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Five broad-based breeding populations were produced by polycrossing natural populations sampled in five clusters developed by a hierarchical method with a geographic-contiguity constraint. As a result, each of these breeding populations originates from a single region and the populations within a cluster are more likely to share the same alleles with similar frequencies. A single generation of intercrossing would therefore be sufficient to establish a panmixia equilibrium. These populations were tested for dry-matter yield in plots and compared to control cultivars in two locations. There were some trends of specific adaptation related to the geographic origin of populations, which, on average, compared well to controls. Their half-sib families were evaluated as spaced plants in one location. This allowed genetic parameters and expected response to selection to be computed. Three out of five breeding populations appeared to be promising for the development of new. improved synthetic varieties. [ABSTRACT FROM AUTHOR]

Genetic control of the capacity to respond to anther culture in perennial ryegrass was studied in F1 offspring from crosses between 11 clones selected for anther-culture response ('inducers') and 10 clones selected from breeding material on the basis of good agronomic performance. Large differences in anther-culture response were observed between the two types of parent, with inducer clones producing an average of 10.7 green plants per 100 anthers, compared with only 0.3 for breeding clones. Hybrid populations produced an average of 2.2 green plants per 100 plated anthers, which is 7.3 times the response of the breeding material. This improvement was mainly due to a 9.4-fold increase in the percentage of green plants regenerated from hybrid populations to 4.7% compared to an average of 0.5% from breeding clones. Most of the GCA (general combining ability) in the experiment was contributed by the breeding material, constituting 55.8, 100.0 and 36.7% of genetic variation among hybrids for embryo formation, regeneration and green plant percentage, respectively. Any remaining genetic variation among hybrids was predominantly due to SCA (specific combining ability) effects, with percentages of 44.2 and 63.3%, respectively, for embryo and green plant formation. These results are discussed with respect to the possible exploitation of genes controlling anther-culture response for haploid production in breeding programmes of perennial ryegrass. [ABSTRACT FROM AUTHOR]

In order to establish an appropriate breeding programme, the reproductive system of a population of Lolisium rigidum Gaud. from Sardinia was analyzed to determine the mechanisms operational in this species. A dual approach was adopted of genotype assay, exploiting the polymorphism at the PGI-2 locus, and an assessment of the effects of inbreeding on agronomic characters. The statistical analysis showed highly significant differences for the number of plants due to selfing among the 35 progenies obtained by controlled crossing of genotypes homozygous for different alleles at the PGI-2 locus. The greatest inbreeding effect was on dry matter yield. Although at a bulk population level the species is outbreeding, highly self-compatible plants can be found within this naturally-derived population. [ABSTRACT FROM AUTHOR]

The in parameters, variances, covariances and heritabilities, caused by the Bulmer effect have been predicted for an artificial breeding population of perennial ryegrass using recursion formulae. This enabled anticipation of the decrease in the expected response to multitrait index selection, using two different sets of economic weights. This theoretical decrease in selection efficiency was found to be quite substantial; it is approximately halved after 4 cycles of individual recurrent selection with a fairly high selection intensity of 5 %. However the synthetic population is improved for 4 out of 5 agronomic traits and could theoretically reach quite a high level of performance after 5 cycles. The choice of economic weights has relatively little influence on the expected genetic progress of each trait. [ABSTRACT FROM AUTHOR]

From 22 genotypes, selfed (S1) and testcross progenies were investigated. The latter were generated by i) polycross (PX) and ii) 2 topcrosses (TC) using cms-inbred lines as a tester. Progenies were tested for annual dry matter yield in 3 successive years, the 3-year average was 76.7 dt/ha for S2 and 76.9, 80.1 and 74.5 for PX, TC 1 and TC 2, respectively. Genetic variance was highest for S11 (20.42), while the average of the 3 testcrosses was 12.22. However, the genotype-year interaction variance of S: Was 52.21, being 2--3 times greater than for the 2 topcrosses. PX progenies were the most stable across years. Predicted response to selection was highest for S1 (10.4 %). Genetic correlation (rg) between S1 and the testcrosses was highest with TC 2 (rg = 0.593+ +). [ABSTRACT FROM AUTHOR]

From 28 genotypes, half-sib families were generated by polycross (PX) and 2 topcrosses (TC). TC-testers were partially inbred cms-lines. Progenies were tested for annual dry matter yield in 3 successive years. The three year average was 80.7, 76.6 and 74.0 dt/ha for TC 1, PX and TC 2, respectively. TC 1 had the highest yielding families and the largest mean in all years. TC 2 revealed the largest range among its families. Genetic variance was highest for TC 2 with 14.02, followed by TC 1 and PX with 12.05 and 10.92. However, genotype × year interaction variance was about 2 and 4 times greater for TC 1 and TC 2 as compared to PX. Genetic correlation between testcross progenies was tightest for PX vs. TC 1 (rg = 0.644++ ), while between the two TC's only rg = 0.307+ was observed. Predicted response to selection yielded very similar results for all test-crosses. [ABSTRACT FROM AUTHOR]

The meiotic behaviour of the hybrid between Festuca gigantea (2n - 6x = 42) and Festuca arundinacea (2n = 6x = 42) indicates distinct structural differences between the two species. These differences are also apparent in the degree of chromosome pairing observed in Lolium multiflorum × F. gigantea compared with previous reports on the L. multiflorum × F. arundinacea hybrids. Although the L. multiflorum × F. gigantea 8x amphiploid combines the complementary characters of the two species and is agronomically interesting, there are some irregularities in meiotic behaviour that could affect the stability of the amphiploid. Seed fertility in the amphiploid is high and preliminary studies show evidence of a high degree of self-fertility. The pentaploid hybrid between autotetraploic L. multiflorum × F. gigantea is sufficiently fertile to be used as the pollen plant in crosses with diploid L. multiflorum (BC[Sub1]. Backcrossing the BC[Sub1] hybrid to L. multiflorum results in mainly diploid progeny. The possibilities of using this crossing scheme to introgress F. gigantea characters into L. multiflorum is discussed as an alternative approach to amphiploid breeding as a means of combining specific complementary characters of the two species. [ABSTRACT FROM AUTHOR]

To predict any genetic response to selection, two breeding populations of perennial ryegrass, consisting of half-sib families, were evaluated as spaced plants from 1987 to 1989 for several agronomical traits. In each population, the best plants selected through a multitrait Smith and Hazel's index were planted in a polycross to produce the second generation half-sib families. Both generations were evaluated together from 1991 to 1993 as spaced plants. The difference between generations was the observed genetic response, which was compared to that predicted. Rust tolerance, aftermath heading and persistence were significantly improved in both populations. In trial plots used to assess the yield, no effect of mass selection was noticed. Thus it is concluded that mass selection failed to increase productivity but produced some improvements in disease tolerance and aftermath heading. [ABSTRACT FROM AUTHOR]