Effect of source/sink ratio on leaf and fruit traits of blueberry fruiting canes in the field

The source/sink relationship affects plant production and fruit quality in the field. This study aims to evaluate leaf and fruit traits of two field-grown blueberry cultivars as affected by variability of source/sink ratio (expressed as cm2 leaf area-to-fruit number ratio) at fruiting cane level. We found that range of source/sink ratio was larger in cv. 'Legacy' than cv. 'Bluegold' with no effect of season on this variable. There was a curvilinear increase of leaf dry mass-to-leaf area ratio (LMA) with source/sink ratio, which suggests that leaves acted as alternative carbon sinks to fruits. The relation between theses variable was no affected by cultivar. Mass-based nitrogen linearly decreased with source/sink ratio, while area-based nitrogen increased in curvilinear form by the effect of LMA. For leaf nitrogen values, a notable difference between cultivars was observed. Stomatal conductance (gs) dropped with increasing source/sink ratios with 'Bluegold' achieving higher gs than 'Legacy' for any given source/sink ratio. Dry (DWf) and fresh mass, diameter and total soluble solids (SS) of the fruit were related to source/sink ratio through curvilinear fit in both cultivars. The observed relations were similar between cultivars for DWf and SS, which suggest that the rate of the response of fruit carbon gain to changing source/sink ratios was conservative between the studied cultivars. Our results showed that fruit-bearing blueberry canes are semiautonomous regulating their resource allocation as function of source/sink ratio.