A Douglas-fir, number 618 located in a seed production area on Vancouver Island in 1967 and subsequently grafted at the Cowichan Lake Experiment Station in 1968 was found to be completely female sterile, producing only flat and undeveloped seeds. Details on this first example of female sterility in Douglas-fir and its significance to a seed improvement program have already been published.
As nothing was known about the fertility of the pollen from this particular clone, twigs bearing unopened male strobili were collected in early April 1978 and then placed in water under sterile conditions. Although a large number of twigs were collected and the strobili were normal in appearance, pollen extraction proved difficult. There was sufficient pollen, however, to dry pollinate 111 female strobili in 14 pollination bags positioned on the clone of another tree known to produce normal seed. One hundred and ten cones were collected in the autumn and these yielded 6694 seeds. After careful cleaning with an air-blower followed by cutting every rejected seed, which were all found to be empty, only six seeds remained. These were X-rayed and all had normal appearing embryos. The results indicated that only 0.05 filled seeds were produced per cone. As a check, 85 cones from wind-pollination were collected from the same clone that was pollinated and 3396 seeds extracted. These were again carefully cleaned and the remaining seeds X-rayed, 494 of these containing normal embryos. This gave a figure of 5.8 germinants per cone which is low but there had been some damage from insects. Nevertheless, it demonstrates the very low viability of the pollen from clone 618. Samples of this pollen and some from a normal clone were subsequently grown for 48 hours in a modified Brewbacker's solution. Figures 1 and 2 (Magnif. x 60) show the subsequent appearance of the normal pollen and that of clone 618 respectively. The latter pollen sample varies greatly in size and in stage of development and is clearly abnormal.
Little is known about the frequency of total and partial sterility in Douglas-fir but these results should well justify much closer examinations of the seed and pollen from individual trees and clones in both established and future seed orchards of this species. A cytological study to investigate this sterility in more detail would be of considerable interest. The assistance of Dr. J. Webber, Research Division, B.G.F.S. in taking the two microphotographs is cordially acknowledged.
For further information write to Dr. A.L. Orr-Ewing, Research Division, Ministry of Forests, Parliament Buildings, Victoria, B.G. VSW 3E7.
BC Forest Service - Research Division. 1978. Partial male sterility in Douglas-fir. British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development. Research Memo (FLNRORD). RM35
Topic: FLNRORD Research Program
Keywords: FLNRORD, Research Memo, British Columbia
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