Abstract. We used a quantitative trait locus (QTL) approach to study the genetic basis of population differentiation in wild barley, Hordeum spontaneum. Several ecotypes are recognized in this model species, and population genetic studies and reciprocal transplant experiments have indicated the role of local adaptation in shaping population differences. We derived a mapping population from a cross between a coastal Mediterranean population and a steppe inland population from Israel and assessed F 3 progeny fitness in the natural growing environments of the two parental populations. Dilution of the local gene pool, estimated as the proportion of native alleles at 96 marker loci in the recombinant lines, negatively affected fitness traits at both sites. QTLs for fitness traits tended to differ in the magnitude but not in the direction of their effects across sites, with beneficial alleles generally conferring a greater fitness advantage at their native site. Several QTLs showed fitness effects at one site only, but no opposite selection on individual QTLs was observed across the sites. In a common-garden experiment, we explored the hypothesis that the two populations have adapted to divergent nutrient availabilities. In the different nutrient environments of this experiment, but not under field conditions, fitness of the F 3 progeny lines increased with the number of heterozygous marker loci. Comparison of QTL-effects that underlie genotype ϫ nutrient interaction in the common-garden experiment and genotype ϫ site interaction in the field suggested that population differentiation at the field sites may have been driven by divergent nutrient availabilities to a limited extent. Also in this experiment no QTLs were observed with opposite fitness effects in contrasting environments. Our data are consistent with the view that adaptive differentiation can be based on selection on multiple traits changing gradually along ecological gradients. This can occur without QTLs showing opposite fitness effects in the different environments, that is, in the absence of genetic trade-offs in performance between environments.

The genetic variability and divergence of eight chicken lines were evaluated using nine microsatellite markers. The chicken lines included three White Leghorn hybrids, three Finnish Landrace lines, a Rhode Island Red line, and a broiler hybrid line. All the microsatellite loci were found to be polymorphic, the number of alleles varying from 4 to 13 per locus and 1 to 10 per line, respectively. Observed heterozygosities ranged from 0.00 to 0.91. The highest (0.67) and lowest (0.29) mean heterozygosity per line was observed in the broiler and in White Leghorn of Mäkelä, respectively. Three of the microsatellite loci deviated from the Hardy-Weinberg equilibrium in some populations. F statistics indicated clearly the subdivision of the total population into different lines. The genetic distances confirmed the classification of Finnish Landraces into different lines. A phylogenetic consensus tree was constructed from resampled data (1,000 times) using the neighbor-joining method. According to the phylogenetic tree, the lines were grouped into three clusters, in which the White Leghorns formed one group, two Landraces a second group, and a Landrace, the Rhode Island Red, and the broiler lines a third group. Allele distribution at the loci does not support either the stepwise or the infinite alleles mutation model, but the distribution pattern was quite irregular at different loci.

We used a quantitative trait locus (QTL) approach to study the genetic basis of population differentiation in wild barley, Hordeum spontaneum. Several ecotypes are recognized in this model species, and population genetic studies and reciprocal transplant experiments have indicated the role of local adaptation in shaping population differences. We derived a mapping population from a cross between a coastal Mediterranean population and a steppe inland population from Israel and assessed F3 progeny fitness in the natural growing environments of the two parental populations. Dilution of the local gene pool, estimated as the proportion of native alleles at 96 marker loci in the recombinant lines, negatively affected fitness traits at both sites. QTLs for fitness traits tended to differ in the magnitude but not in the direction of their effects across sites, with beneficial alleles generally conferring a greater fitness advantage at their native site. Several QTLs showed fitness effects at one site only, but no opposite selection on individual QTLs was observed across the sites. In a common-garden experiment, we explored the hypothesis that the two populations have adapted to divergent nutrient availabilities. In the different nutrient environments of this experiment, but not under field conditions, fitness of the F3 progeny lines increased with the number of heterozygous marker loci. Comparison of QTL-effects that underlie genotype x nutrient interaction in the common-garden experiment and genotype x site interaction in the field suggested that population differentiation at the field sites may have been driven by divergent nutrient availabilities to a limited extent. Also in this experiment no QTLs were observed with opposite fitness effects in contrasting environments. Our data are consistent with the view that adaptive differentiation can be based on selection on multiple traits changing gradually along ecological gradients. This can occur without QTLs showing opposite fitness effects in the different environments, that is, in the absence of genetic trade-offs in performance between environments.

