MUTANTS AFFECTING GERMINATION AND EARLY SEEDLING DEVELOPMENT IN MAIZE

Maize mutants impairing germination or early seedling development have been isolated with the aim to use them as a tool to elucidate the genetic program accounting for seedling development. Some of these mutants were obtained following chemical mutagenesis, while the majority were isolated in the selfed progeny of stocks carrying the Mu trasposon outcrossed to different lines. Only the mutants exhibiting a stable phenotype in two succeeding generations of selfing were further analyzed. The rea mutant (red embryo axis), recognizable on the basis of its red embryonic axis, is unable to undergo embryo dormancy while exhibiting clear symptoms of water stress in the seedling. The des (defective seedling) mutants represent another category, recognizable a few days after germination, because of the enlarged coieoptile or leaf morphology. Their histology discloses further anomalies at the cell or tissue differentiation level. Finally, the d* symbol refers to new dwarf isolates tested for their response to exogenous gibberellins and crossed inter se or with known d mutants (d1, d2, d3 and d5). The allelism test has led to the identification of five gibberellin responding mutants, not attributable to any of the known d genes already described. For one of them (d*3) the segregation ratios and the RFLPs mapping data are consistent with the hypothesis of its duplicated origin.