AN EXEMPLE OF APPLICATION FOR MCQTL SOFTWARE: FINE CHARACTERISATION OF A QTL FOR APPLE SCAB RESISTANCE

¹ INRA, Unité de Biométrie et Intelligence Artificielle, BP 27, 31326 - CASTANET-TOLOSAN Cedex, FRANCE

² INRA, Unité d'Amélioration des Espèces Fruitières et Ornementales, BP 57, 49071 - BEAUCOUZE Cedex, FRANCE

MCQTL is a package software [1] providing the plant geneticist a set of tools for mapping QTLs. It performs regression mapping with or without cofactors. It can deal with a wide range of inbred and outbred families. It allows the global analysis [2]of simple and multiple populations deriving from mating designs such as diallel or factorial with F2, F3 or RIL situation. The advantages of the regression mapping approach used by MCQTL are the following : (i) this approach is asymptotically equivalent to likelihood-based mapping[6], (ii) it is robust to deviation from normality, and (iii) it offers more flexibility to modelise and test QTL effects [3]. Especially, it is a very useful tool for the fine characterisation of QTLs in outbred species (giving full-sib F1 families). An example is given for such a case, using the progeny deriving from a cross between two apple cultivars (Prima x Fiesta, EAGMAP population [4]). A large QTL for apple scab resistance was identified in the region of the Vf gene on linkage group n°1 [5]. Estimations of the Prima additive effect and of the partial dominance effect were improved by defining models with and without dominance or additive effects. The different LOD-values obtained in the different cases were compared. For more information about MCQTL and downloading see our presentation. [1] Rebaï A., Jourjon M.F., Mangin B., Goffinet B., 1997. MulticrossQTL. PAG VI,Poster 389. [2] Rebai A.., Goffinet., 1993, TAG86-1014-1022. [3] Rebai A., Goffinet B., Mangin B., 1995, Biometrics 51:87-99. [4] Maliepaard et al., 1998. Theor Appl Genet 97, 60-73. [5] Durel C.E., Parisi L., Jourjon M.F., Laurens F., Venisse J.S. 1999. EUCARPIA Symposium, Dresden, Poster. [6] Van Ooijen Johan W., Maliepard Chris, 1995, MapQTL, PAG IV, Poster.