Industrial Crops and Products | 2021
Genetic diversity analyses of rubber tree genotypes based on UPOV descriptors
Abstract
Abstract The present study evaluated 57 genotypes of rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg.] utilizing 33 morphological descriptors at juvenile stage to determine importance for phenotypic characterization. This study compares different dissimilarity matrices and proposes a new way of calculating the distance matrix of multicategory descriptor traits; and a new way of analyzing importance of multicategorical traits. All the studied genotypes were obtained from the Rubber Tree Research Center and Agroforestry Systems germplasm collection, which belongs to the Agronomic Institute (IAC), Sao Paulo State, Brazil.The results of the Mantel test showed a greater correlation between the complement of the simple and weighted similarity coefficients (0.94), followed by the similarity coefficient and Euclidean distance (0.75) and, finally, the Euclidean distance and the weighted similarity coefficient (0.62). The weighted similarity coefficient was the dissimilarity matrix that best represented the genetic diversity of the clones used, allowing the separation of the genotypes into 18 groups through Tocher grouping, demonstrating the genetic diversity present in the evaluated material. The morphoagronomic characterization of the accessions detected polymorphisms for all the evaluated traits, showing that the genotypes exhibited genetic variability for the 33 evaluated descriptors. The results obtained by the Shannon-Weaver and fingerprint analyses indicate that the use of the descriptors leaf cluster, leaf length, intensity of green color of leaf, leaf undulation of margin, and trunk diameter is sufficient to characterize the variability in the data analyzed. The comparison between the similarity indices used showed that the weighted similarity coefficient is at least similar to the similarity coefficient and seems to better represent genetic diversity. The IAC clones demonstrate large genetic variability among themselves, highlighting the success of the genetic improvement program as well as the importance of preserving clones in the field.