Expected and realized gains in the CMS-39 maize population after cycles of half-sib family selection.

The CMS-39 maize population synthesized by the National Center of Research for Maize and Sorghum (CNPMS/EMBRAPA) was submited to half-sib family selection for grain yield. Populations representing the original cycle (Co), and cycles I, lI, and III, were evaluated in randomized complete blocks with ten replications in Sete Lagoas, Lavras, Ribeirão Vermelho, and Santo Antônio do Amparo, Minas Gerais Stale, Brazil. The purpose was to evaluate the observed gain from selection and to compare it with the gain expected based on parameter estimates at each selection cycle. The realized gain per cycle, reported as the average for the four cycles was 3.6%. This value was smaller than the average expected gain per cycle, which was 7.2%. The main reasons for lhe non-agreement of these estimates are discussed