Parentage analysis of huyou (Citrus changshanensis) based on internal transcribed spacer sequences

Huyou (Citrus changshanensis K. S. Chen et C. X. Fu) citrus is a natural hybrid with unidentified parents. Previous studies have hypothesized that pummelo and sweet orange might be parents, which contradicts the higher freezing resistance of huyou citrus than both the assumed parents. In this study, the parental analysis was based on internal transcribed spacer (ITS) sequences of huyou as well as six candidate parents: three mandarins, one sweet orange, one sour orange and one pummelo. Two different ITS1 sequences, with eight variable sites within the 250 bp region, were observed for huyou, which were identical only to that of sour orange and pummelo, respectively. The results indicated that huyou is most likely a hybrid between sour orange and pummelo. In addition, the application of ITS 1 sequences in the phylogenetic analysis of citrus was discussed.