AN ORIGINAL MEIOTIC MUTATION IN PASPALUM-REGNELLII

Cytogenetic studies carried out over a period of 2 consecutive years o n a native Brazilian accession of Paspalum regnellii (2n = 40) reveale d a meiotic mutation that has not been previously reported for any oth er species. Among 13 inflorescences investigated during the first coll ection 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 towa rds the poles. Degeneration of spindle fibers occurred at the end of m etaphase I. Chromosome segregation did not occur and the bivalents wer e left scattered at random in the cytoplasm. Remnants of chromosome fi bers could be seen close to the centromere during this stage. The biva lents gave origin to micronuclei in telophase I, with extremely wide v ariations in number and size among cells. With the absence of spindle formation during meiosis II, metaphase and anaphase II were not observ ed. Second cytokinesis occurred in prophase II cells after the occurre nce 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 inflor escences, all microsporocytes presented this anomaly, which caused tot al sterility.