|Abstract or Summary
- The effects of clonal variability, crown position of cones, and top-pruning of ramets to reduce height growth, on 1) the proportion of viable self-fertilized progeny (s) and 2) the proportion of filled seeds (PF), were investigated in a 20 year-old Douglas-fir (Pseudotsuga menziesii [Mirb.1 Franco) seed orchard. Cones were collected from the upper one-third and lower one-third crown positons of pruned and nonpruned raiets (three each) from six clones. Estimates of s were derived from a maximum likelihood procedure using data from 10 allozyme loci (PGII, LAP1, LAP2, GOT2, GOT3, GLYDH, CAT, 6PGD, IDH, and DIA). The six clones sampled varied significantly (P < 0.05) both in s and PF, but estimates of PF and s were not significantly correlated among clones. On the average, seeds from the upper portion of the crown were lower in s (0.055) and higher in PF (0.512) than seeds from the lower crown (s = 0.190, PF = 0.381). Combined over crown positions, pruning appeared to have little effect on s, while pruned ramets (PF = 0.432) had only a slightly lower filled seed proportion than nonpruned ramets (PF = 0.461). A total crown estimate of the proportion of viable progeny due to selffertilization from the six sampled clones was about 10 percent. These results show that crown position of cones, top-pruning, and clonal variation are all factors which could influence orchard management practices and the utilization of orchard seeds. Although the average proportion of viable progeny resulting from selffertilization in the seed orchard appeared to be no greater than that found in natural populations, information on clonal variation may be useful in roguing decisions. It may be desirable to remove clones which are consistently high selfers and low seed producers; or perhaps seed from these clones should be excluded from commercial collections. In addition, orchard managers may consider not collecting lower crown cones because of the lower seed yields and greater proportions of self seed found in the lower crown. In this study, the effects of top-pruning orchard ramets on seed set or self ing appeared to be minimal, but it remains to be seen whether there is a relationship between severity of top-pruning and seed quality or quantity.