Species from productive and unproductive habitats differ inherently in their relative growth rate (RGR) and a wide range of correlated quantitative traits. We investigated the genetic basis of this trait complex, and specifically assessed whether it is under the control of just one or a few genes that can act as 'master switches' by simultaneously affecting a range of traits in the complex. To address this problem, we crossed two Hordeum spontaneum lines originating from two habitats that differ in productivity. The F3 offspring, in which parental alleles are present in different combinations due to recombination and segregation, was analysed for RGR and its underlying components (leaf area ratio, unit leaf rate, photosynthesis, respiration), as well as a number of other physiological and morphological parameters. For this intra-specific comparison, we found a complex of positively and negatively correlated traits, which was quite similar to what is generally observed across species. A quantitative trait loci (QTL) analysis showed three major and one minor QTL for RGR. Most other variables of the growth-trait complex showed fewer QTLs that were typically scattered over various locations on the genome. Thus, at least in H. spontaneum, we found no evidence for regulation of the trait complex by one or two master switches.

The genetic diversity produced by the amplified fragment length polymorphism (AFLP) method was studied in 94 genotypes of wild barley, Hordeum spontaneum (C. Koch) Thell., originating from ten ecologically and geographically different locations in Israel. Eight primer pairs produced 204 discernible loci of which 189 (93%) were polymorphic. Each genotype had a unique banding profile and the genetic similarity coefficient varied between 0.74 and 0.98. The phenogram generated from these similarities by the UPGMA method did not group genotypes strictly according to their geographical origin, which pattern was also seen in the principal coordinate (PCO) plot. Genetic diversity was larger within (69%) than among (31%) populations. Associations between ecogeographical variables and the mean gene diversity were found at one primer pair. The results are discussed and compared with data obtained by the simple sequence repeat (SSR) method.

The genetic basis of phenotypic plasticity of relative growth rate (RGR), its components and associated morphological traits was studied in relation to nutrient limitation. In all, 140 F 3 lines from a cross, made between two Hordeum spontaneum (wild barley) accessions sampled in Israel, were subjected to growth analysis under two nutrient levels. Quantitative trait loci (QTLs) were detected for RGR and three of its components, leaf area ratio (LAR), specific leaf area and leaf mass fraction (LMF). Indications for close linkage (potential pleiotropy) were found, for example, for LAR and LMF. An interesting case is on chromosome 6, at which QTLs for RGR and seed mass were detected in the same region. These QTLs had opposite additive effects, supporting earlier results that plants growing from lighter seeds had a higher RGR. Only two QTLs were significant under both nutrient conditions, suggesting large QTL Â environment interactions for most traits. For 21 out of 26 QTLs, however, the additive genetic effect was of identical sign in both nutrient environments, but reached the significance threshold in only one of them. Nevertheless, some QTLs detected in one of the two environments had virtually no effect in the other, and QTLs for plasticity were detected for RGR, LAR and LMF, as well as for some morphological traits. QTLs with opposite effects under high and low nutrients were not found. Thus, at the genetic level, there was no evidence for a trade-off between faster growth at high versus low nutrient levels.

BackgroundCultivated crops have repeatedly faced new climatic conditions while spreading from their site of origin. In Sweden, at the northernmost fringe of Europe, extreme conditions with temperature-limited growth seasons and long days require specific adaptation. Pea (Pisum sativum L.) has been cultivated in Sweden for millennia, allowing for adaptation to the local environmental conditions to develop. To study such adaptation, 15 Swedish pea landraces were chosen alongside nine European landraces, seven cultivars and three wild accessions. Number of days to flowering (DTF) and other traits were measured and the diversity of the flowering time genes HIGH RESPONSE TO PHOTOPERIOD (HR), LATE FLOWERING (LF) and STERILE NODES (SN) was assessed. Furthermore, the expression profiles of LF and SN were obtained.ResultsDTF was positively correlated with the length of growing season at the site of origin (GSO) of the Swedish landraces. Alleles at the HR locus were significantly associated with DTF with an average difference of 15.43 days between the two detected haplotypes. LF expression was found to have a significant effect on DTF when analysed on its own, but not when HR haplotype was added to the model. HR haplotype and GSO together explained the most of the detected variation in DTF (49.6 %).ConclusionsWe show local adaptation of DTF, primarily in the northernmost accessions, and links between genetic diversity and diversity in DTF. The links between GSO and genetic diversity of the genes are less clear-cut and flowering time adaptation seems to have a complex genetic background.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0424-z) contains supplementary material, which is available to authorized users.

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