Temperatura durante el llenado efectivo del grano y momento de cosecha en maíz para semilla: efectos sobre la dinámica de emergencia en respuesta a la temperatura.

PADILLA, J.M.; OTEGUI, M.E.

Rosario, Santa Fe, Argentina

Congreso; VIII Congreso Nacional de Maíz.; 2005

A.I.A.N.B.A.

High quality seed is the major target of all maize (Zea mays L.) seed producers. The aim of this work was to investigate the effect of harvest time and temperature regime during the effective grain-filling period on seedling emergence dynamics (i.e. % seedling emergence evolution) within the population of seeds in response to temperature. A single-cross hybrid produced obtained from two sister lines was exposed to contrasting temperatures during effective grain filling. Treatments were a factorial combination of temperature (control and increased temperature) and three harvest dates (50%, 25%, and 0% milk line). The last harvest date also included two seed categories, small and medium flat. The population-based model of thermal time was used for the analysis. The base temperature (Tb), thermal time requirements between sowing and 50% of seedling emergence (TT50, in degree days (¨¬Cd)), and the standard deviation of the thermal time requirements within the population (¥òTT, ¨¬Cd) were determined for each treatment. Increased temperature during effective grain filling (27 ¨¬C vs. 19.1¨¬C) caused a reduction in seed dry weigh (from 220.8 to 188.1 mg seed-1) due too a reduced grain-filling rate (mg ¨¬Cd-1), without differences in thermal time requirements for seed filling duration. Temperature along seed filling shifted the seed size distribution from mainly medium in the control (62.7% vs. 35.5%) to mainly small in the increased temperature treatment (55.1% vs. 39.6%). The optimum harvest date was 25% milk line in both temperature treatments, as determined by a reduced TT50 (from 12.7 to 7.3%). Finally, high temperature during effective grain filling increased the ¥òTT by 17.9%. These findings are of great value for maize improvement aimed to anticipate seedling emergence date and to enhance seedling emergence synchrony.