In vitro multiplication is the main method for seedling production of Comanthera mucugensis, an endangered ornamental plant. The technique consists of cultivating plant tissues under aseptic conditions, controlled environment, and using appropriate culture medium. The physical characteristics of the medium are mainly determined by the presence of a gelling agent. Agar is the most used substance on the in vitro cultivation of C. mucugensis, however, it is one of the most costly components to manufacture the medium. The objective of the present study was to evaluate the effect of κ-carrageenan as an alternative gelling agent in the propagation of C. mucugensis. The seeds and stem explants were cultured on medium gelled with agar or κ-carrageenan, both at 7 g L -1 concentration. The results indicated that the plants established in medium with κ-carrageenan presented an increase in length and induced formation of shoots. Direct organogenesis was also improved with the use of this gelling agent. In comparison, agar culture presented HIGHLIGHTS• Agar is the most used gelling agent for plant culture medium, but it is expensive.• Gelling of culture medium with κ-carrageenan improves in vitro growth and direct and indirect organogenesis of Comanthera mucugensis.• The use of κ-carrageenan represents a 23.2% reduction in the cost of producing the culture medium compared with agar.• New studies are needed to improve the in vitro rooting of C. mucugensis.

The high endemism, the natural habitat degradation, and the over-collection for ornamental purposes have led some species such as Melocactus paucispinus and M. glaucescens to be threatened with extinction. The use of in vitro conservation techniques, such as slow growth storage, promotes the preservation of genetic diversity with integrity. The goal of this study was to establish a strategy for in vitro conservation of apical segments of the cladode of M. paucispinus and M. glaucescens and evaluate the genetic diversity of individuals from in vitro germinated plants. For such purpose, different concentrations of the plant regulator ancymidol and the osmotic agent sucrose on the inhibition of the in vitro growth were tested, and the genetic diversity of M. paucispinus and M. glaucescens individuals stored in vitro was evaluated. Sucrose showed higher efficiency in the reduction of growth than ancymidol for both species. However, due to the reduction in survival percentage, the use of sucrose over 75 g L− 1 in the in vitro conservation of both species for 360 days is not recommended. In the genetic diversity analysis, 76.92% of polymorphic loci (P), expected heterozygosity (He) = 0.276 and Shannon index (S) = 0.414 were observed for M. paucispinus. For M. glaucescens, the observed values were P = 95.38%, He = 0.228 and S = 0.369. These values observed here were higher than those previously found for the natural populations of these species, which demonstrated that this in vitro collection showed genetic diversity and can be used in management and reintroduction programs of these species.

O objetivo deste trabalho foi descrever e ilustrar os caracteres morfológicos de fruto, semente e plântula de Annona crassiflora, A. squamosa e A. muricata. Foram avaliados, em 50 frutos de cada espécie, a forma, coloração, peso, diâmetros longitudinal e transversal, peso da polpa, peso da casca + receptáculo, peso das sementes e número de sementes por fruto. Também foram determinados diâmetros longitudinal e transversal, espessura e peso individual de 100 sementes de cada espécie. Para o estudo da morfologia de plântulas, a semeadura foi efetuada em substrato contendo terra e areia (3:1) em DIC, com quatro repetições de 25 sementes para cada espécie. Foram realizadas observações diárias sendo determinadas oito fases de desenvolvimento. Os frutos das três espécies são múltiplos formados por numerosos frutículos, concrescidos entre si, formando um sincarpo; as sementes são glabras de forma oblonga e testa dura. Na análise dos dados biométricos foi observada uma grande variabilidade interespecífica, sendo que em todas as espécies a polpa revelou-se o principal constituinte dos frutos. A. crassiflora e A. squamosa apresentaram germinação epígeo-fanerocotiledonar e A. muricata, hipógea criptocotiledonar. Em cada espécie, os aspectos morfológicos, nas distintas fases, apresentaram-se homogêneos e constantes podendo ser seguramente empregados em estudos taxonômicos e ecológicos.

The influences of explant orientation on in vitro responses of Annona squamosa L. were evaluated. Hypocotyl and epicotyl segments were inoculated into test tubes with WPM medium supplemented with 8.87 µM BAP in the following orientations: horizontally on the medium surface, vertically upright retaining their natural polarity and vertically upright but inverted from their natural polarity (hypocotyl segments only). The test tubes were sealed with normal transparent plastic caps (either covered or not covered with PVC film) or with cotton plugs. After inoculation the tubes with the explants were maintained in a growth room under photosynthetically active radiation levels of 45-56 ìmol.m-2.s-1 and temperatures of 25 ± 3oC. The results showed that explant polarity affected organogenesis, and that the largest numbers of shoots (8.3 per explant) were found on hypocotyl explants placed vertically and retaining their natural polarity. No influences of the different test tube caps on morphogenetic responses of the explants were observed. The incubation of hypocotyl and epicotyl segments in a vertical position constitutes an efficient system for generating A. squamosa plants.

The “sempre-viva” species Comanthera mucugensis is endemic to the municipality of Mucugê, Bahia, Brazil, where it was widely exploited through extractivism to be commercialized as an ornamental, causing a drastic reduction of its population, so that it is now classified as endangered. Although its main area of occurrence is now protected for being within Chapada Diamantina National Park, the continued risks of inclement conditions and anthropic actions make it necessary to develop alternative methods for ex situ conservation of the species, such as in vitro conservation. Therefore, the objective of this study was to test the effect of different concentrations of salts and sucrose on the in vitro conservation of Comanthera mucugensis. Two salts concentrations of the medium MS (½ and ¼) and two sucrose levels (7.5 and 15.0 g L-1) were tested, and the experimental design was completely randomized with four treatments. After 365 days, the survival, growth and regeneration of the conserved plants were analyzed, achieving up to 100% survival, reduced shoot growth and maintenance of regenerative capacity. Reduction of the concentration of salts and sucrose in the culture medium is indicated to conserve the plants in vitro for a period of one year.