J. AMER.SOC.HORT.SCI. 142(2):126–134. 2017. doi: 10.21273/JASHS03968-16 Volatile Compound Profiles of Malus baccata and Malus prunifolia Wild Apple Fruit Chunyu Zhang1 College of Plant Science, Jilin University, Changchun, Jilin 130062, China Xuesen Chen National Key Laboratory of Crop Biology, Shandong Agricultural University, Taian, Shandong 271018, China Hongwei Song, Yinghai Liang, Chenhui Zhao, and Honglian Li Pomology Institute, Academy of Agricultural Sciences of Jilin Province, Gongzhuling, Jilin 136100, China ADDITIONAL INDEX WORDS. apple breeding, cold resistance, ester, a-farnesene, terpene ABSTRACT. Volatile compounds have a tremendous impact on fruit quality. We evaluated the volatile compound profiles of ripening wild apple fruit (10 Malus baccata accessions and three Malus prunifolia accessions) in the National Field Genebank for Hardy Fruits at Gongzhuling, China. Alcohols, esters, aldehydes, terpenes, hydrocarbons, ethers, heterocycles, carboxylic acids, and ketones were detected in the M. baccata and M. prunifolia fruit, with the first four being the main volatile compounds present. Of the 92 volatiles detected, esters were the most diverse (49 compounds). This wide range of abundant volatile compounds suggests that M. prunifolia is a good resource for breeding apple cultivars with novel and interesting flavors. The M. baccata accession ‘Zhaai Shandingzi’ and the M. prunifolia accession ‘Bai Haitang’ had the widest range of volatile compounds and the highest volatile compound contents of the accessions examined, and will therefore be good breeding materials for developing commercial lines with enhanced flavor and for widening the genetic diversity. The number of different ester compounds present was significantly positively correlated (r = 0.877) with the cube root of the weight of an individual ripe fruit. Principal component analysis (PCA) showed that the contents of ester compounds could be used to distinguish between M. baccata and M. prunifolia species. Therefore, ester compounds could be used as a reference of parental choice in apple breeding. Apple (Malus pumila) is a fruit crop of major economic evaluated in this nursery (Zhang, 2008). Malus baccata and importance. In worldwide apple breeding efforts, apple Malus prunifolia are the hardiest wild apple species in this breeders typically intercross elite or commercial cultivars, such nursery and also the main wild cold hardy species in northern as Red Delicious, Golden Delicious, and Jonathan, which China. These cold hardy fruit can tolerate temperatures below results in commercial apple cultivars with a narrow genetic –42 °C (Li et al., 2015; Wang et al., 2013; Zhang et al., 2003), base, low adaptability, and reduced resistance to biotic and and their hardy rootstocks are widely used for apple grafting abiotic stresses (Kumar et al., 2010; Noiton and Alspach, 1996). and apple breeding in northern China. M. baccata and M. Therefore, there is a need to develop breeding strategies that prunifolia accessions with excellent traits were formed by broaden the genetic base, enhance resistance and tolerance to human selection over many years, and were cultivated for their biotic and abiotic stresses, and improve fruit quality, including fruit and as rootstocks (Kuznetsova et al., 2010; Meng et al., flavor (Forsline et al., 2010; Sedov and Serova, 2013). Wild 1997; Zhang, 2008). apples, with their high genetic