MORPHOLOGICAL VARIATION OF OPUNTIA IN CONNECTION WITH ITS DOMESTICATION IN THE MERIDIONAL HIGHLANDS PLATEAU OF MEXICO - J. A. Reyes-Agüero1, J. R. A. Rivera1 & J. L. F. Flores2

1Instituto de Investigación de Zonas Desérticas, Universidad Autónoma de San Luis Potosí, Altair 200, Fracc. del Llano, San Luis Potosí, S. L. P. México. 78377  2Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055, Col. Lomas 4a sección San Luis Potosí, S. L. P. México. 78216

Half of the Mexican richness of Opuntia, at varying levels of domestication, is located in the Meridional Highland Plateau. In this area the cactus pear fruit is utilized, whilst the older cladodes are used as forage and the younger cladodes as nopalitos. In order to elucidate the process of domestication of Opuntia, forty-four morphological attributes, whether of economic importance or not, were analyzed from 243 variants of Opuntia, sampled at 31 localities in seven states of Mexico. The attributes with variation coefficients more than 100% were 1) number of spines smaller than 0.99 cm; 2) number of abortive seeds per fruit; 3) number of radial spines; 4) number of spines longer than 3.0 cm. The first ordination axis corresponded to a domestication gradient toward plants with big fruits and cladodes without spines; the second ordination axis showed another domestication tendency toward plants, also with big fruits, but with cladodes with prominent spines. In the classification 76 groups were obtained. The most important attributes for their classification were the quantity of radial spines, the number of spines per areole in the cladode, and the color and weight of the pulp. The classification reveals the elements of the syndrome of domestication of Opuntia for fruit. The weight of the pulp of the fruit appears to be the most important component, followed by the characteristics of the areoles and spines, and the shelf life and color of the fruit.