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A genetic map of Lolium has been produced using isozyme, restriction fragment length polymorphism (RFLP) and random amplified poiymorphic DNA (RAPD) markers applied to a segregating family derived from an F[sub1] hybrid plant of L. perenne × L. multiflorum provenance, crossed on to a doubled haploid L. perenne A total of 106 markers, out of a total of 160 polymorphic loci analysed, have been ascribed to seven linkage groups covering a map distance of 692 CM. Two of these groups may be allocated to chromosomes 2 and 6 of the Loliurn genome. The remaining unallocated markers, the majority of which showed severe segregation distortion, could be associated into small groups of two or three markers which showed no linkage with the main groups at a LOD of 24.8 or, if associated, could not be mapped in a satisfactory manner. This high incidence of disturbed segregations could be accounted for by the use of an interspecific hybrid between two species of differing genome size, with consequent cytological imbalance. [ABSTRACT FROM AUTHOR]

The segregation of isozyme markers has been examined in the green and albino androgenetic progenies of two plants of Lolium perenne. Overall the pooled data for the loci PGI/2and GOT/2 does not deviate form expectation, but there is considerable heterogeneity between families and between green and albino plants. Specific alleles predominate in the different progeny sets. The results may be accounted for by possible linked loci affecting anther culture response or of linked lethal genes. [ABSTRACT FROM AUTHOR]

A Triple Test Cross and basic generations (i.e. inbred parents, F1's, F2's and backcrosses) have been used to investigate the generics of dry matter yield in a population of Lolium perenne. Two trial designs, short, individual plant drills and larger sown plots were used at each of two sites iii the U.K., at Aberystwyth and Birmingham. The families studied correspond to those raised as spaced plants and reported in the first paper in this series. In contrast to the spaced plants trial, the drill trial resulted in considerable epistasis as well as additivity and dominance variation whilst the plot trial failed to identify any significant genetic variation. There "as considerable G × E interaction over sites and harvests, particularly in the amount of dominance. The latter showed a clear linear relationship with mean per- formance at both sites, the dominance ratio being higher in the poorest environments. This is largely due to the additive variance decreasing in the poor environments rather than the dominance being higher. The implications of these results to grass breeding are discussed. [ABSTRACT FROM AUTHOR]

A series of lines, differing in isozyme genotype, were constructed by selection, from within three cultivars of Lolium perenne. Field assessment of the progeny of these selected lines revealed variation in yield and timing of inflorescence emergence. This variation between lines from within a cultivar could not: be accounted for by the differing levels of homozygosity attained. In some instances differences in yield were associated with homozygosity for specific alleles at the PGI/2 locus, background genotype was however, of major importance. The variation identified could be attributable to founder effects or possible linkage of quantitative trait loci PGI/2 locus. [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]

Crossing bags manufactured from three grades of polyester and three types of paper bags were tested for their permeability to grass pollen. Bags were placed on L. perenne plants of known Pgl isozyme genotype. Any pollen passing through the crossing bag and pollinating the plant was detected by assaying its progeny for PGI isozymes. The results obtained allowed differentiation of the various materials for their suitability for pollen proofing. [ABSTRACT FROM AUTHOR]