Insights into the formation of tomato quality during fruit development

Influence of the source-sink balance on the final quality of tomato was investigated in spring greenhouse production. Four treatments were compared differing by the fruit/leaf number ratio manipulated during either the cell division or the cell elongation periods of the sixth truss. At maturity, quality was assessed through fruit colour, firmness, fresh weight, titratable acidity, refractive index, and contents of dry matter, reducing sugars, beta -carotene, lycopene and C vitamin. beta -carotene and lycopene contents were correlated positively to each other, and negatively to fruit firmness. The refractive index, dry-matter and sugar contents were also positively correlated, but less under low competition during cell division. Fruit fresh weight was correlated with none of the qualitative parameters, and significantly differed among fruits within the sixth truss; however this relied only on the difference between the first fruit and the following ones. Fruit composition did not vary among basal and tip fruits, but significantly depended on the fruit/leaf ratio. Low competition during the whole fruit development promoted sugar, acid and carotenoid contents, indicating a general increase in fruit metabolism, though fruits were not significantly bigger. Decreasing the competition during the cell elongation period tended to decrease the fruit dry-matter content and increase the acid content, whereas affecting the competition only during the cell division period hardly influenced the fruit composition. On the whole, results indicated that drastic removal of fruits may have inhibited the source activity at a period of low sink demand. In contrast to fruit composition and fruit size, other physical quality traits (firmness and colour) were only slightly affected by the source-sink ratio.