One important aim of hybrid breeding is to exploit the heterosis effect appearing in the F1. Nevertheless, the breeders of commercial F1 hybrids have no real information on the extent of heterosis manifested in the combinations they produce, since the mean value of the combination in question is never compared with that of the parents or of the better parent, but only with that of the most popular control variety it is hoped to surpass. The complex variety value of a new hybrid should be greater than that of the control. In the case of pepper hybrids the factors that make up the complex variety value can be divided into four groups: the early and total yield potential predicted from the individual value of the parents (P), special consumption and production traits resulting in F1 quality (Q), F1 resistance value (R) and the heterosis effect (H). The importance of these four factors in the complex variety value of a given pepper hybrid may be summed in innumerable variations, but the individual yield potential and quality traits of the parents are of outstanding importance. This is the basis, without which combining ability, resistance value and heterosis effect will remain unexploited. When selecting pepper lines for combining ability, risks may be involved in over-strict selection for general combining ability alone, so a combined crossing system involving a carefully constructed partial diallel is normally employed to obtain information on the general combining ability of lines preliminarily screened for individual plant performance and on the specific combining ability of their combinations. Cross-breeding aimed at the development of parental lines and constant varieties makes use of single crosses, crossing series, backcrossing and resistance breeding.
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