Tuesday, August 7, 2007: 8:00 AM
N, San Jose McEnery Convention Center
Plants have different strategies to produce seeds. Species which depend on a high colonizing ability may produce many small seeds whereas species which depend on high competitive ability may produce fewer but larger seeds. To assess the evolutionary significance of this trade-off, it should be studied within a species where different genotypes and combinations of seed size/seed number values are available. We used the annual model plant Arabidopsis thaliana to investigate the genetic basis of the trade-off within this species. A 3.5-fold difference among the mean seed weights and an 8-fold difference among the mean seed numbers had been reported for a set of 162 recombinant inbred lines (RILs) derived from reciprocal crosses between the two pure lines Landsberg erecta (Ler) and Cvi. We grew plants of 32 RILs, which represented the full spectrum of seed sizes, in 1-cm and 4-cm diameter pots to determine the amount of genetically- and environmentally-induced variation and covariation in seed size and seed number as well as potential genotype x environment (GxE) interactions. We found significant genetic and environmental variation but no GxE interactions. Although the genetic variance component was much smaller for seed number than for seed size, the genetic covariance component between the two traits was highly significant and negative. We conclude that the negative relationship between seed size and seed number in the investigated experimental population of A. thaliana is due to a genetic trade-off which is partly masked by positive between- and within-environmental covariance components.
