An investigation of differences in fruit yield and components contributing to increased fruit yield in Japanese and Dutch tomato cultivars

Abstract

Tomato fruit yield per area in Japan is 88% lower than that in The Netherlands, because higher-yielding tomato cultivars are bred and cultivated in The Netherlands. In this study, we investigated differences between the Japanese common cultivar ‘Reiyou’ and the Dutch high-yielding cultivar ‘Levanzo’ in fruit yield and components contributing to an increase in fruit yield using the low-node-order pinching and high-density plant training system used in Japan. Fresh and dry fruit yield of ‘Levanzo’ were significantly higher than those of ‘Reiyou’. Estimated leaf blade area of the whole plant and solar radiation on individual leaves were higher in the ‘Levanzo’ canopy than in that of ‘Reiyou’. Although transpiration rate and stomatal conductance were similar in the two cultivars during the latter half of the fruit development period, the photosynthetic rate in ‘Levanzo’ was higher than that in ‘Reiyou’ during the fruit development period. The difference in photosynthetic rate was because chlorophyll a and b content had not decreased in ‘Levanzo’ compared with that in ‘Reiyou’ at 50 days after flowering, corresponding to the latter half of the fruit development period. Transcriptional levels of LeSUT1, which determines sucrose loading activity in source leaves, did not differ between the two cultivars. The higher tomato fruit yield of ‘Levanzo’ compared with that of ‘Reiyou’ was caused by a higher photosynthetic rate, increased solar radiation on individual leaves, and the large sink size due to numerous fruits, but not by sucrose loading activity.