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.

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 multiple shoots from habanero pepper (Capsicum chinense Jacq.), nodes and stem segments were cultivated in MS medium supplemented with varying concentrations of kinetin, benzyladenine, and thidiazuron. The effect of the age of the explant in the medium on shoot formation and their latter development into plants was assessed. Ethylene concentration was measured along the experiments. Thidiazuron was the key growth regulator in the process, which at 3.4 μm induced seven to eight shoots that developed into healthy plants per explant. Plantlets in nonventilated vessels, where ethylene concentration was 0.25 ± 0.1102 μL·L–1, showed early defoliation and the formation of calli on the leaves and stems.

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Catharanthus roseus cell cultures were exposed to different conditions in order to induce alkaloid metabolism. The exposure to jasmonate and fungal elicitors resulted in the transcriptional activation of tryptophan decarboxylase and in the accumulation of the monoterpenoid indole alkaloids ajmalicine and catharanthine, but not of vindoline. The inability of the cell cultures to produce vindoline was related to a lack of expression of the desacetoxyvindoline 4-hydroxylase (D4h) gene. Southern blot analysis revealed that D4h gene was not lost in the cell cultures.