The ideal harvest time for seeds of hybrid maize (Zea mays L.) XY335 and ZD958 produced in multiple environments

To identify the ideal harvest time (IHT) for the seed production of XY335 and ZD958, six seed-related traits were evaluated in seeds harvested at 11 harvest stages in 8 environments. Standard germination (SG), accelerated aging germination (AAG) and cold test germination (CTG) were vigor traits; hundred-seed weight (HSW) and seed moisture content (SMC) were physiological traits; and ≥10 °C accumulated temperature from pollination to harvest (AT10(ph)) was an ecological trait. All the traits were significantly affected by harvest stage. The responses of SG, AAG, CTG and HSW to postponing harvest stage fit quadratic models, while SMC and AT10(ph) fit linear models. The IHT (indicated by the last date to reach maximum SG, AAG and CTG) were 57.97 DAP and 56.80 DAP for XY335 and ZD958, respectively. SMC and AT10(ph) at IHT were 33.15% and 1234 °C for XY335, and 34.98% and 1226 °C for ZD958, respectively. The period to reach the maximum HSW was 5 days later than the IHT. Compared to HSW and SMC, AT10(ph) had a closer relationship to the seed vigor traits. Together with the fact that AT10(ph) was less affected by environment, these results suggested that AT10(ph) may be a novel indicator for determining the IHT.