By Vicky Boyd
Seed companies and university researchers have borrowed the theory behind grafting scion varieties onto rootstocks from the tree-fruit industry and applied it to vegetables.
The result, they say, is a vegetable plant that resists many soil-borne pests and yet produces high-quality fruit.
One of their first candidates is melons, particularly triploid watermelons that have poor germination in the field.
But Bob Dyer, president of Mission, Texas-based Grower Select Product Inc., who’s experimented with grafting in Mexico since 1997, says he’s given up because of the cost and the lack of consistent fruit quality.
“[Grafting] will work where you have diseases in your soil—Fusarium problems and stuff like that,” Dyer says. “But you’ll never, in my experience, get the quality of fruit that I’m looking for. You can cut pieces of fruit off the same plant and have night and day differences.”
Instead, he says he will focus on improving soil health and trying to eliminate or reduce Fusarium-related issues in the soil.
Looking to the East
Although the techniques for grafting melons onto squash and gourd rootstocks have been used for decades in Asian, they are still in their infancy in the United States.
“In Korea, 95 to 100 percent of the watermelon are grafted,” says David Baquerizo, eastern production specialist for Syngenta’s Full Count Plant Program. “They’ve been using this technique since the early 1900s, and the reason why is they’ve been farming the same land for so long that they were battling soil-borne diseases and soil exhaustion.”
Richard Hassell, a Clemson University horticulture professor in Charleston, S.C., has studied cucurbit grafting for several years as part of a four-state research project.
The main benefit, he says, is the squash and gourd rootstocks resist soil-borne Fusarium.
In addition, some of the rootstocks are resistant to Southern rootknot nematode and Phytophthora.
Grafted plants also could offer growers an option to soil fumigation to address soil-borne pests, Hassell says.
But the effects of the rootstock go beyond the roots and impart beneficial qualities to the fruit, he says.
Hassell’s research has shown that watermelon from grafted plants contain significantly more lycopene—a phytochemical that may have health benefits—than those from own-rooted plants.
“Grafting also increases the firmness of the flesh, so the fresh-cut people are very interested in this,” Hassell says. “It firms up the flesh so you don’t get as much leakage and it’s crunchier to the taste.”