Aims: This study aimed at assessing the functional linkage among seed traits (including seed number, seed weight), berry growth and berry sugar and acid concentration by adapting a mathematical growth function with parameters having biological importance.
Methods and results: The evolution of berry diameter of Cabernet-Sauvignon was satisfactorily fitted to a bi-phasic growth function with six parameters. Correlations between the parameters and berry characteristics, including time of skin color change, seed number, seed weight, final berry size and chemical composition, were analyzed. Results showed that berry growth within a bunch deviated according to seed number, which positively related to parameters describing diameter increment (D1) and initial growth rate (GRini) during the first rapid growth phase, but not related to any parameters involved in the second growth phase. The time of skin color change was negatively associated with mean seed weight, and coincided with growth parameter DABmax that denotes the time when growth rate is maximum during the second rapid growth phase. Sugar concentration was negatively correlated to final berry fresh weight (BFW), seed fresh weight (SFW), GRini and diameter increment during the second rapid growth phase (D2). Path analysis further revealed that the negative effects of SFW and D2 were indirectly mediated via BFW and GRini.
Conclusions: We thus conclude that seed affects berry growth and exerts its influence only during the first growth phase via modifying the parameters D1 and GRini. The time of colour change is also affected by seed, and might not be a good indicator of growth restoration after the lag phase. Sugar concentration is linked to final berry size, specific berry growth parameters and seed weight, for the last mainly in an indirect manner.
Significance of the study: This study, integrating the analysis of berry growth and composition with a mathematical growth function, provides a valuable approach for deeper understanding of the functional associations among seed traits, berry growth and berry sugar and acid concentration at the berry level.
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