diversity and antioxidant Volatile components have a huge impact on fruit quality, activity, disease resistance, and stress tolerance, are important and are thus an important factor in apple breeding (Laurens, resources for apple breeding (Chen et al., 2007; Emeriewen 1999). In apple, volatile components are composed of esters, et al., 2014; John et al., 2014; Jurick et al., 2011; Zhang et al., alcohols, aldehydes, ketones, and ethers (Dimick and Hoskin, 2007, 2003). To collect and protect hardy fruit resources, the 1983; Kakiuchi et al., 1986). Research by Kakiuchi et al. National Field Genebank for Hardy Fruits, Gongzhuling, China, was established at Jilin Province (Zhang et al., 2003). (1986) showed that esters are the most abundant flavor Phenotypic properties, biologic characteristics, cold resistance, components in apple cultivars (Hatsuaki, Kogyoku, Golden disease resistance, and fruit quality have been described and Delicious, Mutsu, and Fuji). Similar results were found for ‘Annurca’ and ‘Delicious’ apple fruit (Mattheis et al., 1991; Scalzo et al., 2001). In wild apple, aldehydes, esters, and Received for publication 27 Oct. 2016. Accepted for publication 23 Feb. 2017. alcohols are the main volatile compounds (Li et al., 2008). In This work was supported by a Special Fund for Agro-scientific Research in the Public Interest (201303093). Malus sieversii, alcohols, aldehydes, and esters are the main C. Zhang and X. Chen designed the experiment, performed the study, and volatile compounds (Chen et al., 2007). However, the volatile drafted the manuscript. H. Song and Y. Liang determined the volatile compound compounds present in M. baccata and M. prunifolia are unknown. contents of fruits. C. Zhao and H. Li analyzed data and helped to draft the In this work, we identified the volatile compounds pres- manuscript. All of the authors read and approved the final version of this manuscript. ent in 10 accessions of M. baccata and three accessions 1Corresponding author. E-mail: [email protected]. of M. prunifolia in the National Field Genebank for Hardy 126 J. AMER.SOC.HORT.SCI. 142(2):126–134. 2017. Fruits. The results of this study represent a resource for selecting equal conditions of maturity and of about the same size and and breeding cultivars with a desired volatile phenotype. stature. All the fruit from three trees of the same accession were mixed and divided into three groups, and each group Materials and Methods was a biological replicate. The apples were packed and shipped overnight to the State Key Laboratory for Crop PLANT MATERIALS. Malus baccata and M. prunifolia trees Biology at Shandong Agricultural University, Tai’an, China, were planted in the National Field Genebank for Hardy Fruits for evaluation. (lat. 43°50#N, long. 124°82#E). The average temperature for STATIC HEADSPACE EXTRACTION. Tento50applefruitwere January is –13.6 °C and extreme low temperature is –38 °C rapidly cut into slices of about 3 mm wide and mixed. Six for the nursery. The management level of the nursery is good grams of sample was placed in 10 mL sample bottles, and and consistent. The fully ripened apple fruit with detectable 10 mL 3-nonanone (0.4 mgÁmL–1) was injected into each bottle fragrance and intrinsic color of 10 M. baccata accessions and used as an internal standard. The sample bottles were then (‘Duanba Shandingzi’, ‘Xiaosuanguo’, ‘Zhaai Shandingzi’, sealed using