Critical periods for the expression of vegetative-reproductive plasticity in maize.

ESPELET, F.; ROTILI, D.H.; MADDONNI, G. A.

Rosario

Congreso; XXXIV Reunion de la Sociedad Argentina de Fisiología Vegetal; 2023

SAFV

In maize, low plant densities can trigger vegetative and reproductive plasticity mechanisms (i.e., tillering and prolificacy) with positive impacts on grain yield. We evaluated the effect of growth restrictions during the crop cycle to define the critical periods for the expression of plasticity mechanisms. Field studies were carried out in the experimental field of FAUBA during the 2021-2022 and 2022-2023 seasons. Four commercial hybrids with contrasting plasticity mechanisms (phenotypes) were evaluated (T: tillering; P: prolific; PT: prolific+tillering; F: non-tillering non-prolific or flex). Each phenotype was planted at 3 plants per square meter and growth restrictions were imposed with shading during some stages of the crop cycle (S1: V3-V7; S2: V7-V13; S3: V13-R1 and S4: R1-R2), and an unshaded control. In both years, S1 canceled tiller production in all phenotypes except for T in the second year, where tillering was reduced by 40% compared to the control. S2 consistently reduced tiller fertility. Consequently, the number of ears per plant differed among phenotypes (higher in PT due to the contribution of sub-apical and tiller ears) and shading periods. In the controls, the plastic phenotypes showed a higher number of ears and grains per plant than F. In S1 and S2, the number of grains per plant for the prolific phenotypes was higher than for T and F due to shading effects on tiller ears. Kernel weight differed among phenotypes and shading periods, with the highest weights recorded in T under the control, S1 and S2 and the lowest in the prolific phenotypes under S2. When compared with the control, grain yield decreased depending to the shading time and phenotype: S1: -45% and -30% for T and the rest; S2: -40% and -30% for T or PT and the rest; S3: -35% and -55% for P and the rest and S4: -45% for P, -55% for PT or F and -65% for T. In conclusion, there are different critical periods for grain yield depending on the phenotype´s plasticity.