Micropropagation of Asparagus macrorrhizus, a Spanish endemic species in extreme extinction risk

Asparagus macrorrhizus: is a new species, which has been recently described. It is limited to the area surrounding the “Mar Menor” lagoon, in Murcia (Spain), and is the only “Critically Endangered” species of the genus Asparagus. Despite being protected, the number of plants has decreased in the last years due to the urbanization of its natural habitat. This species is a valuable genetic resource for asparagus breeding because of its special characteristics. So, the development of a micropropagation protocol is crucial to its conservation and use in breeding programs. The micropropagation protocol from asparagus rhizome buds previously developed by our research group has been adapted for A. macrorrhizus. Rhizome buds of A. macrorrhizus were extracted, disinfected, and then cultured on Asparagus Rhizome Bud Medium (ARBM) consisting of MS medium supplemented with 0.3 mg l NAA, 0.1 mg l KIN, 2 mg l ancymidol and 6% sucrose. A percentage of 69.7 ± 8.0% of the rhizome buds developed shoots, but only 17.4 ± 7.9% of them rooted. To increase this low rooting rate, the shoots were cultured on Macrorrhizus Rooting Media (MRM) supplemented with three different concentrations of IBA. The highest rooting rate (55.0 ± 7.9%) was reached when shoots were incubated in MRM-2 consisting of MS medium supplemented with 2 mg l IBA and 4% sucrose. The acclimatization rate of the micropropagated plantlets was 90%. The method developed in this study allows the micropropagation of A. macrorrhizus, offering a new option to preserve this almost extinct species.Authors would like to thank to the Official Nursery of the Directorate General for the Environment belonging to the Council of Agriculture and Water of the Region of Murcia (Spain) for facilitating the plants of A. macrorrhizus used in this work. This study was funded by “Junta de Andalucía” (Project of Excellence AGR3648). INMIBO Publication No. 216. Doctor Regalado Gonzalez is a Post-Doctoral Fellow at CONICET.Peer Reviewe