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  • Author or Editor: Guadalupe López-Puc x
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The in vitro production of ethylene and its effects on the development of Habanero pepper (Capsicum chinense Jacq.) plantlets were evaluated using nonventilated containers (NVCs) and ventilated containers (VCs). Shoots of Habanero pepper between 0.5 and 1.0 cm of height were cultivated in Magenta culture boxes and samples of the headspace atmosphere were taken every four days during the previously established culturing time of 40 days. The presence of ethylene was detected in the NVCs and produced a negative effect on the development of plantlets. In a second phase of this work, the effect of silver nitrate (AgNO3) and cobalt chloride (CoCl2) on ethylene production was evaluated during in vitro development of Habanero pepper plantlets. Concentrations of 50, 300, and 500 μm of each ethylene inhibitor were used in the culture medium. Although cobalt chloride partially inhibited the production of ethylene during in vitro culture of this species, at low concentrations the plantlets presented some degree of vitrification and the highest concentration proved to be toxic for the plantlets. Silver nitrate added to the culture medium did not inhibit ethylene production, however, it did inhibit the effect of this hormone on the plantlets. In fact, when high concentrations of silver nitrate were used (300 μm), high amounts of ethylene were detected in the headspace of the vessels and plantlets were actually healthier.

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To induce somatic embryogenesis in habanero pepper (Capsicum chinense Jacq.), the cultivar BVll-03, belonging to the red type, was used. Different explants were evaluated, as were different culture media, the composition of which varied in the content of plant growth regulators. Results showed the formation of somatic embryos from cotyledons, zygotic embryos, germinated zygotic embryos, hypocotyls, and cotyledonary leaves. Explants were cultured on Murashige and Skoog medium supplemented with 2,4-D (9.05 μm). The somatic embryos always formed directly from the explant, without callus formation, and the greatest efficiency was obtained when segments of hypocotyls were cultured, obtaining 175 ± 20 somatic embryos per explant. Only the somatic embryos obtained on Murashige and Skoog medium containing 2,4-D (9.05 μm) and treated with abscisic acid (ABA) (1.89 μm) before their transfer to the germination media (Murashige and Skoog + 1.1 μm GA3) emitted their radicule and expanded their cotyledonary leaves (60%), whereas the remaining embryos did not achieve germination because of different causes (abnormalities, delayed development). Not only is this protocol of somatic embryogenesis the first to be reported for this species (C. chinense Jacq.), but it is also the most efficient reported so far, within the Capsicum genus.

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To induce the somatic embryogenesis of Habanero pepper, different culture media and different types of explants (node, internode, hypocotyl, half seeds, and fruit segments) were evaluated. For the induction of embryogenic callus, 9.05 μm of 2,4-dichlorofenoxiacetic acid, 3% sucrose, and 0.8% gelrite were added to the basic MS medium over a period of 30 days at 25 ± 2 °C under continuous light (40–50 μmol·m2·s−1). Once the callus formed, they were transferred to liquid medium using the same induction formulation. Somatic embryogenesis only occurred from explants of hypocotyl and in the presence of 3.4 μm thidiazuron. This constitutes the first proposal of a protocol for the “induction of somatic embryogenesis in Habanero pepper (Capsicum chinense Jacq.) from cell suspensions.”

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The ontogenesis of direct high-frequency somatic embryogenesis of C. chinense induced from hypocotyl was characterized through a histological analysis of the different phases in the histodifferentiation process during the development of the somatic embryo. The anatomical analysis was carried out since the hypocotyl segments were placed in the culture medium until 45 days of culture. The somatic embryos were induced and maintained in Murashige and Skoog medium supplemented with 2,4-dichlorophenoxyacetic acid (9.5 μm). Samples of tissues and organs were taken every 24 h, fixed in formalin acetic alcohol, and embedded in plastic resin. They were cut into serial sections (5 μm) and stained with toluidine blue. The analysis revealed that the proembryogenic cells originated just from provascular hypocotyl cells. Provascular cells acquired the embryogenic competence 48 h after induction and an intense mitotic division was observed and embryogenic structures were generated first along the vascular strands, which subsequently evolved into somatic embryos. After 2 weeks, there were observed embryos at different stages of development (preglobular, globular, heart-shaped, torpedo-shaped, and cotyledonary). This is the first report dealing with the ontogenesis of the direct somatic embryogenesis of C. chinense, and it is the most complete histological characterization carried out on somatic embryogenesis in the Capsicum genus to date.

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The aim of this study was to determine the pungency level of different accessions of Habanero peppers. The high-performance liquid chromatography (HPLC) technique was used to evaluate the content of total capsaicinoids in the whole fruit, placenta, and pericarp of 18 accessions of Habanero pepper from the germplasm bank of the Capsicum chinense species maintained in the Scientific Research Center of Yucatan [Centro de Investigación Científica de Yucatán (CICY)]. Thirteen of these accessions belonged to the “orange type”, four to the “red type”, and one to the “yellow type”. During the study, the plants were cultivated and maintained under greenhouse conditions and the fruit was harvested only when it was completely ripe on the plant. The results show considerable intraspecific diversity for this characteristic as well as the existence of cultivars of this species that surpass the levels of pungency reported for Habanero peppers under the conditions evaluated.

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