Induced Resistance in Mycorrhizal Tomato is correlated to Concentration of Jasmonic Acid

The study shows that Arbuscular Mycorrhizal Fungi (AMF) are capable of imparting disease tolerance in tomato plants pre-infected with Fusarium Oxysporum f. sp. Lycopersici (FOL). Inoculation of tomato seedlings with Glomus Macrocarpum (GM) or Glomus Fasciculatum (GF), 20 days after infection with FOL reduced pathogen spread and disease severity by 75 and 78 %, respectively. The mycorrhizal plants showed increased growth, possessed higher Phenylalanine Ammonia Lyase activity (PAL), phenol concentration and foliar trichome density. Upto nine-fold increase in concentration of Jasmonic Acid (JA) was observed in mycorrhizal tomato plants compared to FOL-infected control plants. The increased JA concentration in mycorrhizal plants was concomitant to systemic enhanced defence response measured in terms of increase in PAL activity, concentration of phenols and trichome density in leaves. The above parameters shoFwed strong positive correlation with endogenous level of JA. The results suggest implication of JA in AMF-induced systemic resistance.