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One factor that critically influences the progress of genetic tree improvement programs is the lack of or irregularity of staminate and pistilate strobili (flower) production in seedling and clonal materials. Trees of many species do not flower until they are 20+ years old. In the pines, a number of species have been observed to flower 2-5 years from seed but rarely on a grand enough scale to support a tree breeding or seed orchard program. Similarly, clonal breeding materials may take many years to come into useful production.
It is well known that flowering in some species can be enhanced by treating differentiating buds with certain growth regulating hormones. Two experiments were established to evaluate the response of lodgepole pine seedlings and grafts to exogenous applications of gibberellins and auxins. The hormones were applied in an ethanolic base solution to differentiating lateral and terminal buds using syringe and atomizer techniques. The results were encouraging. Exogenous application of GA 4/7 (gibberellic adds 4 and 7 in mixture) to terminal buds of lodgepole pine grafts significantly enhanced flowering on terminal and adjacent lateral shoots the following growing season (alpha = .05). The number of female flowers on treated ramets was 2-4 times greater than on controls. Similarly, a GA-NAA (NAA is an auxin) mix significantly increased flowering in 7 year-old lodgepole pine seedlings (alpha = .001). Both frequency of flowering branches and number of flowers per branch were affected.
The technique is not unqualified, however. Results indicate quite clearly that flowering can be enhanced only in those seedling and grafts that have undergone the physiological transitionfrom the junvenile to mature state. The effect of the hormones on trees without a flowering history is predictably slight. Also, the hormone treatments had little influence on the production of staminate flower buds. In spite of these disadvantages the exogenous application of hormones to enhance flowering in lodgepole pine appears to be a promising technique for hastening our breeding program.
Further information may be obtained by writing Nicholas C. Wheeler, B.C. Forest Service, Red Rock Research Centre, R.R. #7, 15 Mile Road, Prince George, British Columbia. V2N 2J5.
[Abstract contains full text of memo.]
BC Forest Service - Research Division. 1978. Exogenous application of hormones to enhance flowering in lodgepole pine seedlings and grafts. British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development. Research Memo (FLNRORD). RM24
Topic: FLNRORD Research Program
Keywords: FLNRORD, Research Memo, British Columbia
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