Gum katira - a cheap gelling agent for plant tissue culture media

Gum katira, an insoluble gum derived from the bark of Cochlospermum religiosum, has been successfully used as a gelling agent in tissue culture media for in vitro shoot formation and rooting in Syzygium cuminii and somatic embryogenesis in Albizzia lebbeck. The epicotyl segments, excised from in vitro grown seedlings of S. cuminii, developed shoots when cultured on MS medium (Murashige and Skoog, 1962), supplemented with 4% sucrose and 1 mg l(-1) BA. The so-developed shoots were rooted on Knop's medium, augmented with 2% sucrose and 1 mg l(-1) IAA. For somatic embryogenesis, hypocotyl segments derived from in vitro developed seedlings of A. lebbeck were cultured on B5 medium containing 2% sucrose. Media were gelled with either 3% gum or 0.9% agar. The quantitative response obtained on media fortified with either of the gelling agents was not significantly different. The media gelled with gum katira were almost as transparent as the liquid medium. However, viscosity of gum katira gelled medium was less than one-sixth of the viscosity of agar-gelled media, and therefore, shaking {of} the culture vessel often resulted in submersion of the explants. Nevertheless, even these submerged explants responded positively. To increase the firmness of the gum katira-gelled medium, various combinations of agar (0.2-0.6%) and gum (1-3%) were used. However, the viscosities of the media gelled with 3% gum katira as well as different concentrations of agar (0.2-0.6%) were lower than that of the medium containing only gum katira (3%). Moreover, the explant productivity obtained in neither of these combinations was more than those recorded on the control media, which were gelled either with 0.9% agar or 3% gum alone.