Structural and physicochemical effects on the starch quality of the high-quality wheat genotype caused by delayed sowing.

Background: Bread wheat is one of the most important food crops associated with ensuring food security and human nutritional health. The starch quality is an important index of high-quality wheat. It is affected by a complex series of factors; among which, suitable sowing time is a key factor. Aim and methods: To analyze the integrative effects of sowing time on the starch quality of high-quality wheat, in the present study, we selected a high-quality bread wheat cultivar Jinan 17 and investigated the effect of different sowing times on the starch properties and the related genes by analyzing X-ray diffraction patterns, apparent amylose content, thermal properties, pasting properties, in vitro starch digestibility, and qRT-PCR. Meanwhile, we also investigated the agronomic and yield performance that may be associated with the starch properties. Results: Delayed sowing had little effect on starch crystalline morphology, but there was a tendency to reduce the formation of crystals within wheat starch granules: (1) delayed sowing for 15 days altered the thermal properties of starch, including onset, peak and termination temperatures, and enthalpy changes; (2) delayed sowing for 30 days changed the thermal characteristics of starch relatively insignificant; (3) significant differences in pasting characteristics occurred: peak viscosity and hold-through viscosity increased, while final viscosity, breakdown viscosity, and setback viscosity tended to increase and then decrease, suggesting that delayed sowing caused changes in the surface of the starch granules resulting in a decrease in digestibility. Analysis of related genes showed that several key enzymes in starch biosynthesis were significantly affected by delayed sowing, leading to a reduction in apparent straight-chain starch content. In addition to starch properties, thousand-kernel weight also increased under delayed sowing conditions compared with normal sowing. Conclusion: The impact of delayed sowing on starch quality is multifaceted and complex, from the fine structure, and functional properties of the starch to the regulation of key gene expression. Our study holds significant practical value for optimizing wheat planting management and maximizing the potential in both quality and yield.

Effects of the timing of epibrassinolide spraying on yield and nitrogen use efficiency of wide-belt sowing wheat.

In this study, we investigated the effects of epibrassinolide spraying at different growth stages on grain yield and nitrogen use efficiency (NUE), and uptake efficiency (UPE) of wide-belt sowing wheat. The results showed that epibrassinolide spraying enhanced wheat grain yield by increasing the number of kernels per spike and (or) 1000-kernel weight, and improved NUE by promoting aboveground nitrogen accumulation and improving UPE. However, the magnitudes of such enhancements in yield and NUE differed among spraying times. Spraying epibrassinolide at the erecting and filling stages, jointing and filling stages, erecting, jointing, and filling stages, as well as erecting, flowering, and filling stages, produced the greatest increase in the number of kernels per spike and 1000-kernel weight, which led to substantial yield increases (12.8%-14.0%), and the greatest increase in aboveground nitrogen accumulation, which improved UPE by 16.4%-18.8%, and resulted in a significant improvement in NUE. Therefore, spraying epibrassinolide at the erecting and filling stage or jointing and filling stages could achieve high yield and NUE in wide-belt sowing wheat.

Wide belt sowing improves the grain yield of bread wheat by maintaining grain weight at the backdrop of increases in spike number.

Increasing the seeding belt width from 2 to 3 cm (conventional drilling sowing, CD) to 8-10 cm (wide belt sowing, WB) can markedly improve the grain yield of bread wheat. However, there are insufficient data to explain how WB affects dry matter (DM) remobilization, pre- and post-anthesis production, and ultimately grain weight and grain yield. In the present study, four bread wheat cultivars (Jimai44, Taishan27, Gaoyou5766, and Zhouyuan9369) with similar phenology characteristic were selected as experimental materials and two sowing patterns (CD and WB) were applied during the 2018-2019 and 2019-2020 growing seasons, to investigate the effects of sowing pattern on grain yield and its components of bread wheat. The results showed that WB increased the post-anthesis rate of canopy apparent photosynthesis (CAP) in comparison with CD, by 19.73-133.68%, across the two seasons and four bread wheat cultivars. Furthermore, WB significantly increased the activities of superoxide dismutase, peroxidase, and catalase, and decreased the malondialdehyde content of the flag and penultimate leaf, thereby extending the duration of the high-value CAP period by 1.95-2.51 days. The improved rate and duration of CAP in WB led to an increase in post-anthesis DM production of 13.33-23.58%, thus ensuring DM distribution to the grain of each bread wheat cultivar. Consequently, in WB, the grain weight was maintained, the grain yield was increased markedly by 9.65-15.80%, at the backdrop of increases in spike number and in turn grain number per unit area. In summary, WB could be applied widely to obtain a high yield of bread wheat.

[Effects of nitrogen topdressing at different growth stage on chlorophyll fluorescence of winter wheat flag leaves].

With field experiment, this paper studied the effects of nitrogen topdressing at different growth stage on the chlorophyll fluorescence and photosynthetic rate of winter wheat flag leaves, and on the grain yield of the wheat. Compared with that at getting-up and flagging stages, nitrogen topdressing at jointing stage improved the PSII (Fv/Fo) activity, maximum photochemical efficiency (Fv/Fm,), PSII coefficient of photochemical fluorescence quenching (qP), actual quantum yield of PSII electron transformation (phiPS II), and photosynthetic rate of flag leaves, and made the dissipation of non-radiant energy lower at early and middle filling stage, and higher at late filling stage, which made it possible for flag leaves to absorb more light energy for photosynthesis at early and middle filling stage, and reduce the light inhibition extent and senescence at late filling stage. Nitrogen topdressing at jointing stag increased the spikes and grain weight per kernel, resulting in the highest grain yield.