Inheritance of deeper root length and grain yield in half-diallel durum wheat (Triticum durum) crosses

Inheritance, heterosis and combining ability of deeper root length (DRL) and grain yield (GY) were investigated in durum wheat populations obtained from half-diallel crossings among five parental lines differing in their DRL and GY. The study was conducted with the final objective of identifying parent lines to be used in a breeding programme to develop drought-tolerant wheat varieties. General combining ability and specific combining ability effects were significant for both traits; however, additive gene effects were predominant over non-additive effects. Partial dominance was ambidirectional for DRL and unidirectional for GY. Lines INRAT69 and Omrabia conferred DRL whereas Omrabia and Khiar transmitted high GY to their respective progenies. In the studied material, both characters were controlled mainly by dominant alleles, but they could also be attributed to recessive alleles although less frequently. Both broad-sense and strict-sense heritabilities were high for DRL, confirming the importance of additive gene effects, whereas strict-sense heritability for GY was average, indicating the importance of interaction effects as compared with the additive effects; this could mean reduced selection efficiency for the latter trait. Thus, the expected genetic progress per cycle of selection will be lower for GY compared with DRL. Omrabia should be included in the breeding programme as a parent so that while maintaining high GY, resulting progeny should be better able to resist drought through DRL. © 2007 Association of Applied Biologists.