Cytological Studies of Hybrids between Aneuploid and Eu-diploid Japanese Garden Iris(Iris ensata Thunb.).

Abstract

Cytological studies of hybrids between the aneuploid variety “Ochibagoromo” (2n=25) and the eu-diploid variety “Shishinden” (2n=24) of Iris ensata were made. Among the hybrids (2n=24) examined, F1-1 and F1-2 exhibited normal associations (12 II), and the mean chromosome association per cell was 0.13 I+11.93 II for the former and 0.29 I+11.86 II for the latter, respectively. This indicates that one of three single chromosomes of “Ochibagoromo” has full homology for the second longest m chromosomes of “Shishinden”. On the other hand, F1-3 showed a fairly lower frequency for normal associations than the former two hybrids. The mean chromosome association per cell was 0.98 I+11.16 II+0.24 III. Consequently, this hybrid exhibited the lowest pollen fertility among F1 hybrids due to the irregularity in chromosome associations. Moreover, comparative karyotypic analysis between F1-1 and F1-3, and the meiotic data of F1-3 clarified that this irregularity was caused by structural changes of chromosomes such as translocation and deficiency. Finally, the origin and the development of the aneuploid varieties are discussed.