Caracterização morfoanatômica de clones de theobroma cacao l.: evidências estruturais para distinção clonal

Abstract

Cacao (Theobroma cacao L.) is a tropical crop of high economic relevance, known as the primary source of chocolate production. The diversity of cacao varieties and clones results from centuries of domestication and genetic improvement aimed at high yield and disease resistance, including genotypes widely cultivated in the Amazon region. Morphological and anatomical analyses have proven to be valuable tools for the functional characterization of different clones. Thus, this study aimed to morpho-anatomically characterize the leaves of T. cacao clones grown under non-irrigated conditions to support selection strategies and genetic improvement. Standard anatomical techniques were used. Morphometric variables (leaf dimensions, stomatal and cell densities, and stomatal index), manual anatomical sections (petiole, pulvinus, apex, median, and lateral regions of the lamina), and histochemical tests using permanent slides were analyzed. Statistical analyses included the Kruskal–Wallis test, a nonparametric method used to detect significant differences among clones, and Principal Component Analysis (PCA). The results showed expressive differences among clones. PS1319, Ponta Verde Liso, and Ipiranga 01 exhibited larger leaf dimensions associated with lower stomatal indices, a condition that favors photosynthetic efficiency and water loss control. In contrast, CCN51 and CEPEC 2002/2004 displayed high stomatal density and reduced leaf blades, a characteristic related to their recognized tolerance to stress and high productivity. Accessory vascular bundles were recorded in clones such as CCN51, CCN10, CEPEC 2004, and Ponta Verde Liso. Regarding trichomes, in addition to the common forms in the Theobroma group, trichomes. Digitiform trichomes and trichomes with collapsed apical structures and bulbous bodies similar to the claviform type were also identified in genotypes such as CEPEC 2004, Ipiranga 01, PH 16, and Salobrinho. Histochemical tests revealed the accumulation of phenolics, lignin, lipids, and starch, reinforcing their roles in structural protection and defense. These findings expand the understanding of the anatomical diversity among cacao clones and provide valuable insights for selecting plant material aimed at sustainable management and use in genetic improvement programs.structural diversification was observed in the branching patterns of stellate