THE INFLUENCE OF CROSSING STRATEGY ON THE POTENTIAL FOR BREEDING NEW CROP VARIETIES

Crosses between commercially acceptable varieties and introductions are most likely to generate segregation at many loci of commercial importance. The probability of recovery, after selfing, of individuals in which most of the favourable alleles have been accumulated is very low. Reducing the number of favourable alleles heterozygous in the breeding population would increase the probability of success. The utility of a single backcross (BC1) to the parent with the greatest number of favourable alleles was examined as a method of fixing commercially desirable alleles. The means for stability parameters or yield for BC1F2-derived populations were similar to those for F2-derived populations. The genetic variance for yield in 2 of the 3 crosses studied was greater for the BC1F2- than the F2-derived populations, while the genotype x environment interactions appeared to be smaller for the BC1F2 populations. This suggested that BC1F2-derived populations may be more productive, in terms of varietal production, than F2-derived populations, particularly in species with a long breeding history and/or a large number of desirable characteristics.