Hybridization (N + N and 2N + N) of Facultative Apomictic Species in the Pennisetum Agamic Complex

It has been hypothesized that within agamic complexes, apomixis acts to preserve fertility in wide crosses. Through hybridization studies with two facultative (partially sexual) Pennisetum species (P. flaccidum and P. mezianum), n + n (BII) and 2n + n (BIII) sexual, facultative, and obligate apomictic hybrids were obtained. The objectives of this study were to determine the frequency for wide-cross BIII hybrids in an agamic complex and to compare fertility of BII and BIII hybrids. Sexual all hybrids derived from hybridization of P. flaccidum with P. mezianum were always highly sterile because of male and female abortion, while obligate apomictic BII hybrids obtained through pseudogamy were fertile when supplied with viable pollen. All BIII hybrids from fertilization of 2n apomictic eggs were highly fertile regardless of mode of reproduction. The ability to recover obligate apomictic BIII hybrids allowed for transfer of whole genomes to the female chromosome complement and to synthesize new, fertile, true breeding 2n + n genotypes.