Genetic basis of heterosis for yield in the autotetraploid potato.

A model of overdominant gene action to explain heterosis for yield in the autotetraploid potato has been presented. Loci with multiple allcles and a maximum heterotic value for quadrigenic genotypic structures have been postulated. Various experimental results have been analyzed on the basis of such a model in contrast with a dominance situation. The analysis suggests a close positive correlation between heterozygosity and yield. The implication of the proposed overdominant model to potato breeding would be that substantial genetic advance in yield should be made upon increasing the genetic diversity of the parental clones. However, the alien sources of germplasm should undergo some previous selection for adaptation. A proper balance between heterozygosity and adaptation, mainly to photoperiod, should maximize the heterosis for yield.