Fruit morphological and nutritional quality features of goji berry (Lycium barbarum L.) during fruit development

Goji berry (Lycium barbarum L.) is one of the most pivotal economic crops with an exceptional nutritional value. Based on its high global consumption, understanding the fruit growth patterns and nutrient accumulation at each developmental stage is crucial for the field and production management of high-quality goji berry cultivars. In this study, a fruit growth and development model of goji berry was established using a double sigmoid curve, where the entire fruit development period was divided into three phases (phase Ⅰ, Ⅱ, and Ⅲ) with two key time points. Morphological features and nutritional components were measured at four (young, green, coloring, and red) stages of fruit growth in five cultivars. The nutritional constituents, namely galactose, fructose, and total sugar, monotonically increased from young to red stage. The highest polysaccharide content occurred at the young stage, whereas the sucrose, betaine, and flavonoid content were the highest in the green stage. Moreover, corresponding to the fruit growth model, polysaccharide was mainly accumulated during phase I and III, sucrose, betaine, and flavonoid were produced and concentrated during phase Ⅱ, and the galactose, fructose, and total sugar content rapidly increased during phase Ⅲ. The two key time points in the goji berry fruit development and nutrient accumulation range were 10–13 days and 21–26 days after full bloom, where water and fertilizer management should be enhanced. Correlation analyses suggested that morphological features were significantly correlated in all four growth stages, while a strong correlation among specific nutritional components was found in some certain growth stages with p-values smaller than 0.05 and Pearson correlation coefficients greater than 0.5. Principal component analysis indicates that total sugar and polysaccharide contents can be used as the main factors for evaluating the nutritional quality of different cultivars. Among the selected cultivars, ‘Ningqi 7’ was significantly better than other cultivars with respect to the nutritional levels. These findings can support breeding strategies and improve the effective field management of high-quality goji berry cultivars.