Intergeneric Pollen Tube Growth in Poaceae Utilizing the Iap Allele in Sorghum Bicolor.

The use of hybridization in sorghum (Sorghum bicolor L.) has long served as a tool utilized by breeders to increase and exploit genetic variation within the species.  Recent interspecific hybridization of S. bicolor has produced diversity not previously seen within Sorghum species.  A sorghum accession containing the homozygous recessive mutant gene iap (Inhibition of Alien Pollen) has been determined to remove reproductive isolation barriers.  Development of a S. bicolor accession containing the mutant allele iap and ms3 has allowed introgression of genomic regions from divergent sorghum species into S. bicolor.  The objectives of this study were to determine the range and effectiveness at which the iap allele allows pollen tubes of species from outside of the Sorghum genus to grow into S. bicolor pistils.  Fluorescent microscopy was used to determine the distance through the pistils that foreign pollen tubes grew.  Accessions from the genera of Zea, Miscanthus, Pennisetum, and Sorghastrum were used as pollen donors.  Results of the study showed high levels of pollen tube growth into the ovaries of S. bicolor pistils for some species.  This research shows that a wide range of intergeneric hybridization within S. bicolor may be possible through the use of the iap allele.