Gene Transfer in Apomictic Buffelgrass through Fertilization of an Unreduced Egg

Abstract

Opportunities for gene manipulation are often limited in apomictic species, and conventional breeding methods may be totally ineffective. Lack of good sexual germplasm led us to investigate improvement of apomictic buffelgrass ( Cenchrus ciliaris L.) through fertilization of an unreduced egg (2 n + n ), using an apomict as the female parent. The primary objective of this research was to determine the potential for gene transfer in buffelgrass through 2 n + n hybridization. When an apomictic pentaploid accession with an alien genome (2 n =5x=45) was crossed with tetraploid apomictic birdwoodgrass ( C. setigerus Vahl, 2 n =4x=36), 1.3% of 950 progeny resulted from the fertilization of an unreduced egg (B III hybrids) and had 2 n = 7x=63 chromosomes. Origin of these hybrids from the union of 2 n and n gametes was confirmed by the presence of the alien genome from the female parent and diagnostic morphological characteristics of the male parent. Hybrids were all obligate apomicts and most were relatively high in seed set compared to the parents. The results demonstrated an effective method for gene transfer in some apomictic species. Complete emasculation was considered essential for maximum hybridization.