Response of Solanum lycopersicum L. to Rhizoctonia solani during the germination and seedling stages

Abstract

The fungus Rhizoctonia solani causes significant losses in tomato crops due to the lack of resistance genes to this pathogen. This research aimed to evaluate phenotypic characteristics associated with tolerance to R. solani during the germination and seedling stages of 90 tomato lines, identify promising genotypes for breeding programs, and develop strategies for evaluating tolerance at both developmental stages. The germination test was conducted for 10 days in a germination chamber, under constant darkness for the first 3 days and artificial light for the following 7 days, at 28 ± 2 °C and 70 ± 5 % relative humidity. The seeds were inoculated with 2 mL of a suspension containing 336 × 103 mycelial fragments per mL. Twenty four lines with higher tolerance to R. solani were identified, exhibiting lower disease incidence and higher vigor compared to the control (α < 0.05). In the seedling stage, the evaluation was conducted over 10 days in a floating raft system, with a density of 166 plants∙m-2. Inoculation was performed using the bare-root method for 3 h with the same inoculum suspension. At this stage, 17 tolerant lines were identified, exhibiting greater leaf area and biomass accumulation in both shoot and root (α < 0.05). Lines L12, L13, and RF38 showed tolerance to R. solani in both phenological stages and therefore can be incorporated into tomato breeding programs. Furthermore, the tests developed allowed for the evaluation of a large number of genotypes and the identification of the most tolerant ones.