The potency of the some chemicals from different groups known as inducers of systemic acquired resistance
(SAR) viz., acetylsalicylic acid (ASA), DL-3-aminobutyric acid (BABA), 2,6-dichloroisonicotinic acid
(INA), 5-chlorosalicylic acid (CSA), nitrosalicyl ic acid (NSA), salicylic acid (SA), ascorbic acid (AS) and
selenium (SE) in reducing development and reproduction of Meloidogyne incognita in tomato plants cv.
Castel Rock was investigated under greenhouse conditions. All inducers were applied as soil dren ch to
tomato plants grown in 25 cm-diam. earthen pots. Three days-before nematode inoculation time treatment
maximized the efficacy of tested chemicals in reducing nematode galls, egg-masses and eggs numbers
followed by synchronized addition with inoculation. While, post-inoculation treatment was less effective.
Reiterative doses post-inoculation were improved the efficacy of single dose revealed that three doses
remained more effective than one or two. While, differences between two or three time doses wer e
insignificant. On the other hand, plant fitness was slightly impaired with third dose than second one. INA
and SE showed pronounced effect in inhibition nematode population after third dose compared with the rest
chemicals. However, three doses of SE were reduced plant fitness after enhanced by double doses. While,
INA showed phytotoxicity gradually increased by repeating doses. Gathering between the most effective
application time (before inoculation) and the proper activated dose after inoculation was s tudies for
emphasized their action and comparing with pre-inoculation only in suppressing M. incognita population.
Enzyme activity of both peroxidase and polyphenol oxidase were elevated in infected tomato roots than
healthy ones. Chemical activators showed enhancing in these antioxidant activities, indicating the SAR four
chemicals was occurred. In conclusion, CSA, NSA, BABA and SA have