New Grapefruit Rootstock, Scion Experiment

Daniel CooperGrapefruit, Industry News Release, Research, Rootstocks

grapefruit
grapefruit

The world’s peerless grapefruit grows in the Indian River Citrus District. Balanced with sugar and tart, and a thin rind for easy peeling, the fruit is sold mostly for export to European and Asian markets, where it 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 (HLB) 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 Institute of Food and Agricultural Sciences 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 are working to make it thrive once again,” said Ronald D. Cave, director for IRREC.

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In the early fall, Ferrarezi and his laboratory crew will plant 5,440 new grapefruit, navel and mandarin trees in a grove know as 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 and UF/IFAS.

“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.

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 (USDA) 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 USDA 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 percent 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 Europe’s and California’s fine wine production regions. He notes that devotion to continuous research is the factor that can make a crop an artful, superior fresh fruit.

“You do trials and adjust rootstock to scions and develop a fruit product that is just right,” Minton said.

Source: University of Florida Institute of Food and Agricultural Sciences

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