-four volatile compounds in ‘Delicious’ and 40 compounds in ‘Golden Delicious’ were detected. Among volatiles classified as alcohols, esters, ketones, aldehydes, acetic acid, and ␣-farnesene, esters were the most prevalent compounds, followed by alcohols. Aroma volatile production was high in untreated controls and ethephon treatment. Volatile production by 1-MCP-treated fruit was lower compared with untreated controls throughout the evaluation period. The impact of MeJA application on volatile production was cultivar dependent. The combination of ethephon with MeJA reduced volatile production by ‘Delicious’ compared with ethephon only, but this treatment combination stimulated volatile production by ‘Golden Delicious’ with the exception of esters. In general, the effect of MeJA on volatile production was related to the effect of MeJA on internal ethylene concentration. The results suggest that the effect of MeJA on aroma volatiles in apple fruit may be mediated by ethylene. Furthermore, the effect of MeJA on volatiles may depend on the growth stage of the fruit when treated with MeJA. © 2004 Elsevier B.V. All rights reserved. Keywords: Apple; 1-Methylcyclopropene; Methyl jasmonate; Volatile 1. Introduction production (Song and Bangerth, 1996; Lalel et al., 2003b). Apple fruit volatile compound production is re- Aroma volatile compounds are one of the factors tarded by the application of aminoethoxyvinylglycine that determine apple fruit quality. Aroma production (AVG), an inhibitor of 1-aminocyclopropane-1- increases with ripening and is associated with ethylene carboxylic acid (ACC) synthase (Fan et al., 1998). Methyl jasmonate (MeJA) also influences the produc- ∗ Corresponding author. Tel.: +81 824 74 1773; tion of volatile compounds, but the effect can vary with fax: +81 824 74 1773. volatile compound chemical class (Fan et al., 1997). Al- E-mail address: [email protected] (S. Kondo). though many types of aroma volatiles are synthesized 0925-5214/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.postharvbio.2004.11.005 62 S. Kondo et al. / Postharvest Biology and Technology 36 (2005) 61–68 in apple fruit, the relative abundance of each type separated to six groups of 76 fruit for the following differs among cultivars (Fan et al., 1997; Mattheis treatments: (1) MeJA, (2) MeJA + 1-MCP, (3) 1-MCP, et al., 1998). For most cultivars, esters are qualita- (4) ethephon, (5) ethephon + MeJA, (6) untreated con- tively and quantitatively predominant (Rowan et al., trol. Group 1 and 2 fruit and group 5 fruit were dipped 1999). for 5 min in a solution of 0.177% (v/v) Tween® 20 Aroma volatiles are primarily synthesized in the with 5 mM MeJA or the same solution in combination skin (Knee and Hatfield, 1981), and Kondo et al. (2001) with 400 a.i. mg l−1 ethephon, respectively. For group showed that jasmonates effectively stimulate antho- 2, 1-MCP (5 ␮ll−1) treatment followed MeJA treat- cyanin biosynthesis and that the effect is indepen- ment, and was performed on groups 2 and 3 for 12 h at dent of ethylene. Therefore, jasmonates have been ap- 20 ◦C in a sealed steel chamber according to the method plied prior to harvest in the field for the promotion of of Fan and Mattheis (1999). Group 6 and 4 fruit were red color development in Japan. 1-Methylcyclopropene dipped for 5 min in a solution of the same concentration (1-MCP), which blocks ethylene receptors and re- of Tween® 20 in deionized water (untreated control) tards ethylene action, delays apple fruit ripening and and in Tween® 20 containing 400 a.i. mg l−1 ethephon, senescence (Blankenship and Dole, 2003). However, respectively. After treatment, apples were placed in the 1-MCP also reduces the volatile production by ap- dark at 20 ◦C and sampled at 7 day intervals for anal- ple fruit (Fan et al., 1998). Apples to which MeJA ysis of volatile compounds, ethylene production, and has been applied in the field may subsequently be jasmonate concentrations. Fruit firmness, malic acid, treated with 1-MCP, however, the interaction between and soluble solids concentration (SSC) were also mea- jasmonate and 1-MCP on apple aroma volatile pro- sured at the same time. Fruit firmness was measured on duction is unclear. In this study, effects of MeJA, two pared surfaces of each apple using a penetrometer 1-MCP, and 2-chloroethyl phosphonic acid (ethep- with an 11 mm probe (Lake City Technical, Kelowna, hon), alone or in combination, on aroma volatile and BC, Canada). SSC was estimated using a refractometer ethylene production during apple fruit ripening were (Atago, Tokyo), and malic acid was measured by titrat- investigated. ing 10 ml juice with 0.1 M KOH using an autotitrator (Radiometer, Copenhagen, Denmark). 