Given this, it is important to identify and mark these resistance genes. The mapping work will help identify molecular markers for the specific resistance genes which can be used in combining multiple genes into one genotype to give it a broad based level of resistance. A rose progeny to study this trait has been produced by David Byrne and it is currently being used to develop a genetic map at Clemson University. Fragrance in Roses Fragrance is one of the most subtle, yet a familiar feature that characterizes many roses. Rose species and cultivars display substantial variation in scent as well as intensity of fragrance.
Fragrance is a result of numerous volatile aromatic organic substances present in the flower.
To be able to manipulate fragrance in roses through genetic engineering, the chemicals contributing to the fragrance of roses must be distinguished, their pathways of synthesis understood, and enzymes controlling these pathways identified. Then the genes controlling these enzymes have to be isolated and characterized. Gene mapping is a means to locate such fragrance genes and to identify the DNA markers associated with these genes. Current biochemical understanding of fragrance in plants in general is poor, when compared to our knowledge of flower pigment formation. As mentioned before, flower color has been studied extensively and some genes that encode specific enzymes in the biosynthetic pathway of plant pigments have been isolated and have been used to manipulate flower color.