Minigrafting of shoots, roots, inverted roots, and somatic embryos for rescue of in vitro Citrus regenerants

Minigrafting was used for rescue of tissue culture regenerants of the follo wing four species of Citrus: sour orange (C, aurantium L, 'AA CNR 31'), swe et orange [C, sinensis (L,) Osb, 'Valencia Late'],lemon [C, lemon (L,) Burm , 'Femminello Comune'] and mandarin (C, deliciosa Tenore 'Tardivo di Ciacul li'), The grafting was carried out with different scion types including sho ots, roots, inverted roots and somatic embryos, This material was obtained in vitro from embryogenic style-derived callus, Seedlings of open-pollinate d sour orange (C, aurantium L,), Cleopatra mandarin (C, reshni Hort, ex Tan .) and 'Troyer' citrange [C, sinensis Osb. x Poncirus trifoliata (L,) Raf.] were used as rootstocks, Minigrafting of shoots, roots, inverted roots and embryos regenerated in vitro allowed successful rescue of these four speci es. Percentages of successful minigrafts ranged from 100 % (shoots) to 2.5 % (inverted roots). The probability of successful graft unions Increased wi th the age of the rootstock, The final mean canopy leaf area (120 days afte r grafting) ranged from 5.2 cm(2) ('Tardivo di Ciaculli' mandarin grafted o n 6 month old Cleopatra mandarin) to 157.9 cm(2) ('Valencia Late' sweet ora nge grafted on 18-month-old Cleopatra mandarin). In this work we examined s ome of the variables which influenced minigrafting and we determined the ef ficacy of this method for rescue of in vitro regenerants of Citrus. This me thod is also suggested as a technique to produce a high percentage of viabl e plants from in vitro regenerants difficult to root.