Abstract: Aimed to investigate cold sensitive genes in fingered citron （Citrus medica var. sarcodactylis Swingle） and unveil the differences of cold resistance mechanism between C.medica and Poncirus trifoliata. The expression patterns of 34 cold\|stress induced genes in C.medica and P.trifoliata were analyzed by semi\|quantitative RT\|PCR after being exposed to -4 ℃ for 24 h. The results showed that the expression levels of 17 genes were different between C.medica and P.trifoliata， among which the transcripts levels of 14 genes changed response to cold\|stress， while no changes were observed in P.trifoliate simultaneously. The transcript levels of 3 genes were found with contrary changing models in two plant species. Besides， the expression of 8 genes in C.medica shared similar pattern as in P.trifoliata， and 9 genes failed to be amplified in P.trifoliata. Thus， it was suggested that the 17 genes differentially expressed in these two plant species were related to cold sensitivity of C.medica. The pathway they were involved in might be the important molecular mechanism regarding cold sensitivity of C.medica. Nine genes with different expression levels induced by cold\|stress in C.medica， which could not be amplified in P.trifoliata， might be the important genes involved in the cold sensibility of C.medica and the important reason resulted in the different cold resistance between C.medica and P.trifoliata.

Key words: fingered citron, Poncirus trifoliata, cold\, stress, differentially expressed genes, semi\, quantitative RT\, PCR