Grafting as an Alternative to Methyl Bromide in Field Tomato Production

Vegetable grafting has evolved into a unique component of sustainable vegetable production in Asia and many Mediterranean countries for soilborne disease management and yield improvement. Research efforts have recently taken place to explore the use of grafting as a potential alternative to methyl bromide in open field production of tomato in the U.S. Experiments were carried out in summer and fall 2008 in Live Oak, Florida to investigate the feasibility of grafted tomato production using disease resistant rootstocks in the absence of soil fumigants. A determinate heat tolerant tomato cultivar 'Bella Rosa' was grafted onto a commercially available interspecific rootstock 'Multifort' which has been recommended for open field production. Grafted plants and the controls of non-grafted 'Bella Rosa' and self-grafted 'Bella Rosa' were grown under three soil conditions including non-treated soil, soil treated with preemergent herbicides, and soil fumigated with methyl bromide:chloropicrin (50:50), in a split plot design with four replications. In the summer experiment, grafted 'Bella Rosa' with 'Multifort' showed improved growth vigor in both treated and non-treated soils; however, the yield of grafted tomato was compromised by mismanagement of suckers grown from the rootstock. Disease pressure due to soilborne pathogens and nematodes was considered relatively low during the fall experiment, however, marketable yield of tomato from the fumigated plot was significantly higher than that from the non-treated and herbicide-treated plots. Despite the soil treatment, grafting with 'Multifort' significantly increased the marketable yield of 'Bella Rosa' in contrast to non-grafted and self-grafted plants. Moreover, grafted plants grown in non-treated or herbicide-treated soil yielded similarly as compared with non-grafted plants grown in fumigated soil. Yield improvement by the rootstock was attributed to the increase of fruit number but not fruit size. Fruit quality was not affected by grafting with the interspecific rootstock. Further studies are warranted to update the economic analysis of costs and returns associated with use of grafted transplants and to select rootstocks for solving targeted on-site disease problems.