Changes in the pyruvic acid content correlates with phenotype traits in onion clones

Consumer demand is oriented toward onion cultivars with lower pungency, and the pyruvic acid content of onions is highly correlated with their pungency. Therefore, breeding programmes might be based on the pyruvic acid content of the parental bulbs. The present study was performed using 97 onion clones with the aim of correlating the pyruvic acid levels with phenotype traits in the different genotypes used in breeding programmes. The onion bulbs were provided from the breeding company with blind labels, and four bulbs were individually analysed for each clone. A comparison between the spectrophotometric and HPLC determination of pyruvic acid was also carried out and showed an excellent linear regression with an R 2 = 0.951. The pyruvic acid was studied in correlation with tunic colours, pungency and precocity, and the highest correlation coefficient was found for red skinned onions. The lowest pyruvate content was found in white onions, with 6.5 μmol g -1 FW, whereas higher values (8.4-8.5 μmol g -1 FW) were observed in yellow and red onions. The chemical analyses were compared with panel taste assessments. The results confirmed that the pungency and pyruvic acid content were positively and significantly correlated (P<0.0001),even when the coefficient resulted in a relatively low value (r = 0.515). The precocity trait was associated with pyruvate content: precocious onions, in particular, showed lower pungency.