Selective Breeding versus Crossbreeding. Selective breeding of farmed plants and animals (for fast growth, disease resistance, etc.) focuses on commercially desirable traits that are moderately or highly heritable. The best performers are chosen as breeders in successive generations. The main alternative strategy to selective breeding is crossbreeding, also called hybridization, which takes advantage of the unpredictable but sometimes considerably improved performance exhibited by hybrid progeny compared with that of their parents. This improved performance of crossbreeds is known as hybrid vigor. Unlike selective breeding, in which incremental genetic improvements are achieved with each successive generation, crossbreeding generates a one-time improvement, which must usually be regenerated every time seed is mass produced. This means keeping two separate sets of parental broodstock.