Can Florida Tomato Growers Benefit from Using Grafted Plants?

Can Florida tomato growers benefit from using grafted plants? That is a question Xin Zhao and Eric Simonne, both with the University of Florida Horticultural Sciences Department, are researching. They published a paper on the subject in the 2008 Tomato Institute Proceedings that looks at the potential benefits and challenges of the practice.

“As far as I know, there are some growers trialing grafted tomatoes, but not many,” says Zhao. “It is still a new technique to most Florida growers, and more research is warranted to fully elucidate the potential benefits of growing grafted tomatoes in the state.”

According to the report, one area where grafting might prove beneficial is in the absence of methyl bromide. Several land-grant universities, including the University of Florida, are studying rootstocks that are resistant to diseases like fusarium wilt, verticillium wilt, bacterial wilt, crown and root rot, root-knot nematodes, and/or tobacco mosaic virus. Specifically, Florida is testing Maxifort (De Ruiter Seeds), which is a popular rootstock in greenhouse tomato production.

It is also believed that grafting can speed up the process of tomato breeding and take full advantage of germplasm benefits. For example, tomatoes with desirable above-ground traits can be grafted with rootstocks with desirable below-ground traits.

Efficiency And Yield

Better uptake of water and nutrients has been observed in grafted vegetables, possibly caused by the vigorous root systems of the rootstocks. With appropriate rootstocks for targeted tomato scion varieties, a distinctive nutrient management program for grafted-tomato production may be established to achieve improved fertilizer efficiency in Florida where nutrient leaching and runoff may be of environmental concern.

Yield enhancement has also been observed in grafted tomatoes. A greenhouse study of ‘Florida 47’ grafted onto Maxifort showed an overall increase in fruit number and fruit size compared to the self-rooted ‘Florida 47.’

Considering Challenges

There are a number of obstacles in front of growers considering planting grafted tomatoes that must be taken into account, according to the report. Cost has been a leading limiting factor with additional expenses for seeds (two seeds versus one), greenhouse space (two transplants versus one), supplies, and labor associated with grafting.

A trained person can graft 125 to 150 plants per hour, while machines can graft 300 to 1,200 per hour. However, grafting techniques and technology are evolving, which should bring down costs.

With the loss of soil fumigants, the higher cost of grafting tomatoes may be offset by disease resistance and higher yield. Currently, researchers are closely studying the cost/benefit ratio of traditional production versus grafted production.

Incompatibility between the rootstock and scion can also derail the potential benefits of grafting. To avoid this pitfall it is necessary to experiment with grafting unions prior to full-scale commercial production.

Delay of harvest is another factor that must be considered, as the process may delay first flowering due to the stress of grafting. Growers should account for this in their timing of planting and grafting.

“In general, the benefits from using grafted plants such as disease resistance and high productivity are expected to offset the additional cost associated with grafting and bring extra profits,” says Zhao. “Given that the cost of soil fumigants may continue to rise, and soil-borne disease management still poses a great challenge, other promising alternatives, including the grafting technique, certainly deserve more attention.”