Effect of alternative treatments on seed-borne Didymella lycopersici in tomato

To quantify the phytotoxicity and effect of alternative seed treatments based on acidified nitrite and elicitors of plant resistance (Tillekur and Chitosan) against seed-borne inocula of Didymella lycopersici.

Treatments tested were: nitrite [sodium nitrite in citric acid buffer (pH 2)] at 30, 100 and 300 mmol l(-1) and three exposure times (10, 20 and 30 min); Tillekur (in water) at 12.5, 25, 50, 100 and 200 mg ml(-1); Chitosan (in 0.05% acetic acid) at 2.5, 5, 10 and 50 mg ml(-1). Efficacy of treatments was determined in growth chamber experiments. Nitrite at 300 mmol l(-1) was completely effective, as was the fungicide, at controlling disease when applied for less than 20 min. Tillekur was as effective as the fungicide postemergence, but proved to be phytotoxic pre-emergence. Chitosan was significantly less effective than the other treatments.

The high efficacy and low cost of acidified nitrite indicates that it is a suitable alternative to fungicides.

There is currently a lack of effective seed treatments that can be used in organic and low-input crops. Treatments identified in this study can be considered as an effective alternative to chemical control against seed-borne fungal pathogens.