Initiation and growth of embryogenic callus and suspension cultures of Zea mays L.

Abstract

<p>Somatic embryos formed from immature embryos of maize under certain defined conditions can give rise to embryogenic callus and suspension cultures. Both embryogenic callus and suspension cultures of Zea mays have been examined in this study;Two pathways of somatic embryogenesis have been identified from immature embryos plated on callus inducing medium. Embryos from corn inbred line H99 demonstrate the presence of a generalized area of meristematic tissue in the subepidermal region of the scutellum, indicative of a multicellular origin for the somatic embryos. This is in agreement with observations reported previously in the literature. In contrast, embryos of a G35 x B73 hybrid develop distinct, small groups of meristematic cells that seem to be isolated from the remainder of the scutellar cells. These groups of cells appear to originate from single cells of the epithelial layer;The growth characteristics of suspension cultures derived from embryogenic callus cultures of two maize genotypes, B73 and B73 < 2G35, were studied. These cultures varied in the relationship between the size of the cell clusters and the mitotic index of the culture. For the B73 line, the mitotic index was positively correlated to the average cell cluster size, while suspension cultures of B73 < 2G35 demonstrated a negative correlation. It is unlikely that these observed differences are due to genotype alone;These studies clearly establish that the growth characteristics of embryogenic cultures are highly dependent upon the genotype of the maize line being used. An understanding of the growth patterns of a particular genotype is useful in the selection of a method for utilization of the culture in in vitro selection and transformation studies.</p>