Molecular Plant Breeding 2025, Vol.16, No.4, 211-220 http://genbreedpublisher.com/index.php/mpb 212 the problem of asynchronous male and female flowers, affecting the pollination effect and resulting in a decrease in seed setting rate (Borrás and Vitantonio-Mazzini, 2018). Studies have found that even a difference of 2 to 4 days in the time of silk spinning can significantly reduce the number of kernels produced, especially when planted densely or under environmental stress, the problem becomes more severe. If synchronous pollination can be achieved, it will increase the number of kernels and the seed setting rate, and to a certain extent, make up for the impact of delayed silk production. In addition, the sowing period also affects the temperature and light conditions in the field, thereby influencing the flowering time and development rate, as well as the duration and efficiency of kernel filling (Guo et al., 2021). 2.2 Vegetative-reproductive balance under different plant densities The change in planting density also has a significant impact on the growth of glutinous maize. When the density is high, the plants compete for nutrients more fiercely, the biomass of individual plants decreases, the female spikelets receive less nutrients, the silk production is slower, and it is more likely to cause inconsistent flowering times (Borrás and Vitantonio-Mazzini, 2018). Under low-density conditions, the secondary female panicles can also bear fruit normally, and the number of kernels will increase. However, in high-density planting, basically only the main panicle can develop normally. Whether simultaneous pollination can be achieved has a significant impact on the number of kernels in the main panicle, with the maximum increase being 8% to 31%. The ideal glutinous maize variety should be able to maintain rapid growth of the female ears and timely silk production even when resources are limited, so as to produce as many kernels as possible. 2.3 Environmental sensitivity and genotype-dependent variation Glutinous maize is highly sensitive to changes in temperature, light and moisture. Different varieties show different behaviors in terms of flowering period synchronization, female panicle growth and kernel development (Guo et al., 2021). Some varieties can maintain a relatively fast growth rate of spikelets and silk production even under adverse conditions, reduce delayed flowering and increase seed setting rate (Borrás and Vitantono-Mazzini, 2018). In addition, different genotypes also respond differently to high temperatures and drought. Heat-tolerant varieties can maintain a high supply of photosynthetic products and kernel filling rate at high temperatures, thereby reducing kernel failure (Guo et al., 2021; Niu et al., 2021). Therefore, in actual production, the arrangement of sowing time and density should be combined with the characteristics of different varieties to adjust the synchronization of flowering periods and ensure that the kernels can develop normally. 3 Pollination Synchronization: Mechanisms and Disruptions 3.1 Tassel and silk emergence coordination Whether maize kernels can develop normally largely depends on whether the male ear (producing pollen) and the female ear (producing filaments) develop simultaneously. When planted too densely, the filaments tend to emerge later, but most of the filaments will still be exposed within five days after they are released. Pollination synchrony refers to the fact that these filaments receive pollen simultaneously within a short period of time, which is a key factor in enhancing seed setting rate and kernel count. Research has found that simultaneous pollination can significantly increase the number of kernels in both the main and secondary panicles. Especially when planted at low density, the number of kernels in the secondary panicles can increase by 39% to 535%. Even under high-density conditions, the kernel count of the main panicle can be increased by 8% to 31% (Westgate et al., 2022). In addition, synchronous pollination can also make the kernels of the upper and lower parts of the ear develop more uniformly, promoting the kernels of the entire ear to grow more evenly. 3.2 Asynchronous flowering: causes and agronomic consequences Asynchronous pollen and filaments, that is, asynchronous flowering, are usually caused by environmental stress such as planting too densely, high temperature and drought, or the genetic characteristics of the variety itself. If the filaments emerge too late, or if some are too early and some too late, there may be a situation where all the pollen has fallen but the filaments have not yet come out. These filaments that are not pollinated in time cannot develop kernels and eventually affect the yield (Figure 1) (Shen et al., 2019; Shen et al., 2020). Research shows that if the pollination interval is 2 to 4 days, the number of kernels may drop sharply, by up to half. If
RkJQdWJsaXNoZXIy MjQ4ODYzNA==