polytetrafluoroethylene butyl rubber cap iso- ‘Benyuandaguo Shandingzi’, ‘Benzaodaguo Shandingzi’, lation. A headspace sampler (PerkinElmer TurboMatrix 40 ‘No. 3 Shandingzi’, ‘No. 5 Shandingzi’, ‘No. 6 Shandingzi’, Trap; GenTech, Arcade, NY) was used to extract the volatile ‘No. 7 Shandingzi’, and ‘No. 8 Shandingzi’) and three M. component of fruit and inject the sample. Samples were prunifolia accessions (‘Bai Haitang’, ‘Xiaohuang Haitang’, extracted after 30 min of incubation at 50 °C, with the and ‘Bian Haitang’) were harvested between 20 Aug. 2014 temperature of the static sample probe and transfer line being and 20 Sept. 2014 (Fig. 1). Three trees were sampled for each maintained at 80 °C, and then the sample bottle was pressured accession and 50 fruit were harvested for each tree. Apple to 15 Pa for 5 min. Then, 500 mL of the volatile component fruit were harvested one time from each tree, all with about was captured for analysis. Fig. 1. Ripe fruit of (A) Malus baccata and (B) Malus prunifolia and (C) their weights. M. baccata accessions are abbreviated as follows: B1 = ‘Duanba Shandingzi’, B2 = ‘Benyuandaguo Shandingzi’, B3 = ‘Benzaodaguo Shandingzi’, B4 = ‘No. 3 Shandingzi’, B5 = ‘No. 5 Shandingzi’, B6 = ‘No. 6 Shandingzi’, B7 = ‘No. 7 Shandingzi’, B8 = ‘No. 8 Shandingzi’, B9 = ‘Xiaosuanguo’, and B10 = ‘Zhaai Shandingzi’; M. prunifolia accessions are abbreviated as follows: P1 = ‘Bai Haitang’, P2 = ‘Xiaohuang Haitang’, and P3 = ‘Bian Haitang’. The vertical bar represents ±SE of the mean of 30 fruit. Different letters above the bars indicate significant differences at P # 0.05 based on Duncan’s test. J. AMER.SOC.HORT.SCI. 142(2):126–134. 2017. 127 128 Table 1. The main volatile compounds and their contents in fruit from 10 Malus baccata accessions by static headspace and gas chromatography–mass spectrometry.z Duanba Benyuandaguo Benzaodaguo No. 3 No. 5 No. 6 No. 7 No. 8 Zhaai Shandingzi Shandingzi Shandingzi Shandingzi Shandingzi Shandingzi Shandingzi Shandingzi Xiaosuanguo Shandingzi Compoundsy (mgÁg–1 3-nonanone) 1-Hexanol 0.0983 ax 0.1455 a 0.1998 a 0.1083 c 0.0644 b 0.0408 b 0.3733 c 0.5181 b 0.1503 a 0.3310 b Cyclohexanol 0.0654 b 0.1066 b 0.1633 b — — — — 0.4840 b — 0.3256 b 3-Nonanol 0.0269 c 0.0102 d 0.0061 e 0.0123 f 0.0044 de 0.0021 f 0.0148 e 0.0151 f 0.0072 e 0.0111 fg 1-Penten-3-ol —w — 0.0035 e 0.0066 g 0.0024 e 0.0026 f 0.0066 f 0.0148 f 0.0025 f — 3-Hexen-1-ol — — — 0.4206 b — — — — — — (E)-4-Hexen-1-ol 0.0781 b 0.1369 a — — 0.1436 a 0.1150 a 0.6701 b — 0.1233 a — (E)-2-Hexen-1-ol — — — — 0.0682 b 0.0214 c — — 0.0543 b — Ethyl hexanoate 0.0196 cd — 0.0277 d — — — — — — — Pentyl acetate — — — 0.0059 g — — 0.0228 e — — 0.0055 g Hexyl acetate 0.0175 cd 0.0150 d 0.0029 e 0.1343 c — — 0.1961 d 0.1985 de 0.0135 d 0.1943 c (Z)-3-Hexen-1-ol acetate 0.0704 b — — — 0.0083 d 0.0073 d 0.8677 a 0.3696 bc 0.0383 c — (Z)-2-Hexen-1-ol acetate — — — — — — 0.0899 e — — (4E)-4-Hexen-1-ol acetate — — — 0.0073 fg — — — 0.4244 b — — (Z)-3-Hexenyl formate — — — — — — — — — 0.4027 b (E)-3-Hexenyl acetate — 0.0515 c — 0.7941 a — — — — — — (Z)-3-Hexenyl acetate — — — — — — — — — 0.3817 b (2Z)-2-Hexenyl acetate 0.0073 d 0.0070 e — — — — — — — 0.1521 c Hexanal — 0.0289 d 0.0773 c 0.1247 c 0.0260 c 0.1699 a 0.2121 cd 0.2560 d 0.0234 cd 0.1720 c (E)-2-Hexenal 0.0185 cd 0.0766 c 0.1885 a 0.0617 d 0.0428 c 0.1473 a 0.1062 d 0.8009 a 0.0313 c 0.6354 a a-Longipinene — — — — 0.0398 c — — — — — J.