Optimum number of crosses and progeny per cross in breeding self-fertilizing crops. II. Numerical results based on expected selection responses (special case)

Huehn, M. (2005) Optimum number of crosses and progeny per cross in breeding self-fertilizing crops. II. Numerical results based on expected selection responses (special case). Cereal Research Communications, 33 (2-3). pp. 493-500. ISSN 0133-3720

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Abstract

Aiming at maximization of selection response, methodology for determining the optimum number of crosses and progeny per cross in the breeding of self-fertilizing crops has been developed by adding the individual responses from the two steps of selection: selection between crosses and selection within crosses. Optimum numbers of crosses and maximum selection responses are determined by testing capacity, number of selected crosses, number of lines selected from each selected cross, and heritability.In the special case ‘selection of the best line out of the best cross’, (1) the maximum selection response increases with increasing testing capacity, (2) the maximum selection response increases with increasing heritability, (3) the optimum number of crosses increases with increasing testing capacity, (4) the optimum number of crosses is largest for intermediate heritabilities, lowest for large heritabilities, and intermediate for low heritabilities, (5) the graphs of maximum selection response plotted against testing capacity show that one obtains only insignificant increases of the maximum selection response for larger testing capacities, (6) for increasing heritabilities, the optimum number of crosses exhibits relatively flat maxima; these maxima are located at intermediate or sub-intermediate heritabilities; for small testing capacities (≤ 2000) the optimum numbers of crosses are similar for large and low heritabilities while for intermediate heritabilities one obtains larger values.

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