Balanced Hypotetraploids in Ophiopogon japonicus and O. ohwii

Abstract

In Ophiopogon japonicus and its related O. ohwii, whose basic chromosome number is x=18, two forms of hypotetraploids, 4x-5 (2n=67) and 4x-4 (2n=68), were commonly found. These hypotetraploids were dis-tinguishable not only as to the chromosome number, but also as to the constitution of the nucleolar chromosomes. Among them, the form 4x-4 was divided into three subtypes by the constitution of nucleolar constrictions. The plants tested were collected in various localities ranging from Tokyo to Okinawa, and the form 4x-5 was found in the most collected plants of O. japonicus, and the three subtypes of the form 4x-4 in those of O. ohwii.
The behavior of the meiotic pairings was almost the same in both the forms 4x-5 and 4x-4. The community to both forms was found in the high frequency of bivalent formation at MI, with infrequent occurrence of uni-, tri-, and quadrivalent formations. The frequency of fertile good pollen grains was relatively high in both forms. Furthermore, the progenies obtained from a form 4x-5 of O. japonicus revealed a preponderance of mother type plants under open-pollination. Based on the results of these findings it is highly probable that the hypotetraploids are established by a secondarily induced genetic balance at the aneuploidal level.