Relation between number of parental lines and theoretical performance of synthetic varieties of corn
1945
Kinman, M.L. | Sprague, G.F.
A comparison of observed F2 data and calculated F2 values assuming arithmetic or geometric gene action indicates somewhat closer agreement between the observed values and those computed on the assumption of arithmetic gene action. Slight departures from either scheme of gene action do not invalidate the conclusions regarding the most efficient number of lines constituting a synthetic variety. In general, the most efficient number of lines to be included in a synthetic will vary with the range in combining ability among the inbreds available as parents. On the basis of this study, four to six lines appeared to be the most efficient number. Synthetic varieties involving the same parental lines may be expected to have a slightly higher yield level when combined directly than when combined as top crosses. No data are available which permit a comparison of single cross yields between vigorous lines with little inbreeding and the progeny of these lines when more highly inbred. If it should be established that the combining ability of such lines is essentially equal, then synthetic varieties produced by combining first generation selfed lines should be superior to those produced by combining more highly inbred but less vigorous lines.
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