Adjusting the sowing date of fresh maize to promote grain filling, key starch synthesis enzymes, and yield

Clarifying the effects of meteorological factors on the growth and development of fresh maize after delayed sowing is important for selecting appropriate sowing dates and improving yield. Six sowing dates (B1 (March 10); B2 (March 20); B3 (March 30); B4 (April 9); B5 (April 19), and B6 (April 29)) and three fresh maize cultivars (A1 (Wan Nuo 2000); A2 (Nongke Nuo 336), and A3 (Caitian Nuo 6)) were chosen for experiments conducted between 2021 and 2022 in Guiyang, Qingzhen City, China. The results showed that the whole growth period and sowing-silking period were significantly reduced with delayed sowing, while the grain-filling period was relatively stable. Delayed sowing was beneficial in increasing the number of endosperm cells and the weight of the hundred kernels. The graining filling rate and the activities of four key starch synthesis enzymes (sucrose synthase, ADP-glucose pyrophosphorylase, starch branching enzyme, and starch debranching enzyme) were significantly influenced by light, temperature, and precipitation, and they mainly affected the hundred kernel weight. The yield tended to increase with delayed sowing, and the correlation analysis between precipitation and yield at different sowing periods showed a significant effect of precipitation on yield. Delaying the sowing to mid-early April was more favourable for grain filling, enhanced key enzyme activity, and increased the kernel weight and yield. These results highlight the importance of choosing excellent cultivars and matching them with the most suitable sowing date to fully exploit climatic resources and achieve high-yield and high-efficiency cultivation of fresh maize.