Foster Grapefruit

Foster grapefruit has medium-large, oblate to spherical fruit, very seedy flesh, and pale-yellow rind that may blush pink under favorable conditions. UCR describes the flesh as chamois, sometimes pink, tender, and juicy.^⁠[1]

UCR describes the Foster tree as large, vigorous, and productive. The Citrus ID key separately describes the crown as compact or dense and not weeping; its twig, leaf, and fruit entries list alternative states without identifying a dated or measured accession.^⁠[1]⁠[4]

This variety originated as a limb sport in a tree of the Walters variety in an orchard near Ellenton, Florida, and was discovered in 1907 by R. B. Foster of nearby Manatee. It was introduced in 1914 by the Royal Palms Nurseries, Oneco.^⁠[1]

Hodgson’s 1967 account, reproduced by UCR, described limited planting in Florida and Texas and declining interest after seedless Thompson appeared.^⁠[1]

Another reason for horticultural interest in this variety is the fact that in Texas it gave rise by bud mutation to the seedless pink-fleshed variety, Foster Seedless, which closely resembles Thompson but exhibits somewhat better flesh coloration. Nucellar seedlings of Foster also possess more intense pigmentation than the parent clone.^⁠[1]

The 2007 karyotype study used CMA/DAPI staining and rDNA-FISH. Its abstract reports Foster Grapefruit in a marker group with two C-type and six D-type CMA-positive marker chromosomes and four 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.^⁠[6]