Cytogenetic studies carried out over a period of 2 consecutive years on a native Brazilian accession of Paspalum regnellii (2n=40) revealed a meiotic mutation that has not been previously reported for any other species. Among 13 inflorescences investigated during the first collection year, three presented anomalous meiotic behavior starting from metaphase I. At the beginning of this phase, the chromosomes occupied the entire equatorial plate in a membrane-to-membrane arrangement, and the spindle fibers, which were clearly visible, did not converge towards the poles. Degeneration of spindle fibers occurred at the end of metaphase I. Chromosome segregation did not occur and the bivalents were left scattered at random in the cytoplasm. Remnants of chromosome fibers could be seen close to the centromere during this stage. The bivalents gave origin to micronuclei in telophase I, with extremely wide variations in number and size among cells. With the absence of spindle formation during meiosis II, metaphase and anaphase II were not observed. Second cytokinesis occurred in prophase II cells after the occurrence of first cytokinesis. The final product of meiosis was completely abnormal, with a predominance of polyads with microspores of different sizes that resulted in abortive pollen grains. In the affected inflorescences, all microsporocytes presented this anomaly, which caused total sterility.

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