GENOME ACCUMULATION IN EASTERN GAMAGRASS, TRIPSACUM DACTYLOIDES (L) L (POACEAE)

Intermatings between sexual diploids (2n = 36) and facultative apomictic tetraploids (2n = 4n = 72) of Tripsacum dactyloides var. dactyloides, (L.), L., have been generated. Subsequent exchange and addition of genetic material between the two cytotypes, via a backcrossing program, provides one method for the manipulation of genetic elements involved in apomictic reproduction (diplospory) of this species. Identification and development of fertile triploids, and their innate tendency to exhibit a high frequency of unreduced egg cells which remain receptive to fertilization by a sperm nucleus, allows for the unique development of B-III(2n = 3x + n) tetraploids by genome accumulation. The resultant B-III progeny provide new breeding stock for investigating the inheritance and generation of such materials also allows for the occurrence of genetic recombination between sexual diploids and apomictic tetraploids. Potential use of fertile triploids, their tendency for genome accumulation and their use in exploiting apomictic tetraploid germplasm resources are also discussed.