Genetic Analyses of Soluble Carbohydrate Concentrations in Onion Bulbs

Abstract

Fructans are the main soluble carbohydrate in onion (Allium cepa) bulbs and their concentrations show significant correlations with dry weights and pungency. In previous research, we identified regions on chromosomes 5 and 8 associated with higher amounts of soluble carbohydrates in onion bulbs. In this research, we estimated the genetic effects and interactions between these two chromosome regions using larger inbred families grown in field trials over 3 years. Bulbs were evaluated 30 and 90 days after harvest (DAH) for dry weights and soluble carbohydrates. Fructan concentrations decreased significantly between 30 and 90 DAH, consistent with loss of bulb dormancy over this period. Dry weights were negatively correlated with fructose and positively correlated with sucrose and fructans. Analyses of variance and interval mapping revealed that the region on chromosome 5 affected bulb dry weight, whereas the region on chromosome 8 significantly affected both dry weight and fructan concentrations. Regions on chromosomes 5 and 8 showed dominance for increased dry weights and/or soluble solids. Interactions between regions on chromosomes 5 and 8 were significant only for sucrose and the fructan neokestose, indicating that these regions independently contribute to higher amounts of soluble carbohydrates. These results demonstrate that onions with low concentrations of soluble carbohydrates were developed by selecting for relatively few recessively inherited chromosome regions.