GENERAL (GCA) AND SPECIFIC (SCA) COMBINING ABILITY FOR QUANTITATIVE CHARACTERS OF ORNAMENTAL VALUE IN F₁ INTERSPECIFIC MORNING GLORY HYBRIDS

Incomplete diallelic cross design were performed in 2001, involving four Ipomoea species: I. tricolor, I. violacea, I. purpurea and I. hederacea. F1 hybrids were grown in Cluj-Napoca in 2002 and, based on results obtained, general (GCA) and specific combining ability (SCA) effects were estimated for the main quantitative characters considered as important breeding objectives in these ornamental species: plant height, length of inflorescence, n. of flowers/inflorescence, length of open corolla, length of corolla tube, diameter of open corolla, earliness of flowering and persistence of open flowers. Except for earliness of flowering and persistence of open flowers, all other studied characters showed significant additive effects, revealed by the high values of GCA effects. These results suggest that, in ornamental species of Ipomoea genus, for the quantitative characters taken into consideration, might be found distinct groups of polygenes with positive effects and other groups with negative ones upon these traits. On the other hands, the SCA effects were significant only for two characters: length of inflorescence and earliness of flowering. Considering these results it might be stated that in the four ornamental morning glory species, there are poor chances to obtain simple hybrids which would exhibit a significant heterosis of the main quantitative traits of interest in breeding programs.