Diversity of Phenological Characteristics and Fruit Quality of the Chinese Honeyberry (Lonicera caerulea L.) Collection

Honeyberry (Lonicera caerulea L.) is a recently domesticated fruit crop, and there has been rather limited research on its phenological characteristics. In this study, we comprehensively evaluated the phenological and fruit quality traits of a honeyberry germplasm collection comprising 45 accessions. The annual growth period of the 45 accessions ranged from 153 (part of Russian accessions) to 173 days (part of Japanese accessions) in Harbin, China. The accessions of Japanese origin (‘Ri–5’, ‘Ri–68’, ‘RiM–3’, ‘Riwan’, ‘Riwandianlan’, and ‘Riwan–13’) consistently exhibited delayed flowering and ripening, as well as higher single fruit weights and fruit firmness. In contrast, the accessions of Russian and Chinese origins displayed relatively early to mid-season phenology, along with higher levels of vitamin C, anthocyanins, and soluble solids. Furthermore, there were great coefficients of variation (CVs) in total anthocyanins (CV = 35%), flavonoids (CV = 30%), phenolics (CV = 21%), and titratable acidity (CV = 19%) among the 45 accessions. Principal component analysis and hierarchical clustering revealed distinct clustering patterns among Japanese accessions. Among these accessions, ‘RiM–3’ exhibited both a relatively large fruit size and high firmness, implying its potential to overcome the inevitable trade-off between fruit size and firmness typically observed in Chinese and Russian honeyberry accessions. Our investigation and findings provide valuable information for honeyberry breeding aimed at optimizing the maturity period and enhancing fruit quality, as well as a reference for the current cultivation and management methods.