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. 2023 Jan;136(1):21.
doi: 10.1007/s00122-023-04266-5. Epub 2023 Jan 23.

Effects of systematic data reduction on trend estimation from German registration trials

Jens Hartung  1 , Friedrich Laidig  2 , Hans-Peter Piepho  2
Affiliations

Effects of systematic data reduction on trend estimation from German registration trials

Jens Hartung et al. Theor Appl Genet. 2023 Jan.

Erratum in

  • Correction to volume 136 issue 1.
    [No authors listed] [No authors listed] Theor Appl Genet. 2023 Mar 23;136(4):84. doi: 10.1007/s00122-023-04323-z. Theor Appl Genet. 2023. PMID: 36952001 Free PMC article. No abstract available.

Abstract

VCU trials can provide unbiased estimates of post-breeding trends given that all data is used. Dropping data of genotypes tested for up to two years may result in biased post-breeding trend estimates. Increasing yield trends are seen on-farm in Germany. The increase is based on genetic trend in registered genotypes and changes in agronomic practices and climate. To estimate both genetic and non-genetic trends, historical wheat data from variety trials evaluating a varieties' value for cultivation und use (VCU) were analyzed. VCU datasets include information on varieties as well as on genotypes that were submitted by breeders and tested in trials but could not make it to registration. Therefore, the population of registered varieties (post-registration population) is a subset of the population of genotypes tested in VCU trials (post-breeding population). To assess post-registration genetic trend, historical VCU trial datasets are often reduced, e.g. to registered varieties only. This kind of drop-out mechanism is statistically informative which affects variance component estimates and which can affect trend estimates. To investigate the effect of this informative drop-out on trend estimates, a simulation study was conducted mimicking the structure of German winter wheat VCU trials. Zero post-breeding trends were simulated. Results showed unbiased estimates of post-breeding trends when using all data. When restricting data to genotypes tested for at least three years, a positive genetic trend of 0.11 dt ha-1 year-1 and a negative non-genetic trend (- 0.11 dt ha-1 year-1) were observed. Bias increased with increasing genotype-by-year variance and disappeared with random selection. We simulated single-trait selection, whereas decisions in VCU trials consider multiple traits, so selection intensity per trait is considerably lower. Hence, our results provide an upper bound for the bias expected in practice.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Occurrence of check varieties across years. Check varieties are numbered and shown on the y-axis. Each plus ( +) for a given year of testing means that the check variety is included as candidate genotype within the dataset, a circle (o) indicates that the check variety is included as check within the dataset. Most check varieties first occurred as candidates for three years. One or two years after registration, the registered variety was used as a check
See this image and copyright information in PMC

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