2.4 | Evaluation of quantitative pathogenicity
The quantitative pathogenicity of isolates sampled in 2011 (including
the 63 isolates individually sequenced) was measured in Dumartinet et
al. 2019, on the two cultivars studied (FHIA 18 and Macho ¾) by
performing in-vitro inoculations. Briefly, quantitative
pathogenicity was estimated for 16 to 32 isolates per sample by
measuring the diseased leaf area (DLA) on the susceptible (DLA-S) and
the resistant cultivar (DLA-R) via in-vitro inoculation of
detached leaf fragments. DLA combines two phenotypic traits, i.e., the
within-host growth rate and infection efficiency, which are among the
most influential epidemiological parameters in P. fijiensis(Landry et al., 2017)
and appeared to be a good proxy of parasite fitness. Leaf fragments were
collected on banana plants cultivated in the greenhouse for 5-7 months
and inoculated with conidial suspensions of P. fijiensis. After
inoculation, the fragments were incubated in a climate chamber and the
DLA was measured at 60 dpi (days post inoculation). A mixed linear model
accounting for all the experimental effects was developed to predict the
least-squares means (LSMeans) of DLA-S or DLA-R at the population level
and for each isolate.