XVI International Botanical Congess

The dogroses (x=7, 2n=28-42) are characterized by a meiosis with only 7 bivalents regardless of chromosome number. This results in pollen with 7 chromosome while egg cells have 21-35 chromosome. We have studied the effects of the Canina meiosis on reproduction and genetic diversity in some dogrose species. Evaluation of reciprocal crossed demonstrates matroclinal inheritance of morphological traits as well as of RAPD markers. Apomixis is suggested in some interspecific crosses since the offspring have only maternally-inherited RAPD markers and a higher pollen viability that apparent hybrids. Dogrose species differ widely with respect to the amount and partitioning of genetic diversity, evaluated with morphometrics and RAPD's. Mode of reproduction (apomixis, selfing, intra- and interspecific cross-pollination) appears to be the most important factor explaining these patterns of gene diversity. RAPD marker distribution suggest that the present taxonomy has placed too much emphasis on a few morphological characteristics.