Wheat Source–Sink Metabolic Network Dynamics during Grain Filling under Drought-Heat Combined Stress

Abiotic stresses such as drought (DS), heat (HS), and
drought-heat
combined stress (HD) frequently occur during wheat grain filling,
significantly impacting yield and quality. This study investigated
the response of a widely cultivated high-quality, strong-gluten wheat
variety (Xinong 979) to DS, HS, and HD at the morphological, physiological,
biochemical, and molecular levels during grain filling. Results indicated
that abscisic acid (ABA) accumulation ability and proline accumulation
were significantly enhanced under HD, with significant reductions
in photosynthetic capacity, grain dimensions, and thousand kernel
weight (TKW). Starch granule formation morphology was notably inhibited
under stress. However, starch accumulation was promoted at 10 DAP
under HS and HD, particularly under HS. The relative contents of grain
protein and glutenin macropolymer increased, leading to significant
changes in grain quality. Combined stress more severely impacted yield
and quality formation than individual stress, with source–sink
metabolism showing significant tissue specificity and a correlation
to diverse stresses. This study constructed dynamic changes of source
and sink tissues at the biological level and gene expression levels
under various stress conditions during grain filling, revealing key
regulatory processes in yield and nutritional quality formation under
HD, thereby providing a vital basis for breeding stress-resistant
wheat.

干旱胁迫（drought, DS）、热胁迫（heat, HS）与旱热复合胁迫（drought-heat combined stress, HD）等非生物胁迫（abiotic stresses）在小麦籽粒灌浆期频繁发生，对小麦产量与品质造成显著负面影响。本研究以广泛种植的优质强筋小麦品种西农979（Xinong 979）为试材，探究其在灌浆期于形态、生理、生化及分子层面对上述三种胁迫的响应。结果表明，在HD胁迫下，脱落酸（abscisic acid, ABA）与脯氨酸的积累能力显著增强，而光合能力、籽粒尺寸及千粒重（thousand kernel weight, TKW）则显著降低；胁迫条件下淀粉粒的形成形态受到显著抑制。不过，在热胁迫与旱热复合胁迫处理下，开花后10天（days after pollination, DAP）的淀粉积累量显著提升，其中热胁迫的促进效果更为突出。籽粒蛋白与谷蛋白大聚合体（glutenin macropolymer）的相对含量升高，进而引发籽粒品质发生显著改变。相较于单一胁迫，复合胁迫对产量与品质形成的负面影响更为严重；源库代谢（source–sink metabolism）呈现显著的组织特异性，且与多种胁迫存在相关性。本研究构建了灌浆期不同胁迫条件下源库组织在生物学层面与基因表达水平的动态变化特征，揭示了旱热复合胁迫下产量与营养品质形成的关键调控过程，为抗逆小麦育种提供了重要依据。