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 rica (Oryza sativa L.) cv Karnal Local showed significant enhancement in in vitro green-plantlet regeneration efficiency through modification of nitrogen content of the callusing medium. Using KN0₃ as the source of nitrate nitrogen and (NH₄)₂SO₄ as the source of ammonium nitrogen, forty-five media combinations involving 9 levels of KNO₃ (0–40 mM) and 5 concentrations (0–6.5 mM) of (NH₄)₂SO₄ were examined. The highest frequency of plantlet regeneration (100%) and a maximum number of green-plantlets (∼ 7) per embryo-derived primary callus was obtained in calli derived from the medium having 35 mM KNO₃ and 5 mM (NH₄)₂SO₄. Higher concentrations of KNO₃ and/or (NH₄)₂SO₄ showed a decline in the regeneration efficiency. It was also observed that although the nitrogen content of the callus induction medium had a profound effect on the regenerability of the callus, the nitrogen composition of the regeneration medium also affected it significantly.