Family number in common bean selection

The objective of the present study was to determine the number of families necessary for selection in a segregant population. Nine segregant populatio ns from the bean improvement program of the Federal University of Lavras we re evaluated. The number of families Varied from 169 to 295, and the averag e family heritability estimate (h(2)) for grain production varied from 5.3 to 82.0%. Different sample sizes were simulated using the average family pe rformance. The first sample consisted of 30 families, with each additional sample containing 10 more families, until the total number of families eval uated was reached for each population. One thousand simulations per sample size were performed. These data were used to determine the average, minimum and maximum phenotypic variance and the standard error of the variance. Th e probability of occurrence of a certain level of phenotypic Variance for t he corresponding values of 0.0, 0.25, 0.50 and 0.75 of heritability was det ermined for all families, using a chi(2) distribution. Based on the results obtained and considering the experimental precision and conditions of the bean improvement programs in this region, the use of less than 100 families would reduce the probability of successful selection.