Résumé
Besides the development of the gene for gene resistance, one can observe a limitation of the infection by the installation of a resistance of more or less high level called partial resistance. The aim of this work was to study rice partial resistance against Magnaporthe grisea and its regulation of transcription. Partial resistance was evaluated by quantification (Quantitative PCR) of fungal DNA during late infection (six days post inoculation) and allowed to classify cultivars in groups of partial resistance level (high, average, weak). Thirty rice cultivars (subspecies indica and japonica, subgroups tropical and temperate) were thus classified for partial resistance again four isolates of M. grisea. Transcriptome analyses highlighted genes involved in partial resistance. Analysis of defence gene expression on rice cultivars previously characterized for partial resistance established a correlation between gene expression and partial resistance levels. The results showed that in addition to defence gene induction, basal expression is a key feature of partial resistance. In indica and japonica tropical genetic subgroups, we observe a positive correlation between partial resistance levels and basal expression of defence genes but not in japonica temperate genetic subgroup. Theses results could be explained in part by the differences in culture ecosystems.