The breeding of hybrid rose cultivars is part of the ornamental rose industry, but there have been few studies concerned with the factors limiting reproduction in the genus Rosa L. In this study, 28 species of Rosa were examined under field conditions for self- and cross-compatibility relationships. Twenty-five specimens of 25 species were tested for self-compatibility. All of the 23 diploid plants tested exhibited more than 96%. Twelve of the 16 polyploid plants preserved the 96% self-incompatibility reaction. A distinct separation existed between self-compatible and self-incompatible polyploid plants. Four of the 5 diploid cross-fertilizations produced unexpected reciprocal differences. Significant reciprocal differences were not obtained from the polyploid level cross-fertilizations. Some parthenocarpy occurred in the R. stellata species. Pollen viability and abundance, daily maximum and minimum temperature, and maximum and minimum relative humidity were not correlated with the compatibility reactions.
Former Graduate Student, Dept. of Hort.
Professor, Dept. of Crop and Soil Sci.
Received for publication 8 Mar. 1985. J. Article No. 1158 of the Agr. Expt. Sta. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact,