Abstract
A study was conducted at the Lajas Substation of the University of Puerto Rico to determine the agronomic performance of four maize genotypes. The objective of this research was to determine the genetic coefficients of three maize cultivars, 'Mayorbela' (M), 'Diente de Caballo' (DC), 'Chulo' (Ch), and a transgenic hybrid from Pioneer Hi-Bred International, Inc. (Pioneer hybrid) to be utilized by the CERES-Maize model to predict performance under tropical conditions. The experiments determined genetic coefficients for maize growth and development Including duration of the juvenile phase of the plant (P1); duration of biomass accumulation In the grain (P5); potential kernel number per cob (G2), and kernel linear growth rate (G3). Crop growth was expressed using the concept of thermal units (Td). Also determined were leaf area Index and total biomass accumulation. Field experiments were planted February 2004 and March 2005. Estimates of PI from the experiment planted In 2004 were 219 Td for Pioneer hybrid, 253 Td for M, 252 Td for DC, and 362 Td for Ch. In 2004 the P5 values were 715, 757, 691, and 413 Td for Pioneer hybrid, M, DC, and Ch, respectively. Nevertheless, the Pioneer hybrid produced the highest G2 value, 616 kernels per cob. There were no significant differences In G2 among genotypes, which varied from 529 to 616 kernels per cob. The G3 values were 7.7, 6.7, 5.7 and 3.7 mg/day for Pioneer hybrid, M, DC and Ch, respectively. There were no significant differences among genotypes for leaf area Index and biomass accumulation. Estimates of P1 from the 2005 experiment were higher than those obtained on 2004. The P1 values from the experiment planted In 2005 were 352 Td for Pioneer hybrid, 422 Td, 479 Td, and 405 Td for M, DC and Ch, respectively. The P5 values were 756 Td for Pioneer hybrid; 755 Td, M; 795 Td, DC; and 777 Td, Ch. The estimated values for G3 were 8.5, 6.9, 9.6, and 7.1 mg/day for Pioneer hybrid, M, DC, and Ch, respectively. No significant differences were found among genotypes for biomass accumulation. In 2004 'Mayorbela' produced the greatest seed yield (4,148 kg/ha) followed closely by Pioneer with no significant difference, whereas in 2005 Pioneer hybrid surpassed 'Mayorbela' by 14%.