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 mm 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.

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.

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Abstract:The genus Crotalaria comprises about 600 species that are distributed throughout the tropics and subtropical regions of the world; they are antagonistic to nematodes in sustainable crop production systems, and have also shown antimicrobial capacity. Chipilín (C. longirostrata), which belongs to this genus, is a wild plant that grows in the state of Chiapas (Mexico) and is traditionally is used as food. Its leaves also have medicinal properties and are used as hypnotics and narcotics; however, the plant has received little research attention to date. In the experimental part of this study, dried leaves were macerated by ethanol. The extract obtained was fractionated with ethyl ether, dichloromethane, ethyl acetate, 2-propanone, and water. The extracts were evaluated against three bacteria-namely, Escherichia coli (Ec), Citrobacter freundii (Cf), and Staphylococcus epidermidis (Se)-and three fungi-Fusarium oxysporum A. comiteca (FoC), Fusarium oxysporum A. tequilana (FoT), and Fusarium solani A. comiteca (FSC). During this preliminary study, a statistical analysis of the data showed that there is a significant difference between the control ciprofloxacin (antibacterial), the antifungal activity experiments (water was used as a negative control), and the fractions used. The aqueous fraction (WF) was the most active against FoC, FsC, and FoT (30.65, 20.61,and 27.36% at 96 h, respectively) and the ethyl ether fraction (EEF) was the most active against Se (26.62% at 48 h).

Fusarium are considered as the major plant pathogen fungi, that cause the majority of soil-borne diseases to more than 100 plant species in the world, including maize. Thus, there are emerging demands of biocontrol reagents, and Crotalaria longirostrata showed fungicidal activity. The C. longirostrata branch extract was phytochemically characterized and evaluated for efficacy for the control of Fusarium wilt in maize. The application of the extract reduced the percentage of disease incidence significantly caused by Fusarium verticillioides from 70.4% to 40.12% as compared to non-treated plants, and evenly the disease severity was reduced from 40.15% to 29.46%. The phytochemical components of the extract were cinnamic acids (caffeic acid and ferulic acid) and phenolic acid (gallic acid). Furthermore, multiple structures were detected through mass spectrometry such as: phenols, alkaloids, esters, terpene, ketones, and amides. The bioautography assay showed that to separate the compounds of C. longirostrata branch extract causes it's the loss of fungicidal activity. This is due to the synergy or additive interactions of secondary metabolites present in the raw extract. Our results suggest that the application of C. longirostrata branch extract is a promising strategy to be applied to the soil as a preventive treatment.

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.