Eugenio Pérez-Molphe-Balch

In vitro propagation of Pelecyphora aselliformis Ehrenberg and P. strobiliformis Werdermann (cactaceae)

SummaryDevelopment of efficient in vitro propagation, systems for Pelecyphora aselliformis Ehrenberg and P. strobiliformis Werdermann, two endangered Mexican species of cacti, are described. Multiple shoot formation from areoles of in vitro-germinated plantlets was achived in two types of explants (apical and transversal) cultured in Murashige and Skoog (MS) basal media supplemented with 30 or 50 gl−1 sucrose, 10 gl−1 agar and various treatments with cytokins. Shoot production in these proliferation media was evaluated after one (60 d) and three (180 d) culture cycles. In P. asellifornis 13.7 shoots per explant were produced after the first cycle using apical explants in medium with 8.8 μM 6-benzylaminopurine (BA) and 30 gl−1 sucrose. In P. strobiliformis the highest proliferation rate (12.4 shoots per explant) was reached using 8.8 μM Ba and 50 gl−1 sucrose with shoot transverse segments as explants. After the third proliferation cycle, 128.1 and 136.3 shoots per explant were obtained in P. aselliformis and P. strobiliformis, respectively. The shoots were clongated in MS basal medium with 3 gl−1 activated charcoal and rooted in MS basal media indoleacetic acid (2.85 or 5.71 μM) or indolebutyric acid (2.46 or 4.90 μM). On averge, rooting efficiency was 89% for P. aselliformis and 87% for P. strobiliformis. The survival frequency, of the plants once transferred, to soil was on average 88%.

IN VITRO PROPAGATION OF EIGHT SPECIES OR SUBSPECIES OF TURBINICARPUS (CACTACEAE)

SummaryIn vitro propagation systems by means of areole activation were developed for Turbinicarpus laui, T. lophophoroides, T. pseudopectinatus, T. schmiedickeanus subsp. flaviflorus, T. schmiedickeanus subsp. klinkerianus, T. schmiedickeanus subsp. schmiedickeanus, T. subterraneus, and T. valdezianus. In vitro-germinated seedlings were used as a primary source of explants. Multiple shoot formation from areoles was achieved for three explant types (apical, lateral, and transverse), cultured on Murashige and Skoog (MS) basal medium supplemented with 3% sucrose, 10 gl−1 agar and several treatments with cytokinins. Efficiencies were in the range from 7.8 shoots per explant in T. valdezianus up to 19.7 shoots per explant in T. pseudopectinatus, using the best treatment for each species and in a single proliferation cycle. Four of the studied species responded best when 6-benzylaminopurine (3.3–8.8μM) was used, while 6-(γ,γ-dimethylallylamino)purine (19.7–24.6μM) showed better results in two species. The two remaining species showed no significant differences in their response to both cytokinins. Regarding explant type, the best results were obtained with transverse cuts for five species, with apical explants for one species, and the two remaining species showed no significant differences among the explants tested. Rooting of the in vitro-generated shoots was achieved most efficiently on half- or full-strength MS basal medium. Rooting frequencies were in the range from 54.2 to 94.2%, and the frequency of survival of the plants once transferred to soil was 91.6% on average.

In Vitro Conservation of Turbinicarpus (Cactaceae) Under Slow Growth Conditions

Absctract: The current work describes an in vitro conservation technique employing slow growth conditions in 16 threatened species and subspecies of the genus Turbinicarpus (Cactaceae), all native to the Chihuahuan Desert in Mexico. It was demonstrated that the addition of osmotic agents like mannitol (30 g L-1) and sorbitol (30 g L-1) to the culture medium, as well as low-temperature incubation (4 ± 0.5 °C), are able to reduce the in vitro growth rate without affecting the viability of shoots subjected to these treatments. The material that was kept under the aforementioned treatment conditions for 12 months was able to regenerate shoots through areole activation when transferred to media containing cytokinins. These shoots are able to root, and the generated plants can adapt and survive in soil, with similar efficiencies to those that were not subjected to slow-growth treatment. With this methodology it is possible to maintain a bank of viable tissues of these species in vitro, with minimal maintenance and the possibility of obtaining complete plants whenever required.

Tissue culture of ornamental cacti

Cacti species are plants that are well adapted to growing in arid and semiarid regions where the main problem is water availability. Cacti have developed a series of adaptations to cope with water scarcity, such as reduced leaf surface via morphological modifications including spines, cereous cuticles, extended root systems and stem tissue modifications to increase water storage, and crassulacean acid metabolism to reduce transpiration and water loss. Furthermore, seeds of these plants very often exhibit dormancy, a phenomenon that helps to prevent germination when the availability of water is reduced. In general, cactus species exhibit a low growth rate that makes their rapid propagation difficult. Cacti are much appreciated as ornamental plants due to their great variety and diversity of forms and their beautiful short-life flowers; however, due to difficulties in propagating them rapidly to meet market demand, they are very often over-collected in their natural habitats, which leads to numerous species being threatened, endangered or becoming extinct. Therefore, plant tissue culture techniques may facilitate their propagation over a shorter time period than conventional techniques used for commercial purposes; or may help to recover populations of endangered or threatened species for their re-introduction in the wild; or may also be of value to the preservation and conservation of the genetic resources of this important family. Herein we present the state-of-the-art of tissue culture techniques used for ornamental cacti and selected suggestions for solving a number of the problems faced by members of the Cactaceae family.

Micropropagation of Yucca Species

Yuccas are plants adapted to arid and semiarid regions and have been used as source of food and raw materials and for ornamental purposes. Lately, the interest in this genus has grown due to the presence of potential useful compounds such as saponins and polyphenolics. However, they present very low reproductive rates and virtually all the plants used are wild individuals; as consequence, their natural populations have been depleted. We present an efficient method to establish in vitro cultures of Yucca species starting with seeds and then obtaining shoots from the seedling meristems using cytokinins and auxins. These shoots can be rooted and transferred to soil or can be used as explants for another multiplication cycle. Hence, it is necessary to acquire seeds just once to establish a large-scale micropropagation protocol.

EFFECT OF CULTURE CONDITIONS ON STOMATAL DENSITY AND STOMATAL INDEX IN FOUR CACTUS SPECIES

Abstract: We evaluated type of stomata, as well as differences in stomatal frequency in three areas of the plant (apical, middle and basal) under two culture conditions (in vitro and ex vitro), in four cactus species (Opuntia ficus-indica, Hylocereus undatus, Escontria chiotilla and Mammillaria petterssonii). We measured stomatal density (SD) and the stomata index (SI) for both factors, plant area and culture condition. Stomata typology were cyclocytic, tetracytic or opuntioid type in O. ficus-indica and parallelocytic type in E. chiotilla, H. undatus and M. petterssonii. It was observed that SD was higher ex vitro than in vitro in H. undatus and M. petterssonii, but the opposite was true for O. ficus-indica and E. chiotilla. The apical region had the highest SD both in in vitro and ex vitro, and the interaction between culture condition and explant areas was highly significant, implying that the impact of culture type is different for each distinct stem area.