AN IMPROVED PROCEDURE FOR PLANT-REGENERATION FROM INDICA AND JAPONICARICE PROTOPLASTS

Plant regeneration fi-om protoplasts of two commercially cultivated In dian indica rice varieties, Pusa Basmati 1 and Jaya, has been accompli shed by plating embryogenic cell suspension-derived protoplasts on the surface of filter membranes overlying agarose-embedded feeder cells o f Lolium multiflorum and Oryza ridleyi, combined with the use of a mal tose-containing shoot regeneration medium. Embryogenic cell suspension cultures of Puss Basmati 1 and Jaya were initiated from mature seed s cutellum-derived calli in liquid R(2) medium modified by the addition of 560 mg l(-1) of proline and 1.0 % (w/v) maltose. In both varieties, protoplast plating efficiencies up to 0.4 % were obtained, depending on the nature of the feeder cells. L. multiflorum feeder cells induced a 6-fold higher plating efficiency than feeder cells of O. ridleyi. I n combination, O. ridleyi and L. multiflorum feeder cells further enha nced protoplast plating efficiency. Protoplast-derived cell colonies w ere not obtained from protoplasts of either indica varieties in the ab sence of feeder cells. MS-based medium containing kinetin (2.0 mg l(-1 )) and alpha-naphthaleneacetic acid (0.5 mg l(-1)), together with sucr ose and maltose both at 1.5 % (w/v), induced green shoot regeneration in 44 % of protoplast-derived tissues, depending on the feeder cells u sed for protoplast culture. In both varieties, tissues obtained using O. ridleyi feeder cells were more morphogenic than tissues obtained us ing L. multiflorum feeder cells, either alone or in combination with c ells of O. ridleyi. In the japonica rice variety Taipei 309, this new procedure resulted in a 30-fold increase in plant regeneration from pr otoplasts compared to previous published procedures.