In vitro regeneration of the endangered cactus Turbincarpus mombergeri (Riha), a hybrid of T. laui × T. pseudopectinatus

Turbinicarpus mombergeri is a cacti species formed by a hybridization process between Turbinicarpus laui and Turbinicarpus pseudopectinatus. Under natural conditions, it is very difficult for two species be genetically compatible for hybridization, and to produce flowers at the same time. Thus, T. mombergeri is a very interesting and a rare species. Unfortunately, the current populations are decreasing and now it is considered critically endangered. The aim of this research was to develop a successful protocol for propagating T. mombergeri using the in vitro culture techniques. Seed disinfection was performed with Plant Preservative Mixture, and 80% of germination occurred at day 45 in Murashige-Skoog medium. The shoots were cut longitudinally, and the segments were transferred to media containing 2.22 or 4.44 µM benzyladenine to induce shooting. The generated shoots were highly hydrated, and presented abundant callus. The hyperhydricity was controlled by reducing salt medium concentration, by increasing calcium levels and by using polyethylenglycol. The reduction of callus was attained by adding tri-iodo benzoic acid. Vigorous and thick shoots were generated in medium containing urea, and rooting improved in the presence of 0.5 µM indoleacetic acid. Plantlets with normal morphology were obtained, and the survival rate of the plants in soil was 80%. The methodology developed represents an alternative for propagation of T. mombergeri under controlled conditions for commercial or conservation purposes. Key message The paper describes several approaches to avoid the hyperhydricity and callus formation, to improve quality of shoots and to increase the development of roots during the micropropagation process of the endangered cacti T. mombergeri.