Clavibacter michiganensis subsp. michiganensis MANAGEMENT STRATEGIES IN TOMATO (Solanum lycopersicum L.)

Clavibacter michiganensis subsp. michiganensis (Cmm) is the causal agent of bacterial canker, which is the most destructive disease of tomato (Solanum lycopersicum L.). This study compared the effectiveness of two nitrogen fertilization regimes, Steiner 100 % NO3- and Steiner 85/15 NO3-/NH4+, in supplying total nitrogen for tomato nutrition under greenhouse conditions. These treatments were tested in combination with the plant activators Romel (Brevibacillus sp.), Fungifree (Bacillus sp.), and Messenger Gold (Harpin protein αβ 3 %) to evaluate their effects on Cmm severity and yield in a completely randomized factorial experiment. Each fertilization regime was applied daily in drip irrigation, while plant activators were sprayed weekly. Inoculation of Cmm in plants was performed by cutting the petiole with scissors soaked in a suspension with 108 CFU mL-1. Yield and severity were assessed by evaluating the nutrition and plant activator factors, as well as their interaction. A two-way analysis of variance (treatment and nutrition) and Tukey’s comparison of means (p ≤ 0.05) were performed. The Steiner 100 % NO3- nutrition regime showed significant differences (p ≤ 0.05) in yield, fresh and dry weight of leaves, number of bunches, and number and diameter of fruits. Significant differences (p ≤ 0.05) were found in the weighted percentage of leaf damage and whole-plant wilting severity; the highest severity was recorded with the Steiner 85/15 NO3-/NH4+ + Romel treatment and the lowest with Steiner 100 % NO3- + Messenger Gold. The application of Harpin protein and exclusive nitrogen fertilization with nitrates (NO3-) is an efficient management strategy that promotes higher yield and fruit quality while reducing the severity of Cmm under greenhouse conditions.