Efficiency changes due to use of doubled-haploids in recurrent selection methods.

Efficiency comparisons are made among standard recurrent selection methods and for the same methods modified by the inclusion of haploid and cloning techniques. These comparisons are made with respect to five different gene models representing different levels of heritability and also with respect to unrestricted versus restricted total plant numbers.When comparisons are made either among the standard diploid or among the modified haploid selection methods, the advantages of clonal and general combining ability selection over individual selection largely disappear when a restriction on total plant numbers is imposed. However, the very considerable advantages of haploid over diploid selection methods, measured on a per cycle basis, do not disappear when total plant numbers are restricted.When the genetic gains are measured on a yearly basis, it becomes clear that the key to the successful inclusion of the haploid technique, as a device to increase the efficiency of standard recurrent selection methods, is the development of rapid doubled-Haploid extraction procedures.