QTL affecting soluble carbohydrate concentrations in stored onion bulbs and their association with flavor and health-enhancing attributes

Abstract

Onion bulbs accumulate fructans, a type of soluble carbohydrate associated with lower rates of colorectal cancers. Higher fructan concentrations in bulbs are correlated with higher pungency, longer dormancy, and greater onion-induced antiplatelet activity (OIAA). We analyzed replicated field trials of a segregating family for types and concentrations of soluble carbohydrates in onion bulbs 90 days after harvest. Means were adjusted using dry weight as the covariant to reveal highly significant (P < 0.001) differences among parents and families for glucose, fructose, sucrose, and the fructans 1-kestose, neokestose, and (6G,1)-nystose. Fructan concentrations showed significant (P < 0.05) phenotypic correlations with each other and with sucrose, pungency, and OIAA. These observations are consistent with the hypothesis that onion bulbs accumulating fructans take up or retain less water, concentrating both soluble carbohydrates and thiosulfinates responsible for pungency and OIAA. Interval mapping of family means from the covariant analyses revealed regions on linkage groups A and D significantly (LOD > 2.68) affecting soluble carbohydrate concentrations. The enzyme catalyzing the first step of fructan polymerization, 1-sucrose-sucrose fructosyltransferase (1-SST), mapped independently of these genomic regions. One region on linkage group D near an acid-invertase gene was significantly (LOD = 3.45) associated with sucrose concentrations. This study reveals that the accumulation of sucrose in stored onion bulbs may allow for the combination of sweeter flavor with significant OIAA.

Genetic mapping of a major gene affecting onion bulb fructan content

“…The EST-SSR marker ACM171, which is closely linked to the sucrose transporter RFLP locus API66C-E5-6.7/9.5 on chromosome 5 (Martin et al 2005), showed significant association with bulb DM (Table 4), as reported previously (Galmarini et al 2001). Only weak association of the chromosome 3 acid invertase locus API89 with bulb composition was observed (Table 4), in contrast to observations in 'BYG15-23 · AC43' (Galmarini et al 2001;Havey et al 2004).…”

“…Inspection of trait correlations (Table 2) revealed consistently high (r$0.9) negative correlations between total fructan and fructose content in these populations but no consistently high correlation of sucrose concentrations with other components. PCA of carbohydrate concentrations in these populations and also the F 3 M families evaluated by Havey et al (2004) showed that the first PC accounted for 60-70% of phenotypic variation (Table 3). Inspection of the weightings for individual components in the first PC showed that in all cases fructose and glucose were of opposite sign to fructans, suggesting that this PC can be interpreted as a measure of the balance between reducing sugars and fructans.…”

Effect of single alien chromosome from shallot (Allium cepa L. Aggregatum group) on carbohydrate production in leaf blade of bunching onion (A. fistulosum L.)

“…Recently, the mode of inheritance for soluble carbohydrate production has been clarified by localizing candidate genes (McCallum et al, 2001) and QTLs (Havey et al, 2004) related to sucrose and soluble carbohydrate accumulations on an onion linkage map based on molecular markers (King et al, 1998). The combination of both a molecular marker map and a monosomic addition set will reveal the chromosomal locations of QTLs related to carbohydrate production in onion bulbs, as well as to an understanding of the localizations of the different QTLs on the same chromosome.…”

Antioxidant capacity, total phenolic and ascorbate content as a function of the genetic diversity of leek (Allium ampeloprasum var. porrum)

“…Lawson, & Bauer, 1998). The Allium genus, which includes about 700 species, has been recognised as a rich source of secondary metabolites (Havey, Galmarini, Gokce, & Henson, 2004). Its organosulphur compounds, responsible for the organoleptic parameters, are implicated as contributing in part to its health-promoting properties (Lanzotti, 2006;Mostafa, Mima, Ohnishi, & Mori, 2000;Singh et al, 1998;Xiao, Pinto, Gundersen, & Weinstein, 2005;Yin, Hwang, & Chan, 2002).…”