PHENOTYPIC AND GENETIC DIVERSITY IN GUAVA ORCHARDS FROM CALVILLO, AGUASCALIENTES

Abstract

Significant morphological and biochemical variability among and within guava (Psidium guajava L.) orchards of México has been found, but their genetic diversity remains unknown although it could be useful for the crop breeding. The phenotypic and genetic diversity of four guava orchards located in San Tadeo, Calvillo, Aguascalientes was determined. Twelve trees per orchard and ten fruits per tree were randomly selected and different morphological characteristics were determined in both fruits and trees; the 48 trees were analyzed by the Random Amplified Polymorphic DNA (RAPD) technique. Phenotypic and genetic differences across and within the tested orchards were detected, on basis to mesocarp color (beige, white, yellow, pink) and fruit shape (ovoid or pear-like). Principal component analysis revealed that polar diameter, equatorial diameter, mesocarp thickness, fruit weight, leaf length, and leaf width were the characteristics that best explained the phenotypic variation among trees. The 15 RAPD oligonucleotides amplified 112 ADN fragments (7-8 fragments per oligonucleotide) and all were polymorphic. Cluster analysis of phenotypic and RAPD data demonstrated no clear clustering of trees in relation to the orchard of origin. The morphological and genetic diversity is unfavorable due to the variation in fruit shapes and mesocarp color, which affect uniformity and quality of production.