Inhibitory effect of allicin against Meloidogyne incognita and Botrytis cinerea in tomato

Allicin (diallyl thiosulfinate) is the key natural antimicrobial compound of garlic. Extensive studies have been conducted to understand the effects of allicin in medicine; however, little information is currently available in China about its effects on root-knot nematodes, plant pathogens, plant growth and yield. Laboratory and greenhouse experiments were conducted to evaluate the potential of allicin to control Meloidogyne incognita and Botrytis cinerea in tomato, and its effect on tomato plant growth and yield. The responses of antioxidant enzyme activity to allicin application were also investigated. Results from the laboratory experiments showed that allicin exhibited effective inhibition against M. incognita and B. cinerea, with the median lethal concentration (LC50) of 18.23 and 14.11 mg active ingredient (ai) L-1, respectively. In the greenhouse experiments, allicin not only had an active effect on tomato growth but also showed excellent efficacy to control M. incognita and B. cinerea, resulting in increased tomato yield. Application of allicin also significantly increased the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in tomato leaves compared with the untreated control. Results from this study indicated that allicin was a promising natural compound to control M. incognita and B. cinerea in tomato, providing a potential substitute to synthetic chemical compounds for control of the root-knot nematodes and gray mold of tomato.