Embryogenesis and Plant Regeneration in Tissue Cultures Derived from Mature and Immature Somatic Tissues of Rice (Oryza Sativa) and Wheat (Triticum Aestivum)

Abstract

Immature embryos at various stages of development, whole excised mature embryos, detached scutella of mature embryos, whole seeds, and shoot apical tissue of rice and wheat were cultured on various callus-inducing media. In rice, embryogenic callus was formed from the scutellum of immature embryos at all stages of development examined, as well as from the scutellum of physiologically mature embryos. Rice embryogenic callus produced well-defined somatic embryos and exhibited a high capacity for regeneration. The regeneration potential of embryogenic callus derived from the scutellum of mature embryos did not differ significantly from that of embryogenic callus derived from immature scutella. In wheat, callus produced from the scutellum of immature embryos decreased with increasing size of the embryo. No callus was formed from physiologically mature wheat scutella. Initiation of embryogenic callus in both rice and wheat was more dependent on the source of expiant material than on the initiation medium. The ability of mature rice scutella to produce embryogenic callus is a demonstration in the Gramineae that some highly differentiated cells, that have ceased to divide in vivo, can remain competent to form somatic embryos and subsequently regenerate plants in vitro.