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Self-incompatibility (SI) in plants is a classic example of a trait evolving under strong frequency-dependent selection. As a consequence, population genetic theory predicts that the S locus, which controls SI, should maintain numerous alleles, display a high level of nucleotide diversity, and, in structured populations, show a lower level of among-population differentiation compared to neutral loci. Population-level investigations of DNA sequence variation at the S locus have recently been carried out in the genus Arabidopsis, largely confirming results from theoretical models of S-locus evolutionary dynamics, but no comparable studies have been done in wild Brassica species. In this study, we sequenced parts of the S-locus genes SRK and SCR, two tightly linked genes that are directly involved in the determination of SI specificity in samples from four natural populations of the wild species Brassica cretica. The amount and distribution of nucleotide diversity, as well as the frequency spectrum of putative functional haplotypes, observed at the S locus in B. cretica fit very well with expectations from theoretical models, providing strong evidence for frequency-dependent selection acting on the S locus in a wild Brassica species.

Self-incompatibility (SI) in the Brassicaceae plant family is controlled by the SRK and SCR genes situated at the S locus. A large number of S haplotypes have been identified, mainly in cultivated species of the Brassica and Raphanus genera, but recently also in wild Arabidopsis species. Here, we used DNA sequences from the SRK and SCR genes of the wild Brassica species Brassica cretica, together with publicly available sequence data from other Brassicaceae species, to investigate the evolutionary relationships among S haplotypes in the Brassicaceae family. The results reveal that wild and cultivated Brassica species have similar levels of SRK diversity, indicating that domestication has had but a minor effect on S-locus diversity in Brassica. Our results also show that a common set of S haplotypes was present in the ancestor of the Brassica and Arabidopsis genera, that only a small number of haplotypes survived in the Brassica lineage after its separation from Arabidopsis, and that diversification within the two Brassica dominance classes occurred after the split between the two lineages. We also found indications that recombination may have occurred between the kinase domain of SRK and the SCR gene in Brassica.

In the Brassicaceae plant family, which includes the Arabidopsis and Brassica genera, self-incompatibility (SI) is controlled by genes at the S locus. Using experimental crosses, we studied the pattern of inheritance of S-locus alleles in the wild species Brassica cretica. Four full-sib families were established and unequal segregation of alleles at the SRK SI gene was found in one family. The segregation distortion acted in favour of a recessive (class II) allele and was best explained by some form of gametic-level selection. Our findings are discussed in the light of theoretical predictions of differential accumulation of deleterious mutations among S-locus alleles.

Nuclear and chloroplast microsatellite markers were used to study population structure and gene flow among seven Cretan populations of the Aegean endemic plant species Brassica cretica (Brassicaceae). Both nuclear and chloroplast markers revealed exceptionally high levels of population differentiation (overall F(ST)=0.628 and 1.000, respectively) and relatively little within-population diversity (overall H(S)=0.211 and 0.000, respectively). Maximum-likelihood estimates of directional migration rates were low among all pairs of populations (average Nm=0.286). There was no evidence that differences in flower colour between populations had any influence on historical levels of gene flow. In addition, a haplotype network showed that all five chloroplast haplotypes found in the sample were closely related. Together, these results suggest that current patterns of diversification in B. cretica are mainly a result of genetic drift during the last half million years. The main conclusions from the present study are consistent with the prevailing hypothesis that plant diversification in the Aegean region is driven by random rather than adaptive differentiation among isolated populations.

