Comparison of two breeding strategies by computer simulation

Breeding strategies used by plant breeders are many and varied, making it difficult to compare efficiencies of different breeding strategies through field experimentation. The objective of this paper was to compare, through computer simulation, two widely used breeding strategies, the modified pedigree/bulk selection method (MODPED) and the selected bulk selection method (SELBLK), in CIMMYT's wheat breeding program. The genetic models developed accounted for epistasis, pleiotropy, and genotype X environment (GE) interaction. The simulation experiment comprised the same 1000 crosses, developed from 200 parents, for both breeding strategies. A total of 258 advanced lines remained following 10 generations of selection. The two strategies were each applied 500 times on 12 GE systems. Findings indicated that genetic gain from SELBLK was on average 3.9% higher than that from MODPED, and genetic gain adjusted by target genotypes from SELBLK was on average 3.3% higher than MODPED for a wide range of genetic models. A greater proportion of crosses were retained (25% more) by means of SELBLK compared with MODPED, and from F1 to F8, SELBLK required one third less land than MODPED and produced fewer families (40% of the number for MODPED). For the genetic models considered in our study, computer simulations showed that the SELBLK method resulted in slightly greater genetic gain and significant improvements in cost effectiveness.