Somatic Hybridization, an Integral Component of Citrus Cultivar Improvement: II. Rootstock Improvement

Production of tetraploid somatic hybrids that combine complementary diploid rootstock germplasm via protoplast fusion has become a practical strategy for citrus rootstock improvement, with the overall objective of packaging necessary disease and pest resistance into horticulturally desirable, widely adapted rootstocks. Citrus somatic hybridization techniques have been advanced to the point where numerous somatic hybrid rootstocks can now be produced and propagated for evaluation on a timely basis. Herein we report the production of 11 new somatic hybrid rootstock candidates from 12 different parents, including Milam lemon hybrid (Citrus jambhiri Lush. Cleopatra mandarin (C. reticulata Blanco), sour orange (C. aurantium L. ). 'Succari' sweet orange [C. sinensis (L.) Osbeck], 'Redblush' grapefruit (C. paradisi Macf.), 'Nova' tangelo [C. reticulata x (C. paradisi x C. reticulata)], 'Kinkoji' (C. obovoidea Hort. Ex Takahashi ), Swingle citrumelo [C. paradisi x Poncirus trifoliata (L.) Raf.], Carrizo citrange (C. sinensis X P. trifoliata), rough lemon 8166 (C. jambhiri), and Palestine sweet lime (C. limettoides Tan.). All hybrids were confirmed by cytological and VNTR-PCR analyses, and have been propagated, budded with a commercial scion, and field-planted for performance evaluation.