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.