ENHANCED IN-VITRO PLANTLET REGENERATION FROM MATURE EMBRYO-DERIVED PRIMARY CALLUS OF A BASMATI RICE CULTIVAR THROUGH MODIFICATION OF NITRATE-NITROGEN AND AMMONIUM-NITROGEN CONCENTRATIONS

Mature-embryo derived primary calli of the basmati rice (Oryza sativa L.) cv Karnal Local showed significant enhancement in in vitro green-p lantlet regeneration efficiency through modification of nitrogen conte nt of the callusing medium. Using KNO3 as the source of nitrate nitrog en and (NH4)(2)SO4 as the source of ammonium nitrogen, forty-five medi a combinations involving 9 levels of KNO3 (0-40 mM) and 5 concentratio ns (0-6.5 mM) of (NH4)(2)SO4 were examined. The highest frequency of p lantlet regeneration (100%) and a maximum number of green-plantlets (s imilar to 7) per embryo-derived primary callus was obtained in calli d erived from the medium having 35 mM KNO3 and 5 mM (NH4)(2)SO4 Higher c oncentrations of KNO3 and/or (NH4)(2)SO4 showed a decline in the regen eration efficiency. It was also observed that although the nitrogen co ntent of the callus induction medium had a profound effect on the rege nerability of the callus, the nitrogen composition of the regeneration medium also affected it significantly.