Microsatellite analysis of the regeneration process of Magnolia obovata Thunb.

We analysed the regeneration process of Magnolia obovata using polymorphic microsatellite markers. Eighty-three adult trees standing in a watershed co vering an area of 69 ha, and saplings collected from a smaller research plo t (6 ha) located at the centre of the watershed were genotyped using micros atellite markers. Among 91 saplings analysed, 24 (26%) had both parents, 31 (34%) had one parent and 36 (40%) had no parent within the watershed. The proportion of genes in saplings inherited from the adults within the waters hed was 43%, and therefore 57% were from outside the site, indicating activ e gene exchange across the watershed area. Average distance between parents and saplings (264.6 +/- 135.3 (SD) m) was significantly smaller than that of pairs randomly chosen between adults and saplings (436.7 +/- 203.0 (SD) m). The distance of pollen movement inferred from the distance between the two parents of each sapling ranged from 3.2 m to 540 m with an average of 1 31.1 m +/- 121.1 m (SD). Because 34% ( = 31/91) of saplings had only one pa rent within the watershed, the estimate of average pollen movement must be smaller than the actual one. Long-distance seed dispersal by birds, inbreed ing depression and limitation in acceptance of pollen because of the differ ence of phenology in each individual flower were considered to be the proba ble causes of large gene exchange across the watershed.