Genetic basis of speed of development in Senecio vulgaris L var vulgaris, S-vulgaris ssp denticulatus (O.F. Muell) P.D. Sell, and Senecio vernalis Waldst & Kit

The genetic basis of differences in speed of development from germination to first bud formation was investigated in Senecio vulgaris var. vulgaris and S. vulgaris ssp. denticulatus, and also in S. vernalis sampled from Israel and Germany. In the case of S. vulgaris, Fz segregation analysis and the recovery of very late and very early lines from extreme Fz phenotypes showed that differences can be explained by a single major gene model, whereas segregation data from FZ and backcross progenies in S. vernalis are not incompatible with a digenic model of inheritance. Senecio vernalis from Israel and S. vulgaris var. vulgaris reached the different developmental stages in a substantially shorter time than did C. European S. vernalis and S. vulgaris ssp, denticulatus. In both species the increased speed of development was achieved through drastic abbreviation of the rosette stage of development rather than through an acceleration of the entire developmental programme. It is suggested that the genes controlling speed of development in S. vulgaris and S. vernalis may be homologous to major heterochronic genes identified from mutants of Arabidopsis thaliana (e.g. early flowering [elf1-3]).