Résumé
Plant pathogens often adapt to plant genetic resistance so
characterization of the architecture underlying such an adaptation is
required to understand the adaptive potential of pathogen populations.
Erosion of banana quantitative resistance to a major leaf disease caused
by polygenic adaptation of the causal agent, the fungus Pseudocercospora
fijiensis, was recently identified in the northern Caribbean region.
Genome scan and quantitative genetics approaches were combined to
investigate the adaptive architecture underlying this adaptation.
Thirty-two genomic regions showing host selection footprints were
identified by pool sequencing of isolates collected from seven plantation
pairs of two cultivars with different levels of quantitative resistance.
Individual sequencing and phenotyping of isolates from one pair revealed
significant and variable levels of correlation between haplotypes in 17 of
these regions with a quantitative trait of pathogenicity (the diseased
leaf area). The multilocus pattern of haplotypes detected in the 17
regions was found to be highly variable across all the population pairs
studied. These results suggest complex adaptive architecture underlying
plant pathogen adaptation to quantitative resistance with a polygenic
basis, redundancy, and a low level of parallel evolution between pathogen
populations. Candidate genes involved in quantitative pathogenicity and
host adaptation of P. fijiensis were identified in genomic regions by
combining annotation analysis with available biological data.