Improvement of Indica rice (Oryza sativa L.) in vitro regeneration efficiency from callus mediated by stress

Plant regeneration frequency and average number of plant per callus significantly enhanced in Indica rice callus maintained under the stimulatory effect of stressing conditions. Culture on high sucrose concentration for one week before regeneration, increasing gelling agent concentrations in the regeneration medium above the recommended levels, or blotting on filter paper for drastically reducing callus water content prior regeneration lead to significant improvements of regeneration efficiency from callus, although no selection of embryogenic clusters was performed. The simple procedures described in this paper provide an alternative for improving regeneration capacity in other rice cultivars and recalcitrant cereal species for in vitro regeneration of whole plants.