Résumé
A Quantitative Trait Locus (QTL) mapping study is underway to analyse the genetic determinism underlying sugarcane smut resistance. One thousand and three hundred polymorphic AFLP markers have been generated on a population of 200 individuals derived from a cross between R570 (resistant) and MQ 76/53 (highly susceptible). This population is under evaluation for its resistance to smut in the field over three successive crop cycles and in two different locations of Reunion island. Inoculation was performed by dipping three buds cuttings in a spore suspension and susceptible clones have been regularly interspersed in the field to trigger the epidemy. Different inoculation methods have been compared in greenhouse trials. The bud puncture method appeared to be the most efficient and will be used for further greenhouse evaluations of the progeny. Detection of marker-trait associations has been performed and so far may indicate a complex determinism for smut resistance. Many markers are involved with little effects. Nevertheless, among the other traits we looked at, two putative major genes originating from MQ 76/53 have been tagged: a gene involved in the red color of the internode and a rust resistance gene. Locus specific markers, SSR markers from sugarcane and maize and sequences differentially expressed in response to challenge by smut (provided by SASEX), will be mapped. It might help explain the genetic variation of smut resistance observed in our trials. (Texte intégral)