Habanero pepper ( Capsicum chinense Jacq.) is a very important crop in Mexico and demand for it is increasing in national and international markets. The habanero pepper produced on the Yucatan Peninsula is considered of superior quality to that grown in the rest of the world as a result of its shelf life and pungency. Despite its importance, little research has been done on cultivation conditions that may affect its productivity and fruit quality. The effect of N or K fertilization on habanero pepper development and fruit pungency was evaluated. Plants under fertilization stress (control) had high capsaicin content. Nitrogen fertilization significantly increased plant growth and fruit while maintaining high capsaicin levels. Optimum response was produced with 15 m m urea as the N source. Potassium fertilization had no positive effects on growth or productivity. The N treatments modified endogenous K levels in the pepper plants and vice versa. The K : N ratio (specifically in leaves and roots) varied between treatments with values greater than 1 in the K treatments, near 0.5 in the control, and less than 0.5 in the N treatments. This parameter may be an important indicator of habanero pepper productivity and requires study under different fertilization regimes.

The pungency of chili peppers is conferred by compounds called capsaicinoids that are produced only in the fruits of the Capsicum genus. Accumulation of capsaicinoids in these fruits may be affected by environmental conditions such as water and nutrient stresses, although these effects may vary even among genotypes within a species. The Habanero pepper ( Capsicum chinense Jacq.), grown in the Yucatán, is in especially high demand as a result of its unique flavor, aroma, and pungency and is the second most important commercial crop in the state after the tomato. Although the Habanero pepper is a significant economic resource for the region, few studies have investigated the effects of abiotic stresses on capsaicinoid production. In this study, the effects of water stress on plant growth, capsaicinoid accumulation, and capsaicin synthase activity were evaluated. Habanero pepper plants under water stress had a lower height, root dry weight, and root/shoot relation than control plants, which were irrigated daily. However, fruit growth and production were unaffected by water stress. Capsaicin and dihydrocapsaicin concentrations increased in fruits of stressed plants compared with control plants, and this effect was correlated with fruit age. However, capsaicin synthase activity was reduced in response to water stress, and this effect depended on both stress severity and fruit age. These results provide new information on the regulation of capsaicinoid metabolism in response to abiotic stress from the fruit of a highly pungent chili pepper.

Tempisque (Sideroxylon capiri Pittier) is classified as a threatened species and has been reported with a high content of phenols and flavonoids in the leaves. The use of abiotic elicitors such as radiation has been reported due to the changes it produces in the metabolism of plants by activating their defense mechanisms and increasing the biosynthesis of bioactive compounds with antioxidant capacity such as phenols and flavonoids. Therefore, the aim of this work was to evaluate the effect of UV-B radiation on growth parameters and the synthesis of bioactive compounds in in vitro culture of tempisque callus. For the callus induction, we used thidiazuron (TDZ) and 2,4-dichlorophenoxyacetic acid (2,4-D) at 0, 0.5 and 1 mg/L. Calluses were exposed to UV-B radiation (0, 1, 2, 3 and 4 h/day) for two and four weeks. The highest callus formation index was obtained with TDZ and 2,4-D at 1 mg/mL. The greatest increase in the concentration of phenols and flavonoids was detected in the fourth week with 4 h of exposure per day. The highest concentrations of quercetin (230 µg/g dry weight), kaempferol (235 µg/g dry weight) and gallic acid (240 µg/g dry weight) were found in callus obtained from leaves explants.

The essential oils of plants of the genus Piper have secondary metabolites that have antimicrobial activity related to their chemical composition. The objective of our work was to determine the chemical composition and evaluate the antifungal activity of the aerial part essential oil of P. auritum obtained by hydrodistillation on Fusarium oxysporum and Fusarium equiseti isolated from Capsicum chinense. The antifungal activity was evaluated by direct contact and poisoned food tests, and the minimum inhibitory concentration (MIC₅₀) and maximum radial growth inhibition (MGI) were determined. The identification of oil metabolites was carried out by direct analysis in real time mass spectrometry (DART-MS). By direct contact, the essential oil reached an inhibition of over 40% on Fusarium spp. The 8.4 mg/mL concentration showed the highest inhibition on F. oxysporum (40–60%) and F. equiseti (>50%). The MIC₅₀ was 6 mg/mL for F. oxysporum FCHA-T7 and 9 mg/mL for F. oxysporum FCHJ-T6 and F. equiseti FCHE-T8. DART-MS chemical analysis of the essential oil showed [2M-H]⁻ and [M-H]⁻ adducts of high relative intensity that were mainly attributed to eugenol and thymol/p-cimen-8-ol. The findings found in this study show a fungistatic effect of the essential oil of P. auritum on Fusarium spp.

In this work, we analysed the natural variation in mechanisms for protection against salt stress in pepper varieties (Capsicum chinense Jacq. cv. Rex, Chichen-Itza and Naranja and Capsicum annuum L. cv. Padron), considering primary root growth and viability of the post-stressed seedlings. NaCl-induced K+ and H+ efflux in roots was also studied by ion-selective microelectrodes under application of pharmacological agents. In these pepper varieties, the magnitude of the K+ leakage in the roots positively correlated with growth inhibition of the primary root in the presence of NaCl, with Rex variety showing a higher level of tolerance than Chichen-Itza. The K+ leakage and the activity of the H+ pump in the roots were dependent on the NaCl concentration. Pharmacological analysis indicated that the NaCl-induced K+ leakage was mediated by TEA+-sensitive KOR channels but not by NSCC channels. In addition, we present evidence for the possible participation of proline, and a Na+-insensitive HAK K+ transporter expressed in habanero pepper roots for maintaining K+ homeostasis under salt stress conditions.