Genetic gains in grain yield and related physiological attributes in Argentine maize hybrids.

LUQUE, S.F.; CIRILO, A.G.; OTEGUI, M.E.

FIELD CROPS RESEARCH

Elsevier

Lugar: Amsterdam, The Netherlands; Año: 2006 vol. 95 p. 283 - 397

0378-4290

Genetic gains in grain yield and related phenotypic attributes have been extensively documented in maize (Zea mays L.), but the effect of breeding on the physiological determinants of grain yield is yet poorly understood.We determined genetic gains in grain yield and related physiological traits for seven maize hybrids developed for the central region of Argentina between 1965 and 1997. Gains were expressed as a function of the year of release (YOR). Hybrids were cropped in the field at five stand densities (from almost isolated plants to supra-optimal levels) during two contrasting growing seasons (E1 and E2). Water and nutrient stress were prevented and pests controlled. Genetic gains in grain yield (
13.2 g m2 YOR1) were mainly associated with improved kernel number, enhanced postsilking biomass production, and enhanced biomass allocation to reproductive sinks, but computed gains were affected by the environment. Differences among hybrids arose at the start of the critical period, and were evident as improved mean radiation use efficiency (
0.026 g MJ1 YOR1), enhanced plant growth rate at near optimum stand density (
0.04 g pl1 YOR1), and improved biomass partitioning to the ear around silking (0.0034 YOR1, only for E1). Improved biomass production after silking was related to an increased light interception (
4.7 MJ m2 YOR1), and allowed for an almost constant source–sink ratio during grain filling. This trend determined no trade-off between kernel number and kernel weight. In contrast to previous studies, genetic gains were detected for potential productivity (e.g., maximum grain yield) on a per plant basis (i.e., under no resource competition), a promising aspect for the improvement of crop grain yield potential.Zea mays L.), but the effect of breeding on the physiological determinants of grain yield is yet poorly understood.We determined genetic gains in grain yield and related physiological traits for seven maize hybrids developed for the central region of Argentina between 1965 and 1997. Gains were expressed as a function of the year of release (YOR). Hybrids were cropped in the field at five stand densities (from almost isolated plants to supra-optimal levels) during two contrasting growing seasons (E1 and E2). Water and nutrient stress were prevented and pests controlled. Genetic gains in grain yield (
13.2 g m2 YOR1) were mainly associated with improved kernel number, enhanced postsilking biomass production, and enhanced biomass allocation to reproductive sinks, but computed gains were affected by the environment. Differences among hybrids arose at the start of the critical period, and were evident as improved mean radiation use efficiency (
0.026 g MJ1 YOR1), enhanced plant growth rate at near optimum stand density (
0.04 g pl1 YOR1), and improved biomass partitioning to the ear around silking (0.0034 YOR1, only for E1). Improved biomass production after silking was related to an increased light interception (
4.7 MJ m2 YOR1), and allowed for an almost constant source–sink ratio during grain filling. This trend determined no trade-off between kernel number and kernel weight. In contrast to previous studies, genetic gains were detected for potential productivity (e.g., maximum grain yield) on a per plant basis (i.e., under no resource competition), a promising aspect for the improvement of crop grain yield potential. Keywords: Maize; Zea mays L.; Grain yield; Physiological attributes; Genetic gainMaize; Zea mays L.; Grain yield; Physiological attributes; Genetic gain