To improve our understanding about the physiological mechanism of grain yield reduction at anthesis, three spring wheat genotypes [L1 (advanced line), L2 (Vorobey) and L3 (Punjab-11)] having contrasting yield potential under drought in field were investigated under controlled greenhouse conditions, drought stress was imposed at anthesis stage by withholding irrigation until all plant available water was depleted, while well-watered control plants were kept at 95% pot water holding capacity. Compared to genotype L1 and L2, pronounced decrease in grain number (NGS), grain yield (GY) and harvest index (HI) were found in genotype L3, mainly due to its greater kernel abortion (KA) under drought. A significant positive correlation of leaf monodehydroascorbate reductase (MDHAR) with both NGS and HI was observed. In contrast, significant negative correlations of glutathione S-transferase (GST) and vacuolar invertase (vacInv) both within source and sink were found with NGS and HI. Likewise, a significant negative correlation of leaf abscisic acid (ABA) with NGS was noticed. Moreover, leaf aldolase and cell wall peroxidase (cwPOX) activities were significantly and positively associated with thousand kernel weight (TKW). Distinct physiological markers correlating with yield traits and higher activity of leaf aldolase and cwPOX may be chosen as predictive biomarkers for higher TKW. Also, higher activity of MDHAR within the leaf can be selected as a predictive biomarker for higher NGS in wheat under drought. Whereas, lower activity of vacInv and GST both within leaf and spike can be selected as biomarkers for higher NGS and HI. The results highlighted the role of antioxidant and carbohydrate-metabolic enzymes in the modulation of source-sink balance in wheat crops, which could be used as bio-signatures for breeding and selection of drought-resilient wheat genotypes for a future drier climate.

中文翻译：

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在水分充足和干旱条件下生长的三种春小麦基因型中，叶片和穗状糖的碳水化合物代谢和抗氧化酶的活性与产量表现相关。

为了更好地了解花期减产的生理机制，研究了在干旱条件下田间具有较高增产潜力的三种春小麦基因型[L1（先进系），L2（Vorobey）和L3（Punjab-11）]。在温室条件下，在花期阶段通过不灌溉来施加干旱胁迫，直到所有植物可用水都枯竭为止，而灌溉良好的对照植物则保持在95％的盆栽持水量。与基因型L1和L2相比，基因型L3的籽粒数（NGS），籽粒产量（GY）和收获指数（HI）明显降低，这主要是由于干旱条件下其更大的谷粒流产（KA）。观察到叶片单脱氢抗坏血酸还原酶（MDHAR）与NGS和HI呈显着正相关。相反，NGS和HI发现谷胱甘肽S-转移酶（GST）和液泡转化酶（vacInv）在源和汇内均呈显着负相关。同样，注意到叶脱落酸（ABA）与NGS呈显着负相关。此外，叶片醛缩酶和细胞壁过氧化物酶（cwPOX）活性与千粒重（TKW）显着正相关。可以将与产量性状和叶片醛缩酶和cwPOX的较高活性相关的独特生理标志物选作较高TKW的预测生物标志物。同样，可以选择叶片内较高的MDHAR活性作为干旱条件下小麦较高NGS的预测生物标记。而叶和穗状花序中vacInv和GST的较低活性可以被选作较高NGS和HI的生物标记。