Breeding and Cytogenetic Characterizations of New Hexaploid Drosera Strains Colchicine-Induced from Triploid Hybrid of D. rotundifolia and D. spatulata

Abstract

An in vitro technique was connected with application to produce colchicine-induced hexaploid from the artificial-crossing triploid hybrid of Drosera rotundifolia and D. spatulata. The colchicine-treated plants of artificial-crossing triploid hybrid showed morphologically mutated characteristics. Three hexaploid strains by chromosome doubling were produced after screening of clones treated with 0.05 and 0.1% colchicine solutions for one or three days. Each of the strains had 2n=60 with 20 middle size and 40 small size chromosomes (2n=6x=20M+40S). The stomata guard cell sizes of colchicine-induced hexaploid and the wild hexaploid species D. tokaiensis were larger than that of the artificial-crossing triploid hybrid. Flow cytometry analysis showed that 2C DNA-values of D. rotundifolia (2n=2x=20M), D. spatulata (2n=4x=40S) and D. tokaiensis (2n=6x=20M+40S) were 2.73, 1.41 and 3.74 pg, respectively. In contrast, the artificial-crossing triploid hybrid (2n=3x=10M+20S) and colchicine-induced hexaploid (2n=6x=20M+40S) were 2.31 and 4.41 pg, respectively. The genome size of the artificial-crossing triploid hybrid (2.31 pg) was nearly half the size of the colchicine-induced hexaploid (4.41 pg). Compared to the colchicine-induced hexaploid, the genome size of D. tokaiensis was unexpectedly small, even though they contained the same genome constitutions.