New Grapefruit Rootstock, Scion Experiment Rises from UF/IFAS Experimental Grove
BY ROBIN KOESTOYO
FORT PIERCE, Fla. — The world’s peerless grapefruit grows in the Indian River Citrus District. Fruit balanced with sugar and tart, and a thin rind for easy peeling, the fruit is sold mostly for export to European and Asian markets. Abroad, the fruit is a high-price delicacy. But the once-thriving industry is in decline, and a plant pathogen is present in all of the state’s grapefruit groves.
Huanglongbing is a disease that reduces fruit yield and quality drastically and can kill citrus. Its common name is citrus greening because the tree’s leaves become lighter shades of green as the disease matures. Rhuanito “Johnny” Ferrarezi and his colleagues call it HLB. Ferrarezi is an assistant professor of citrus horticulture at the University of Florida’s Institute of Food and Agricultural Science’s Indian River Research and Education Center (UF/IFAS IRREC), in the heart of the state’s grapefruit production region.
“UF/IFAS and the citrus research scientists at IRREC are committed to helping our local grapefruit industry and is working to make it thrive once again,” said Ronald D. Cave, director for IRREC.
In the early fall, Ferrarezi and his laboratory crew will plant 5,440 new grapefruit, navel and mandarin trees in a grove that is called “The Millennium Block.” The grove was named in 2000 but was pushed five years later during a canker eradication program. Today, the Millennium Block grove is rising anew; green berms swell from rows of sandy soils bordered by ditches that hold irrigation water. It is a 30-acre field trial, the state’s largest grapefruit grove in which scientists will conduct research, according to Ferrarezi.
The study, from which he expects new grapefruit hybrids that can tolerate HLB will emerge, will continue for six years. Funding for the work is provided by the Citrus Research and Development Foundation, Inc., the UF/IFAS Research office and IRREC.
“We are planting 19 different grapefruit scions on three different types of rootstock for 57 combinations,” said Ferrarezi. “We will test the trees mainly for resistance to HLB – focusing on sustained yield and high-quality fruit. We want to get growers back into production.”
Ferrarezi said rootstock liners grow from seeds, tissue culture or rooted cuttings; a scion bud is grafted into these young trees. Grafting a scion into a rootstock is how every citrus grove begins.
The Millennium Block will feature grapefruit trees bred by UF/IFAS plant breeders Jude Grosser and Fred Gmitter and by U.S. Department of Agriculture scientists Ed Stover and Kim Bowman. The selections were developed at the UF/IFAS Citrus Research and Education Center in Lake Alfred and at the U.S.D.A. Agriculture Service Horticultural Research Laboratory in Fort Pierce, adjacent to IRREC.
Some of the varieties are new: ‘Summer Gold’ produces fruit that holds golden flesh with specks of peach. The rind is a yellow gold with a spray of pink. Its flavor is tart early in the season and sweetens as the year matures. Another distinct characteristic of ‘Summer Gold’ is that it grows through the summer months. The new variety will be tested against widely planted and other promising varieties like ‘Ray Ruby,’ ‘Jackson,’ and ‘Star Ruby.’
Grapefruit is a valuable crop to citrus growers who relish a lifestyle of planting, harvesting and exporting a world-class product. For more than a century, citrus has spread across the coastal and Indian River Lagoon region’s landscape. But the industry has fallen about 90% of what it was in during its mid-to-late 20th century heyday.
Rick Minton, whose ancestors led the local industry to worldwide recognition, continues his family tradition with thoughtful leadership for research. He was present on the first days of the plantings in late September; a steady breeze ruffled the healthy young trees.
“Feel the breeze? It’s the balmy Atlantic Ocean breeze, in conjunction with a warm, humid climate and flatwood soils up and down the Eastern Seaboard that create a thin peel for a juicier fruit and exceptional taste,” said Minton.
Minton likens the Indian River District to European and California fine wine production regions. He notes that devotion to continuous research is the factor that can make a crop an artful, superior fresh fruit product.
“You do trials and adjust rootstock to scions and develop a fruit product that is just right,” Minton said.
The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at ifas.ufl.edu and follow us on social media at @UF_IFAS.