Published online by Cambridge University Press: 24 October 2001
Publications commenting on the possibility of fixing heterosis and the possibility to transgress heterosis through partition of crop yield into genetic components have prompted us to reconsider our views on the relative importance of hybrid versus inbred vigour. The three genetic components of crop yield, all assessed in the absence of competition, are: (1) yield per plant assessed by the progeny mean, (2) tolerance to stresses assessed by the progeny standardized mean, and (3) responsiveness to inputs assessed by the progeny standardized selection differential. Although fixation of heterosis using the top commercial tomato hybrids was based only on the first genetic component of crop yield and quality, inbreds outyielding the original hybrid were obtained relatively easily. The results indicated that selection for homozygote superiority on the basis of the three genetic components of crop yield and quality, would lead to the development of tomato inbreds outperforming the hybrids.