SOMATIC EMBRYOGENESIS AND PLANT REGENERATION FROM TISSUE CULTURES OF PENNISETUM AMERICANUM, AND P. AMERICANUM x P. PURPUREUM HYBRID

Abstract

Immature embryos as well as explants obtained from young inflorescences of Pennisetum americanum (pearl millet) give rise to callus tissues on nutrient media containing 2,4‐dichlorophenoxyacetic acid (2,4‐D). A compact and pale‐yellow callus that arises from the peripheral cells of the scutellum, and from the young inflorescences, undergoes further organized growth. When transferred to a 2,4‐D‐free medium, supplemented with indole‐acetic acid or kinetin, or both, embryoids are formed in the organized areas of the callus. Embryoids show a bipolar organization with a shoot‐coleorhiza (root) axis and have a coleoptile‐like structure surrounded at the base by a cup‐shaped structure that resembles the scutellum in texture and morphology. Embryoids show bilateral or radial symmetry and “germinate” in vitro to form plants that have been grown to maturity in soil. Similar embryogenic callus cultures have been produced from young inflorescence tissues of hybrid Pennisetum , a triploid sexually sterile hybrid of P. americanum x P. purpureum. Plants derived from these have also been transferred to soil. The regenerated plants showed normal chromosome numbers.