Salicylic acid as an elicitor of resistance to root-knot nematodes in tomato

The Meloidogyne-tomato incompatible interaction was studied under in vivo and in vitro conditions. Resistant roots always reacted to root-knot nematode attack by decreasing catalase activity. As salicylic acid (SA) is a physiological inhibitor of this enzyme, it was tested as an elicitor of resistance in tomato attacked by these parasites. Different methods of treatment were carried out one day before inoculation with active juveniles: 1) immersion of roots of seedlings in SA solutions (root dip); 2) foliar spray with SA solutions; and 3) soil-drench with SA solutions to seedlings planted in pots. Reproduction of the parasites, expressed as number of eggs per gram of root fresh weight, on plants of the susceptible cv. Moneymaker treated by root dip and soil-drench showed 20–25% reduction, compared with untreated plants. Moreover, treated plants appeared in a healthier condition at the end of the nematode life-cycle when data were recorded, thus indicating that the observed moderate reduction of nematode reproduction was not associated with loss in plant fitness.