Budwood from a nucellar Ruby Red source was irradiated in 1963, and one of the products found in 1971 was a darker pigmented grapefruit designated A&I 1-48. This was never released commercially, but a budsport from it producing fruit almost as red as Star Ruby was found in 1976, and released as Rio Red in 1984. The tree grows vigorously to a large size. Plantings of Rio Red grapefruit have performed quite well in the Coachella Valley desert region, where it receives the high heat necessary to produce high-quality fruit. The fruit is large, with a slightly pebbled surface. The rind frequently has a pink blush, especially where two fruits grow against each other. The flesh is juicy and well-pigmented, with the darkest color next to the segment membranes. Rio Red is mid to late-season in maturity.