Evaluation of intraspecific grafted tomato on Fusarium wilt disease protection, tomato scion growth, and grafting compatibility

Tomato (Solanum lycopersicum L.) is a widely grown horticultural crop globally, including Thailand. However, it is infected by Fusarium oxysporum f. sp. lycopersici (Fol), causing a reduction in yields. Grafting has been utilized widely in tomato production to prevent losses caused by soil pathogens. This study aims to investigate the disease resistance of the intraspecific tomato rootstock/scion grafting and evaluate the grafting compatibility and peroxidase gene expression and plant growth under non-infected conditions. Tomato, a susceptible cultivar ‘Sidathip 3’ (STD3), was grafted onto four different Fol disease-resistant tomato accession rootstocks with grafting combinations, including self-graft (SDT3/SDT3) and intraspecific heterograft (SDT3/LE314, SDT3/LE472, SDT3/LE482, and SDT3/LE501). The survival rate of grafted plants was 100% at 20 days after grafting (DAG) compared to non-grafted tomatoes. All the intraspecific heterografted tomatoes had significantly reduced Fol disease symptoms at 60 days post-inoculation. The heterografted plants performed a disease severity score (DSS) of 1 and 0% of disease index (DI) compared to a self-grafted and non-grafted SDT3 with 5 DSS and 100% DI. It was found that there were no significant differences for grafting incompatibility (GI) of grafted tomatoes at 28 days after transplanting (DAT). However, the self-grafted plants showed a slightly lower GI than the heterografted ones. Peroxidase (Solyc02 g084800.2) gene expression was compared between LE472/LE472 and SDT3/LE472. The expression level was threefold significantly higher in heterografted plants than in self-grafted LE472 at 15 DAG. The rootstocks had not significantly affected plant height, number of branches, fruit size, and yield production of grafted tomatoes. These results showed the effectiveness of intraspecific grafting by using the potential rootstock source to increase disease resistance with normal growth, which is of great importance as a tool for controlling tomato pathogen infection.