Cultivar- and dose-dependent efficacy of wheat resistance inducers against Septoria tritici blotch in laboratory and field conditions

Abstract: Septoria tritici blotch (STB) is one of the most devastating diseases of wheat worldwide. Since no fully resistant wheat genotype is available so far, disease control depends mainly on the systematic and extensive use of fungicides, which may have a negative impact on the environment and human health. Resistance inducers could be considered as either an alternative or a complementary tool in crop protection to conventional fungicides. However, protection efficacy conferred by such inducers at the laboratory scale is often minimized in field conditions since their activities depend on several factors, including plant physiology and environmental conditions. Here, we investigated cultivar and dose effects of four resistance inducers (referred as FSOV2, FSOV4, FSOV7 and FSOV10) on the protection of wheat against Mycosphaerella graminicola, the causal agent of STB. Investigations were performed in laboratory and field conditions on three wheat cultivars differing in their resistance levels toward STB (from the most susceptible to the most resistant: Alixan, Premio and Altigo). In field experiments, each inducer was applied twice (at growth stages GS Z30 and Z37). First application was performed at the recommended dose and with the inducer on its own and the second one in association with the Cherokee® fungicide. Disease assessments revealed that the protection efficacies conferred by treatments were cultivar-dependant. In laboratory conditions, the three cultivars were treated by the inducers at four different doses and 48 hours before artificial inoculation with the T01193 M. graminicola strain. Our results corroborated the cultivar-dependant efficacy observed in the field and also revealed a dose-efficacy response with all inducers used. Additional investigations suggest that all inducers exhibited, but at the highest dose only, a direct in vitro effect on M. graminicola. The cultivar- and dose-dependent efficacy of plant resistance inducers in wheat against STB will be discussed.