How can transgressive variation be useful for rice breeding?
Transgressive variation is frequently observed in populations that are derived from genetically divergent parents. Divergent parents differ in allelic constitution at many loci), giving rise to individuals that are both “better” and “worse” for specific traits than either parent. Crossing genetically diverse lines provides the breeder with a larger array of genetic variation in the offspring from which to make selections, enhancing the possibility of identifying offspring that outperform the “better parent” by a substantial amount. However, because most offspring contain some traits that are “better” and others that are “worse” than their parents, breeders have to spend time selecting against the deleterious alleles as well as for the advantageous alleles in each generation. The use of molecular markers can greatly improve the efficiency of the process, and markers are often used in combination with backcrossing to capture positive transgressive variation for rice improvement.
