A NOTE ON THE ESTIMATION OF THE EFFECTIVE NUMBER OF ADDITIVE AND DOMINANT LOCI CONTRIBUTING TO QUANTITATIVE VARIATION

A method of estimating the number of loci contributing to quantitative variation has been proposed by S. Wright in 1921. The method makes us e of the means of inbred lines and the variances of their F1, F2 and b ackcrosses. The method has been extended to crosses between outbreedin g populations by R. Lande in 1981. Additive gene action is one of the major assumptions required for obtaining valid estimates. It is shown here that this assumption may be relaxed. One can estimate both a tota l number of effective loci and a number of dominant loci (the latter o nly when the parents are inbred) by comparing the variances of the F1, F2 and backcrosses. Numerical illustrations are given, based on cross breeding data.