To provide the subject new primer containing a set of several oligonucleotides each containing a specific base sequence at the 3' terminal and capable of quickly separating a chalcone synthetase gene of various vegetables over various families by using the primer in PCR method.

This new oligonucleotide primer is useful for the separation of a chalcone synthetase gene by PCR method using a set of primers consisting of an oligonucleotide containing a base sequence of the formula YTDGCNGA on the 3' terminal (the base sequence is expressed from the left 5' terminal side to the right 3' terminal side; D is a base selected from adenine, guanine and thymine; N is a base selected from adenine, guanine, cytosine and thymine; Y is cytosine or thymine) and an oligonucleotide containing a base sequence of the formula GGNCCRAA (R is adenine or guanine) on the 3' terminal side. It is useful e.g. for the preparation of vegetable variety having disease resistance and unique flower color.