In Chinese cabbage breeding, artificial pollination has been conducted for two main purposes; the self-pollination for developing and maintaining inbreds, and the cross-pollination for creating genetic recombinants. It has been a very firmly established practice for Chinese cabbage breeders to use bags before and after hand-pollinations in intending to minimize the contamination by unintended pollen. However, there has been no attempt to measure the actual benefit of the very laborious baggings in Chinese cabbage breeding. In this paper, we report the actual frequency of off-types, which was considered as a result of contamination during pollinations, under several different combinations of pollination methods and environments.
The rate of contamination was affected by many different factors such as age of flowers, kinds of pollination (either self- or cross-), competition between legitimate and illegitimate pollen, expression of self-incompatibility, and availability of bees. In case of self-pollination, the highest seed production was achieved when bud-pollination was ferformed at 2 days before anthesis due to activity of self-incompatibility, while in case of cross-pollination, fertility was the highest at the day of anthesis. It would be generally accepted that more contamination could be occured in self-pollination at bud stage than cross-pollination at full flowers.
It is our conclusion that seed productions in both of self- and cross-pollination can be done under a polyethylene house without baggings in Chinese cabbage, if bee activity can be well controlled and plant density be lowered. Pollination without baggings can significantly reduce the labor requirement for hand-pollination in Chinese cabbage.
|