Impact of grafting on yield and plant health of tomato varieties cultivated under protected subtropical climate

Introduction In subtropical protected cultivation, continuous solanaceous cropping favors the persistence of soilborne Ralstonia solanacearum, which limits tomato production. This study evaluated the productive and phytosanitary performance of two tomato cultivars, Ravena and Grazianni, grafted or non-grafted onto Woodstock rootstock in a greenhouse with a history of bacterial wilt. Methods A randomized complete block design with a 2×2 factorial arrangement (cultivar × grafting) and six replications was used. Yield components, total and marketable fruit mass, and bacterial wilt incidence under naturally occurring soil inoculum were evaluated. Bacterial strains from symptomatic plants were characterized phenotypically (TZC medium, Gram staining) and genotypically (species-specific PCR, primers 759/760), the latter without positive or negative controls and without amplicon sequencing. Results Grafting increased fruit number (18.8%), fruit mass and marketable yield relative to non-grafted plants in both cultivars, with no significant differences between cultivars for these traits. Grafted plants showed 0% bacterial wilt incidence, compared with 86.7–100% in non-grafted plants. Isolates showed colony and Gram characteristics consistent with R. solanacearum and yielded a single amplicon of the expected size (approximately 280 bp). Discussion Grafting onto Woodstock rootstock is an effective agronomic strategy to increase tomato yield and to manage bacterial wilt under natural soil inoculum pressure in subtropical protected cultivation, although controlled inoculation trials would be required to formally characterize the underlying resistance mechanism.