Geographical Influences on Morphological Variation in Rubus ursinus Subsp. macropetalus

Abstract

Morphological variation was examined in 20 populations of Rubus ursinus subsp. macropetalus from British Columbia, Washington, and Oregon grown in a common garden. There was significant variability between and within populations for most traits studied. Principal component analyses separated populations along geographical clines for traits of horticultural significance. PC1 represented a general vigor component in all trials, and formed a negative correlation with elevation in four of five analyses (r = 0.60, 0.58, 0.50, 0.49; P < 0.05). Autumn leaf senescence tended to increase from west to east and with elevation. With higher elevation, there was a tendency for fruit weight to decrease, for later vegetative budbreak and fruit ripening, and for a shorter budbreak to first flower interval. From north to south, budbreak became somewhat earlier, cane spot susceptibility decreased, and budbreak to first flower interval increased. Characterization of this species will assist breeders to identify possible sources of cold hardiness, disease resistance, improved vigor, and acceptable fruit traits for the improvement of cultivated trailing blackberry.