Genetic characterization and distinctiveness of forage cactus accessions in Northern Minas Gerais, Brazil

Forage cactus is a vital alternative food source for livestock in arid and semiarid regions. This study aimed to estimate the genetic dissimilarity among forage cactus genotypes grown in the semiarid region of northern Minas Gerais, Brazil. The study evaluated forage cactus accessions through morphological characteristics over different periods and molecular marker data. Key morphological traits assessed included cladode length, width, thickness, and the number of cladodes per plant. The experiments were conducted at the Agricultural Research Company of Minas Gerais (EPAMIG Norte) using a completely randomized experimental design with five replications in a split-plot arrangement. The design consisted of 21 forage cactus accessions in the plots and 7 evaluation times in the subplots. Morphological dissimilarities were compared individually (Scott-Knott test; p<0.05) and jointly (Euclidean distance). Molecular genotyping involved DNA extraction from young cladodes using inter-simple sequence repeat (ISSR) oligonucleotides. Dissimilarity based on molecular markers was estimated using the Jaccard index. Separate dendrograms were generated for each analysis (morphological and molecular) using the unweighted pair group method with arithmetic mean (UPGMA), and a tanglegram was created to illustrate the relationships between the two dendrograms. Significant differences were found in cladode length and width and in the fresh and dry weight of plants. The molecular analysis differentiated genotypes at the species and genus levels, even among those that appeared morphologically similar. Comparing morphological and molecular data revealed both divergences and similarities, providing valuable insights into the diversity and structure within the groups.