Morphological diversity of xoconostles (Opuntia spp.) or acidic cactus pears: a Mexican contribution to functional foods

Abstract

Introduction . Xoconostles or acidic cactus pears (Opuntia spp.) are fruits prized for their fleshy and acidic mesocarp; they are morphologically different from cactus pears which are sweet, juicy and seedy. Both thrive in semiarid highlands of Central Mexico, tolerate poor soils and scanty rainfall, and have evolved into formal crops during the last five decades. Wild xoconostles are ubiquitous in Mexican semiarid regions. Domesticated genotypes are found in backyards and commercial orchards. Folk wisdom attributes xoconostle with antihypoglycemic effects, cholesterol control and obesity reduction. The peel presents higher antioxidant capacity than strawberry, raspberry, red plum, grapefruit, pear and apple. Our investigation describes the main cultivars of xoconostles with horticultural value for human consumption in Central Mexico; it contributes to the elucidation of their morphological relationships. Materials and methods . Twenty-one accessions from the Hidalgo and Zacatecas states of Mexico were described using 27 variables from cladodes, flowers and fruits; significant variables were selected by correlation and PCA, and thereafter a cluster analysis and discriminant canonical analysis were performed. Results . Thirteen variables were found to be significant to discriminate accessions: cladode length, number of rows of areoles, number of areoles in the central row, pericarp length and width, fruit length, fruit diameter, [length / diameter] ratio, areole density, receptacle depth, fruit and peel weight, and pulp acidity. Two canonical roots (Can) explained variability: Can1 (fruit areola density, acidity, number of areole rows, and number of areoles in the central row) explained 87.55%, and Can2 (peel weight, fruit weight and fruit diameter) explained the remaining 12.45%. Discussion . Can1 was related to plant productivity, while Can2 comprised mainly fruit quality traits. Both of these traits are of primary interest for human utilization and have had a clear effect on domestication. Clusters did not match the actual taxonomic classification.