Martha Isabel Torres-Morán

Assessment of genetic fidelity among Agave tequilana plants propagated asexually via rhizomes versus in vitro culture.

Agave tequilana is a species of great economic importance for the Mexican society. Like most agaves, it can be propagated either sexually or asexually. However, plants originating from rhizomes are mainly used for commercial production. The aim of this study was to determine the genetic fidelity of plants that were obtained from the field and propagated from rhizomes and of those propagated by in vitro culture methods (somatic embryogenesis and proliferation of axillary buds). We used an inverse ISTR (sequence-tagged repeat) molecular marker based on retrotransposon sequences to detect variability among related individual plants. Cluster analysis showed that plants could be grouped according to the propagation method employed. Plants propagated by the same in vitro method were found to be distinct from those propagated in the field. Even within each method, plants were not genetically identical. Genomic changes were evidenced not only in plants subjected to somaclonal variation in vitro but were also evident in those propagated through the natural asexual process, despite the fact that they were considered true clones. The differences observed in plants confirm the existence of asexual genetic variability.

Flavonoid composition and antioxidant capacity of the edible flowers of Agave durangensis (Agavaceae)

The antioxidant properties and the flavonoid composition of extracts of different hydrophobicity prepared from the entire edible flowers of Agave durangensis were evaluated. Separately, total extracts of tepals and anthers–pollen were analyzed in the same manner. The high performance liquid chromatography with photodiode array detection (HPLC–DAD) analysis revealed a total of eight flavonols (five quercetin glycosides and three kaempferol glycosides), varying in number and concentration in the different extracts. The total extracts of the entire flowers showed the highest flavonoid content (1210.4 µg/g dry extract) and the most complex flavonoid profile (eight compounds). All the extracts showed important antioxidant activity, which was not evidently associated with their flavonoid content. The total extracts of tepals showed the highest antioxidant properties (total antioxidant capacity, free radical scavenging activity, and iron reducing capacity: 30.2 mg ascorbic acid equivalents, EC50 = 0.074 µg/mL, and IC50 = 43.28 µg/mL, respectively). The flowers of A. durangensis represent an important source of antioxidant flavonols.

Evaluation of foliar phenols of 25 Mexican varieties of common bean (Phaseolus vulgaris L.) as antioxidants and varietal markers

The antioxidant properties and the foliar phenol composition of 25 Mexican varieties of Phaseolus vulgaris L. (common bean) were evaluated. Phaseolus coccineus was analysed with comparative aims. The high performance liquid chromatography with photodiode array detection analysis revealed 27 phenolics in the leaves of P. vulgaris (13 quercetin-3-O-glycosides, 8 kaempferol-3-O-glycosides, 2 myricetin glycosides and 4 phenolic acids) and 5 in P. coccineus (2 kaempferol-3-O-glycoside, 2 apigenin-7-O-glycoside and 1 luteolin-7-O-glycoside). All extracts showed high levels of phenols and flavonoids (0.964–5.601 mg g− 1 dry tissue, and 0.287–1.418 mg g− 1 dry tissue, respectively) and relevant antioxidant properties, suggesting that the leaves of the varieties of P. vulgaris are a significant source of natural antioxidants. The foliar phenol profiles were species-specific and, besides, the qualitative variation allowed discriminating among varieties of P. vulgaris. These profiles can represent an important varietal authenticity proof.

Efficient protocols for in vitro axillary bud proliferation and somatic embryogenesis of the medicinal plant Anemopsis californica

Anemopsis californica, commonly known as yerba mansa, is an important medicinal plant that has traditionally been used to treat a variety of digestive, respiratory and skin ailments, and has been reported to possess anticancer properties. The increase in demand for this medicinal plant puts wild populations at risk due to over-harvesting; therefore, the development of alternatives such as in vitro propagation may help reduce this pressure on natural plant resources. The aim of this work was to develop protocols for the in vitro propagation of A. californica through axillary bud proliferation and somatic embryogenesis. Shoot bud multiplication was achieved using nodal explants from axenic seedlings, reaching the highest multiplication rate (on average 15 shoots per explant) when the culture medium was supplemented with 4 mg/L kinetin. Propagated shoots produced roots in medium containing 1 mg/L indole-3-butyric acid. Best induction of somatic embryogenesis (on average 19.75 embryos per explant) was obtained from leaf explants cultured on medium supplemented with 4 mg/L naphthalene acetic acid. These protocols may be used either for the commercial mass propagation of the species, studies on the production of secondary metabolites or as a basis for the development of genetic improvement strategies.

Morphological Changes of Mexican Native Succulent Plants in a Vertical Greenery System Compared with Pot Conditions

Adaptation parameters as leaf width, leaf length, mesophyll thickness, number of adaxial and abaxial stomata, and biomass were measured in eight stonecrop species (Crassulaceaae), spider plant (Chlorophytum comosum), and maria’s heart (Peperomia tepoztecoana) in vertical greenery system (VGS) and containers (POT). Statistical significance among parameters was probed by t test and principal component analysis was performed to detect global morphological changes. Mexican gem (Echeveria elegans), graptosedum (· Graptosedum ‘Vera Higgins’), lavender scallops (Kalanchoe fedtschenkoi), coppertone sedum (Sedum nussbaumerianum), ghost plant (Graptopetalum paraguayense), and jelly-beans (Sedum rubrotinctum) were the species that did not change significantly their morphological traits during growth in the VGS. This provides evidence of the potential for these species to be used in green walls or any VGS while maintaining their characteristic shape and beauty. Graptopetalum (Graptopetalummacdougalli), gray sedum (Sedum griseum), maria’s heart, and spider plant showed changes in its morphology during growth in the VGS when compared with growth in POT, indicating a lower potential for adaption to VGS.

