Abstract
To ensure the quality of seeds produced from a seed orchard composed of Hinoki (Chamaecyparis obtusa) with few male flowers, pollen contamination from outside the orchard must be reduced. We established two seasonal plastic-house seed orchards (SPH seed orchard) and an outdoor seed orchard, and compared pollen contamination rates. An alternative method to reduce pollen contamination is polycrossing. In this study, progeny from polycrossed C. obtusa, in which three mixtures from three paternal donors were crossed with each of three maternal parents, were analyzed to detect departures from equal paternal contribution. In the results of this study, SPH seed orchards were effective to reduce pollen contamination rate. However, the SPH seed orchard that had its plastic cover removed earliest resulted in high contamination rates and low seed germination rates. On the other hand, there was no pollen contamination in seedlings produced from polycrossed female strobili covered by nonwoven bags. In addition, the clone with the lowest pollen germination rate did not show low paternal contribution in the polycrossing. Therefore, polycrossing using nonwoven bags was more effective in reducing pollen contamination than SPH seed orchards to produce seeds of C. obtusa with few male flowers.
