DIVERSIDAD GENÉTICA DE UN SISTEMA TRADICIONAL DE POLICULTIVO EN MÉXICO: VARIACIÓN ISOENZIMÁTICA

Abstract

En este artículo se explora una forma de estimar la cantidad y distribución de la diversidad genética en los sistemas tradicionales de cultivos a través del registro de las asociaciones inter específicas de las variedades locales y de la cuantificación de la diversidad entre y dentro de los cultivos. Para esto, fueron visitados el 10% de los hogares de la comunidad de Yaxcaba, Yucatán y México, para conocer qué tipo de asociación de cultivos realizan más frecuentemente y en particular que variedades locales son las asociadas. Al mismo tiempo se colectaron 65 muestras representativas de la diversidad de variedades locales de maíz, fríjol y calabaza para su análisis isoenzimático.

A partir de los datos isoenzimático se estimó la diversidad genética entre y dentro de los cultivos mediante los estadísticos de F. En los campos de los agricultores mayas de Yaxcaba se observaron comúnmente en cultivo un promedio de cuatro variedades locales, en un rango de dos a once, y hasta siete especies en la misma parcela de cultivo (por ejemplo Zea mays, Cucurbita pepo, C. mochata, C. argyrosperma, Phaseolus vulgaris, P. lunatus y Vigna anguiculata).     

ABSTRACT

This paper explores one way to estimate the extent and the distribution of genetic diversity in the traditional cropping systems throughout the record of the types of inter - specific associations of landraces and the estimation of the genetic variation among and within crops. 10% of households from the Yaxcaba, Yucatan Mexico community was surveyed for knowing what type of associa­tion of crops and specifically on those landraces that they are associated with, more frequently. A total of 65 samples of maize, squash and bean landraces were collected and isizymatically analyzed in order to estimate the genetic diversity amon and within crops through F's statistics. In the fields of Mayan farmers of Yaxcaba was observed commonly that the preserve from two to eleven local varieties, and until seven species (i.e. Zea mays. Cucurbita pepo, C. mochata, C. argyrosperma, Phaseolus vulgaris, P. lunatus y Vigna anguiculata), in the same plot. Two types of crop associations were recorded; double as maize - squash or maize - bean and triple as maize - squash -bean. Isozymatic diversity of the maize, squash, and bean populations allowed estimate temporal and spatial genetic variation under interspeciflcs competition and interaction. On the base of samples isozymatically analyzed, the asso­ciation maize - squash - bean presenting 64, 51 and 38 loci, respectively Heterozygosity, percentage of polymorphic loci and diversity among populations (F₅₁) in maize and squash were lightly higher than in bean, but diversity whitin - populations (F₁₈) was significantly lower.

Structure genetic of maize and squash populations presented an evolutionary pattern of outcrossing spe­cies, high diversity among populations, and in bean (Phaseolus vulgaris and Vigna anguiculata) a self fertilization species, presented higher homozygosity and diversity within populations.