Meiotic stability in two valuable interspecific hybrids of Brachiaria (Poaceae)

With 2 figures and 2 tables ABSTRACT: In an attempt to increase genetic variability in the genus Brachiaria, crosses were made between sexual tetraploidized accessions of B. ruziziensis and apomictic tetraploid accessions of B. brizantha (2n = 4x = 36). Among the F1 progenies, two hybrids (Hb331, apomictic; and Hb336, sexual) displayed several agronomically desirable traits. These hybrids were evaluated for several years, and the apomictic one is now being tested under grazing to be released as a new cultivar, whereas the sexual one is in a reciprocal recurrent selection programme. The possibility of gene exchange through recombination of genitors and their meiotic behaviour was investigated. Both hybrids were evaluated for meiotic stability during three consecutive years. Analyses of meiocytes at diakinesis revealed multivalent chromosome associations among the parental genomes, indicating that their gene pools are interchangeable. Irregular chromosome segregation, chromosome stickiness and a putative meiotic mutation were recorded. The frequency of abnormalities varied among years and also between the hybrids. The sexual hybrid Hb336 had a more stable meiotic behaviour, but pollen fertility was higher in apomictic Hb331, ensuring more viable seed formation.