A comparison of bulk testing and direct-line testing in self-fertilizing crops

Summary

Computer simulation techniques were used to compare the efficiency of bulk-yield testing with direct-line yield testing. Bulk testing was almost always more efficient than direct-line testing for a wide range of values for population parameters. The differences between the two methods were smaller when the among-bulk heritability was low, the within-bulk genetic variance was high relative to the among-bulk variance, the variance of the within-bulk genetic variance was high, and the correlation between bulk means and within-bulk genetic variances was highly negative.

With the direct-line testing method, discarding lines with low means after the first year of testing was always more efficient than retaining all lines for 2 years. Selection of 25% of the lines was slightly more efficient than selection of 50%. In general, it was better to evaluate more crosses and less lines per cross with the direct-line testing procedure.