GENETIC-CONTROL OF BUD PHENOLOGY IN POLE-SIZE TREES AND SEEDLINGS OF COASTAL DOUGLAS-FIR

The extent to which bud phenology is genetically controlled and related to growth traits was examined in seedlings and pole-size trees of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco). Data on bud burst, bud set, and stem growth were collected from pole-size trees of 60 open-pollinated families growing in four plantations, and from seedlings of 45 of these same families growing in three trials. In both age-classes, bud burst was under moderate to strong genetic control (h2 greater-than-or-equal-to 0.44) and family breeding values were stable across test environments, indicating that this trait could be readily altered in breeding programs. Bud set was inherited strongly in pole-size trees (h2 = 0. 8 1) but weakly in seedlings (h2 less-than-or-equal-to 0.30). Both bud burst and bud set were positively correlated with growth in seedlings and pole-size trees. Thus, selection for greater growth at either age-class is expected to delay bud burst and bud set. We also evaluated the accuracy of two alternatives for assessing bud burst phenology in pole-size trees compared with the traditional method. We show that bud-burst date on lateral branches can be used to accurately rank both individuals and families for bud-burst date on less accessible leader shoots. In addition, we found that families can be ranked for mean bud-burst date by the proportion of trees per family that have flushed on a given scoring day. This method is only effective, however, when between 25 and 75% of all trees in the test have flushed at the time of scoring.