Predicting hybrid value in bread wheat: biometric modelling based on a ”top-cross” design

Abstract 

Multi-environmental experimentation made it possible to compare 311 hybrids and their 59 parental lines for five characters: yield, two yield components (number of grains per m² and 1000-grain weight), height and date of heading. At all three sites, average high-parent heterosis exceeded 6%, and our results confirm that hybrids in general head as early as the earlier parent does and are as high as the taller parent. For the five characters studied ecovalences were significantly lower in the F1 than in the parents, indicating a higher level of homeostasis for hybrids. The experimental model, based on a ”top-cross” design comprised of 55 lines used as females and four testers, made it possible to implement different hybrid-value prediction models. For yield, by far the most important character to predict, the predictor based on the general combining ability and the per se value of the parents, appears to be the most interesting. The prediction remains, however, imperfect as specific combining ability (SCA) has a strong impact for this character. Attempting to take account of SCA in the prediction, by using a multiplicative model for ”male×female” interaction modelling, did not prove convincing.