The phenomenon of heterosis or hybrid vigor has long been recognized to have a genetic basis. Heterosis expressed in hybrids often has been correlated with the heterozygosity inherent to a hybrid produced from the cross of parents of different genetic backgrounds. Our understanding of the molecular mechanisms that elicit heterosis remains incomplete; however, a number of critical experiments have contributed to our understanding of the physiological processes and biochemical mechanisms operative in the expression of heterosis. These experiments and the genetic mechanisms thought to underlie them are considered here. Based upon these findings, heterosis does not appear to have a single cause, but rather may result by reason of the action of either single or multiple genes’ in the nucleus or the cytoplasm or both. Pertinent examples of gene action which potentiates heterotic effects are discussed.

David Isaac Kridel

Papers

Mitochondrial complementation and heterosis in Pisum sativum L.