Amaury M. Arzate-Fernández

Some aspects of avocado (Persea americana Mill.) diversity and domestication in Mesoamerica

Avocado (Persea americana Mill.) is a major tropical fruit, with origin in Mesoamerica area. Avocado is a very variable species and taxonomically poorly understood. It has been grown in the Neotropics since ancient times and it seems that the domestication of this tree in Mesoamerica started before other annual crops. In addition, it seems that much of avocado diversity as ecological differences, were originated as a result of cultural diversity. In view of this, avocado represents an interesting model to study domestication of tropical trees and develop forest management and germplasm conservation strategies. At present time, P. americana is worldwide distributed with Mexico as the main producer. However, there are some aspects on the origin, dispersion, and domestication of the species that remain to be answered. In this paper, we present a survey of these issues from the earliest to present time in Mesoamerica.ResumenEl aguacate (Persea americana Mill.) es una importante fruta tropical, originaria del área de Mesoamérica. El aguacate es una especie altamente variable y su taxonomía aún no ha sido totalmente definida. El aguacate se ha desarrollado en el Neotrópico desde tiempos antiguos y es posible que su domesticación en Mesoamérica se iniciara antes que otras plantas anuales. También es probable que en gran medida su diversidad se originara además de las diferencias ecológicas, también como resultado de la diversidad cultural. Debido a esto, el aguacate representa un modelo interesante para estudiar procesos de domesticación en árboles tropicales y desarrollar estrategias de manejo en bosques y conservación del germoplasma. Actualmente, P. americana está distribuida en todo el mundo y México es el principal productor. Sin embargo, algunos aspectos del origen, dispersión y domesticación de la especie no han sido clarificados. En este artículo presentamos una investigación sobre estos aspectos, desde tiempos antiguos hasta el presente en el área de Mesoamérica.

The Avocado (Persea Americana, Lauraceae) Crop in Mesoamerica: 10,000 Years of History

ABSTRACT Abstract. The most ancient evidence of the existence of the avocado tree (Persea americana, Lauraceae) in Mesoamerica is about 10,000 years ago in Coaxcatlan, Puebla (Mexico). Since then, the history of the avocado has been preserved and recorded in Mesoamerica, the domestication center for the species, and in northern South America, where pre-Hispanic Mesoamerican cultures dispersed it. In colonial times, the Spanish valued the avocado fruit highly and documented it in numerous texts. Since then, the avocado tree has been introduced into places where the climate is appropriate for its cultivation. Avocado is now the fourth most important tropical fruit in the world, and Mexico is the main producer, with more than one million metric tons produced in 2005. Resumen. La evidencia más antigua de la presencia del aguacate (Persea americana, Lauraceae) en Mesoamérica es de hace 10,000 años, en Coaxcatlán, Puebla (México). Desde entonces, la historia del aguacate ha sido documentada en Mesoamérica, su centro de domesticación, y en el norte de Sudamérica, en donde fue dispersado por las culturas que habitaron en Mesoamérica en la época pre-Hispánica. En el tiempo de la Colonia, los españoles apreciaron esta fruta y la documentaron en numerosos textos. Desde entonces el aguacate ha sido introducido en los lugares donde el clima es apropiado para su desarrollo. Actualmente el aguacate es la cuarta fruta tropical más importante en el mundo y México es el principal productor con más de un millón de toneladas métricas producidas en el año 2005.

Karyotype analysis and physical mapping of the 5S and 45S rDNA genes in Tigridia pavonia var. Dulce (Iridaceae)

Abstract Tigridia pavonia Redouté (Iridaceae) is a species with great ornamental potential of which nine different varieties are known. Among them, Tigridia pavonia var. Dulce presents the lowest seed formation. Despite this, there are no reports on cytogenetic characteristics for this variety. In the present study its karyotype was determined, and physical mapping of the 5S and 45S rDNA genes was performed by FISH. The results show that Tigridia pavonia var. Dulce exhibited a chromosomal number of 2n = 2x = 28+3B. The karyotypic formula was 26 m + 2sm + 3B. Also, physical mapping of the 5S and 45S rDNA genes was achieved by means of the FISH technique, where the 5S rDNA gene could be mapped in eight different regions, whereas the 45S rDNA gene was observed in 10 chromosome regions, of which four corresponded to secondary constrictions. The information generated can serve as a basis for future analysis of evolutionary and/or genetic improvement in the species.

Marker Assisted Characterization in Tigridia pavonia (L.f) DC

Conventional plant breeding programs largely depend on phenotypic selection, breeders’ experience, and knowledge of plant genetics for traits of agronomic importance. A large amount of biological data is available from genetic studies of a crop of interest related to important target traits in crop breeding, which may in turn directly assist genotypic selection (Xu & Crouch, 2008). However, conventional breeding is time consuming and often testing procedures may be complex, unreliable or expensive due to the nature of the target traits (e.g. abiotic stresses) or the target environment (Choudhary et al., 2008).