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We conducted a 3-year (2017-2020) field experiment in the wheat base of Jinzhong Agricultural Hi-tech Industries Demonstration Zone, aiming to determine the measures of nitrogen topdressing and the regulatory effect of cycocel in spring to increase wheat yield. Four nitrogen topdressing dates were set up under the condition of cycocel spraying and control (CK) during the rising period: 10 days (D10), 20 days (D20), 30 days (D30), and 40 days ( D40) after regreening stage, to analyze the impact of different N topdressing dates on winter wheat yield and the regulation effect of cycocel on stem characteristics, lignin content and related synthetase activities. The results showed that compared to other nitrogen topdressing dates, D30 increased spike number by 1.4%-5.2%, grain number per spike by 0.4%-12.0%, 1000-grain weight by 1.7%-9.4% and yield 8.8%-22.1% respectively. Compared to D10 and D20, D30 significantly improved the activities of phenylalanine ammonia-lyase ( PAL) at 0-21 days and 35-42 days after the formation of the second section and increased that of tyrosine ammonia-lyase (TAL) at 0-42 days after the formation of the second section, and increased the lignin content of stem, the internode quality, and the breaking resistance of stem, reduced plant height, and thereby improved the lodging resistance. However, D40 increased grain number per spike by 4.5%-10.1% and yield 0.04%-11.3%, but reduced the activities of PAL and TAL at 0-42 days after the formation of the second internode, reduced the lignin content, weakened the stem strength, and increased the risk of lodging. After spraying cycocel, plant height decreased significantly, the activities of PAL and TAL enhanced, the lignin content in internodes increased, the stem strength advanced, and reached a significant level under D30. Under the condition of nitrogen topdressing combined with cycocel spraying in spring, PAL and TAL activities were significantly positively correlated with lignin content. Lignin content was significantly positively correlated with stem breaking resistance. Stem breaking resistance was significantly positively correlated with lodging resistance index. Yield and its components were significantly positively correlated with internode diameter, weight and breaking resistance, and significantly negatively correlated with plant height and internode length. Overall, nitrogen topdressing combined with spraying cycocel 30 days after regreening could promote the synthesis and accumulation of lignin, and improve stem plumpness, plant lodging resistance and yield [ABSTRACT FROM AUTHOR]

Summary: Regulation of grain size is a crucial strategy for improving the crop yield and is also a fundamental aspect of developmental biology. However, the underlying molecular mechanisms governing grain development in wheat remain largely unknown. In this study, we identified a wheat atypical basic helix–loop–helix (bHLH) transcription factor, TabHLH489, which is tightly associated with grain length through genome‐wide association study and map‐based cloning. Knockout of TabHLH489 and its homologous genes resulted in increased grain length and weight, whereas the overexpression led to decreased grain length and weight. TaSnRK1α1, the α‐catalytic subunit of plant energy sensor SnRK1, interacted with and phosphorylated TabHLH489 to induce its degradation, thereby promoting wheat grain development. Sugar treatment induced TaSnRK1α1 protein accumulation while reducing TabHLH489 protein levels. Moreover, brassinosteroid (BR) promotes grain development by decreasing TabHLH489 expression through the transcription factor BRASSINAZOLE RESISTANT1 (BZR1). Importantly, natural variations in the promoter region of TabHLH489 affect the TaBZR1 binding ability, thereby influencing TabHLH489 expression. Taken together, our findings reveal that the TaSnRK1α1‐TabHLH489 regulatory module integrates BR and sugar signalling to regulate grain length, presenting potential targets for enhancing grain size in wheat. [ABSTRACT FROM AUTHOR]

BACKGROUND: High‐molecular‐weight glutenin subunits (HMW‐GSs) have important effects on bread‐making quality. Allelic variations of HMW‐GS in bread wheat varieties contribute in different ways to dough properties and bread volume. However, no systematic analysis has been done on the effects of allelic variation on bread‐crumb structure, an important parameter when evaluating bread‐making quality. In this study, seven Glu‐1 deletion lines and one intact line harboring different encoding loci and derived from a cross between two spring wheat cultivars were used to investigate the contribution of a single Glu‐1 locus, or combination of Glu‐1 loci, to the crumb structure. RESULTS: Deletion of HMW‐GS locus combinations resulted in a decline in slice size, brightness, and fineness of the bread crumb. A desirable crumb structure correlated well with preferred subunit combinations: high levels of GMPs, superior dough properties, and loaf volume. The effects of the HMW‐GS combinations were ranked as Dx5 + Dy10 > Bx17 + By18 > Ax1 + Null. The Ax1 + Null allele affected the crumb structure by interacting with the Bx17 + By18 or Dx5 + Dy10. CONCLUSION: High‐molecular‐weight glutenin subunits had significant effects on the loaf volume and crumb structure; varying effects from different subunit combinations were observed. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]