Accurate information regarding crop reproductive development and yield formation in response to water deficits is needed for informed vineyard irrigation management decisions, particularly when water supply is limiting. Fifteen red winegrape cultivars grown in the San Joaquin Valley of California were subjected to two regulated deficit irrigation (RDI) treatments for four years to determine yield component responses to water deficits (no applied water) preveraison (ED) and postveraison (LD). In the fifth year, the cultivars were kept well-watered to determine carryover effects. In the first four years, early water deficits (ED) consistently and significantly reduced yields compared to the control (sustained deficit, SD; applied water at 50% of estimated crop evapotranspiration (ETc) throughout the growing season) across all years and cultivars, but the late (postveraison) deficit (LD) treatment vines were not different from the control. The reduction in yield with ED was primarily due to a significant reduction in berry fresh weight (FW) and clusters per vine, with little change in berries per cluster. Neither flowers per cluster nor percent berry set were affected by the treatments, although flowers per cluster varied significantly among cultivars. Berries per cluster increased linearly with flowers per cluster until saturation at ~150 berries per cluster as percent berry set declined at ~250 flowers per cluster. In the fifth year, yields of the two RDI treatments recovered somewhat because of increases in berry FW and a small, but significant, increase in clusters per vine. These results show that berry size, because of a reduction in FW, is the most sensitive yield component to water deficits, followed by clusters per vine and berries per cluster, with sensitivity maximum preveraison and few differences among cultivars.

中文翻译：

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预防性水分亏缺对15个葡萄品种产量构成的影响

明智的葡萄园灌溉管理决策需要有关作物生殖发育和产量形成以应对缺水的准确信息，尤其是在供水有限的情况下。在加利福尼亚州圣华金河谷种植的 15 个红葡萄品种进行了四年的两次调节亏缺灌溉 (RDI) 处理，以确定产量成分对缺水（不施用水）preveraison (ED) 和 postveraison (LD) 的响应。在第五年，栽培品种保持充足的水，以确定结转效应。在前四年中，与对照（持续亏缺，SD；在整个生长季节以估计作物蒸散量 (ETc) 的 50% 施用水）相比，所有年份和品种的早期缺水 (ED) 始终显着降低产量，但是后期（后期）缺陷（LD）处理的葡萄藤与对照没有什么不同。ED 的产量减少主要是由于每株浆果鲜重 (FW) 和簇数显着减少，每簇浆果变化不大。每簇花和浆果百分比均不受处理的影响，尽管每簇花在栽培品种之间差异很大。每簇浆果随着每簇花的增加而线性增加，直到每簇约 150 个浆果饱和，因为浆果百分比下降到每簇约 250 朵花。在第五年，两种 RDI 处理的产量有所恢复，因为浆果 FW 的增加和每株葡萄藤簇的小幅但显着增加。这些结果表明，由于 FW 的减少，浆果大小，