Kernel filling and desiccation in temperate maize: Breeding and environmental effects

Abstract

Sowing date (SD) modifies the environmental conditions during the kernel-filling period as well as during kernel dry down after physiological maturity (PM), particularly for late-sown maize (Zea mays L.) crops that currently cover 50 % of the maize area in Argentina. The main goal of this work was to evaluate breeding effects on kernel filling and kernel desiccation traits in a set of five commercial maize hybrids released by a single breeding program between 1980 and 2016 when grown under contrasting environments in the temperate Central Pampas region. The evolution of kernel weight (KW) and kernel moisture (KM) were assessed. Maximum KW (KWMAX), maximum kernel water content (KWCMAX), kernel filling rate (KFR), kernel filling duration (KFD) and KM at silking+20 days (KMR1+20) and PM (KMPM) were computed together with husks number. Pre-PM kernel desiccation was described using an exponential decay model with k1 as the proportionality drying coefficient. For the post-PM period, kernel desiccation was modelled assuming that the change in KM in a given period is proportional to the difference between the kernel and the equilibrium moisture contents, where k2 was the corresponding proportionality drying coefficient. For KWMAX, a genetic progress of 0.26 % year −1 (p < 0.05) was estimated from 1993 to 2016. This trend was explained by the increase registered in KFD (0.32 % year−1, p < 0.01), which was partially compensated by a reduction in KFR (−0.08 % year−1, p < 0.05). No genetic progress was detected for husks number, KWCMAX, KMR1+20, KMPM, k1 and k2, but introduction of dent germplasm produced an increase in KWCMAX, KMR1+20 and KMPM and a decrease in k2. KFR and KFD as well as kernel desiccation dynamics were strongly affected by SDs. Breeding effects that extended KFD, together with the broad adoption of late sowings, promote a reduction in k2, which must be considered for the correct assessment of trade-offs between drying costs and kernel quality penalization by pests and diseases.