Seed survival in the soil and genetic differences in seed dormancy cycle in Arabidopsis thaliana

• For species with a seed bank, there should be strong selection for the annual seed dormancy cycle to match seasonal changes in conditions for seedling establishment, and the adaptive value of the seed bank should depend on survival rate in the soil. We investigated the importance of genetic differentiation in a region at the end of chromosome 5 for differences in the seed dormancy cycle between two locally adapted populations of Arabidopsis thaliana, and quantified seed survival in the soil at their sites of origin in Sweden and Italy. To characterize the seed dormancy cycle, we buried seeds of the Italian and Swedish genotypes and of two Near Isogenic lines (NILs) at the site of origin of the Swedish genotype during the period of seed dispersal in the local population, and we monitored changes in seed dormancy during the following 1.5 years. In the two NILs, a segment of chromosome 5 including the dormancy locus DELAY OF GERMINATION 1 had been reciprocally introgressed into the Italian and Swedish genetic backgrounds. To quantify seed survival in the soil, we buried seeds of both the Italian and the Swedish genotype at their respective sites of origin and recorded seed survival for 3 y. Both the Italian and the Swedish genotype displayed an annual dormancy cycle and had acquired strong secondary seed dormancy after the end of the germination period the first year. The following year, the Italian genotype lost dormancy much later than the Swedish genotype. The effect of the introgressions tested in the NILs corresponded to 37-41% of this difference in timing of seed dormancy release. Seed survival in the soil was >95% at the Swedish site after 3 y, but only 6% after 2 y of burial in Italy. Our results suggest that genes in the introgressed genomic segments strongly affect the timing of secondary seed-dormancy release, and that the contribution of seed banks to numerical and evolutionary dynamics can vary markedly among populations.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

DOG1

intraspecific variation

seed bank

seed burial

secondary dormancy

seed dormancy QTL

seed longevity

seed mortality

Ecological Botany

Ekologisk botanik

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)