Fig. 1.

Comparison between conventional and apomixis-mediated methods for breeding F₁ hybrid varieties. In traditional breeding, within a segregating population (e.g., F₂ population) some genotypes are selected and after some generation of selfing followed by phenotypic selection, tested for their specific combining ability in order to be used as parental lines for the constitution of heterotic F₁ hybrid seeds. The best performing inbred lines are selected, multiplied in isolated fields, and crossed in pairwise combinations to obtain uniform, vigorous, and high-yield F₁ hybrids. This scheme, however, requires a series of actions: the two inbred lines must be kept pure and multiplied in separate fields. Then, to obtain the hybrid seed, it is necessary to establish a dedicated field where about one quarter of the plants is used as pollinator (i.e., pollen donor inbred) and on the remaining plants (i.e., seed parent inbred) the hybrid F₁ seeds will be harvested. Farmers cannot re-use seeds collected from F₁ hybrids as these seeds will give rise to highly variable populations because of genetic segregation and recombination. Using apomictic lines, however, the situation would be much simpler. Once superior inbred lines to be used as seed parent are selected, they can be crossed with clonal lines as pollen donors carrying the gene for apomixis, in order to obtain F₁ hybrid seeds sharing a highly heterozygous genotype. From this moment on, each F₁ hybrid variety can be maintained for several generations with permanently fixed heterosis