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To develop the bunching onion (Allium fistulosum L.; genomes, FF) chromosome-specific genetic markers for identifying extra chromosomes, eight shallot (A. cepa L. Aggregatum group; genomes, AA)--A. fistulosum monosomic addition plants (AA+nF) and 62 shallot--A. fistulosum single-alien deletion plants (AAF-nF) were analyzed by 23 different chromosome-specific genetic markers of shallot. The eight monosomic addition plants consisted of one AA+2F, two AA+6F, and five AA+8F. Of the 62 single-alien deletion plants, 60 could be identified as six different single-alien deletion lines (AAF-1F, -3F, -4F, -6F, -7F, and -8F) out of the eight possible types. Several single-alien deletion lines were classified on the basis of leaf and bulb characteristics. AAF-8F had the largest number of expanded leaves of five deletion plants. AAF-7F grew most vigorously, as expressed by its long leaf blade and biggest bulb size. AAF-4F had very small bulbs. AAF-7F and AAF-8F had different bulbs from those of shallot as well as other types of single-alien deletion lines in skin and outer scale color. Regarding the sugar content of the bulb tissues, the single-alien deletion lines showed higher fructan content than shallot. Moreover, shallot could not produce fructan with degree of polymerization (DP) 12 or higher, although the single-alien deletion lines showed DP 20 or higher. The content of S-alk(en)yl-L-cysteine sulfoxide (ACSO) in the single-alien deletion lines was significantly lower than that in shallot. These results indicated that chromosomes from A. fistulosum might carry anonymous factors to increase the highly polymerized fructan production and inhibit the synthesis of ACSO in shallot bulbs. Accordingly, alien chromosomes from A. fistulosum in shallot would contribute to modify the quality of shallot bulbs.

The objective of this study was to report on the variation of DP 6 isomers (6b, 6c + 6d1 + 6d2), 7a, 8, and 9-12 fructooligosaccharides (FOS) and their hydrolysis parameters [percent hydrolysis, consumption rate, hydrolysis rate constant (k(obsd)), and half-life time (t(1/2))] in onion bulb tissues stored for 6 months at 10, 15, or 20 degrees C. The hydrolysis of DP 6 isomers, 7a, and 8 ranged from 74 to 85%, whereas that of DP 9-12 averaged 86%. The consumption rate of 6b, 6c + 6d1 + 6d2, 7a, 8, and -12 averaged 25, 58, 38, 26, and 48 microg/g of fresh weight per week, respectively. The k(obsd) showed large variation from 53 x 10(-3) week(-1) (lowest value) to 92 x 10(-3) week(-1) (highest value), whereas the half-life t(1/2) of the different FOS ranged between 7.5 and 13.1 weeks. DP 6b isomers increased during the first month, and then the content decreased sharply during the second month at 20 degrees C but remained stable during the last 4 months, whereas at 10 and 15 degrees C, 6b decreased progressively from the first to the six month. In contrast, DP 6c + 6d1 + 6d2 decreased abruptly within the first 3 months at 10, 15, and 20 degrees C; however, during the last 3 months they remained stable, ranging between 0.32 and 0.39. Variation of DP 7a, 8, and 9-12 FOS was close to that of DP 6 FOS isomers. DP 7a increased slightly during the first month, and afterward 7a started decreasing progressively during the last 5 months. DP 8 FOS showed a similar pattern independent of temperature regime: they increased slightly within the first month, but from the second month, DP 8 began decreasing progressively and continued decreasing to the sixth month. DP 9-12 FOS also varied similarly to DP 6c + 6d1 + 6d2. They decreased sharply within the first 2 months, and during the last 4 months, they continued to decrease slowly. Surprisingly, these variations occurred independently of temperature regimes and were affected only by storage duration. It was concluded that highly polymerized FOS are preferably hydrolyzed rather than low DP FOS isomers because they have a relatively high content of fructosyl end chains.

