Growers and Researcher Discuss Millennium Block Trials

Josh McGillResearch, Rootstocks, Varieties

Two citrus growers recently explained the benefits to be gained from research at the Indian River Research and Education Center’s (IRREC) Millennium Block in Fort Pierce, and a scientist discussed a grapefruit study there. The IRREC is a University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) facility.

Millennium Block
Plant breeders Jude Grosser (left) and Fred Gmitter (center) discuss new varieties with citrus grower Travis Murphy at the recent Millennium Block Field Day.

The 20-acre block was planted in 2019 to help growers find trees that might produce high-quality fresh fruit with tolerance to citrus greening and diaprepes root weevil. The grove features trials for navel oranges, mandarins and grapefruit on numerous rootstocks, but the largest trial is for grapefruit and grapefruit-like scions.

“The grove is in a high greening and diaprepes root weevil area,” said Pete Spyke, a grower and member of the IRREC Advisory Committee. “One of the things the researchers want is for the trees to become infected with greening at a very early age. We are not doing anything to prevent trees becoming infected with greening, just basic grove care.”

“The work put into the Millennium Block involves over 30 rootstocks,” continued Spyke. “The assumption is that a few of them will eventually replace the traditional industry rootstocks. The rootstock portion of the trial is primarily designed to compare rootstocks in the UFR (University of Florida Rootstock) group with other industry standard rootstocks. The Millennium Block is the most complete side-by-side UFR rootstock trial in Florida.”

Travis Murphy, also a grower and IRREC Advisory Committee member, said a goal of the research is to use promising plant breeding results for new varieties and UFR rootstocks that better fit the market. Researchers look at rootstock components that tolerate disease and produce fruit that holds high internal quality for the fresh market.

“The new scion varieties being tested may produce fruit that is good for juice just like an ‘old’ variety might on a new rootstock,” said Murphy. “We never know what we will face with new diseases and pests, so the need for continuous plant breeding work and trials is more likely to grow even larger in the future.”

UF/IFAS researchers are examining the UF 914 scion, a grapefruit-like hybrid created by UF/IFAS plant breeder Fred Gmitter. Gmitter said the fruit was developed without the chemicals that are responsible for the grapefruit-drug interactions that discourage people who take various medications from enjoying grapefruit. “The variety potentially could be marketed to consumers to safely consume grapefruit while using blood pressure or cholesterol control medications,” Gmitter said.

But Gmitter prefers to focus on the eating quality of UF 914. “At its peak, its taste is superior, according to taste testers in many different locations over the years,” said Gmitter. He added he was surprised to see that it is holding up well to greening, particularly on the X-639 rootstock. Some of the best-looking trees in the trial are the UF 914 and X-639 combination.  

Source: UF/IFAS

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