Variation in the Nucleolar Organizing Regions in Regenerated Plants of Japanese Garden Iris (Iris ensata Thunb.).

Abstract

Somatic chromosome numbers of 63 regenerated plants in the cultivar 'Okichidori' of Iris ensata were counted and tetraploid plants were recognized in 11.1 % of the regenerants examined. This indicated that polyploidization for these plants was induced during the subcultures of its multiple shoots. Variation in NORs of 30 diploid regenerants was further examined by the silver-staining method. Half of these regenerants had 4 NOR-bearing chromosomes which were recognized in 'Okichidori'. On the contrary, the other half showed variation in NORs. Among these regenerants, 14 plants had 5 NOR-bearing chromosomes. The increase of one NOR-bearing chromosome compared with 'Okichidori' could be explained by the translocation of a NOR to a non NOR-bearing chromosome during the subcultures of its multiple shoots. In addition, one regenerant (R91) had 3 NOR-bearing chromosomes with 1 Ag-NOR band and 1 NOR-bearing chromosome with 2 Ag-NOR ones. The appearance of the latter chromosome provided conclusive proof that the translocation of a NOR to a NOR-bearing chromosome was induced during the subcultures of multiple shoots in 'Okichidori'. Thus, it was proved that there were somaclonal variations in somatic chromosome numbers and NORs in the regenerated plants obtained from the subcultures of its multiple shoots.