Exploring Strategies for Yield Stability in Maize.

Kernel number (KN) at harvest is the main component associated with maize grain yield (GY). KN is a function of the physiological conditions of the plant during the period bracketing silking. Breeding efforts resulted in a large increase in GY associated with improvements in KN. In addition, there is great variability in GY stability for modern hybrids in multi-environment experiments. The objective of this study was to identify moments of higher susceptibility to stresses of different intensities within the critical period for KN determination for hybrids exhibiting contrasting yield stability. An experiment was carried out in Balcarce, Argentina during the 2011/12 growing season. Two hybrids, DK747MGRR2 (lower GY stability) and DK670MGRR2 (higher GY stability) were sown and exposed to short shading stresses (5 days) of two intensities (65 and 85 percent of incident radiation reduction) at three moments (R1, R2, R3), including a control treatment. GY and its components (KN and weight per kernel (KW)) were estimated. KN was most reduced by the 85% shading across moments and hybrids. KN was reduced by approximately 30% and 17% when the stresses occurred at R1 and R2 respectively, for both hybrids. Conversely, with stresses at R3 reductions in KN were greater for DK747MGRR2 (30%) than for DK670MGRR2 (10%). Moment of stress, intensity and hybrid factors affected GY, with no evident interactions. Reductions in GY were associated with reductions in KN, but in some cases attenuated by variations in KW. This information contributes to understand differences in hybrids stability, and indicates that hybrids with low stability would present an extended period of KN susceptibility to stress after flowering.