2. Materials and methods 2.3. Analysis of aroma volatile compounds and ethylene 2.1. Chemicals Analysis of volatile compounds was performed with 1-Methylcyclopropene (a.i. 0.14%) was obtained a modification of the method previously described by from AgroFresh Inc. (Spring House, PA). 2- Mattheis et al. (1991). Four apples per treatment (three Chloroethyl phosphonic acid (a.i. 21.7%) was pur- replications) were placed in 4 l glass jars and the jars chased from Rhone-Poulenc Co. (Research Triangle purged with air that had been passed through acti- Park, NC). Methyl jasmonate (95%) was purchased vated charcoal and molecular sieve. Air flowed through from Sigma–Aldrich Co. (Milwaukee, WI). the jars at 50 ml min−1 for 3 h before collection of volatile compounds onto glass traps containing 50 mg 2.2. Plant material Tenax GC (Alltech Assoc., Deerfield, IL). The ab- sorbed contents in the trap were desorbed into the in- Ten randomly selected 23-year-old ‘Delicious’ and jection port of a gas chromatograph with a mass se- ‘Golden Delicious’ apple trees, grafted onto Malling lective detector (GC-MSD) (HP 5890, 5971A, Hewlett 7 (M.7) rootstocks, at the Columbia View Experimen- Packard, Avondale, PA) equipped with a DB-1 (J&W tal Plots in Wenatchee, Washington (USA) were the Scientific, Folsom, CA) fused silica capillary column source of apples for this study. Fruit were harvested (60 m × 0.32 mm i.d.), using an automated thermal des- 179 days after full bloom (DAFB) (‘Delicious’) and orption and cryofocusing autosampler (Techmar As- 186 DAFB (‘Golden Delicious’) in 2003. Immediately soci., Cincinnati, Ohio). The column oven temperature after harvest, 456 fruit of each cultivar were randomly was held at 35 ◦C for 3 min, then increased from 35 S. Kondo et al. / Postharvest Biology and Technology 36 (2005) 61–68 63 to 225 ◦C at a rate of 8 ◦C min−1. Compounds were 3. Results identified by matching spectra using the Wiley NBS library followed by comparison of sample retention in- For both ‘Delicious’ and ‘Golden Delicious’, dices and mass spectra with those of authentic stan- untreated control and ethephon-treated fruit had high dards (Sigma–Aldrich, Milwaukee, WI). Compounds internal ethylene concentrations (Fig. 1). However, were quantified using selected ion monitoring for base the effects of MeJA or the combination of ethephon peaks with amounts calculated using response factors and MeJA differed among the cultivars. For ‘Deli- generated with authentic standards. Internal ethylene in cious’, ethylene concentrations in MeJA-treated fruit the core from seven fruit per treatment was sampled and were second or third lowest, and the combination with analyzed, to determine harvest maturity and the effect ethephon decreased the levels compared with ethephon of each treatment, using a HP5890 gas chromatograph treatment only. In contrast, ethylene concentrations (Hewlett-Packard, Avondale, PA) equipped with a glass in MeJA-treated ‘Golden Delicious’ fruit were, along column (610 mm × 3.2 mm i.d.) packed with Porapak with untreated controls and ethephon-treated fruit, Q (80–100 mesh) (Supelco, Bellefonte, PA) and flame highest for all treatments. MeJA levels in the pulp of ionization detector. Oven, detector, and injection tem- ◦ peratures were 90, 200, and 100 C, respectively. N2, Table 1 −1 H2, and air flows were 25, 25, and 300 ml min , re- Primary aroma volatiles detected in ‘Delicious’ and ‘Golden Deli- spectively. cious’ apples Compound % In total volatile compound −1 2.4. Extraction and analysis of jasmonates amount (ng kg l) Delicious Golden Delicious Extraction and quantification of MeJA were carried Alcohol out as described previously by Kondo et al. (2000). The 1-Butanol 0.96 4.51 2 ± Ethanol 4.20 8.40 deuterium-labeled MeJA [( H2)-MeJA: methyl ( )- . 2 1-Propanol 2 46 7 51 [9,10- H2] jasmonate] used for the internal standard Others 0.48 1.70 was prepared according to the method of Seto et al. Ester (1996). Lyophilized skinless pulp samples (5 g dry Butyl acetate 13.12 23.84 weight (DW)); three replications) were homogenized Butyl butyrate 1.06 0.92 2 with 1 ␮g( H2) MeJA in 50 ml diethyl ether containing Butyl hexanoate 1.10 1.05 11.3 ␮M butylated hydroxytoluene as an antioxidant, Butyl 2-methylbutyrate 1.32 0.95 .