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Joint Regression Analysis is a widely used technique in the analysis of series of experiments for cultivar comparison. We show how this technique may be used in the selection of recommended cultivars. We apply this technique to a series of experiments on spring barley cultivars carried out from 2001 to 2004. The data in these designs were kindly made available by the Central Institute for Supervising and Testing in Agriculture in Brno, Czech Republic. [ABSTRACT FROM AUTHOR]

Using data from a triticale advanced line yield trial network, we attempt to define the zones, in Portugal, within which the pint regression can be established with enough accuracy and precision to be of practical value. The procedure comprises the following steps: adjustment of the joint regressions for the whole area; evaluation of the residuals in each trial; previous identification of geoclimatic zones; comparison of these zones with the residuals; adjustment of the regressions for the zones confirmed in the previous analysis, and testing the differences between the regressions for each zone. The experimental conditions allowed the differentiation of two main zones: "Nordeste Transmontano" and "Sul de Montejunto-Estrela", however, another zone, included in the latter and designated "Alentejo Litoral e Algarve", is suggested though further experimental data are needed for sound conclusions. [ABSTRACT FROM AUTHOR]