Variations in bog bilberry fruit characteristics along an altitudinal gradient on Changbai Mountain, China

To better understand the influence of altitude on fruit characteristics of bog bilberry (<i>Vaccinium uliginosum</i> L.), here we investigated the adaptation of its fruit morphological and chemical traits to the environment at six growing positions along an altitudinal gradient (706, 957, 1 226, 1 315, 2 000 and 2 190 m) on the northern slope of Changbai Mountain, China. Fruit longitudinal diameter, fruit transverse diameter and fruit weight decreased significantly with increasing altitude. Vitamin B1 content reached its highest at 2 190 m, while both vitamin B2 and vitamin C contents reached their highest and lowest at 1 226 and 706 m, respectively. Anthocyanin content and DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical scavenging ability initially decreased and then improved with increasing altitude. We observed a highly significant (<i>P</i> < 0.001) negative correlation between external fruit quality traits (fruit length, diameter and weight) and internal fruit quality traits (vitamins B1, B2, C and anthocyanin), and found that environmental factors significantly influenced fruit characteristics. Taken together, we concluded that on the northern slope of Changbai Mountain, bog bilberry fruits were larger at low altitudes, fruits at mid altitudes contained higher vitamins B2 and C, while high altitude (especially at 2 190 m) was beneficial for vitamin B1, anthocyanin, and DPPH free radical scavenging ability.