Natural allelic variation at seed size loci in relation to other life history traits of Arabidopsis thaliana

We have analyzed two Arabidopsis strains differing in the mean seed size an d seed number they produced. The accession Cape Verde Islands (Cvi) yielded on average about 40% fewer seeds than the laboratory strain Landsberg erec ta (Ler), but Cvi seeds were almost twice as heavy. Maternal and nonmaterna l genetic factors were involved in the seed size variation, and interaction s between both types of factors presumably occurred. The Ler/Cvi seed size difference increased through seed development from ovule maturation until s eed desiccation, suggesting that multiple processes of seed development wer e affected. In addition, it involved changes in the final cell number and c ell size of the seed coat and the embryo. Cell number variation was control led mainly by maternal factors, whereas nonmaternal allelic variation mostl y affected cell size. By using a recombinant inbred line population derived from Ler and Cvi, we mapped quantitative trait loci (QTLs) affecting 12 li fe history traits related to seed size, fruit size, seed number, and plant resources. Five of the seed size QTLs colocated with QTLs for other traits, suggesting that they control seed size via maternal components affecting o vule number and/or carpel development, ovule development, or reproductive r esource allocation in the mother plant. The six remaining putative seed siz e QTLs did not show a significant effect on any other trait, suggesting tha t this allelic variation may be involved specifically in seed development p rocesses.