Digitaria sanguinalisseedling development pattern: Relationship with seed origin

In the context of a long-term study of the pathosystem Digitaria sanguinalis–Ustilago syntherismae, seeds were collected over several years from a naturally infested field. Two different patterns of germination were found depending on the embryonic organ that first emerges: radicle or coleoptile. The mean frequencies of each pattern of germination were obtained in sets of seeds from non-smutted field plants of five consecutive years, and in a set of seeds belonging to the offspring of partially smutted field plants. The percentage of seeds showing radicular germination ranged from 54% to 69% in the field-collected lots, but it was only 1% in the offspring of partially smutted plants. Furthermore, while seeds with a radicular pattern reached 63% germination 43.5 hours after imbibition, the seeds with a coleoptilar pattern needed 101.5 hours to reach the same percentage. The effect of the amount of water during the imbibition period was also tested in two sets of seeds of different origin. There were no significant differences attributable to this factor, even in the levels of the factor that simulate flooding. We discuss the importance of the different germination behaviour observed in relation to the U. syntherismae infection process.