Chromosome Association in Dichanthium Hybrids

Abstract

Chromosome behavior was studied in 8 species and 8 hybrids of Dichanthuym Willemet. Species with 2n = 20 appear to be functional diploids; tetrapoloids (2n = 40) are segmental allopolyploids. Hybrids between two tetra-ploid races of the same species or between different species have either 2n = 40 or 2n = 60 chromosomes. Normal male gametes will fertilize, the reduced as well as the unreduced female gamete. Both reduced and unreduced embryo sac in the hybrids will develop par -thenogenetically to produce viable offspring. A cytological study of these polyhaploid plants and their parents indicates that autosyndesis is the most frequent mode of pairing in Dichanthium. Further, chromosome pairing will take place within the basic genome (n = 10), suggesting that the original basic number may have been n = 5.