In vitro shoot regeneration from leaves of Pyrus communis L. rootstock and cultivars

The influence of TDZ on adventitious shoot regeneration from leaves of the pear cultivars Conference and Abate Fetel, and the rootstock Farold((R))87 was investigated. Our main aim was to set up efficient in vitro regeneration protocols for all these pear genotypes by using expanding leaves from elongated shoot cultures as starting plant material. Our best results in terms of percentage of regeneration were achieved by using half-strength Murashige and Skoog basal medium supplemented with 1 mu M NAA, combined with 13.5 mu M TDZ for Conference (87.3%) and Farold((R))87 (53.3%), and 9 mu M TDZ for Abate Fetel (68%). The impact on leaf organogenesis of the antibiotics timentin, cefotaxime, and carbenicillin, alone or in combination, usually used for the control of Agrobacterium overgrowth, and of kanamycin, commonly used for the selection of putatively transformed plants, were also evaluated to be exploited in future transformation trials. In general, the use of carbenicillin (475 mM), cefotaxime/carbenicillin (210/238 mM) and cefotaxime (630 mM) did not negatively affect the regeneration efficiency of Conference, Abate Fetel and Farold((R))87, respectively. The use of 4 mu M kanamycin should be suitable to select transformed shoots from Abate Fetel and Farold((R))87 leaves, while a lower concentration or a different selection strategy should be applied for Conference. We report new regeneration and selection protocols usable for the application of new biotechnologies in the genetic improvement of pear cultivars and rootstocks.