Procedures for selecting composites based on prediction methods.

Procedures for selecting among parental varieties to be used in the synthesis of composites are discussed. In addition to the criterion based on the mean and variance of composites of the same size (k) proposed by Cordoso (1976), we suggest the index Ij=w1vj+w2 ĥj or I'j=(2/k) Ij for a preliminary selection among parental varieties. We show that by increasing k (size of the composite) I'j tends to gj, the general combining ability effect. Such a criterion is particularly important when n, the number of parental varieties, is large, so that the number of possible composites (Nc=2(n)-n-1) becomes too large to be handled when using the common prediction procedures. Yield data from a 9 × 9 variety diallel cross were used for illustration.