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The aneuploid frequencies were determined in two autotetraploid populations of Festuca pratensis, St 839 and Sv 01243. Vegetative and generative properties of euploids, hypoploids, and hyperploids were studied. Before chromosome counts, the seed lots were sieved into five seed size fractions. Chromosome numbers were determined by a modification of conventional root tip squash. Chromosome number varied with seed size. This variation was caused by differences in hypoploid frequencies between the fractions. In St 839 the lightest seeds contained 30% hypoploids and the heaviest ones 2%. In Sv 01243 the hypoploid frequencies varied from 20% to 1%. The total aneuploid frequency in St 839 was 29.3% with a slight predominance of hyperploids. In Sv 01243 the aneuploid frequency was 26.0%, with about equal size of the aneuploid chromosome classes. Vegetative and generative characters were measured. Euploids were superior to aneuploids, and hyperploids to hypoploids in both populations. The effects of aneuploidy were more pronounced on the generative characters. The euploids were heading earlier than the aneuploids. The differences were generally highly significant.

Klinga, K. 1987. Aneuploidy in induced autotetraploid populations of Festuca pratensis, Lolium muitiflorum, and Lolium perenne. IV. Competitive interactions between euploid and aneuploid plants in a simulated perennial sward of tetraploid Festuca pratensis. —Hereditas 107 249–256. Lund, Sweden. ISSN 0018–0661. Received August 5,1987 The competitive interactions in dense perennial stands of autotetraploid Fesruca pratensis were investigated by studying the following factors: (a) the persistence of euploid and aneuploid plants in pure stands and in mixtures; (b) the productivity of the persisting euploid and aneuploid plants in pure stands and mixtures; (c) the dry yield per unit area in the different kinds of growing regimes. About 80 % of the original euploid plants in the mixtures and about 50 % in the pure stands were left at the end of the experiment. The persistence of aneuploids did not differ between the two growing regimes. The aneuploid frequency changed from about 30 % to 20 % during the experimental period. In terms of persistence the euploids were better competitors, displayed by the significantly higher persistence in the mixtures. The yielding capacity and the competitive ability of individual euploids in the mixtures exceeded the aneuploids the year of planting and the first summer of the sward development. Later, the yielding capacity did not differ between the two chromosome categories. The negative agressivity values in the last year of the sward indicated a better competitive ability of the aneuploid plants. The presence of aneuploids in the mixed stands did not cause any conspicuous loss of yield. This was displayed by the lack of significant differences in the dry yield per unit area between the two kinds of stands.

Frequencies of aneuploids were determined in three induced autotetraploid populations of Lolium, two of L. multiflorum, and one of L. perenne. Vegetative and generative properties of euploids, hypoploids, and hyperploids grown as spaced plants were studied. Before chromosome counts, the seed lots were sieved into five seed size fractions. Chromosome numbers were determined by a modification of conventional root tip squash. The total aneuploid frequency in Lolium multiflorum, Sv 02054 was 52.6%, in Sv 02056 50.7%, and finally in Lolium perenne, Sv 01413, the total aneuploid frequency was 41.9%. There are no or only weak relations between seed size and chromosome number in these populations. Among the aneuploid chromosome classes, the hypoploid was the largest one in all fractions in the three populations Vegetative and generative characters were measured. Significant negative effects of aneuploidy were only found in the generative characters There were no significant differences in heading time between chromosome classes in either of the populations.

Klinga, K. 1987. Aneuploidy in induced autotetraploid populations of Festuca pratensis, Lolium multiflorum, and Lolium perenne. III. Performance of plants at different sowing densities in a perennial sward of tetraploid Festuca pratensis‐Hereditas 106:277–287. Lund, Sweden. ISSN 0018–0661. Received February 6, 1987 The productivity of an induced tetraploid population of Festuca pratensis at different sowing densities displayed a typical yield‐density response. There was a positive response in yield with increasing densities only early in the development of the sward. As the time passed, the variations in sowing densities were compensated by an altered growth made by individual plants. The mortality pattern of plants varied among seasons. During the establishing phase of the sward the mortality was not density dependent. The inferior ability of aneuploids to establish in the sward relative to the euploids was diplayed by a higher mortality of aneuploids. As the plants had grown larger, the mortality of plants became density dependent. Competition started to affect the aneuploids earlier in the development of the sward than the euploids, reflected by a differentiated mortality pattern of aneuploids and euploids. The aneuploid frequency in the seed lot was 29.1 %, and in the end of the experiment the aneuploid frequency was reduced to percentages ranging from 7.9% to 15.7%. The lower productivity of the aneuploids affected the yield only at the early stages of the sward development. Later, the surviving aneuploids were too few to influence the total yield.