Cell fusion and cytomixis during microsporogenesis in Brachiaria humidicola (Poaceae)

Abstract

During cytological analysis of microsporogenesis in 28 polyploid accessions of Brachiaria humidicola (Poaceae) from the Embrapa Beef Cattle germplasm collection for breeding purposes, cell fusions were recorded in two accessions and chromosome transfer among meiocytes in one of them. Cell fusion between two to more than ten cells was recorded from prophase I to telophase II. In the syncyte, each nucleus maintained its integrity. In one of these accessions, cytomixis with characteristics never reported in any other plant species was recorded. It occurred among very small meiocytes that transferred the entire genome or part of it to normal meiocytes. Chromosome transfer occurred preferentially during telophase I and, during migration, chromatin showed structural alteration. Both abnormalities compromise pollen fertility. In the Brachiaria genus, polyploid accessions are, in general, apomictic, albeit pseudogamous. Consequently, fertile pollen is essential to fertilize the central nucleus of the embryo sac and ensure viable seeds production. Thus, accessions with high frequencies of meiotic abnormalities might be eliminated early from the breeding program.