FREEZING TOLERANCE AND GROWTH-CHARACTERISTICS OF USDA INTERGENERIC CITRUS HYBRIDS US-119 AND SELECTION-17-11

Two USDA intergeneric, hybrid citrus scions, US 119 {[Citrus paradisi Mac. 'Duncan' x Poncirus trifoliata (L.) Raf.] x C. sinensis Osb. 'Suc cory'} and selection 17-11 {C. grandis US 145 x [Citrus paradisi Mac. 'Duncan' x P. trifoliata (L.) Raf.]} on 'Swingle' citrumelo (C. paradi si x P. trifoliata) rootstocks were examined for freeze hardiness trai ts (4 years) and general growth characteristics (2 years). Hardiness w as compared with that of 'Hamlin' orange [C. sinensis (L.) Osb,] and s atsuma mandarin (C, unshiu Marc) from Fall 1993 to Spring 1997. As exp ected, US 119 and 17-11 were both hardier than 'Hamlin' orange as dete rmined by leaf disc electrolyte leakage (EL), Both showed freezing tol erance similar to that of satsuma mandarin, but 17-11 was significantl y hardier than satsuma or US 119 at several times during the 4-year st udy. Trunk diameter and tree height were similar for US 119 and select ion 17-11.