Estimation of gene flow via pollen spread for the orchard layout prior to the field release of apple transformants

Several genetically modified apples (Malus × domestica) have been produced in Japan and adequate orchard layout of test plots is needed prior to the field release of transgenic apple trees. Crabapples 'Adams' and 'Purple Lemoine', possessing a heterozygous dominant gene for red leaf color, were used as pollinizers to assess the range of pollen dispersal in apple trees. 'Fuji' trees in pots were scattered as pollen recipients 2 to 400 m apart from the 'Adams' pollinizer towards four directions in the field experiment All fruits were harvested from the trees and seeds collected were germinated in a greenhouse after stratification. Without bees present in the screen cage, very few fruits set at a distance less than 1 m from the pollinizer. In field trials, the number of red seedlings arising from seed samples declined sharply with increasing distance from the pollinizer. The area of pollen dispersal in this experiment was wider as compared with the result of Wertheim in the Netherlands. The results of our experiments suggest that the distance to prevent unintended pollination from a pollinizer is over 150 m under Japanese environment conditions.