Water productivity (WP) is becoming a key issue in understanding the relationship between water availability and rainfed sorghum ( Sorghum bicolor L. Moench) yields in agricultural systems across sub–Saharan Africa. The objective of this study was to determine water productivity of three sorghum genotypes under different environmental conditions. Three sorghum genotypes, a hybrid (PAN8816), a commercial open-pollinated variety (Macia) and a landrace (Ujiba) were planted at two sites (Ukulinga and Mbumbulu) in South Africa during 2013/2014 and 2014/2015. High clay content in Mbumbulu lowered plant available water in the soil compared to Ukulinga. Sorghum adapted to low water availability by significantly (P < 0.05) lowering plant growth (green leaf number, plant height and canopy cover), crop physiology (chlorophyll content index and stomatal conductance), biomass and grain yield. Ujiba and PAN8816 genotypes hastened phenological development, whilst Macia delayed phenological development in response to low water availability. Total and grain WP were lower at Mbumbulu (14.93 and 7.49 kg/ha/mm) relative to Ukulinga (21.49 and 11.01 kg/ha/mm), respectively. Results showed that Macia had significantly higher (P < 0.05) WP (10.51 kg/ha/mm) relative to PAN8816 (9.34 kg/ha/mm) and Ujiba (7.90 kg/ha/mm). Lack of significant genotypic differences in grain WP highlights that all three genotypes are equally suitable for production under sub–optimal and dryland conditions.

中文翻译：

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雨养条件下选定高粱基因型的水生产力

水资源生产力 (WP) 正成为理解撒哈拉以南非洲农业系统中水资源可用性与雨养高粱 ( Sorghum bicolor L. Moench) 产量之间关系的关键问题。本研究的目的是确定三种高粱基因型在不同环境条件下的水分生产力。2013/2014 年和 2014/2015 年，在南非的两个地点（Ukulinga 和 Mbumbulu）种植了三种高粱基因型，即杂种 (PAN8816)、商业开放授粉品种 (Macia) 和地方品种 (Ujiba)。与 Ukulinga 相比，Mbumbulu 的高粘土含量降低了土壤中的植物可用水。高粱通过显着（P < 0.05）降低植物生长（绿叶数、植物高度和冠层盖度）来适应低可用水量，作物生理（叶绿素含量指数和气孔导度）、生物量和谷物产量。Ujiba 和 PAN8816 基因型加速物候发育，而 Macia 延迟物候发育以响应低可用水量。相对于 Ukulinga（21.49 和 11.01 kg/ha/mm），Mbumbulu（14.93 和 7.49 kg/ha/mm）的总和谷物 WP 分别较低。结果表明，与 PAN8816 (9.34 kg/ha/mm) 和 Ujiba (7.90 kg/ha/mm) 相比，Macia 的 WP (10.51 kg/ha/mm) 显着更高 (P < 0.05)。谷物 WP 缺乏显着的基因型差异突出表明，所有三种基因型同样适合在次优和旱地条件下生产。而 Macia 延迟了物候发育以响应低可用水量。相对于 Ukulinga（21.49 和 11.01 kg/ha/mm），Mbumbulu（14.93 和 7.49 kg/ha/mm）的总和谷物 WP 分别较低。结果表明，与 PAN8816 (9.34 kg/ha/mm) 和 Ujiba (7.90 kg/ha/mm) 相比，Macia 的 WP (10.51 kg/ha/mm) 显着更高 (P < 0.05)。谷物 WP 缺乏显着的基因型差异突出表明，所有三种基因型都同样适合在次优和旱地条件下生产。而 Macia 延迟了物候发育以响应低可用水量。相对于 Ukulinga（21.49 和 11.01 kg/ha/mm），Mbumbulu（14.93 和 7.49 kg/ha/mm）的总和谷物 WP 分别较低。结果表明，与 PAN8816 (9.34 kg/ha/mm) 和 Ujiba (7.90 kg/ha/mm) 相比，Macia 的 WP (10.51 kg/ha/mm) 显着更高 (P < 0.05)。谷物 WP 缺乏显着的基因型差异突出表明，所有三种基因型都同样适合在次优和旱地条件下生产。