Research on Rootstocks: More Than HLB

Ernie Neff Rootstocks


Plant breeders Fred Gmitter and Jude Grosser report on their efforts to develop rootstocks that perform well in Florida from several perspectives. In addition to seeking tolerance to HLB, they are working on rootstocks that might control tree size, deal with other diseases and pests and perform in a range of soils. Gmitter and Grosser are University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers at the Citrus Research and Education Center.

“We’ve been screening rootstocks for their ability to either mitigate or eliminate HLB from grafted scions,” Grosser says. “We are finding a number of candidates that look like they can pretty much mitigate the disease … We’re also seeing rootstocks that were previously selected for stress tolerance, particularly salinity tolerance, that seem to be doing very well in our screens for ability to mitigate HLB … There’s a lot of progress being made, and I think we’re going to have some rootstocks that can really help our industry. We’re already getting there.”

“Both Jude and I have been doing some work to develop tree-size-control rootstocks,” Gmitter adds. He says such rootstocks could be used to grow very small trees “that are very efficient (fruit) bearers.” Some such rootstocks are being studied in the European Union and Florida “to be used in what they’re calling ultra-high-density orchards,” he says. “These are orchards that would be entirely mechanically harvested oranges for juice … There are some in our industry who think this may be the wave of the future for orange juice production in Florida.”

Grosser points out that “we can’t forget about all the rootstock traits that we were breeding for before HLB.” For instance, rootstocks are needed to cope with citrus blight, a disease that was costing some growers 10-15% of their trees annually, he says. He adds that growers also have to cope with Diaprepes root weevil, the phytophthora complex, nematodes and a range of challenging soils. So rootstocks are needed that handle HLB “but all these other things” as well, he says. “We’ve been paying attention to the whole package.” Grosser says for some Florida growers in coastal areas, salinity has become a bigger problem than ever before, so rootstocks are needed that can tolerate salinity.

Gmitter chimes in: “HLB is clearly the number one public enemy. But there were a lot of problems we had before HLB, and they still exist.”

This interview with Gmitter and Grosser is part of the October All In For Citrus podcast, a joint project of UF/IFAS and AgNet Media. Listen to the full podcast here.

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Ernie Neff

Senior Correspondent at Large

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