Influence of the antimitotic agents colchicine and oryzalin on in vitro regeneration and chromosome doubling of diploid bananas (Musa spp.)

In vitro cultures of the four diploid banana cultivars, Sannachenkadali (AA), Anaikomban (AA), Kunnan (AB) and Thattillakunnan (AB) were treated with two antimitotic agents, colchicine (C22H25NO6) and oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) to induce ploidy alterations, particularly the induction of tetraploids, which would serve as useful breeding material for creating newer, improved triploids. Both antimitotic agents, but particularly colchicine, had a negative effect on the in vitro regeneration of the four cultivars. This was reflected in terms of delay in regeneration, reduced multiple shoot regeneration rates, regeneration of smaller microshoots with lower fresh weights, and reduced response to rhizogenesis. Colchicine, as expected, had a negative effect on the number of multiple shoots regenerated. However, oryzalin at lower concentrations (10 muM and 20 muM) resulted in the regeneration of more microshoots per culture than the untreated control. The chromosome doubling capacity of colchicine was equal to that of oryzalin only at 125-200 times higher concentrations. The cultivars exhibited a genome-related response.