Intrinsic transpiration efficiency (i TE), the ratio of photosynthesis (A) to stomatal conductance (gs ), is considered a useful trait for improving productivity; however, higher i TE with high A is more desirable than that with low gs . This study dissects i TE of twenty sugarcane genotypes to understand its relationship with total dry matter (TDM) and cane yield (TCH) under irrigated and rainfed conditions. Water stress reduced mean A and gs by 56 and 61%, and mean TDM and TCH by 55 and 59%, respectively; however, genotype × irrigation treatment interaction was smaller than genotype variance. Mean i TE increased from 117.4 μmol mol-1 in the irrigated treatment to 130.6 μmol mol-1 in the rainfed treatment. In irrigated conditions, i TE had high heritability (H2 b = 0.67) and significant genetic correlation with TDM (rg = 0.58) and TCH (rg = 0.72). Under water stress, at gs below 0.1 mol m-2 s-1 , non-stomatal limitation to A was evident and i TE had low heritability (H2 b = 0.2). Whereas in the gs range of 0.1-0.4 mol m-2 s-1 , heritability of i TE (H2 b = 0.63) and its genetic correlation with TDM (rg = 0.78) and TCH (rg = 0.75) were maximised. There was significant genotypic variation in photosynthetic capacity (Ac ), and the differences were related to TDM and i TE. Selecting genotypes with higher i TE and Ac could offer potential for improving productivity without the unfavourable effect of low gs .

中文翻译：

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雨养和灌溉田间条件下内在蒸腾效率的基因型变异与甘蔗产量相关

内在蒸腾效率 (i TE)，即光合作用 (A) 与气孔导度 (gs) 的比率，被认为是提高生产力的有用特性；然而，高 A 的高 i TE 比低 gs 更可取。本研究分析了 20 种甘蔗基因型的 TE，以了解其与灌溉和雨育条件下的总干物质 (TDM) 和甘蔗产量 (TCH) 的关系。水分胁迫使平均 A 和 gs 分别降低了 56% 和 61%，平均 TDM 和 TCH 分别降低了 55% 和 59%；然而，基因型×灌溉处理交互作用小于基因型变异。平均 i TE 从灌溉处理中的 117.4 μmol mol-1 增加到雨养处理中的 130.6 μmol mol-1。在灌溉条件下，i TE 具有高遗传力 (H2 b = 0.67) 并且与 TDM (rg = 0.58) 和 TCH (rg = 0.72) 具有显着的遗传相关性。在水分胁迫下，gs 低于 0.1 mol m-2 s-1 时，对 A 的非气孔限制很明显，并且 i TE 具有低遗传力（H2 b = 0.2）。而在 0.1-0.4 mol m-2 s-1 的 gs 范围内，i TE (H2 b = 0.63) 的遗传力及其与 TDM (rg = 0.78) 和 TCH (rg = 0.75) 的遗传相关性最大化。光合能力（Ac ）存在显着的基因型变异，差异与TDM和i TE有关。选择具有较高 i TE 和 Ac 的基因型可以提供提高生产力的潜力，而不会产生低 gs 的不利影响。75) 被最大化。光合能力（Ac ）存在显着的基因型变异，差异与TDM和i TE有关。选择具有较高 i TE 和 Ac 的基因型可以提供提高生产力的潜力，而不会产生低 gs 的不利影响。75) 被最大化。光合能力（Ac ）存在显着的基因型变异，差异与TDM和i TE有关。选择具有较高 i TE 和 Ac 的基因型可以提供提高生产力的潜力，而不会产生低 gs 的不利影响。