The genetic basis of floral variation in Senecio jacobaea (Asteraceae).
Journal - The Journal of heredity (United States )
The self-incompatible composite Senecio jacobaea (ragwort) exhibits geographic variation in the frequency of rayed and discoid (rayless) individuals. Hybrid progenies from within- and between-morph crosses were established in a seminatural (garden) environment to determine whether patterns of segregation conform to single-gene predictions (as found in other Senecio species), whether the direction of dominance is conducive to rapid evolutionary change in ray morphology, and whether geographically distant populations of the discoid morph utilize the same or different genes to suppress ray development. Data from segregating F2 and BC families were consistent with a genetic model involving one major locus and an unknown number of modifiers. Analysis of F1 progenies from different intermorph crosses using the same rayed plant as a seed parent revealed a variable and incomplete pattern of dominance, with a trend toward partial dominance in some crosses. Hybridizations between discoid populations produced a few rayed progeny (4%), but there was no tendency for the frequency of rayed progeny to increase with the geographic distance separating the parent populations. Results of this study indicate that major mutations have been important for the evolution of discoid populations of ragwort, that ray-suppressing mutations should be directly available to selection in most populations, and that the suppression of rays is conditioned by the same or similar gene(s) in Atlantic and Baltic populations of the discoid taxon.
|ISSN : ||0022-1503|
|Mesh Heading : ||Adaptation, Biological Alleles Genes, Dominant Heterozygote Homozygote Plant Components Senecio genetics anatomy & histology|
|Mesh Heading Relevant : ||Genetic Variation genetics|
Inbreeding depression in a rare plant, Scabiosa canescens (Dipsacaceae).
Journal - Hereditas (Sweden )
Plants from a population of Scabiosa canescens, a locally rare species with a narrow ecological amplitude, were raised under uniform growth conditions to examine the phenotypic effects of one generation selfing and outcrossing. Particular attention was given to direct components of fitness (seedling biomass, rosette leaf number, head number, flower number per head), but two morphological characters (plant height, flower size) were also considered. Estimates of inbreeding depression (delta), adjusted for maternal effects and lack of balance, were compared and tested for significance using randomization and boostrap procedures. Inbreeding significantly depressed several characters during both early and late stages of the life cycle, with delta ranging from 0.14 (flower size) to 0.37 (seedling biomass). Based on these and other results, we propose that S. canescens is susceptible to inbreeding and that the genetic basis of inbreeding depression varies across life stages.
|ISSN : ||0018-0661|
|Mesh Heading : ||Angiosperms genetics growth & development|
|Mesh Heading Relevant : ||Inbreeding physiology|