This study was conducted to determine the most effective biological stage of root knot nematode( Meloidogyne javanica) that can intensify disease severity of Fusarium oxysporum f.sp. lycopersici, the vascular wilt pathogen on tomato roots, as well as to investigate changes in total phenol content along with its relation to disease resistance. Total phenol content was evaluated in tomato plants (cv. Roma VF) inoculated with the fungus and nematode separately and in combination during an 11 day- period after inoculation and then compared with the non-inoculated plants (control). Tomato cv. Roma VF is resistant to F. o. f. sp. lycopersici whereas it is susceptible to M. javanica. The results of the study indicated that fungal inoculation of tomato roots induced phenol production significantly. Phenol content increased at three days-post inoculation (dpi), and reached a maximum level at ninth day. Nematode induced phenol production in tomato roots occurred rather slowly as compared to the fungus induced. Phenol content reached a maximum level at sixth dpi during the nematode infection. When changes in phenol content were compared during the various biological stages of nematode, 15 days post penetration of nematode was found to be the most effective time for reducing induction (suppression) or synthesis of total phenol against the fungal infection. Other time intervals at which such changes were compared included 4 and 21 days post penetration of nematode and simultaneous inoculation of fungus and nematode. Therefore it can be suggested that nematode parasitism and nutrient uptake somehow suppresses phenol synthesis, induced by the fungus, in tomato roots.
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