Analysis of varietal differences in the fructo-oligosaccharide accumulation profile among onion (Allium cepa L.) cultivars grown by spring-sown cultivation
2017
Maeda, T. (Hirosaki University, Hirosaki (Japan). Faculty of Agriculture and Life Science) | Watanabe, A. | Wambrauw, D.Z. | Osanai, S. | Honda, K. | Oku, S. | Shimura, H. | Suzuki, T. | Yamasaki, A. | Okabe, Y. | Ueno, K. | Onodera, S.
Onions (Allium cepa L.) accumulate fructo-oligosaccharides (FOSs) as storage carbohydrates. FOSs exist in various chemical forms with different degrees of polymerization (DP) and chemical bonding states. Therefore, it is difficult to determine the precise FOS composition and quantity of each type of FOS. The objective of this study was to analyze the varietal differences in FOS composition and relative quantities among onion cultivars grown by spring-sown cultivation in Hirosaki City, Japan, using a high performance liquid chromatography (HPLC) system equipped with an evaporative light scattering detector (ELSD). FOS compositions of a number of varieties, as determined by HPLC/ELSD, were confirmed using matrix-assisted laser desorption/ionization time-of-flight -mass spectrometry (MALDI-TOF MS). Sugar and FOS analyses revealed distinct patterns of sugar and FOS accumulation, which led to categorization of the tested varieties into three types: (1) those with a relatively high overall quantity of FOSs and with a higher DP (DP3 to over DP9); (2) those containing mainly monosaccharides (fructose and glucose), disaccharide (sucrose), and low amounts of FOSs; and (3) those with a carbohydrate content that was intermediate compared to that of the other two types. Measurements of enzyme activities suggested that varietal differences in FOS composition are the result of differences in enzyme activities associated with the FOS biosynthetic and biodegradation pathways.
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