Induction of systemic acquired resistance against rust, ascochyta blight and broomrape in faba bean by exogenous application of salicylic acid and benzothiadiazole

Exogenous applications of salicylic acid (SA) and benzothiadiazole (BTH) solutions have been used in faba bean to induce systemic acquired resistance (SAR) to rust (Uromyces viciae-fabae), ascochyta blight (Ascochyta fabae) and broomrape (Orobanche crenata). Both SA and BTH solutions were effective inducing SAR to U. viciae-fabae and A. fabae on susceptible accessions under controlled conditions, although SA was less effective than BTH for A. fabae. BTH treatments reduced the infection of all pathogens studied under field conditions in susceptible accessions, and rust infection was also reduced by SA applications. Moderately resistant accessions became immune to ascochyta blight with BTH treatment, and showed a lower degree of infection to rust after SA or BTH treatments. No effect was observed in the highly resistant accessions. Chemical induction of systemic resistance may provide an additional method for controlling faba bean diseases to be considered in an integrated diseases management.

► Foliar applications of SA and BTH induced SAR in faba bean.
► Rust was reduced by both SA and BTH not being associated with hypersensitivity.
► Ascochyta blight on upper leaf layers was more effectively reduced by BTH.
► Broomrape was reduced by BTH indicating that the effect moves to the roots.