US-812 Citrandarin

US-812 is a Sunki mandarin × Benecke trifoliate orange rootstock selection made by Joe Furr at USDA’s Date and Citrus Station in Indio in 1965.^⁠[1] During early testing, seed was transferred to USDA’s Orlando laboratory. Florida testing used the names Sunki-Benecke, HRS-812, and US-812.^⁠[9] USDA-ARS released US-812 for unrestricted commercial use in May 2001.^⁠[9] UCR records receipt of Florida DPI clone DPI-814-A budwood in 2002 and identifies its Riverside accession as CRC 4261 / VI 965.^⁠[1]

In IAC rootstock studies, US-812 is identified as accession IAC 1697; IAC 1711 is a separate accession identified as US-852.^{⁠[12]⁠[13]} IDtools describes US-812 fruit that are as broad as long or longer than broad, with orange flesh, rind from yellow through red-orange, slightly rough to rough texture, leathery firmness, and no navel.^⁠[10] The identification entry also describes a compact or dense, nonweeping crown, trifoliate leaves, and malodorous scent from crushed leaflets.^⁠[10]

UCR’s 2006 note quotes the May 2001 release notice as reporting good Florida trial performance, growth, survival, and crops for trees on US-812 rootstock; in its Polk County trial, trees were generally healthy and medium in stature, similar to Carrizo.^⁠[1] The same quoted notice describes its health evidence as preliminary: it lists resistance evidence for citrus tristeza virus, citrus nematode, and Phytophthora nicotianae foot/root rot; low blight-like decline interpreted as resistance but not immunity; Diaprepes larval-feeding susceptibility equal to Swingle; and expected exocortis sensitivity. It says other evaluations were incomplete.^⁠[1] In a separate rainfed Paraná trial, Valencia sweet orange on US-812 yielded 91.4 kg/tree in 2017 and was described as low-vigor, productive, and high in juice industrial properties; fruit-quality findings concern Valencia scion fruit.^⁠[12] The Pera IAC trial at Bebedouro also evaluated IAC 1697 (US-812) as a rootstock, with tree and scion-fruit outcomes limited to that combination.^⁠[13]