Exploitation of Biostimulatants and Vitamins as an Alternative Strategy to Control Early Blight of Tomato Plants

Early blight of tomato is a fungal disease, caused by Alternaria solani (Ellis and Martin) Jones and Grout, is a major disease of Solanaceae. Therefore, for commercial cultivation in the field controlling early blight is necessary. The use of natural compounds as alternatives or complements to chemical fungicides would be helpful because the crops require continued prolonged harvesting, during which young unsprayed leaf tissue continuously become available for infestation. Several natural compounds were tested on tomato plants grown under field condition and natural infestation to evaluate the potential of biostimulants on improving tomato plant growth, yield and to induce protection from early blight disease. Foliar application of chitosan (Chit), humic acid (HA), seaweed extract (SE) and thiamine (Thi) proved to be effective in reducing early blight disease incidence in tomato plants. All tested biostimulants, in particular, thiamine significantly increased tomato growth parameters (shoot length, no. of branches and leaves per plant, shoot fresh and dry weight and leaf area per plant) and some physiological aspects (nitrogen, potassium, phosphorus and chlorophyll as well as total carbohydrate content) in the shoot. In addition, tomato yield/fed was also increased. Thi at 50 mg L-1 and SE at 500 mg L-1 were the most effective in this concern. Thi and SE could be recommended for controlling early blight disease of tomato in the field and improving its growth and yield.