Sexual reproduction in a greenhouse and reduced autumn frost hardiness of Picea abies progenies.

In 1989, identical crosses (2-3 females within males) were performed with Picea abies (L.) Karst. in a greenhouse seed orchard at Biri nursery and in an outdoor seed orchard at Huse, 32 km north of Biri. Pollination began 17 days earlier in the greenhouse than outdoors at Huse. The potted grafts in the greenhouse were moved outdoors when the seed cones were no longer receptive. Twelve full-sib family pairs (Biri and Huse) from these crosses were grown in a phytotron and tested for height and autumn frost hardiness during their first growing season. No significant difference was found between the indoor (Biri) and outdoor (Huse) progenies for height growth. However, the progenies from the greenhouse seed orchard were significantly more susceptible to frost than their full-sibs from the outdoor seed orchard. There was no significant interaction between males and the flowering environment, but a significant female x flowering environment interaction was present as a result of greater differences in frost hardiness between progenies from females in the greenhouse seed orchard than in the outdoor seed orchard. Although seeds from the outdoor seed orchard generally had a greater biomass than seeds from the greenhouse seed orchard, the difference in seed weight did not explain the difference in frost hardiness. We hypothesize that temperature and photoperiod during pollination and fertilization affect the frost hardiness of the progenies.