Soluble solids content is positively correlated with phosphorus content in ripening strawberry fruits

Soluble solids content (SSC) is one of the main parameters for evaluating the nutritive value of strawberry (Fragaria × ananassa), which is affected by a number of factors including genetics, environmental conditions and cultivation practices. In this study, we found that there was a positive correlation between SSC and phosphorus (P) content in fully ripened strawberry fruits. The positive correlation between SSC and P content was first verified among 24 strawberry cultivars with the correlation coefficient r = 0.95. Furthermore it was also verified among strawberry fruits harvested at different dates (r = 0.96) and among different parts (top, middle and bottom) of strawberry fruits (r = 0.87). To provide further confirmation, plants of strawberry cultivar 'Yanli' in solar greenhouse with the conventional cultivation management were irrigated with different concentrations of P fertilizer (phosphoric acid) once a week from the beginning of white stage and the result showed that P content and SSC in fruits from plants treated with 6.0 mM phosphoric acid increased 45.0% and 16.7%, respectively. Photosynthetic rate (Pn) and water use efficiency (WUE) of phosphoric acid treated plants increased 28.8% and 16.1% compared with the control plants. Our research lays the theoretical basis for improving the flavor of strawberry by applying P fertilizer.