Abstract: Young leaves of several rare germlasm resources in litchi and longan were used to observe chromosome numbers and identify their ploidy after pretreated with the mixture of 1︰1 aqueous solution of saturated paradichlorobenzene and 2 mmol • L-1 8-hydroxyquinoline，fixed by Carnoy’s fixative，hydrolyzed with HCl and enzymes，and stained in improved Carbol-fuchsin. The results showed that ‘Lieye’longan was a haploid（2n = x = 15）and grew normally. The parents used to create three mapping groups，including litchi parent ‘Maguili’ and paternal ‘Jiaohesanyuehong’，and longan parent‘Fengliduo’，‘Shixia’and paternal‘Dawuyuan’，‘Zhongqiu 1’were all diploids（2n = 2x = 30）. The intergeneric hybrids（A and B）between Litchi and Dimocarpus were also diploids and could grow normally. Moreover，several germplasm resources with distinct trait including litchi‘Ziniangxi’，‘Wuheli’，‘MS-07’，‘SGA’，‘YA1’and‘YN4’as well as a longan‘Shuangji’were all diploids.

Key words: litchi, longan, young leaf, chromosome, haploid