Abstract
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 fungusPseudocercospora 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 highlighted in genomic
regions combining annotation analysis with available biological data.