关键词: 小麦, 倒春寒, 强弱势粒, 代谢组, 差异代谢物

Abstract:

【Objective】Late spring coldness is a major agro-meteorological disaster constraint limiting large-scale yield improvement of wheat in the Huang-Huai Plain of China. It not only affects spikelet and floret development but also influences grain weight. This study combined grain phenotype determination and untargeted metabolomics analysis to systematically investigate the morphology, grain weight, and metabolic responses of superior and inferior grains under varying degrees of late spring coldness at the anther connective stage, aiming to elucidate the intrinsic mechanisms underlying the differences in grain filling between superior and inferior grains of wheat with different resistances to late spring coldness from the perspectives of grain sink capacity formation and metabolic regulation. 【Method】In this study, the cold-tolerant wheat cultivar Yannong 19 (YN19) and the cold-sensitive cultivar Xinmai 26 (XM26) were used as experimental materials. Low-temperature treatments were conducted in an artificial climate chamber at the anther connective stage of young spike differentiation to simulate late spring coldness conditions in the field, with three temperature gradients (CK: 10 ℃; T1: 2 ℃; T2: −2 ℃). At maturity, the main agronomic traits of wheat were investigated. Grain morphology and grain weight were dynamically measured at 7, 14, 21, 28, and 35 days after anthesis to analyze the changes in grain sink capacity and grain weight under different temperature treatments. Superior and inferior grains were collected at 14 and 21 days after anthesis, respectively, and untargeted metabolomics analysis was performed using liquid chromatography-mass spectrometry (LC-MS). Multivariate statistical analysis was combined to screen differential metabolites, and the shared and specific responses of metabolites among different cultivars, stress intensities, grain-filling stages, and grain positions were compared. KEGG was used for metabolic pathway enrichment analysis. 【Result】Late spring coldness significantly inhibited the increase in grain sink capacity and reduced grain volume at maturity. In both wheat cultivars, the thousand-grain weight of superior and inferior grains decreased significantly with increasing stress intensity, with a more pronounced reduction observed in inferior grains. Metabolomic analysis identified a total of 2 474 metabolites, including 1 118 annotated metabolites. The number of differentially accumulated metabolites increased markedly with increasing intensity of late spring coldness, and XM26 exhibited more differentially accumulated metabolites than YN19. Only a small number of common differentially accumulated metabolites were shared among different treatments and cultivars. Notably, L-phenylalanine in superior grains at 21 d was identified as a common significantly different metabolite in multiple comparison groups. KEGG pathway enrichment analysis revealed that, under late spring coldness, differentially accumulated metabolites in superior grains were mainly enriched in energy metabolism-related pathways, such as the tricarboxylic acid (TCA) cycle and glycolysis/gluconeogenesis. In contrast, differentially accumulated metabolites in inferior grains were predominantly enriched in pathways associated with energy compensation and antioxidative responses, including starch and sucrose metabolism, oxidative phosphorylation, and glutathione metabolism. 【Conclusion】Late spring coldness exacerbated the differences in grain filling between superior and inferior grains by disrupting energy metabolism and assimilate accumulation during the grain-filling period. These findings provided the metabolomic evidence for elucidating the damage mechanisms of late spring coldness in wheat and for the breeding of cold-tolerant wheat cultivars.

Key words: wheat, late spring coldness, superior and inferior grains, metabolome, differentially accumulated metabolites