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- Author or Editor: Nancy Santana-Buzzy x
The tropical plant Bixa orellana L. (annatto) is the sole source of bixin, the most frequently employed natural pigment in the food industry. Little is known about the physiology, biochemistry, and molecular genetics of this crop. Our purpose was to establish a set of analytical tools that could be applied in the genetic improvement of B. orellana, particularly for the screening of characteristics such as bixin content and resistance to diseases or pests. Some preliminary results on the study of carotenoid synthesis are presented. In vitro cultures from several B. orellana tissues were established and DNA, RNA, and proteins were extracted from them and analyzed. Similarly, bixin and total carotenoids were quantified.
This article describes the performance of nodal segments from Habanero pepper (Capsicum. chinense) during shoot induction and elongation under different semisolid and liquid culture conditions with various degrees of ventilation in which they were exposed to different levels of immersion and growth regulators. The ethylene content in non-ventilated containers, the age of the explant donor plants as well as the effect of thidiazuron and paclobutrazol on shoot induction and of gibberellic acid and AgNO3 on shoot elongation were also evaluated. A temporary immersion bioreactor (BioMINT™) was used for the multiplication and elongation of isolated shoots with very good results. We report an efficient protocol for the in vitro propagation of Habanero pepper that produces plants with a high survival rate when transplanted to soil.
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.
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.
The Yucatan Peninsula is recognized as the center of genetic diversity of Habanero peppers (Capsicum chinense Jacq.), which can be distinguished from those cultivated in other regions of the world by their aroma, taste, and—most of all—by their pungency. We evaluated three commercial varieties of chili peppers reported as being the hottest in the world: ‘Bhut Jolokia’, ‘Trinidad Moruga Scorpion’, and ‘Carolina Reaper’. The aim of our study was to determine the behavior of the pungency when cultivated under the edaphoclimatic conditions of Yucatan. Our results show that the three varieties registered greater contents in comparison with those reported in other regions of the world. ‘Carolina Reaper’—considered to be the hottest variety in the world, with a pungency of 2,200,000 Scoville heat units (SHU)—when cultivated in Yucatan, had a pungency of 3,006,330 SHU, which was greater than all the other varieties analyzed.
The effect of NaCI salinity on growth and development of somatic embryos of Habanero pepper was examined. Addition of 75 and 100 mm NaCI into the medium greatly increased the growth and development of somatic embryos and both of these concentrations favored the proliferation of somatic embryos. However, supplementation of 200 and 300 mm NaCI to the medium showed a negative effect on the growth and development of somatic embryos. Concentration increases of NaCl provoked a significant reduction of the embryos survival rate with the average lethal dose (46%) being registered in the treatment of 100 mm. Furthermore, a lower tolerance to salt stress (NaCl) was observed in deformed somatic embryos. Concentrations of 200 and 300 mm NaCl significantly delayed development in the surviving embryos in both treatments. These embryos remained at the globular stage throughout culture time. At 75 mm NaCl, most of the embryos were observed in the torpedo stage. However, the embryos exposed to 100 mm NaCl were observed mainly in globular and cotiledonar stages. It is quite likely that the transition from one intermediate stage of development to another occurs rapidly. With the exception of the concentration at 300 mm NaCl, salt stress stimulated embryonic germination, particularly at 100 mm NaCl. The content of proline in somatic embryos increased substantially in response to salinization. The results suggest that somatic embryos of C. chinense can tolerate concentrations of NaCl up to 100 mm without their development being affected. Moreover, they have sufficient cellular mechanisms to tolerate salinity at relatively higher levels.
Intersimple sequence repeat (ISSR) markers were used to evaluate the effects of in vitro culture on genetic variation in Habanero pepper (Capsicum chinense Jacq.) regeneration protocols. A total of 219 ISSR clear and reproducible fragments were generated with 13 ISSR primers in direct organogenesis, direct and indirect somatic embryos, and the embryogenic callus system. A cluster analysis was performed to express in the form of dendrogram the relationships among different regeneration systems and the genetic variability detected. Genetic distance analysis indicated that our regeneration protocols are inappropriate for micropropagation, conservation, or genetic transformation; however, they may be applicable to breeding. This is the first report on the use of molecular analysis to evaluate genetic variation of in vitro-regenerated plants of Habanero pepper using ISSR markers.
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.”
To determine the effect of different nitrogen sources and osmotic regulators on minimal growth of Habanero pepper (Capsicum chinense Jacq.) germplasm for in vitro conservation, different concentrations of nitrate, sucrose, mannitol, and sorbitol were evaluated. The micropropagation system based on culture medium was modified in its nitrate concentrations: reduced to 50% and increased to 150%, and osmoregulators were added to the basal culture media: sucrose (6% and 8%), mannitol (2%, 4%, and 8%), or sorbitol (2%, 4%, and 8%). The apical meristems of germinated plants were cultivated in the different treatments for 35 weeks without subculture. Results have demonstrated that mannitol at 2% had the better effect on minimal growth of the plantlets and did not affect the plant physiology and quality. The plantlets remained small in size, turgent, with green leaves and stems and looked like normal plants until to the end of the evaluation period. Changes in nitrogen media concentration did not prove to be adequate for conserving because they affected the plantlet quality (they became chlorotic). The presence of sorbitol and high osmolite concentrations induced minimal growth but reduced the plant quality. Sucrose at mid or low concentrations did not induce minimal growth.