Aspetti sementieri nella produzione di ibridi di frumento

Aspects of hybrid seed production in wheat Hybrid wheat breeding began during the sixties after the discovery of a male sterility system induced by nuclear substitution in alien cytoplasm. Triticum timopheevii was a promising cytoplasm source of male sterility due to its negligible negative effects on agronomic traits; nuclear genes for fertility restoration were found as well in this species, but the need of several of them to achieve a satisfactory fertility in a wide range of environments limited the practical utilisation of this source. Other donors of sterile cytoplasm or restorers have been investigated, although with little success so far. Alternative biotechnological approaches, implemented in other crops, were proposed in the last two decades also for wheat. Among them the “barnase–barstar” system, and more recently the “split gene”, a derivation of the previous one but easier to implement in the breeding work, and the “Seed Production Technology” system, particularly interesting because it produces non-transgenic hybrids. Since these tools are not yet available for wheat, current production of hybrid varieties is based on the use of chemical hybridizing agents whose efficiency has improved in recent years. Morphological traits favourable for cross pollination are also discussed.