Rio Red Grapefruit

The 2004 origins account identifies Rio Red as a darker-pigmented bud sport found on A&I 1-48 in 1976 and released in 1984, citing Hensz (1981, 1985).^⁠[3]

UCR describes CRC 3916 as a vigorous, large tree producing large, juicy grapefruit with pink flesh and a sometimes pink-blushed rind, and lists Riverside ripening from February to June. ^⁠[1]Citrus Australia reports low seed numbers and notes that flesh color varies in southern Australian conditions. ^⁠[7]The 2004 paper also reports a higher tendency for sheep-nosed fruit and rough peel late in the season.^⁠[3]

Grower tastings in Australia and North Carolina describe juicy fruit, with individual specimens reported as having little bitterness or sourness; a later North Carolina tasting described sweet fruit.^{⁠[10]⁠[13]⁠[15]} Growers in Central California and near Buda, Texas, also report productive managed trees, but their crop estimates and tasting impressions are local observations rather than standardized cultivar measurements.^{⁠[9]⁠[11]⁠[12]}

The 2007 karyotype study used CMA/DAPI staining and rDNA-FISH. Its abstract reports Rio Red Grapefruit in a marker group with three C-type and five D-type CMA-positive marker chromosomes and five 45S rDNA sites; it also reports two 5S rDNA-bearing chromosomes in each accession examined. These marker patterns are not a ploidy determination, full chromosome count, shared cultivar identity or proof of parentage.^⁠[22]