Abstract
Over the last six decades, steady improvement in plant density tolerance (PDT) has been one of the largest contributors to genetic yield gain in field corn. While recent research indicates that PDT in modern sweet corn hybrids could be exploited to improve yield, historical changes in PDT in sweet corn are unknown. The objectives of this study were to: (a) quantify the extent to which PDT has changed since introduction of hybrid sweet corn and (b) determine the extent to which changes over time in PDT are associated with plant morpho-physiological and ear traits. An era panel was assembled by recreating 15 sugary1 sweet corn hybrids that were widely used at one time in the United States, representing hybrids since the 1930s. Era hybrids were evaluated in field experiments in a randomized complete block design with a split-plot arrangement of treatments, including hybrid as the main factor and density as the split-plot factor. Plant density treatments included “Low” plant density (9,900 plants/ha) free of crowding stress or “High” plant density (79,000 plants/ha) with crowding stress. On average, per-area marketable ear mass (Mt/ha) increased at a rate of 0.8 Mt/ha/decade at High densities, whereas per-plant yield (i.e., kg/plant) remained unchanged over time regardless of the density level. Crate yield, a fresh market metric, improved for modern hybrids. However, processing sweet corn yield metrics like fresh kernel mass and recovery (amount of kernel mass contributing to the fresh ear mass) showed modest or no improvement over time, respectively. Modern sweet corn hybrids tend to have fewer tillers and lower fresh shoot biomass, potentially allowing the use of higher plant density; however, plant architecture alone does not accurately predict PDT of individual hybrids.
Highlights
Grain yield gains in field corn over the past six decades have attributed to genetic gains and improved management practices (Tollenaar et al, 1994; Duvick, 2001)
Using an era panel of sugary1 sweet corn hybrids, the objectives of this study were to: (a) quantify the extent to which plant density tolerance (PDT) has changed since introduction of hybrid sweet corn and (b) determine the extent to which changes over time in PDT are associated with plant morpho-physiological and ear traits
Plants in the High plant density treatment had fewer tillers per plant, lower fresh shoot biomass, but greater Leaf area index (LAI) compared to plants in the Low plant density treatment
Summary
Grain yield gains in field corn over the past six decades have attributed to genetic gains and improved management practices (Tollenaar et al, 1994; Duvick, 2001). Genetic gains are associated with increased plant density tolerance (PDT, known as crowding stress tolerance) in modern field corn hybrids (Tollenaar and Wu, 1999), as evidenced by increases in plant density at a rate of ∼700 plants/ha/year from 1987 to 2016 (Assefa et al, 2018). Previous research has shown variability for PDT among widely used sweet corn hybrids (Williams, 2015). Recent research has shown that both vegetable processors and sweet corn growers benefit from using higher (i.e., economic optimum) plant densities for PDT hybrids without changing other management practices (Dhaliwal and Williams, 2019). While there is evidence that improved PDT in sweet corn could be exploited in ways to increase profitability for the sweet corn industry, the extent to which PDT has changed since introduction of hybrid sweet corn remains an open empirical question
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