- With 2 figures and 1 table Abstract Self-incompatibility (SI) is the major factor that limits the development of the exotic fruit crops belonging to Hylocereus species. The selection of self-compatible (SC) hybrids would greatly benefit growers by eliminating the need to grow complementary cultivars for cross-pollination. With this breeding objective in mind, a total of 182 plants that resulted from the first and second generations of hybrids and a first generation of back-crosses were screened for SC. Five hybrids, all of which were a cross between the triploid hybrid ‘S-75’ and the diploid Hylocereus undatus, were found to be fully SC; they exhibited similar fruit weights and similar total seed numbers following cross- or self-pollination. Flow cytometric analyses revealed that all the SC hybrids were tetraploids, suggesting a possible relation between SC and ploidy level. Further studies will be needed for an efficient identification of SC hybrids during their juvenile period.