Meiotic irregularities in diploid and tetraploid plants of <Emphasis Type="Italic">Lolium multiflorum</Emphasis> Lam.

The genus Lolium comprises several species of economical importance in temperate countries, mostly due to their high nutritional value and adaptability to cold environments, including southern regions of Brazil. Recently, several diploid cultivars and populations, as well as synthetic tetraploid cultivars have been explored. In order to viabilize or to direct crossings, it is important that the accessions present regular meiosis, thus, producing viable pollen grains. In this way, this study aimed at investigating the meiosis of nine accessions of Lolium multiflorum used in breeding programs, seeking to evaluate its viability in future crossings. The meiosis of diploid plants (2n?=?2×?=?14) is more regular than the artificially tetraploidized genotypes (2n?=?4×?=?28). In the tetraploids, univalent, bivalent, and multivalent configurations were observed. The irregularities were associated to mixoploidy, irregular segregation of chromosomes, spindle disorders, asynchrony, micronuclei, and cellular fusion and formation of syncyte. The abnormalities affected the meiotic index of tetraploid cultivars, characterizing them as unstable. Nevertheless, both diploid and tetraploid genotypes are considered able to participate in crossings because, although there are abnormalities, they do not occur at levels that could affect the production of viable pollen grains.