Expression of fasciation mutation in apical meristems of soybean, Glycine max (Leguminosae).

The phenotype of the apical meristem was used to examine the effect of fasciation mutation at the f locus in different genetic backgrounds in soybean Glycine max (L.) Merr. Comparisons of meristem development in fasciation mutant and wild type were conducted with scanning electron microscope (SEM) on isogenic lines BARC-11-11-ff and BARC-11-11-FF at postgermination and early vegetative stages. Studies of apical meristems of three independently originated fasciation mutants, PI 83945-4, PI 243541, and T173, were carried out at vegetative and early floral transition stages. Corolla Fasciation, the extreme mutant phenotype, was used for comparison of meristem development. Enlargement of the apical meristem and shortened plastochron were observed in the mutant lines 2 d after germination. Similar to Corolla Fasciation, in PI 83945-4, PI 243541, and T173, enlargement of the apical meristem was followed by growth along one axis at the V3 stage and establishment of a ridge-like meristem at the V4 stage. Influence of pedigree on the expression of the fasciation phenotype was demonstrated by different growth patterns (subangular vs. ridge-like) of the apical meristem in BARC-11-11-ff and PI 243541 with the same f gene. During transition of the apical meristem from vegetative to reproductive stage in all mutant lines further production of leaf primordia ceased. The developmental pattern of the apical meristems suggests that the f locus may have the same allele in fasciation mutants of independent origin in soybean.