Maize developmental mutants

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Abstract
Among a large collection of maize defective kernel mutants 14 were identified that have embryos lacking leaf primordia at maturity. These are a type of developmental mutant; all are single-gene recessive mutants in which both the endosperm and the embryo are defective and all are lethal because their mature kernels fail to germinate. Five of the mutants are ailelic and located on chromosome arm is, while four other mutants are located on 1L, 3L, 4L, and 5L. The five allelic mutants are blocked at the proembryo stage, two other mutants are blocked at the transition stage, four at points intermediate between the transition and the coleoptilar stages, and one at the coleoptilar stage of embryo development. The other two developmental mutants produce embryos that range from the transition to the coleoptilar stage at maturity. One additional defective kernel mutant ranges from the coieoptilar stage to stage 1 (first leaf primordium) and two other mutants reach stage 1 or later by maturity. Endosperm-embryo interaction of 11 defective kernel mutants, Including nine developmental mutants (five are allelic), was examined by observing embryo development and germination capacity of mature kernels containing genetically normal endosperm and genetically mutant embryos as well as kernels containing the reciprocai arrangement. In all cases a normal endosperm failed to rescue a mutant embryo. When the endosperm was mutant and the embryo was normal, in all cases the embryos formed primordia and germinated; in eight cases (including five that are alleiic) more or less normal seedlings were produced, in one case the seedlings were weak, and in two cases the seedlings were lethal. It appears that for these mutants it is the genotype of the embryo that determines its developmental fate and its capacity to germinate but that a mutant endosperm can, in some instances, impair seedling growth. The developmental mutants offer promise for studying the genetic regulation of plant embryo development.

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