ESTIMATING GAINS FROM GENETIC TESTS OF SOMATIC EMBLINGS OFINTERIOR SPRUCE

摘要

To assess the growth of somatic emblings versus seedlings and to estimate genetic parameters and gain that would accrue from a clonal testing and selection program, seedlings and 313 embling clones from 11 full-sib families of interior spruce Picea glauca Moench Voss and P. engelmannii Parry and their hybrid complex were assessed at two test sites in British Columbia.Seedlings were 11% taller than emblings after 7 years, however, when height at planting age-one was accounted for, the differencebetween the two stocktypes was reduced to 8 % p = 0.0414. Height-age trajectories between stocktypes were similar. Repeatabilities for height at age-7 were strong for clones hc = 0.71; h.Fl = 0.69 and families ffp- 0.80. Variation was relativelyhigh among clones CVC% = 14.6 %; CVCFI % = 13.3 %, but low among families CV,,% = 5.9. Genetic gains in excess of the seed orchard alternative were estimated for selection scenarios involving hypothetical tests containing between 200 and 2000 clones from 40 families. Gain for direct selection for height at age-7 was large: 21.5 % for mass clonal selection if the tallest 20 of 200 clones were selected, increasing to 32.8 % if 20 of 2000 clones were selected. Substantial relatedness among the tallest clones was avoided by using 2-stage family and clone-within-family selection, however, gains were about 4 % less e.g., 17.0 % and 28.9 % for tests of 200 and 2000 clones respectively than for unrestricted mass clonal selection. Gain estimates arecontingent on improved propagation methods being able to produce seedlings and emblings that possess equivalent growth rates. These results indicate that testing and deployment of embling clones can produce significant gains beyond that expected from seed orchards, however several technical and economic issues remain to be addressed.