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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]

Is a shorter life with more years lived in poor health a defining attribute of the life cycle of disadvantaged groups? Based on the 1990 5% Public Use Microdata Survey, we develop life table models of healthy (or active) life for the major racial groups, by sex, in the United States. The analysis underscores the complexity of the relationship between morbidity and mortality in the population. For Asians, longer life is associated with fewer years lived in poor health. In contrast, Native Americans' relatively longer lives are accompanied by extended periods of chronic health problems. Of all racial groups, blacks live the fewest years, and they live a high proportion of those years with a chronic health problems. Hispanics also live substantially fewer years, yet the period of life they spend with a health problem is relatively compressed. Racial differences in the link between morbidity and mortality point to the importance of investigating how chronic diseases and disease prevention and treatment are related to active life across the population subgroups. [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]

The two-locus gametophytic incompatibility system in perennial ryegrass (Lolium perenne L.) is not always fully effective: obligate selfing of plants sieves self-compatible pollen mutants, and self-fertility becomes fixed in subsequent generations. Self-compatibility (SC) was investigated in an F2 family. In vitro self-pollinations were analysed and recorded and plants were classified as being either partially or fully compatible. Distorted segregation ratios of markers on linkage group (LG) 5 were found, which indicate the possible presence of a gametophytic SC locus. Interval linkage analysis of pollen compatibility after selfing confirmed that this distortion was due to a locus (T) analogous to the S5 locus of rye. However, even though markers in this region were, on average, less than 1?cM apart, the minimum number of plants possessing the unfavoured allele was never less than 6%for any marker locus. We proved that this was because of the presence of another SC locus, exhibiting gametophytic selection, segregating in this population and identified by interval mapping analysis of compatibility classes of in vitro self-pollinations. This locus was located on LG1, and probably corresponds to the S locus. We show that the T locus, a relic of a multilocus system, functions through interaction with the S locus: F2 segregation of incompatibility phenotypes and linked markers demonstrated that the S/t pollen genotype combination, expected to be compatible on selfing, was sometimes incompatible. Further evidence is presented to show that this interaction must be dependent on yet another locus located on LG2. A prime candidate would be the Z incompatibility locus.Heredity (2005) 94, 356-363. doi:10.1038/sj.hdy.6800582 Published online 29 September 2004 [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is one of the most destructive soybean [Glycine max (L.) Merr.] pests worldwide. The most common source of SCN resistance used in soy- bean breeding in the northern USA is PI 88788. Previous research has shown that P188788 carries a major quantitative trait locus (QTL) conferring SCN resistance on linkage group (LG) G, which is believed to be rhg1. The objective of our research was to map and confirm additional SCN resistance QTL in Bell, a cultivar with resistance from PI 88788. One hundred four F4-derived fines (F4 population) developed from crossing the cultivars Bell and Colfax were tested for associations between 54 molecular markers and resistance to SCN populations PA3 (HG type 7, race 3) and PAl4 (HG type 1.3.5.6.7, race 14). Three populations of near isogenic lines (NILs) were developed from F4 plants heterozygous for a region on LG J where a significant QTL was identified in the F4 population. The NIL populations were tested with genetic markers and also for resistance to both SCN populations. In the F4 population, SCN resistance QTL were identified at both rhg1 and on LG J. The LG J QTL was confirmed in NIL populations and was given the confirmed QTL designation cqSCN-003. The effect of cqSCN-003 was diminished in the NIL populations compared to the F4 population. This was at least partially the result of segregation distortion in the F4 population between the region containing rhg1 and the region containing cqSCN-003. These results show the importance of verifying QTL in confirmation populations to estimate accurately their effects. [ABSTRACT FROM AUTHOR]

We calculate aggregate indicators of population health for occupational groups to gauge changes in health disparities during the 1980-1991 period. The study is based on the experiences of French adult men in three major occupational classes: managers, manual workers, and an intermediary occupational group. Life table models show that managers have longer life expectancy and disability-free life expectancy (DFLE) than manual workers, and a shorter life expectancy with disability. The concurrent increases in life expectancy and DFLE during the period maintained the occupational disparities in health; the years lived with disability, however, declined for all groups, as for the entire French population. [ABSTRACT FROM AUTHOR]