Abstract
A new amphiploid, sativa-australiensis (AAEE, 2n=48) was successfully synthesized by treating the young shoots with 0.05 % colchicine solution which were derived from the dormant buds on the stems of the F1 hybrid. In MI of PMC's in F1, some bivalents were observed. The modal chromosome configuration was 2II+20I. In amphiploid, most of PMC's examined formed the regular pairing of 24II. The remarkable difference was shown in chromosome size of amphiploid as well as F1. From the frequency of occurrence of heteromorphic bivalents in F1, it was infered that there are some homology between the chromosomes of O. sativa and O. australiensis. F1 ybrid was completely sterile. Amphiploid induced was also sterile, although it formed anthers seemingly normal in shape. At the stage immediately after tetrad, the fusion of microspores was observed as the result of the failure of cell wall formation. Multi-germ-pores were also observed on the pollen grains developed from the isolated microspores as well as the fused ones.
