Physiological Basis of Genetic Improvement of Maize Hybrids in Ontario from 1959 to 1988
Genetic improvement in grain yield of North American maize (Zea mays L.) hybrids during the past three to five decades can be attributed to increased phytomass production. The objective of this study was to identify the physiological traits that have contributed to the improvement in dry matter production of maize hybrids in Ontario. Experiments were conducted during 1987 and 1988 at two locations in Ontario with nine maize hybrids representing three decades of yield improvement in Ontario. Hybrids were grown at 2, 4, 8, and 13 plants m‒2 and phenological development was studied from planting to maturity. Phenological development differed very little between old and new hybrids. Rates of leaf appearance, days from planting to silking and from silking lto maturity, and kernel moisture loss during the grain-filling period did not show a consistent trend with year of release of the hybrid. The interval from tassel to silk emergence, however, tended to be shorter for new than for old hybrids. Differences in rate of dry matter accumulation among hybrids were largest at late stages of development (3 wk post silking to maturity). Effects of plant density and hybrid on leaf senescence and loss of stover weight from 3 wk post silking to maturity were additive, with older hybrids and higher plant densities showing greater losses of stover weight and higher rates of leaf senescence. The improvement in dry matter accumulation from old to new hybrids may be attributable, in part, to increased tolerance of high plant density.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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