Relationship between sugar content and °Brix as influenced by cultivar and ripening stages of strawberry

Abstract

We have evaluated eight cultivars of strawberry, seven short-day and one day-neutral, for two years with two sampling dates and two repetitions by date to assess the relationship between sugar content and degree Brix. The fruits were collected and evaluated at the ripe stage. Contents of sucrose, glucose, fructose, °Brix, citric acid, ascorbic acid and malic acid in the fruit were measured. The data were analyzed using principal component analysis (PCA) and Pearson correlations. The PCA groups most of the variability in the first component (62.2%). This component shows a positive relationship between the Brix degrees, sugars and acids (higher values of this component indicate increased Brix degrees, and the contents of sugars and acids). The second component collects 20.74% of the variability, which is mainly related to differences in the sugars/acids ratio. The plotting of the factor barycenter over the two principal components of PCA analysis shows that second harvest date has a higher content of sugars, organic acids and °Brix. With regard to cultivars representation over PCA, the good quality cultivar 'Primoris' is characterized by a high sugar content and a balanced total sugars/acids ratio. Moreover, the day-neutral cultivar 'Nieva' shows the lowest values of sugars, acids, °Brix and total sugars/acids ratio. Featured correlations exist between ascorbic acid content and glucose and fructose content (R2=0.82 and 0.81, respectively). The °Brix shows a relative correlation with the total sugars content (R2=0.74). In conclusion, the genotype has large effect in the content of sugars and organic acids. Therefore, the high content of sugars and acids and a balanced relationship between them could be used as a quality trait for the selection of strawberry varieties. On the other hand, °Brix is a relative good measure of the total sugar content.