Inbreeding depression and changes in variation after selfing in Eucalyptus globulus ssp. globulus.

Abstract

The effect of self pollination (selfing), open-pollination (OP) and controlled cross pollination (outcrossing) on progeny of 11 Eucalyptus globulus ssp: globulus seed parents was examined from seed set to 43 months after planting. Selfing severely depressed seed set and field growth relative to outcrossing. No effect was found on germination percent and rate, nursery and field survival, nor the proportion of plants possessing adult foliage or flower buds. Inbreeding depression for height first occurred between germination and 8 months after planting but occurred later for diameter. There was a trend for inbreeding depression to increase with age. The performance of OP families was intermediate between self and outcross treatments but was only significantly different from outcrossing for volume at 43 months after planting. Selfing also appeared to increase variation between and within families relative to outcrossing. The results are discussed in terms of the biology and genetics of the species and the relevance to tree improvement programs.