Plant breeding for organic and sustainable, low-input agriculture

Do varieties rank differently in organic and conventional systems?
M. Przystalski 1 , E. Thiemt 2 , B. Rolland 3 , L. Ericson 4 , A. Osman 5 , H. Østergård 6 , L. Levy 7 , M.
Wolfe 8 , A. Büchse 9 , H.-P. Piepho 9 , P. Krajewski 1
1 Institute of Plant Genetics PAS, Poznań, Poland; 2 State Plant Breeding Institute, University
of Hohenheim, Germany; 3 INRA, Rennes, France; 4 SLU, Umeå, Sweden; 5 Louis Bolk
Instituut, Driebergen, The Netherlands; 6 Risø National Laboratory, Denmark; 7 Agroscope
Changins-Waedenswil, Switzerland; 8 The Organic Research Centre Elm Farm, UK;
9 University of Hohenheim, Department of Bioinformatics, Stuttgart, Germany
Recently, interest has increased in plant varieties specifically adapted to organic farming
conditions. The aim of this study was to answer the question if varieties rank differently in
organic and conventional systems and if separate organic trials are needed. The problem was
approached by a comprehensive analysis of several data sets using a common statistical model
involving parameters related to decisions concerning planning of the trials.
The data come from experiments performed in two systems in several environments (years or
sites) in Danmark, the Netherlands, France, Germany, Sweden, Switzerland and U.K., with
wheat, barley and Triticale varieties. Measurements of yield, height, thousand grain weight,
hectoliter weight, protein content, soil coverage, lodging, breaking of straw, and infection by
septoria and brown rust were taken into account. The analysis was done using a mixed models
methodology allowing to estimate genetic variance and genetic covariance. Estimates of the
genetic correlation between organic and conventional trials were interpreted in terms of
ranking agreement. An approach based on index selection was used to study the effect of the
number of organic trials on the response to selection.
Trait means in the organic system were lower than in conventional trials. Environments had a
large influence on the level of the traits. System x environment interaction was significant in
most cases. The genetic correlation between systems for yield and height was between 0.79
and 1. For lodging and septoria it was from 0.80 to 0.90. For other traits the genetic
correlation usually was close to 1. It was found that for the genetic correlation of 0.90 the
probability of ranking agreement in the top 10% of varieties is about 0.65. The gain from
adding organic trials was found to depend on the relation between the values of the genetic
and non-genetic variance components; the functional form of this dependence was given.
The genetic correlation between the organic and conventional system was found to be high in
most cases. Results presented in this paper provide a way to interpret this correlation in terms
of the agreement of ranking of varieties and in terms of the gain of information rovided by
organic trials. Such interpretation can be helpful to the experimenters in making decisions
about the future series of trials.
Acknowledgement: The work was partially supported by COST Action 860 SUSVAR within
WG 2 Biostatistics and WG6 Variety Testing and Certification; the work of M. Przystalski was
additionally supported by the grant SPB/COST/KN/DWM 74/2005-2008 from the Polish
Ministry of Science and Higher Education.
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