Effect of some chemical inducers on chocolate spot disease of faba bean in Tunisia

Botrytis fabae is one of the most important fungal pathogens attacking the leaves and the stem of faba bean Viciafaba L. and causes severe yield losses. This study was carried out to evaluate the effect of four chemical inducers (salicylic, citric, ascorbic and oxalic acids) and one fungicide (Carbendazim) against B. fabae in field and glasshouse conditions. Under field conditions for two seasons and glasshouse experiments, plants treated with salicylic acid showed substantial and significant decrease in the disease severity on the leaves and the stem compared with the control and the fungicide. Salicylic acid was highly effective and controlled the disease better than Carbendazim which provided only partial protection. In vitro, the inhibition of fungal growth was investigated and showed that salicylic acid was the best inhibitor of fungal growth (48%) followed by oxalic (39%), ascorbic (33%) and citric (10%) acids 6 days after incubation. An important increase of total phenols was recorded in treatment by salicylic acid in the healthy and infected leaves of faba bean 12, 24, 48, 72, 96 and 120 hours after inoculation. These promising results on the control of the main fungal disease damaging faba bean in Tunisia and other regions will have an important impact on faba bean production.