Complex adaptive architecture of quantitative resistance erosion in a
plant fungal pathogen
Plant pathogens often adapt to plant genetic resistance so
characterization of the architecture under-lying 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 se-lection 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 be-tween
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 varia-ble
across all the population pairs studied. These results suggest complex
adaptive architecture un-derlying 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 highlighted in genomic regions combining annotation
analysis with available biological data.