Organogenesis and Agrobacterium rhizogenes-induced rooting in Pinus maximartinezii Rzedowsky and P-pinceana Gordon

Pinus maximartinezii (Rzedowsky) and P. pinceana (Gordon), two endemic species of Pinus from Mexico, were successfully regenerated in vitro by organogenesis starting from mature embryos. In both species, 100% of the explants produced adventitious buds after an 18-day induction period on media containing 6-benzylaminopurine (BA) and a subsequent 8 weeks of incubation on growth regulator-free media. The most successful treatment (13.3 muM BA) resulted in an average of 14.6 and 25.9 buds per explant in P. maximartinezii and P. pinceana, respectively. Rooting was achieved by auxin pulses or by Agrobacterium rhizogenes inoculation. In the first case, roots formed on 13% and 7% of the auxin-treated shoots of P. maximartinezii and P. pinceana, respectively. In the second case, A. rhizogenes induced root formation on 60% and 67% of the inoculated shoots from P. maximartinezii and P. pinceana, respectively. The presence of the foreign genes transferred by A. rhizogenes into these roots was demonstrated by histochemical staining for beta-glucuronidase activity, the polymerase chain reaction and Southern blot analysis.