Skip to main content Accessibility help
×
Home

Prediction of variety distinctness decisions under yearly heterogeneity

  • A. M. I. ROBERTS (a1), I. M. NEVISON (a1) and T. CHRISTIE (a2)

Summary

To gain protection under the International Convention for the Protection of New Varieties of Plant, new plant varieties must be distinguishable from existing varieties in at least one important characteristic. Assessment of quantitative characteristics often uses a procedure based on analysis of variance of variety-by-year means for 2 years of trials. In the current paper, a new method is described that can identify those reference varieties that are so different from a candidate that there would be no reason to compare them in the subsequent year, resulting in potential cost savings. It is more objective and transparent than existing practice for quantitative characteristics based on expert opinion. The method calculates thresholds for quantitative characteristics. The thresholds are defined so that if in the first year the difference between two varieties in a characteristic is larger than the characteristic's threshold then it is highly likely that the varieties would be distinct after 2 years. Thresholds were derived based on statistical predictions of the full decision after 2 years using the first year results combined with historical data. It is shown that these thresholds are sensitive to yearly heterogeneity in the variety-by-year variation. The method accommodates this heterogeneity by modelling yearly residual variances with the inverse gamma distribution. This extension meant that exact analytical formulae were not available so an approximation was suggested. Using simulation it was found that the approximation was reasonable; for thresholds corresponding to a high probability of distinctness, the approximate thresholds were a little higher than required. The method was evaluated on a 19-year data set for field pea, comparing decisions based on first year thresholds with those based on the full 2 years. It was found that with the probability of distinctness set at 0·99, the calculated thresholds were generally lower than the existing expert-set thresholds but had acceptable levels of false positives and false negatives.

Copyright

Corresponding author

* To whom all correspondence should be addressed. Email: a.roberts@bioss.ac.uk

References

Hide All
Anon (2002). General Introduction to the Examination of Distinctness, Uniformity and Stability and Development of Harmonized Descriptions of New varieties of Plants. UPOV document TG/3/1. Geneva, Switzerland: UPOV.
Anon (2013). Guidance on the Use of Biochemical and Molecular Markers in the Examination of Distinctness, Uniformity and Stability (DUS). UPOV document TGP/15/1 adopted by the Council at its forty-seventh ordinary session on October 24, 2013. Geneva, Switzerland: UPOV.
Anon (2014 a). Trial Design and Techniques used in the Examination of Distinctness, Uniformity and Stability. UPOV document TGP/8/2 adopted by the Council at its forty-eighth ordinary session on October 16, 2014. Geneva, Switzerland: UPOV.
Anon (2014 b). Pea: Guidelines for the Conduct of Tests for Distinctness, Uniformity and Stability. UPOV document TG/7/10 Rev. Geneva, Switzerland: UPOV.
Arens, P., Mansilla, C., Deinum, D., Cavellini, L., Moretti, A., Rolland, S., van der Schoot, H., Calvache, D., Ponz, F., Collonnier, C., Mathis, R., Smilde, D., Caranta, C. & Vosman, B. (2010). Development and evaluation of robust molecular markers linked to disease resistance in tomato for distinctness, uniformity and stability testing. Theoretical and Applied Genetics 120, 655664.
Bernardo, J. M. & Smith, A. F. M. (2000). Bayesian Theory. Chichester, UK: Wiley.
Camlin, M. S., Watson, S., Waters, B. G. & Weatherup, S. T. C. (2001). The potential for management of reference collections in herbage variety registration trials using a cyclic planting system for reference varieties. Plant Varieties and Seeds 14, 114.
Choi, S. C. & Wette, R. (1969). Maximum likelihood estimation of the parameters of the gamma distribution and their bias. Technometrics 11, 683690.
Ibanez, J., Dolores Velez, M., Teresa de Andres, M. & Borrego, J. (2009). Molecular markers for establishing distinctness in vegetatively propagated crops: a case study in grapevine. Theoretical and Applied Genetics 119, 12131222.
Jones, H., Norris, C., Smith, D., Cockram, J., Lee, D., O'Sullivan, D. M. & Mackay, I. (2013). Evaluation of the use of high-density SNP genotyping to implement UPOV Model 2 for DUS testing in barley. Theoretical and Applied Genetics 126, 901911.
Minka, T. P. (2002). Estimating a Gamma Distribution. Technical Report. Cambridge, UK: Microsoft Research. Available from http://research.microsoft.com/en-us/um/people/minka/papers/minka-gamma.pdf (verified 20 November 2015).
Nevison, I. M. & Roberts, A. M. I. (2011). Predicting distinctness decisions after one growing cycle. Biuletyn Oceny Odmian 33, 3547.
R Core Team (2014). R: A Language and Environment for Statistical Computing. Vienna: R Foundation for Statistical Computing.
VSN International (2012). GenStat for Windows, 15th edn, Hemel Hempstead, UK: VSN International.

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed