High oil, scutellum, embryo and endosperm

While the endosperm is the primary storage organ in the corn kernel and monocots in general, the scutellum may also serve this purpose. In fact, in dicots it is the cotyledons, the counterpart of the scutellum, which are the sole storage organs. There is no obvious reason why the scutellum could not be bred to become the primary storage organ in corn. This would dramatically change the composition of stored material to that of oil which resides in the scutellum and embryo. Selection for high oil by Alexander's group in Illinois has over the years produced an enlarged scutellum. Enlargement of the embryo associated with pointed kernels would further increase the oil level, as would a reduction of the endosperm with mutants such as sugary, shrunken and brittle. These mutants, by extending the period of flow by soluble polysaccharides into the embryo, also increase the growth duration and size of embryo and, consequently, the level of oil.

The pointed shape of certain kernel types results from more rapid growth of the embryo and scutellum (the germ) relative to that of the endosperm, all under the pericarp enclosure. The pericarp and its stylar extension grow from the base. Growth of the style stops at the time of fertilization, and at the same time growth by the pericarp is reactivated. Enlargement of the pericarp is necessary in order to adequately accommodate the two products developing from double fertilization. If the reactivated pericarp grows faster or in greater duration than the germ and endosperm, it becomes loose and does not give adequate protection.

Walton C. Galinat

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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