Plants of the partially self-incompatible perennial herb Brassica cretica, derived from controlled cross- and self-pollinations within each of seven populations, were raised under uniform conditions and scored for two measures of developmental stability, flower asymmetry (quantified as the difference in length and width between opposite petals) and cotyledon asymmetry (quantified as the difference in the area of the two lobes of each cotyledon). The primary goals were to assess the level of heritable variation in asymmetry, the effect of selfing on mean asymmetry, and the relationship between asymmetry and components of fitness. A paternal half-sibling analysis of data on flower asymmetry failed to detect significant levels of genetic variation at the within-population level, whereas the between-population component reached significance for all measures of asymmetry. Analysis of family-structured data from another crossing experiment revealed significant between-population variation in cotyledon asymmetry and a tendency for inbred progeny to produce more asymmetric cotyledons than outbred progeny. However, the response to inbreeding was weak and differed in magnitude between populations. Judging from the ranking of populations, we found no support for the hypothesis that the mean expression of developmental stability is controlled by genomewide characteristics such as the level of inbreeding. Correlations between measures of asymmetry and fitness were too low to be declared statistically or biologically significant. The present study provides little evidence that flower and cotyledon asymmetry serve as more appropriate predictors of genetic health than conventional (direct) measures of fitness.

The chromosome number of the polyploid species Glechoma hederacea was found to be 2n = 36 in a sample of 93 ramets derived from 27 sites in N and C Europe. Variation in 10 enzymes was surveyed in material from S Sweden and S Czech Republic. The genetic control of variation was investigated using segregating progeny from crosses and self-fertilized heterozygous plants. The genetic analysis comprised 30 of 32 putative alleles detected in the geographical survey. Five loci (Aat-2, Tpi-1, Tpi-2, Pgd-2 and Mnr) behaved as isoloci with one copy of a locus being monomorphic for a common allele, the other di-allelic for a common allele and a variant allele. In four isoloci (Pgd-1, Pgi-2, Mdh-2 and Adh), both copies of the duplicated locus were polymorphic, with one allele common to both copies and with another allele unique for each copy except for Pgd-1 where both copies were tri-allelic. Three loci, Pgm-3, Skd-1 and Skd-2 were regarded as being non-duplicated. Segregation ratios for all enzyme loci were in close agreement with expectations based on disomic inheritance. Our data suggest that the tetraploid G. hederaca is a diploidized autotetraploid.

Pollen movement is often restricted in natural populations, and insufficient pollination is a potential constraint on sexual reproduction in outcrossing species. Seed-set should decrease with increased distance from the pollen source in outcrossing plants. This prediction was tested using females of the clonal, gynodioecious herb Glechoma hederacea in three natural populations. In controlled pollinations, both hermaphrodites and females had similar high percentages of fruit-set and seed-set. In a natural population where a female clone was isolated from the nearest hermaphroditic clone by c. 100 m, fruit-set was low (1%). In another population where hemaphroditic clones were rare and female clones had a patchy distribution, fruit-and seed-set in females were pollen-limited and decreased with increased distance from the nearest pollen source. The estimated mean pollen dispersal distance was 5.9 m when calculated on fruit-set and 5.3 m when calculated on seed-set. The most frequent pollinators were bumblebees. The mean and median distances moved by pollinators between ramets were 0.13 m and 0.05 m. In a third population where female clones were isolated from the nearest hermaphrodites by more than 200 m, fruit-set was 0%. After introduction of 16 hermaphroditic ramets in the center of the female clone, fruit-set varied between 0% and 100% in individual female ramets. Fruit-set decreased with increased distance from the pollen source. The mean and median pollen movement distances were 1.06 m and 0.54 m.

The experience of 1 year of home intravenous antibiotic treatment of patients with cystic fibrosis is reported. Ninety-two courses were given to 31 patients, aged 4-67 years (mean age, 21 years). All patients improved clinically and biochemically. The mean weight gain was significant (p less than 0.001). Blood PO2 increased significantly (p less than 0.01), and the forced expiratory volume in 1 sec in percentage of predicted values also improved significantly (p less than 0.001). The patients could attend school and work and wanted to have the same kind of home treatment at the next subclinical exacerbation. The possibility of avoiding hospitalization improved social life and made the patients feel responsible and therefore were cooperative with treatment before clinical deterioration.