From the lab to the field scale: dose-dependent efficacy and mode of action of resistance inducers in wheat against Septoria tritici leaf blotch
Abstract: The use of resistance inducers in crop protection is one of the most promising strategies that could be considered as either alternative or complementary to the use of conventional fungicides. However, the protection efficacy conferred by such inducers is often compromised in field conditions since their activity depends on many environmental factors. Here, we investigated the dose effect of four resistance inducers (referred as FSOV2, FSOV4, FSOV7 and FSOV10) on the protection of wheat against Mycosphaerella graminicola, the causal agent of Septoria tritici leaf blotch (SLB). Our investigations were performed on the susceptible wheat cultivar Alixan in both laboratory and field conditions. At the laboratory scale, each inducer was used on its own at four different doses. At the field level, each inducer was used at a single dose, on its own or in mixture with other inducers, and in association with the Cherokee® fungicide (50 g/l cyproconazole + 62.5 g/l propiconazole + 375 g/l chlorothalonil). A significant protection level was observed for all products, but the efficacy obtained clearly increased with the dose used. Further investigations revealed that all inducers exhibited at the highest dose only a direct in vitro effect on the fungus. A dose-dependent effect on host penetration and on the induction of peroxidase (PO) activity involved in plant defence mechanisms was highlighted for FSOV7 and FSOV10.