Three-way cross designs for test lines vs. control line comparisons

The selection of appropriate parental lines and crossing plans are the most important keys for a successful breeding programme. Three-way crosses are intermediate between single and double cross hybrids and hence are economical with respect to uniformity, yield, stability and the relative simplicity of selecting and testing. When a number of test lines are to be compared to a control line, the main interest of the experimenter centers around comparing test vs. control lines with a high precision. For such situations, two series of designs have been developed using partially balanced incomplete block designs and their association schemes. In the designs obtained, three-way crosses are arranged in incomplete blocks and hence heterogeneity in the experimental field can be controlled in blocks of smaller sizes. It is found that the proposed designs make test vs. control lines comparisons with a higher precision.