The association between pollen size and Renner complex in Oenothera villaricae and O. picensis ssp. picensis and their hybrids: evidence for preanthesis pollen competition.

In both Oenothera villaricae Dietrich and O. picensis ssp. picensis, chromosomes are transmitted as two Renner complexes. Reciprocal combinations of the Renner complexes produce eight different F1 hybrids, but only seven are viable. Each species, and each F1 hybrid, produces three sizes of pollen, approximately 50% small sterile grains, 15% medium-sized viable grains and 35% large viable grains. Medium- and large-sized grains were separated manually and subjected to random amplified polymorphic DNAs (RAPDs) analysis. A pattern of RAPD amplifications was obtained which indicates that, for each species and F1 hybrid, one specific Renner complex characterizes the medium- and another the large-sized viable pollen. The results indicate that pollen size is determined in part by the pollen genotype and in part by the genotype of the other pollen grains developing within the same anther.