Click on the links or picture thumbnails to view the Rubus maps we have already developed.
| Map of linkage group 123 | |
| Map of linkage group 456 | |
| Map of linkage group 789 | |
Breeding in raspberry is time-consuming due to the highly heterozygous nature of this perennial fruit crop, coupled with relatively long periods of juvenility. The speed and precision of raspberry breeding can be improved by genetic linkage maps, thus facilitating the development of diagnostic markers for polygenic traits and the identification of genes controlling complex phenotypes. A genetic linkage map of the red raspberry R. idaeus has been constructed from a cross between two phenotypically different varieties; the recent European variety Glen Moy and the older North American variety Latham.
A full-sib family from this cross, estimated to be around 60% similar (Graham and McNicol 1995) was used for mapping purposes. Latham was one of the first varieties produced through controlled breeding in the 1930s, and is an exceedingly hardy, extremely spiny, brown-caned, small-fruited plant with resistance to raspberry root rot and a range of cane diseases. Glen Moy, released in 1981, in contrast, is large fruited with good flavour and good sensory characteristics, susceptible to low temperature damage, spine free and green-caned with little pest and disease resistance.
Effects of inoculating raspberry plants with Phytophthora root rot. Variety Latham (left) is unaffected and root growth is good, Glen Moy (right) is severely affected and roots are killed.
The entire segregating population of 300 individuals and both parents were cloned by the propagation of root material and planted at different field locations in randomised complete block trials with three replicates and two plant plots at both locations. SSR markers were developed from both genomic and cDNA libraries from Glen Moy. These SSRs, together with AFLP markers, were utilised to create a linkage map. In order to test the utility of the genetic linkage map for QTL analysis, morphological data based on easily scoreable phenotypic traits were collected. The segregation of cane spininess, and the root sucker traits of density and spread from the mother plant, was quantified in two different environments. These traits were analysed for significant linkages to mapped markers using MapQTL and were found to be located on linkage group 2 for spines and group 8 for density and diameter. The availability of co-dominant markers allowed heterozygosities to be calculated for both varieties.
Graham J & McNicol RJ (1995) An examination of the ability of RAPD markers to determine the relationships within and between Rubus species. Theoretical and Applied Genetics 90:1128-1132.