Author
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McMaster, Gregory |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 3/2/2016 Publication Date: N/A Citation: N/A Interpretive Summary: Crop parameters, such as the timing of developmental events, are critical for accurate simulation results in crop simulation models, yet uncertainty often exists in determining these parameters. Many factors contribute to the uncertainty including: a) sources of variation within a plant (i.e., within different shoots of the plant), b) spatial variation in the trait within small areas of presumably “uniform” conditions for many reasons (e.g., seed size, vigor, and planting depth; differences in microenvironment), and c) the well-recognized reality of the Genotype by Environment by Management interactions. Diverse approaches have been used to deal with uncertainty in parameter estimation One common approach is to estimate the parameter from standard statistics (e.g., mean, median, variance, range), and occasionally extended to consider the distribution, with a static value used for the simulation. Experience has shown a couple of complications. The first is the existence of anomalies, or outliers, which cannot be explained by experimental error that can significantly impact the statistics or distributions. The second is that the both the genotype and environment (and interaction) can influence the statistics and distributions. While plasticity has many aspects, phenotypic plasticity describes the range of phenotypes produced by a single genotype under varying environmental conditions. Studies have examined the heading date and yield phenotypic plasticity of 299 winter wheat (Triticum aestivum L.) genotypes, and considered allelic variants known to effect flowering time in differing environments. On-going efforts are examining how the environment influences phenotypic plasticity, and whether developmental parameters can be better estimated by groupings based on maturity classes, environmental classification, or other criteria. The objectives of this work are to present analyses of winter wheat phenological data for both individual genotypes and collections of genotypes grown in different environments, and provide thoughts on the implications of these analyses for crop modeling. Technical Abstract: Crop parameters, such as the timing of developmental events, are critical for accurate simulation results in crop simulation models, yet uncertainty often exists in determining the parameters. Factors contributing to the uncertainty include: a) sources of variation within a plant (i.e., within different shoots of the plant), b) spatial variation in the trait within small areas of presumably “uniform” conditions for many reasons (e.g., seed size, vigor, and planting depth; differences in microenvironment), and c) the well-recognized reality of GxExM interactions. (Note here on “management”: in most instances “M” can be viewed as altering E, and therefore won’t be mentioned again here.) The importance of these sources of variation in estimating parameters is largely dependent on the objectives of the modeling project. Diverse approaches have been used to deal with uncertainty in parameter estimation One common approach is to estimate the parameter from standard statistics (e.g., mean, median, variance, range), and occasionally extended to consider the distribution, with a static value used for the simulation. Experience has shown a couple of complications. The first is the existence of anomalies, or outliers, which cannot be explained by experimental error that can significantly impact the statistics or distributions. The second is that the both the genotype and environment (and interaction) can influence the statistics and distributions. While plasticity has many aspects, phenotypic plasticity describes the range of phenotypes produced by a single genotype under varying environmental conditions Bradshaw (1965). Studies have examined the heading date and yield phenotypic plasticity of 299 winter wheat (Triticum aestivum L.) genotypes (Grogan et al.,2016A?), and considered allelic variants known to effect flowering time in differing environments (Grogan et al., 2016B). On-going efforts are examining how environment influences phenotypic plasticity, and whether developmental parameters can be better estimated by groupings based on maturity classes, environmental classification, or other criteria. The objectives of the presentation will be to present analyses of winter wheat phenological data for both individual genotypes and collections of genotypes grown in different environments, and provide thoughts on the implications of these analyses for crop modeling. |
