Abstract:The chromosomes of two new varieties ‘Yunyan 77-2’ and ‘Yunyan 77-4’ and their parents ‘PR107’ and ‘GT1’ were observed, and the breeding process of the new varieties was summarized. The results showed that the chromosome number of ‘PR107’ and ‘GT1’ is 2n=2x=36, whereas 2n=3x=54 for ‘Yunyan 77-2’ and ‘Yunyan 77-4’. ‘Yunyan 77-2’ and ‘Yunyan 77-4’ are triploids. It is an effective way to breed new Hevea varieties by establishing a pollination garden of special parents, setting reasonable screening criteria and selecting the polyploid seedlings under stress circumstances.