Cyto-genetic investigations in diploid and autotetraploid populations of Lolium perenne L.

Abstract

Meiotic properties, fertility, yielding capacity and earliness were studied in diploid and induced autotetraploid clones of a Norwegian population of Lolium perenne L. (Kleppe). The meiotic investigation in 50 randomly selected diploid genotypes showed that 42 per cent of the clones studied were heterozygous for paracentric inversions and that 10 per cent were heterozygous for interchanges. Estimates of chromosome numbers at meiosis in 191 randomly selected autotetraploid genotypes of the C2-generation showed that 51.8 per cent had a normal chromosome number (2n = 28), whereas the rest was aneuploids. Among the aneuploids, those with 27 chromosomes were most common and those with 31 most rare. At first metaphase of meiosis quadrivalents were regularly formed and the mean number per PMC varied among the eutetraploid clones from 1.72 to 3.05. Quadrivalents with linear and indifferent orientation, univalents and trivalents were the major causes of aneuploid gametes. The mean percentage of stained pollen grains in the eutetraploid clones exceeded that of the diploids by 7.4 per cent units, whereas the mean percentage of seed set was 5.8 per cent units higher in the diploid basic population than in the eutetraploid C2-clones. The fertility of the aneuploid classes with 27, 29 and 26 chromosomes was significantly lower than the fertility of the eutetraploids, but between these three aneuploid classes there was no statistically significant difference. The mean yield of eutetraploids was considerably higher than the yield of the aneuploid classes. The relative mean yield of aneuploid classes with 29, 27 and 26 chromosomes was 66, 62 and 40 respectively (eutetraploids = 100). Eutetraploid clones were earlier than clones in the aneuploid classes, and they were also earlier than diploid clones.