Genetic basis for variability in Arabidopsis seed germination time

Variability in seed germination time has been proposed to function as a bet-hedging strategy against unpredictable seedling environments and studies of natural populations support this idea. However, little is known about the genetics or mechanisms underlying this trait. We have characterised natural variation in germination time variability within Arabidopsis thaliana using natural accessions and the MAGIC multi-parent recombinant inbred population. We found that there is extensive variation in the extent of variability and that the level of variability in germination time is reproducible for a given genotype. We also show that variability exists among seeds of the same silique and is likely not associated with gradients along the fruit. Using a bulk-segregant mapping approach and QTL analysis, we have identified multiple loci underlying the level of variability in germination time. We show that the extent of variability is weakly correlated with the average germination time and percentage germination, but that the traits can be uncoupled. We show that one QTL identified has correlated effects on mean and variability and that one likely affects variability independently from the mean. This suggests that at least two different mechanisms may underlie the generation of variability in germination time in Arabidopsis.