SALICYLIC ACID ACTS AS A RESISTANCE ELICITOR ON TOMATO SEEDLINGS ATTACKED BY ROOT-KNOT NEMATODES: EFFECT OF PLANT AGE

Exogenously provided salicylic acid (SA) was tested as a resistance elicitor to root-knot nematodes in tomato by dipping young and old plants in 1 mM SA solutions. Doses of application were expressed as pg SA provided per g fresh weight of the adsorbing plants (ppm). Plant fitness, numbers of egg masses/root system, numbers of eggs/root system and numbers of eggs/egg mass were recorded in treated and untreated plants 40 and 60 days after inoculation with Meloidogyne incognita. Young plants were damaged by SA treatment. Conversely, plant fitness of treated old plants was not affected by SA applications, as compared with untreated plants. SA treatment consistently decreased the numbers of egg masses/plant with respect to untreated plants, although it did not alter the numbers of eggs/plant, because of an increase in female fertility. Plant age, that by the method used in this study determines the applied dose of the chemical treatment, has revealed to be crucial for the effectiveness of SA to act as a resistance elicitor to root-knot nematodes. At opportune provided amounts, SA treatment may be valid to lower nematode infestation, although further investigation is needed to support its practical usage as a control method of root-knot nematodes on tomato.