We present a new linkage map for sugar beet (Beta vulgaris) which has been
developed using a population segregating for genetic factors that confer to
lerance to the leaf spot fungus (Cercospora beticola), the causal factor of
leaf spot disease in sugar beet). In the F-2 population studied, a subset
of 36 RFLP probes, mapping on eight out of the nine linkage groups of sugar
beet, provided the anchor markers to assign chromosomes. A total of 224 ma
rkers, including RFLPs, AFLPs, SCARs and microsatellites, were mapped. Esti
mates of leaf damage in F-2 and test-cross families were repeated at differ
ent stages of plant development. Each set of data was analysed as such. An
average estimate was also considered. QTLs with highly significant LOD scor
es revealed both by the F-2 and test-cross analyses were localized on linka
ge groups 2, 6 and 9. Linkage groups 4 and 5 gave a clear indication of the
presence of a QTL only when F-2 data were considered. One highly significa
nt QTL with a LOD of 16.0 was revealed only by the data obtained under cond
itions of artificial inoculation. This QTL maps at position 90 on chromosom
e 3.