Cultivar 362: Sigma

Sigma is a University of Saskatchewan Prunus introduction from the Sapa x Oka breeding line. It was introduced in 1960.[S1] [S3] The introduction list describes it as a spherical, dark fruited selection with dark bluish skin, dark red flesh, and a sweetish flavor. It is part of the prairie sand cherry plum hybrids developed for Saskatchewan conditions.[S3]

Sources identify Sigma as a Sapa x Oka selection. The 1960 University of Saskatchewan introductions sheet adds that it came from mixed open pollination.[S1] [S3] This places it in a recognizable group of related prairie hybrids built around Sapa, Oka, and similar material in the Saskatchewan program.[S1] It was introduced under the selection code C59-357, but that code is only an identifier, not part of its origin.[S3]

The fruit appears to be small to medium, about 1 to 1 1/8 inches in diameter in a Saskatchewan comparison table.[S2] [S3] Descriptions agree on dark bluish to dark purple skin and dark red to purple flesh.[S1] [S2] [S3] The flesh is described as juicy, the flavor as sweet or sweetish, and dessert quality as fair to very fair.[S2] [S3] One table also notes medium thick, tough, astringent skin.[S2]

Tree detail is limited, but the 1960 introduction note says the plant is more upright than others in the same group.[S3] That is the clearest growth habit note in the present sources.

Hardiness is not clearly documented for this plum in the current evidence. One 1976 University of Saskatchewan bulletin mentions a "Sigma" tested mainly in Zones 4 and 5 with moderate to severe winter injury, but that page is in a small fruits context and may not refer to this same Prunus introduction.[S2] For now, Sigma is best understood as a Saskatchewan bred prairie hybrid with incomplete hardiness evidence, not a cultivar with a firm zone rating.

Sigma matters mainly as part of the University of Saskatchewan Sapa x Oka series. It is a named seedling from an important prairie breeding line, with dark fruit, fair dessert quality, and an upright plant habit that distinguished it from related introductions.[S1] [S3]

Summary source basis

• S1: An index of fruit cultivars tested or developed on the Canadian prairies.
• S2: hortfacts_1976_3.pdf
• S3: University of Saskatchewan fruit introductions 1959-1960

This summary currently draws chiefly from hortfacts_1976_3.pdf, with 2 additional supporting sources linked below.

Featured source descriptions

“Skin described as medium thick, tough, astringent; flesh as purple and juicy.”
— ^[3]

“Tested primarily in Zones 4 and 5, where it showed moderate to severe winter injury.”
— ^[3]

“Flavor listed as sweet.”
— ^[3]

“Dessert quality listed as fair.”
— ^[3]

Direct parent cultivars

• No direct linked parent cultivars promoted yet.

Parentage claim text

• Listed as 'Sapa' x 'Oka'.
• Parentage listed as Sapa x Oka, from mixed open pollination.

Derived or downstream cultivar links

• No derived or downstream lineage links yet.

Source-story quotations

• C59-357 Sigma ... Sapa x Oka Mixed open pollination ... 1960 ... Spherical, skin dark bluish flesh dark red, sweetish and of very fair quality. Plant more upright than others.University of Saskatchewan fruit introductions 1959-1960, p9
• C59-357 Sigma ... Sapa x Oka Mixed open pollination ... 1960 ... Spherical, skin dark bluish flesh dark red, sweetish and of very fair quality. Plant more upright than others.University of Saskatchewan fruit introductions 1959-1960, p9
• C59-357 Sigma ... Sapa x Oka Mixed open pollination ... 1960 ... Spherical, skin dark bluish flesh dark red, sweetish and of very fair quality. Plant more upright than others.University of Saskatchewan fruit introductions 1959-1960, p9
• C59-357 Sigma ... Sapa x Oka Mixed open pollination ... 1960 ... Spherical, skin dark bluish flesh dark red, sweetish and of very fair quality. Plant more upright than others.University of Saskatchewan fruit introductions 1959-1960, p9

Taxonomy context: No family-tree context surfaced yet.

Related cultivars mentioned in source context