Colchicine induced polyploidy from thallus segments of Kappaphycus alvarezii (Doty) for genetic improvement

Abstract

Regeneration of polyploidy from young thallus segments of Kappaphycus alvarezii was optimized for genetic improvement. Kappaphycus thallus segment cultured on sterile sea water supplemented with various combinations of Indole acetic acid, Kinetin and Acardian Marine Plant Extract Powder revealed differential response on callus proliferation and development of new thallus. Presence of Acardian Marine Plant Extract Powder (3 mg/l) in combination with Indole acetic acid and Kinetin (0.01 mg/l each) had induced the longest emerging thallus. Exposure of thallus to colchicine at 0.01% with above combination was optimal to induce high frequency regeneration of polyploidy mostly from the meristematic cells. Anatomical study of colchicine induced polyploidy revealed larger cortical cells with irregular thickening of epidermal layer. Phase contrast and Scanning Electron Microscopic study revealed increase in cell size in cortical region with significantly larger number of spherical shaped carrageenan globules in colchicine induced polyploidy than normal thallus. Single cells isolated using enzymatic treatments from colchicine induced polyploidy, shown chromosome number with a ploidy status of 4n ≈ 40. Whereas in normal thallus, only half the number of chromosomes (2n ≈ 20) were observed. Polyploidy were successfully acclimatized gradually using raft method for further evaluation. This is the first report reveals the induction and regeneration of polyploidy in Kappaphycus. The possible application of this finding in genetic improvement of Kappaphycus is discussed.