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

Abstract

Incomplete diallel crosses 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, no. of flowers/inflorescence, length of open corolla, length of corolla tube, diameter of open corolla, earliness of flowering and persistence of open flowers. The great majority of the studied characters, except for earliness of flowering and persistence of open flowers, 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, there might be found distinct groups of polygenes with positive effects and other groups with negative ones upon these traits. The SCA effects were found significant only in tow characters: length of floral peduncle and earliness of flowering. In the first of these two characters, the SCA effects had, practically, the same significant values as those of GCA effects while in the second one, solely the SCA effects showed significant values. Taking into consideration these results, it could be stated that, with the four ornamental morning glory species under study, there are poor chances to develop commercial hybrids in which the considered ornamental characters would express an obvious heterosis in the expected direction (negative or positive).