Genetic Variability in Natural Populations of Agave durangensis (Agavaceae) Revealed by Morphological and Molecular Traits

Abstract Agave durangensis is an endemic species that occurs in a reduced area in southern Durango and northern Zacatecas, Mexico. We analyzed the genetic variability of three populations of the species using two pairs of Inverse-Sequence-Tagged-Repeat primers and nine morphological characters to determine the species of the morphologically variable populations. The primers generated characteristic amplification profiles, which distinguished between populations of A. durangensis and revealed interspecific variability when compared with individuals of A. asperrima. Some incongruence between morphological and molecular variability was detected. High genetic variability was indicated by an elevated level of polymorphism (24.18–61.50%) among 91 genetic loci amplified and by the level of gene diversity (0.0807–0.2337) among populations. Genetic differentiation (0.0328–0.4857), gene flow (0.5294–14.7511), genetic distance (0.0200–0.3019), and genetic identity (0.7653–0.9802) among populations suggested that one of the three populations of A. durangensis is in a present advanced diversification process but may still maintain some level of gene flow with the other two populations. Urgent conservation efforts, including protection from harvest, should be addressed for maintaining the genetic variability of the natural populations of A. durangensis. Resumen Agave durangensis es una especie endémica que crece en un área reducida del sur de Durango y norte de Zacatecas, México. Analizamos la variabilidad genética de tres poblaciones de esa especie usando dos pares de iniciadores de los marcadores de Repetición de Secuencias Inversas Marcadas (ISTR por sus siglas en inglés) y nueve atributos morfológicos para determinar las especies de las poblaciones morfológicamente muy variables. Los iniciadores generaron perfiles de amplificación característicos, mostrando su capacidad para distinguir entre poblaciones de A. durangensis y para revelar variabilidad intereespecífica cuando los perfiles se compararon con los de A. asperrima. Incongruencia entre la variabilidad morfológica y la molecular fue detectada. Alta variabilidad genética fue encontrada, indicada por los elevados niveles de polimorfismo (24.18–61.50 %) entre 91 loci genéticos amplificados y por los valores de diversidad génica (0.0807–0.2337) entre poblaciones. Diferenciación genética interpoblacional (0.0328–0.4857), flujo genético (0.5294–14.7511), distancia genética (0.0200–0.3019) y la identidad genética (0.7653–0.9802) sugieren que una de las tres poblaciones de A. durangensis se encuentra en un proceso actual avanzado de diversificación, pero que aún existe flujo genético con las otras dos poblaciones. Esfuerzos urgentes de conservación incluyendo la protección de recolección se deberían de contemplar para mantener la variabilidad genética de las poblaciones naturales de A. durangensis.

In vitro clonal propagation and regeneration of the commercially important plant Mexican oregano (Lippia graveolens)

Lippia graveolens (Verbenaceae family), commonly known asMexican oregano, is an important plant widely used as both a condiment and raw material for extraction of essential oil, having multiple applications in food, pharmaceutical, and cosmetic industries (Sánchez et al. 2007; Martínez-Rocha et al. 2008). The species is an evergreen, woody shrub, native to the southern part of the USA,Mexico, and Central America (Fig. 1a). Three closely related species belonging to the genus Lippia are customarily known as Mexican oregano: L. graveolens H.B.K., Lippia berlandieri Schauer, and Lippia palmeri; though the two former species have been reported as synonyms by several authors (Avila-Sosa et al. 2010). Mexico produces about 6,500 t of dry oregano leaves annually. The industry is primarily export oriented with up to 90% of total production being traded abroad, making this country the main exporter of Mexican oregano in the world (Villavicencio-Gutiérrez et al. 2010). The average biomass yield of this crop can vary between 1 and 4 t per hectare per year, with a typical recovery of 2 kg of essential oil per metric ton, which corresponds to an average yield of 30 kg of essential oil per hectare. Since sun drying destroys the essential oil, leaves must be shade dried and the extracted oil then stored in dark flasks to protect it from light (CONAFOR 2011). Mexican oregano offers great potential for further development in terms of economic profit, since the chemical composition of the essential oil is considered superior to that obtained from Mediterranean oregano (Origanum vulgare) produced mainly in Greece and Turkey. Moreover, the proportion of essential oil contained in L. graveolens (∼2%) is higher compared to O. vulgare subsp. hirtum and O. vulgare subsp. gracite (∼1.5% in both cases; Silva-Vázquez et al. 2008). Mexican oregano is harvested mainly from natural populations and the harvest period coincides with the flowering time, which consequently alters fruit and seed development. This fact, in conjunction with deficient crop management practices, has led to critical reductions in population size and density. Additionally, it has been reported that only about 11% of flowers produce fruit, and each fruit usually contains only one seed (Ocampo-Velázquez et al. 2009). The commercial value of this nontimber forest resource increased significantly upon recognition of its medicinal properties due to the antioxidant, antimicrobial, and cytotoxic activities attributed to carvacrol, thymol, caffeic acid, flavonoids, apigenol derivatives, luteolol, kaempferol, sesquiterpenes, and p-cimene which is present in the oil (Hernández et al. 2009). Specifically, antioxidant activity has been demonstrated in leaf extracts through inhibition of linoleic acid oxidation (Avila-Sosa et al. 2010). Extracts O. A. Castellanos-Hernández (*) :G. J. Acevedo-Hernández : F. Zurita :M. Gutiérrez-Lomelí :C. L. Del Toro-Sánchez : A. Rodríguez-Sahagún Centro Universitario de la Ciénega, Universidad de Guadalajara, Av. Universidad 1115, Col. Lindavista, 47820 Ocotlán, Jalisco, Mexico e-mail: ocnoscr@gmail.com