Male and Female Sporogenesis and Gametogenesis in Apomictic Brachiaria-brizantha, Brachiaria-decumbens and F1 Hybrids With Sexual Colchicine Induced Tetraploid Brachiaria-ruziziensis

A calendar of female sporogenesis and gametogenesis was made for both apomictic tetraploid (2n = 4x = 36) Brachiaria brizantha and Brachiaria decumbens and their apomictic Fl hybrids with sexual tetraploid (2n = 4x = 36) Brachiaria ruziziensis. Microgametogenesis was used as a reference. Apospory was facultative in both species and hybrids. Environmental conditions had variable effects on the level of apomixis according to each genotype. Ratios of segregation into sexuals and apomicts in the interspecific hybrids suggest an oligogenic determinism with dominant apomixis in the genus Brachiaria. Highly apomictic and partially male fertile hybrids were identified and will be used in an improvement program to transfer genes for apomixis into the sexual species B. ruziziensis.