BACKGROUND AND AIMS Dutch tomato cultivars tend to have a greater yield than Japanese cultivars even if they are grown under the same conditions. Factors contributing to the increased yield of the Dutch cultivars were a greater light use efficiency and greater leaf photosynthetic rate. On the other hand, the relationship between tomato yields and anatomical traits is still unclear. The aim of this study is to identify the anatomical traits related to the difference in yield between Dutch and Japanese cultivars. METHODS Anatomical properties were compared during different growth stages of Dutch and Japanese tomatoes. Hormone profiles and related gene expression in hypocotyls of Dutch and Japanese cultivars were compared in the hypocotyls of 3- and 4-week-old plants. KEY RESULTS Dutch cultivars have a more developed secondary xylem than Japanese cultivars, which would allow for greater transport of water, mineral nutrients and phytohormones to the shoots. The areas and ratios of the xylem in the hypocotyls of 3- to 6-week-old plants were larger in the Dutch cultivars. In reciprocal grafts of the Japanese and Dutch cultivars, xylem development at scion and rootstock depended on the scion cultivar, suggesting that some factors in the scion are responsible for the difference in xylem development. The cytokinin content, especially the level of N6-(Δ2-isopentenyl) adenine (iP) type cytokinin, was higher in the Dutch cultivars. This result was supported by the greater expression of Sl-IPT3 (a cytokinin biosynthesis gene) and Sl-RR16/17 (a cytokinin-responsive gene) in the Dutch cultivars. CONCLUSIONS These results suggest that iP-type cytokinins, which are locally synthesized in the hypocotyl, contribute to xylem development. The greater xylem development in Dutch cultivars might contribute to the high yield of the tomato.

中文翻译：

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荷兰和日本番茄（Solanum lycopersicum）木质部发育的差异与下胚轴中的细胞分裂素水平相关

背景和目的荷兰番茄栽培品种即使在相同条件下生长，也往往比日本栽培品种具有更高的产量。促成荷兰品种产量增加的因素是更高的光利用效率和更高的叶片光合速率。另一方面，番茄产量与解剖性状之间的关系仍不清楚。本研究的目的是确定与荷兰和日本品种产量差异相关的解剖特征。方法比较荷兰和日本番茄不同生长阶段的解剖学特性。在 3 周龄和 4 周龄植物的下胚轴中比较了荷兰和日本品种的下胚轴中的激素谱和相关基因表达。主要结果 荷兰品种比日本品种具有更发达的次生木质部，这将允许更多的水、矿物质养分和植物激素向枝条输送。荷兰品种的 3 至 6 周龄植物下胚轴中木质部的面积和比例较大。在日本和荷兰品种的相互嫁接中，接穗和砧木的木质部发育取决于接穗品种，这表明接穗中的某些因素是造成木质部发育差异的原因。荷兰品种的细胞分裂素含量，尤其是N6-(Δ2-异戊烯基)腺嘌呤(iP)型细胞分裂素的含量较高。这一结果得到了荷兰栽培品种中 Sl-IPT3（一种细胞分裂素生物合成基因）和 Sl-RR16/17（一种细胞分裂素反应基因）的更高表达的支持。结论 这些结果表明在下胚轴中局部合成的 iP 型细胞分裂素有助于木质部发育。荷兰品种的木质部发育更大可能有助于番茄的高产。