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In sugar beet breeding, sugar yield is mainly influenced by root yield and sugar content. In this short communication several indices to select for both traits simultaneously are compared in order to find the best one. The indices are correlated with the base index of Williams (1962) from independent experiments. The indices differ in the amount of information necessary for the calculation of their weights. Three different series of each eight sites gave similar results. The optimum index, using all information from phenotypic and genotypic variances and covariances, did not perform best. Sugar content with its higher heritability must have a larger weight than root yield. Heritabilities as index weights performed best, but two other indices using heritabilities and phenotypic but no genetic covariances also performed well. [ABSTRACT FROM AUTHOR]