Osteoporosis is a common disease with a strong genetic component, characterized by reduced bone mass and an increased risk of fracture. Bone mineral density (BMD) is a highly heritable trait and a key determinant of osteoporotic fracture risk, but the genes responsible are incompletely defined. Here, we identified quantitative trait loci (QTL) for regulation of BMD by a genome wide scan involving 3691 individuals from 715 families, who were selected because of reduced BMD values at the lumbar spine (LS-BMD) or femoral neck (FN-BMD) in probands. Linkage analysis was conducted in the study group as a whole with correction for age, gender, weight and height. Further analyses were conducted for men and women separately to identify gender-specific QTL and for those under and over the age of 50 years to distinguish QTL for peak bone mass from those that influence bone mass in older people. No regions of suggestive or significant linkage were identified when data from all subjects were analyzed together. On subgroup analysis, however, we identified a significant QTL for FN-BMD on chromosome 10q21 (LOD score +4.42; men < or =50 years) and two suggestive QTL for LS-BMD on chromosomes 18p11 (LOD score +2.83; women >50 years) and 20q13 (LOD score +3.20; women < or =50 years). We identified five other QTL for BMD with LOD scores of greater than +2.20 on chromosomes 3q25, 4q25, 7p14, 16p13 and 16q23. This study provides evidence for gender-specific, site-specific and age-specific QTL, which regulate BMD in humans, and illustrates the importance of conducting subgroup analysis to detect these loci.

Abstract. Identification and deployment of disease resistance genes are key objectives of Australian barley breeding programs. Two doubled haploid (DH) populations derived from Tallon × Kaputar (TK) and VB9524 × ND11231 (VN) crosses were used to identify markers for net type net blotch (NTNB) (Pyrenophora teres f. teres). The maps included 263 and 250 markers for TK and VN populations, respectively. The TK population was screened with 5 pathotypes and the VN population with 1 pathotype of NTNB as seedlings in the glasshouse. In addition, the TK population was subjected to natural infection in the field at Hermitage Research Station, Qld. Analyses of the markers were performed using the software packages MapManager and Qgene. One region on chromosome 6H was strongly associated with resistance to NTNB in both populations (R 2 = 83% for TK and 66% for VN). In the TK population, 2 more quantitative trait loci (QTLs) were identified on chromosomes 2H and 3H, with R 2 values of 30% and 31%, respectively. These associations were consistent over all pathotypes studied during the seedling stage. The same QTL on chromosome 6H was also found to be highly significantly associated (R 2 = 65%) with the adult plant (field) response in the TK population. There are several very closely linked markers showing strong associations in these regions. Association of the 4 markers on chromosome 6H QTL with resistance to the NTNB has been validated in 2 other DH populations derived from barley crosses Pompadour × Stirling and WPG8412 × Stirling. These markers present an opportunity for marker assisted selection of lines resistant to NTNB in barley breeding programs.

Improvement of oil and protein concentrations is a primary breeding objective for canola (Brassica napus L.) grown in the low rainfall areas across southern Australia. This study investigates the relative influences of genotype and environment on the relationship between seed oil concentration and protein concentration of meal, and between seed components. The study also estimates the magnitude of genetic and genotype × environment variances in oil and protein concentrations in a set of interstate field evaluation experiments of genotypes with early and mid-season maturity conducted across southern Australia in 1996 and 1997.The oil concentration of seed ranged from 36 to 46% across maturity groups, locations, and years. The range of protein concentration of meal was 30–46%. Environment had a much larger impact than genotype on oil concentration of seed and protein concentration of meal. Several genotypes in this study had higher concentrations of oil in the seed and protein in the meal than the commercial cultivars used as controls. Significant (P < 0.05) genetic variance (σg2) and significant genotype × year × location interaction (σgyl2) was present in these 2 quality traits. However, the variance components for the interaction of genotype with location (σgl2) and with year (σgy2) were not significant (P > 0.05), indicating that ranking of genotypes remained constant across locations averaged over many years and across years averaged over many locations, respectively. A significant negative correlation (r�=�–0.73) between seed oil concentration and protein concentration of meal was observed across locations in 1997. Among the genotypes tested, there was no genetic correlation between these 2 traits, suggesting that seed oil concentration and protein concentration of meal can be increased simultaneously by selection. Increase in oil concentration of seed and protein concentration of meal was at the expense of seed residue.

Annual legumes rely on hardseededness, a form of seed dormancy, to spread the risk of mortality associated with germination and to encourage germination at the optimal time in a season. This paper examines seed softening strategies of a number of clover (Trifolium) species collected over a range of environments. Three hypotheses are tested. The first is that within species, long-term hardseededness increases with aridity due to the greater chance of failure to reproduce in dry environments. It is tested by comparing seed softening patterns of populations of a number of clover species collected from a range of environments. The second hypothesis, that annual legumes from dry environments have a smaller subset of seed softening strategies than legumes from wetter environments, is tested by comparing the range of seed softening patterns from all species found at collection sites. The third hypothesis is that within-year patterns of seed softening that prevent germination after summer rainfall may partially substitute for long-term hardseededness. It is tested by examining the relationship between within-year hardseededness and between-year hardseededness. Accessions of the same species from different collection sites differed in both within-year pattern of seed softening and long-term hardseededness but there was little evidence that these differences were between ecotypes. Different species from the same collection site did not have similar seed softening strategies, and seed softening strategies of clovers from dry sites were as variable as those from wetter environments. Within-year pattern of seed softening does not appear to substitute for between-year hardseededness as a dormancy strategy.

The aim of this work was to determine whether different species of annual clover (Trifolium spp.), obtained from the same environment, have different reproductive strategies (combinations of reproductive traits) to achieve ecological success. A better understanding of the traits that improve persistence should allow agronomists to narrow the selection criteria for new clover cultivars for ley-farming systems in southern Australia. Seeds of 18 annual clover species were obtained from 3 Australian and 6 Mediterranean sites and were subsequently grown in a common garden in Western Australia. Reproductive traits, including time of flowering, weight per seed, fecundity, pollen to ovule ratio, and pattern of seed softening, were observed. Accessions of different clover species from the same site of collection had different reproductive strategies. Across a range of collection sites, accessions of the same species demonstrated the same broad reproductive strategy; however, some traits, e.g. the timing of flowering, varied within species across collection sites. Principal component analysis suggested that there are 3 broad reproductive strategies demonstrated by these clover species. At one extreme were the relatively large-seeded clovers (T. subterraneum, T. clypeatum, and T. stellatum). The associated cost of these large seeds is reduced fecundity. The large-seeded clovers do not have high long-term hardseededness (the predominant form of seed dormancy in clovers). The relatively small-seeded clovers were all characterised by high fecundity. Many of the small-seeded clovers have high levels of long-term hardseededness, which allow the risk of failure to be spread across seasons (T. spumosum, T. hirtum, T. lappaceum, T. angustifolium, and T. tomentosum). Some of the small-seeded clovers (T. glomeratum, T. nigrescens, T. campestre, T. cernuum, and T. suffocatum) are generalists, producing as many seeds as possible in each season, with very little hardseededness. There are several possible explanations for the apparent success of such different reproductive strategies among clover accessions of different species at the same site. A plant may achieve the same goal by trading one reproductive trait for another. For example, it may either produce many small seeds to spread the risk of failure or produce fewer large seeds with an inherent competitive advantage. Alternatively, temporal and spatial variation may favour clovers with a number of different reproductive strategies. It is likely that a mixture of species with different reproductive strategies will maximise production and persistence of legume-based pastures in ley-farming systems.