3.4. Compared to D. dianthicola, D. solaniexhibited a fitness advantage in hyacinths
The aggressiveness and fitness of the two species was further compared
in hyacinths, that constitute a reservoir or/and primary or intermediate
host of D. solani. The five D. dianthicola and fiveD. solani bacterial strains were inoculated separately on eight
plants per strain and the number of symptomatic and asymptomatic plants
were counted. A Kruskal-Wallis test revealed differences betweenD. solani and D. dianthicola in terms of symptom incidence
(k=3.03; DF=1; p=0.08). D. solani was found more aggressive thanD. dianthicola ; means ± SE of the percentage of symptomatic
plants reached 43% ± 17 and 23% ± 9, respectively (Figure
S4a) .
In co-inoculation assays with species mixtures (Figure S4b ),
the qPCR quantification of the pathogens in five symptomatic tissues
showed that the calculated CI were different from one (Kruskal-Wallis
test: k=7.8; DF=1; p= 5 x 10-3). The CI median value
of 4 x 109 indicated a high competitive advantage ofD. solani over D. dianthicola in rotted tissues of
hyacinths. Bulb plants thus appeared promoting competitive exclusion ofD. dianthicola by D. solani , which would lead to an
enrichment in D. solani in the bulb plant agrosystems.