GENETIC ARCHITECTURE OF RUST RESISTANCE IN POPLAR

¹ Laboratoire de Biologie ForestièreUniversité Nancy-IBP 239F-54506 VANDOEUVRE-LES-NANCY CedexFRANCE

² Amélioration, Génétique et Physiologie forestièresINRA - Centre d'OrléansBP 20619 ARDONF-45166 OLIVET CedexFRANCE

Genes involved in qualitative resistance to Melampsora larici-populina pathovars E1 and E3 in interspecific hybrids between Populus deltoides and P. trichocarpa are closely linked (Lefèvre et al., 1998, Phytopathol.). In the chosen model family, qualitative resistance was also found to pathovar E4. Quantitative resistance to pathovars E2 and E5 was analysed. Leaf disks were inoculated in laboratory conditions with pure pathovars, this lead to high heritabilities of quantitative resistance components (latency, uredia number and size). In order to map most components of resistance in P. deltoides and P. trichocarpa, genetic maps have been produced by analysing the model family and using the double pseudo-testcross strategy. About 600 AFLP, RAPD, RFLP, SCAR, STS and SSR markers have been mapped. The major linkage groups account for about 2200 cM for each species. Some discrepancies in linkage group composition with previous poplar map (Bradshaw et al., 1994, TAG) have been noticed. Genes of qualitative resistance to E4 are closely linked to genes of resistance to E1 and E3 in P. deltoides. This region is also involved in quantitative resistance. Three other genomic regions control quantitative resistance in P. deltoides, one of them is colocalized with CHS gene. In P. trichocarpa, seven genomic regions are involved in quantitative resistance, one of them is closely linked to PAL gene. Quantitative resistance genes are noticed in both species. QTLs of resistance have been also detected for Xanthomonas populi, Marssonina brunnea and Chrysomela tremulae. Interactions between resistance loci will be discussed.