Submitted to: Southern Nursery Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/15/2003
Publication Date: 12/1/2003
Citation: Reed, S. Self-Incompatibility in Hydrangea Paniculata and H. Quercifolia. Proceedings of the Southern Nursery Association Research Conference. 2003. v:48, pp:477-479. Interpretive Summary: Several Hydrangea species are widely cultivated as ornamentals. While many cultivars are available in some species, little is known about the breeding or genetics of this genus. The objective of this study was to determine whether H. paniculata (panicle hydrangea) and H. quercifolia (oakleaf hydrangea) produce self-seed. Pollen germination and pollen tube growth were compared in cross- and self-pollinated flowers. Pollen tubes in self-pollinated flowers grew much slower than did those in cross-pollinated flowers. This indicates the presence of a self-incompatibility system in these species. Because of this self-incompatibility, it may not be necessary to remove anthers when making controlled pollinations in H. paniculata and H. quercifolia. Information presented in this study will assist plant breeders as they attempt to develop improved H. paniculata and H. quercifolia germplasm.
Technical Abstract: The objective of this study was to evaluate self-incompatibility in H. paniculata and H. quercifolia. Flowers from three genotypes of each species were collected 1, 2, 4, 8, 24, 48 and 72 hours after cross- and self-pollination, stained with aniline blue and observed using fluorescence microscopy. In both species, pollen germination was observed on stigmas of over half of the flowers collected 4 to 72 hours after cross- or self-pollination. Pollen tubes had grown to the base of the style by 24 hours after cross-pollination in H. paniculata and by 48 hours after cross-pollination in H. quercifolia. In both species, self-pollen tubes had only penetrated one-fourth to one-third the length of style by the time cross-pollen tubes had reached the bottom of the style. This study provides evidence of a gametophytic self-incompatibility system in H. paniculata and H. quercifolia. Occasional self-seed set previously observed in these species was theorized to have been due to pseudo-self compatibility.