The genetic segregations of several agronomic characters in the next generation were often found in the rice variety "Nipponbare". In order to clarify the causes of this phenomenon, the amount of outcrossing was studied, from 1977 to 1983, with several varieties included "Nipponbare".
The results obtained were as follows;
1. The outcrossing percentages of "Nrpponbare", when used "Murasaki-ine" as a pollen parent, were ranged 2.64 to 4.51%, which were significantly higher than those of the other varieties, except one variety tested.
2. The outcrossing percentages of "Brittle culm" strain, when "Nipponbare" was used as a pollen parent, were extremely low, as compared when the other varieties used as pollen parents.
3. It can be assumed that the genetic segregation observed in "Nipponbare" was fairly caused by outcrossing, and the such high frequency of outcrossing might be caused by poor pollen shedding of the variety.