Field Day Featured Favorable Fresh Fruit Rootstock and Scion Combinations

The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Indian River Research and Education Center recently hosted a field day showcasing its Millennium Block citrus grove. The field day went on despite the grove being impacted by a tornado associated with Hurricane Milton in October.

The Millennium Block is one of the largest experimental trials examining fresh fruit varieties and rootstocks in Florida. The grove includes four different trials. The largest one compares 18 scions from various sources, including UF/IFAS, U.S. Department of Agriculture (USDA) and the Florida Department of Agriculture and Consumer Services germplasm collection. Those varieties are being compared on three popular commercial rootstocks: sour orange, US-942 and X-639.

“The other three trials are rootstock trials where we compare what we have from the UF/IFAS breeding program to what the USDA breeding program has developed,” said Flavia Zambon, UF/IFAS assistant professor of citrus production. “We have 30-plus rootstocks. Each one of those are independent trials and each has a different scion. Trial two we have Ray Ruby grapefruit on different rootstocks. Trial three we have Glen navel, and the last is mandarin UF-950. The mandarin trial is on hold because we’ve not gotten much fruit production on it yet.”

The field day featured the better-performing combinations from each trial, except the mandarin. Among those was the grapefruit/pumelo hybrid UF-914.

“It (UF-914) has so much potential and so much Brix. We are reaching 8.9 to 9.0 Brix close to harvest, so that is very substantial for our industry,” Zambon said. “It looks especially good on US-942 and X-639 rootstock.” 

Attendees also got to see what Zambon called a “fortuitous mistake” planted in one trial. Mislabeled trees were planted in one plot. The variety has been identified as Triumph grapefruit, which is a very old selection long out of production. But what stands out about the variety is its seemingly high tolerance to HLB. It has a full, green canopy with few visible symptoms of the disease even though it is HLB-positive. Triumph’s only drawbacks are that the fruit is not red, and it is quite seedy. But Zambon says it is fortunate Triumph’s tolerance to HLB has been identified because it could offer new breeding material to impart tolerance to the disease.

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