A fructosyltransferase that transfers the terminal (2 --> 1)-beta-linked D-fructosyl group of fructo-oligosaccharides (1(F)(1-beta-D-fructofuranosyl)(n) sucrose, n >/= 1) to HO-6 of the glucosyl residue and HO-1 of the fructosyl residue of similar saccharides (1(F)(1-beta-D-fructofuranosyl)(m) sucrose, m >/= 0) has been purified from an extract of the bulbs of onion (Allium cepa). Successive column chromatography using DEAE-Sepharose CL-6B, Toyopearl HW65, Toyopearl HW55, DEAE-Sepharose CL-6B (2nd time), Sephadex G-100, Concanavalin A Sepharose, and Toyopearl HW-65 (2nd time) were applied for protein purification. The general properties of the enzyme, were as follows: molecular masses of 66 kDa (gel filtration chromatography), and of 52 kDa and 25 kDa (SDS-PAGE); optimum pH of c. 5.68, stable at 20-40 degrees C for 15 min; stable in a range of pH 5.30-6.31 at 30 degrees C for 30 min, inhibited by Hg(2+), Ag(+), p-chloromercuribenzoic acid (p-CMB) and sodium dodecyl sulfate (SDS), activated by sodium deoxycholate, Triton X-100 and Tween-80. The amino acid sequence of the N-terminus moiety of the 52-kDa polypeptide was ADNEFPWTNDMLAWQRCGFHFRTVRNYMNDPSGPMYYKGWYHLFYQHNKDFAYXG and the amino acid sequence from the N-terminus of the 25-kDa polypeptide was ADVGYXCSTSGGAATRGTLGPFGLL VLANQDLTENTATYFYVSKGTDGALRTHFCQDET. The enzyme tentatively classified as fructan: fructan 6(G)-fructosyltransferase (6G-FFT). The enzyme is proposed to play an important role in the synthesis of inulin and inulinneo-series fructo-oligosaccharides in onion bulbs.

The activity of soluble invertase, and the variation in glucose, fructose and sucrose contents in onion bulbs (Allium cepa) during long-term storage at 10 degrees C and 20 degrees C were investigated. Invertase activity increased progressively after 8 weeks to 0.084 and 0.092 nkat/g fresh weight (FW), then sharply to 0.29 and 0.35 nkat/g FW at 20 degrees C and 10 degrees C, respectively, and remained high during 5 weeks. Then, activity decreased abruptly to 0.039 and 0.041 nkat/g, and remained low during the last 8 weeks and close to that observed initially. Glucose increased to 17.73 and 14.62 mg/g FW after 4 weeks at 20 degrees C and 10 degrees C, respectively, then decreased sharply between week 5 and week 7 to 4.13 and 4.91 mg/g FW, respectively, and remained rather stable ranging from 9 and 10 mg/g FW at both temperatures. Fructose showed a similar pattern and was 14.8 and 21.68 mg/g FW at 20 degrees C and 10 degrees C, respectively. Between week 10 and week 24, fructose ranged from 5 and 6 mg/g FW, and from 6 and 7 mg/g FW at 20 degrees C and 10 degrees C, respectively. Sucrose increased to 19.63 and 14.43 mg/g FW at 20 degrees C and 10 degrees C, respectively, decreased during 3 weeks, and then increased randomly from 5.69 to 9.42 mg/g FW at 20 degrees C, but remained in a steady state at 10 degrees C ranging 5.03 +/- 0.78 mg/g FW. During the last 6 weeks, the sucrose content was higher at 20 degrees C than at 10 degrees C. The fructose-glucose ratio varied during the first 8 weeks but remained at a steady level during the last 16 weeks. The (glucose+fructose)/sucrose ratio increased randomly at 10 degrees C, whereas at 20 degrees C the ratio increased during 10 weeks then decreased progressively during the final 14 weeks.

About 80 percent of onion bulb dry matter is non-structural carbohydrates. These carbohydrates are predominantly glucose, fructose, sucrose and low-molecular weight fructans, while starch and raffinose are absent. The metabolism of sugars is closely linked to the dormancy and sprouting state, and the most important biochemical change occuring during post-harvest life of bulbs, as with other vegetables, is the content variation in the carbohydrate constituents.