Materials and reagents

‘CH’ and ‘FC’ pummelo (Citrus maxima) fruits exhibiting typical characters at each corresponding fruit development stage were collected from the scientific research orchard of the Forestry Science Academy of Lishui, Zhejiang Province, in 2011. The fruits were collected at 45, 75, 100, 125 and 150 days postanthesis (DPA) (Fig 2). The fruits of ‘CH’ and ‘FC’ were commercially mature between 125 DPA and 150 DPA. The flavedo, albedo, SMs and JS of the fruits were carefully dissected [22]. The JS of Huanong Red (HR, red-fleshed), Chandler (QDC, red-fleshed), Hirado Buntan (HB, pink-fleshed), Wubu Red-fleshed (WBH, red-fleshed), Thai (T, pale yellow-fleshed), Kao Pan (KP, pale green-fleshed), Fenghuang (FH, pale green-fleshed) and Acidless (WS, pale green-fleshed) pummelo fruits at full maturity were collected from the National Citrus Breeding Center at Huazhong Agricultural University. Three biological replicates for each sample were prepared, with each biological replicate consisting of 6–8 fruits.

All the samples were treated with liquid nitrogen and then stored at –80°C. Some of them were lyophilized in a Heto Lyolab 3000 (Heto-Holten A/S, Allerød, Denmark) and homogenized to a powder in liquid nitrogen for the extraction of metabolites.