US-852 Citrandarin Trifoliate Hybrid Budwood

Citrus duttae.

Hybrid of C. reticulata 'Changsha' X P. trifoliata 'English large flowered'.

US-852 is well adapted for production of sweet oranges and other citrus crops in some parts of Central Florida. The major attributes of this new rootstock cultivar are its resistance to several important diseases and low production of root sprouts in the field, and its favourable effects on scion tree size, fruit quality, and productivity. The shorter stature of trees on US-852 in comparison to Swingle and many other common rootstocks allows a more rapid and economical harvest. US-852 rootstock was tested for resistance to Phtyophthora nicotianae by stem inoculation of potted greenhouse plants and found significantly more resistant to damage than several common rootstocks, including Sour orange and Carrizo citrange. Trees of 'Hamlin' on US-852 rootstock were observed to grow and yield well in the presence of severe Florida isolates of citrus tristeza virus. Molecular marker analysis suggests that US-852 carries the CTV resistance gene from Poncirus trifoliata. There is preliminary evidence that US-852 may be unacceptable for use where there is high salinity or pH. Seed propagation of US-852 is inefficient due to relative unfruitfulness, a low number of seed per fruit, and a high proportion of off-type seedlings. Only about half of seedlings recovered are of nucellar (apomictic) origin and have uniform morphology typical of US-852. Cuttings root easily, but a sizeable proportion of these never develop well-anchored plants for nursery handling. Tissue culture propagated plants of US-852 appear healthy, true-to-type, and develop strong root systems in the nursery.

Rootstocks of accession:  Carrizo citrange.

Prepared by the Givaudan Citrus Variety Collection at The University of California Riverside.