The environment, especially the minimum temperature, affects summer maize grain yield by regulating ear differentiation and grain development

Abstract

Ear differentiation, grain development and their interaction with factors in the growing environment, such as temperature, solar radiation and precipitation, greatly influence grain number and grain weight, and ultimately affect summer maize production. In this study, field experiments involving different sowing dates were conducted over three years to evaluate the effects of temperature factors, average solar radiation and total precipitation on the growth process, ear differentiation, fertilization characteristics, grain filling and yield of summer maize varieties with different growth durations. Four hybrids were evaluated in Huang-Huai-Hai Plain (HHHP), China from 2018 to 2020 with five different sowing dates. The results showed that the grain yield formation of summer maize was strongly impacted by the environment from the silking (R1) to milking (R3) stage. Average minimum temperature (ATmin) was the key environmental factor that determined yield. Reductions in the length of the growing season (r=–0.556, P<0.01) and the total floret number on ear (R2=0.200, P<0.001) were found when ATmin was elevated from the emerging (VE) to R1 stage. Both grain-filling rate (R2=0.520, P<0.001) and the floret abortion rate on ear (R2=0.437, P<0.001) showed quadratic relationships with ATmin from the R1 to physiological maturity (R6) stage, while the number of days after the R1 stage (r=–0.756, P<0.01) was negatively correlated with ATmin. An increase in ATmin was beneficial for the promotion of yield when it did not exceeded a certain level (above 23°C during the R1–R3 stage and 20–21°C during the R1-R6 stage). Enhanced solar radiation and precipitation during R1–R6 increased the grain-filling rate (R2=0.562, P<0.001 and R2=0.229, P<0.05, respectively). Compared with short-season hybrids, full-season hybrids showed much greater suitability for a critical environment. The coordinated regulation of ATmin, ear differentiation and grain development at the pre- and post-silking stages improved maize yield by increasing total floret number and grain-filling rate, and by reducing the floret abortion rate on ear.