Variation Patterns of the Volatile Compounds in Flowers of Chinese Native Citrus Species and Their Taxonomic Implications

Abstract

In this study, the volatile compounds in the flowers of nine Citrus species/varieties, seven of which are native to China, were analyzed using headspace-solid phase microextraction (HS-SPME) coupled with gas chromatography mass spectrometry (GC-MS). A total of 94 compounds were identified, including various terpenes, such as monoterpenes, sesquiterpenes, terpene alcohols and aldehydes, which together accounted for 80.4% to 92.4% of the total compounds analyzed. Limonene, linalool and γ-terpinene were the dominant terpenes. Different species/varieties were characterized by their volatile compounds. Papeda was characterized by a high level of β-ocimene, linalyl acetate, myrcene and neo-alloocimene; Citrophorum was characterized by a high level of limonene and caryophyllene, and Cephelocitrus by a high level of limonene, β-pinene and linolool. Sinocitrus had the highest amount of linolool. Sweet orange had the highest level of limonene, while sour orange was distinct from others with the highest level of γ-terpinene. The four basic types of the genus Citrus L., Papeda, Cephalocitrus, Citrophorum and Sinocitrus, can be clearly classified based on a cluster analysis of their volatile compounds. All of the presumed hybrid species, including Jinchengbeibei 447 ( C. sinensis Osb.), Goutoucheng ( C. aurantium L.), Ningmeng 4 ( C. limon Burm.f.), and Changshanhuyou ( C. paradisi cv. Changshanhuyou), were grouped closely together with a suggested parent species in the constructed dendrogram. Our study clearly demonstrates that Citrus flower volatile compounds and their variation patterns can be used for Citrus species identification and taxonomic study.