Non-structural carbohydrate composition of long-day onion in vitro

Abstract

SummaryBulb formation in onion (Allium cepa L.) is strongly influenced by environmental factors, particularlyby light via photosynthesis and daylength. Dry-matter content (DM) in an onion bulb varies between 6 and 25%. Of this, 60–80% is made up of non-structural carbohydrates (NSC). This study compared the relative influence of genetics and environment on the concentration and composition in NSC of onion bulbs. The effects of clonal genotype, light spectrum quality and sucrose concentration in the culture medium were investigated in vitro on a long-day onion type. NSC analyses were performed enzymatically and by HPLC on growing material. Fructans characterized the basal tissues, and the sucrose content in the medium influenced the NSC distribution of the onion tissues. Bulb induction by supplementary incandescent light stimulated fructan accumulation in basal tissues. The high DM clones stored fructans faster and at higher concentrations than the low DM ones. They expressed a higher potential for fructan sink or biosynthesis. A similar biochemical composition in vitro as field-grown bulbs resulted from the light spectrum quality of light.