Molecular ecology of plant populations using microsatellite genetic markers

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1.Microsatellite polymorphisms of Arabidopsis thaliana were surveyed for 29 loci using 12 Japanese natural populations as material. All the individuals examined were homozygous at all the microsatellite loci. Although there was considerable variation among populations, no intra-population polymorphism was detected in three selected populations when eight loci were studied. The microsatellites examined proved to be a suitable genetic marker for studying the genetic variation among natural populations of A.thaliana. To compare the genetic similairty and infer the evolutionary relationships among populations, neighbor-joining trees were constructed on the basis of distance matrices calculated by two different methods. Genetic relationships among the populations as revealed in the trees do not necessarily correspond to their geographic telation-ships. This may reflect their different origins or different times of introudction into the lslands of Japan.2.Phenotypic plasticity of A.thaliana collected from 11 different wild populations in Japan was experimentally examined under four different conditions : (1) GVLD (green vernalization-long day, 16hrs), (2) GVSD (green vernalization-short day, 8hrs), (3) LD (no vernalization-long day), and (4) SD (no vernalization-short day). 440 plants (10 replicates*4 treatments*11 populations) were included for this experiment. The results indicate that long-day and/or low temperature shortened the days to flowering except Kanagawa, and long-day was more effective than low temperature. The effects of two treatments were additive because the flowering was most accelerated when the long-day and vernalization treatment were applied in combination. Several other correlated patterns of character changes were recorded, reflecting the origin of populations and experimental treatments.