US-942 Citrandarin

US-942 is a citrandarin from a Sunki mandarin × Flying Dragon trifoliate orange cross made by USDA citrus breeder Herb Barrett. The published accounts do not give the cross date, location or seed and pollen roles. USDA released the rootstock in 2010; the release notice identifies the field selection as HRS-942 or US-942.^{⁠[12]⁠[20]}

The USDA release notice describes US-942 as seed-propagated with nucellar polyembryony and reports semi-dwarfing, productivity and disease-response claims, including resistance or tolerance to citrus tristeza virus, blight and Phytophthora. In the St. Lucie County Valencia trial, no rootstock maintained good yield after trees became HLB-affected; these observations do not establish immunity.^⁠[20]

USDA-ARS reports that US-942 was Florida’s most popular rootstock during 2018–2020, with about 1.8 million trees propagated, around 22% of all Florida citrus tree propagations. Early Valencia economics trials at three Florida sites reported positive revenue differences compared with local controls, with the advantage varying by site and season.^{⁠[22]⁠[23]}

In an Immokalee seed-tree study, US-942 fruit collected in December 2019 averaged about 50 g, 41 mm long and 46 mm wide. Separately, The Mulberries reported one received fruit at 58 g, 11 °Bx and pH 2.8. These sample-specific observations do not represent every tree or harvest.^{⁠[21]⁠[13]⁠[15]}