The effect of variation of genetic variance and correlation between mean and variance on efficiency of bulk yield testing

Summary Computer simulation techniques were used to examine the effect of variation of genetic variance and correlation between mean and genetic variance on the efficiency of bulk yield testing procedures. Assessment of the effect of variation in various parameters was made by comparing genetic gains with the maximum potential gain. The maximum potential gain was defined as that which would be achieved if the particular bulk which maximizes genetic advance were chosen for selection.Maximum potential gains increased with increasing mean genetic variance within bulks but showed only a slight response to increasing variation of the within bulk genetic variance. Negative correlations between bulk mean and genetic variance reduced maximum potential gains and positive correlations increased them but the effects were not large.A selection intensity of 5% among bulks seemed close to optimal for a wide range of parameters. Slightly more intense selection may be an advantage where the between bulk heritability is high, the within bulk variance is high, and the correlation between bulk mean and variance is high and positive.