| dc.description.abstract | To evaluate the importance of phenology and strobilus
production in a clonal seed orchard of white and black
spruce, 14 clones of each species represented by 4 ramets
each, were selected from the Mattawin seed orchard. Thunder
Bay District, Ontario. The times of flushing of the
terminal buds of the leaders and 4 lateral branches were
determined using an index of vegetative bud and shoot
development. Dates of growth cessation were determined at
95 percent of shoot elongation. An index was used to score
stages of pollen release and female receptivity of black
spruce. Counts were made of male and female strobilus
production per ramet in black spruce. The time of
reproductive bud differentiation, in two clones of black spruce, was estimated to be mid-July after viewing dissected
buds under a dissecting microscope and epimicroscope.
Analyses of variance showed significant differences among
clones in times of flushing and growth cessation of the
leaders and lateral branches of white and black spruce, and
significant differences in times of pollen release and
female receptivity in black spruce but not white spruce.
However, few clones were significantly different from each
other using Duncan's NMR test. Generally there was a small
range in clonal mean dates for these characteristics,
perhaps because the clone ortets all originated from the same northern seed zone. Early-flushing black spruce clones
produced the greatest leader extension. Peak pollen release
and female receptivity coincided in most clones, thus
increasing the probability of selfing. An analysis of
variance of the number of female strobili per ramet and an
analysis of covariance of the number of male strobili per
ramet, using ramet height as covariant, showed significant
clone differences. A few clones produced the largest number
of strobili, especially in male strobilus production. Heavy
male strobilus producing clones were not necessarily heavy
female strobilus producers. The genetic composition of the progeny was estimated from: 1) the daily stages of pollen
release and female receptivity, and 2) the number of male
and female strobili per clone. A few clones were the
largest contributors to the genetic composition of the
progeny; the timing of pollen release and female
receptivity had little effect on these estimates. The total
percentage of selfed-crosses was estimated at 1 1 percent,
although the individual clone rates of selfing varied from 1
to 25 percent. | |
