“Valencia” oranges (Citrus sinensis (L.) Osbeck) were obtained from orchards on June 08, 2022 (Xiema, Beibei district, Chongqing, China). Citrus fruits were harvested from visually CBS symptomatic trees (displaying black spots on the fruit peel) and visually healthy trees (no CBS symptoms). Thirty fruits were picked from one tree and the experiment was repeated with three trees. Different CBS-infected fruits were picked from symptomatic trees and classified into a mild-infection group (MIG), a moderate-infection group (MOG), and a severe-infection group (SEG) according to the size and number of black spots on the fruit peel by using Bold extract software (Fig.1 ). Citrus fruits obtained from the visually healthy trees were designated the healthy group (HG). By integrating data from a large number of CBS citrus fruits, when the area proportion of black spots to the whole citrus fruits is 0,0–4%, 4–7%, and >7%, it is defined as HG, MIG, MOG, and SEG (Fig.S1). The essential oil extraction and juice preparation of the orange fruits in symptomatic and CBS noninfected groups were performed using the same processing method. The peel essential oil was prepared by a cold-pressing method as described previously with modifications (Njoroge, Ukeda, & Sawamura, 1996 (link)). The citrus fruits were washed with water and dried, and the flavedo layer was peeled with a rotary peeler. The oil emulsion was pressed by a CJ3000 blender (Braun Co., Kronberg, Germany) and centrifuged at 13400 ×g for 10 min at 4 °C. Then, the collected samples were frozen for two days at −20 °C, the lower layer of precipitation was discarded, and the upper layer of clear liquid was the cold-pressed oil for the study. The peeled citrus fruits were cut in half and hand-squeezed into juice by a blender (CJ3000, Braun Co., Germany). The juice was filtered through an 80-mesh filter and kept at −20 °C until further analysis.Fig. 1 ![]()
Fruit appearance of HG, MIG, MOG, and SEG citrus fruits.
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